LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2015 Charles Iliya Krempeaux :: http://changelog.ca/
+Copyright (c) 2015 Charles Iliya Krempeaux <charles@reptile.ca> :: http://changelog.ca/
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,115 +1,18 @@
-# go-log
+# go-flog
 
 A library that provides structured and formatted logging for the Go programming language.
 
-(This Go package was originally named `flog`, but in version 2 was renamed to `log`.)
 
-## Online Documention
+## Documention
 
-Online documentation, which includes examples, can be found at: http://godoc.org/github.com/reiver/go-log
+Online documentation, which includes examples, can be found at: http://godoc.org/github.com/reiver/go-flog
 
-[![GoDoc](https://godoc.org/github.com/reiver/go-log?status.svg)](https://godoc.org/github.com/reiver/go-log)
+[![GoDoc](https://godoc.org/github.com/reiver/go-flog?status.svg)](https://godoc.org/github.com/reiver/go-flog)
 
-## Basic Usage
 
-Basic usage of this logger looks like this:
+## More Routers
 
-```golang
+In addition to the builtin routers that go-flog comes with, other external
-router := log.NewPrettyWritingRouter(os.Stdout)
+routers are also available. These include:
 
-logger := log.New(router)
+* [go-slackchannelrouter](https://github.com/reiver/go-slackchannelrouter) Makes it so log messages get posted to a [Slack](https://slack.com/) channel.
-```
-Once you have the logger, you can do things such as:
-
-```golang
-logger.Print("Hello world!")
-logger.Println("Hello world!")
-logger.Printf("Hello %s!", name)
-
-logger.Panic("Uh oh!")
-logger.Panicln("Uh oh!")
-logger.Panicf("Uh oh, had a problem happen: %s.", problemDescription)
-
-logger.Fatal("Something really bad happened!")
-logger.Fatalln("Something really bad happened!")
-logger.Fatalf("Something really bad happened: %s.", problemDescription)
-```
-
-BTW, if the PrettyWritingRouter was being used, then this:
-
-```golang
-logger.Print("Hello world!")
-```
-
-Would generate output like the following:
-
-```
-Hello world!	(2015-10-10 17:28:49.397356044 -0700 PDT)
-```
-
-(Although note that in actual usage this would have color.)
-
-(Note that for for other routers the actual output would look very different!
-What the output looks like is router dependent.)
-
-## Structured Logging
-
-But those method calls all generated unstructure data.
-
-To include structured data the logger's With method needs to be used.
-For example:
-
-```golang
-newLogger := logger.With(map[string]interface{}{
-	"method":"Toil",
-	"secret_note":"Hi there! How are you?",
-})
-```
-
-Then if the PrettyWritingRouter was being used, then this:
-
-```golang
-newLogger.Print("Hello world!")
-```
-
-Would generate output like the following:
-
-```
-Hello world!	(2015-10-10 17:28:49.397356044 -0700 PDT)	method="Toil"	secret_note="Hi there! How are you?"
-```
-
-(Again, note that in actual usage this would have color.)
-
-## Deployment Environment
-
-Of course in a real application system you should (probably) create a different kind
-of logger for each deployment environment.
-
-Even though the PrettyWritingRouter is great for a development deployment environment
-(i.e., "DEV") it is probably not appropriate for a production deployment environment
-(i.e., "PROD").
-
-For example:
-```golang
-var logger log.Logger
-
-switch deploymentEnvironment {
-case "DEV":
-	router := log.NewPrettyWritingRouter(os.Stdout)
-	
-	logger = log.New(router)
-case "PROD":
-	verboseRouter = log.NewDiscardingRouter()
-	if isVerboseMode {
-		verboseRouter = NewCustomVerboseRouter()
-	}
-	
-	panicDetectionRouter := log.NewFilteringRouter(NewCustomerPanicRecordingRouter(), filterOnlyPanicsFunc)
-	
-	errorDetectionRouter := log.NewFilteringRouter(NewCustomerPanicRecordingRouter(), filterOnlyErrorsFunc)
-	
-	router := NewFanoutRouter(verboseRouter, panicDetectionRouter, errorDetectionRouter)
-	
-	logger = log.New(router)
-}
-```

calltrace.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"

context.go

@@ -0,0 +1,24 @@
+package flog
+
+
+func newContext(cascade ...interface{}) map[string]interface{} {
+
+	context := make(map[string]interface{})
+
+	for _,x := range cascade {
+		switch xx := x.(type) {
+		case map[string]string:
+			for key, value := range xx {
+				context[key] = value
+			}
+		case map[string]interface{}:
+			for key, value := range xx {
+				context[key] = value
+			}
+		case string:
+			context["text"] = xx
+		}
+	}
+
+	return context
+}

context_test.go

@@ -0,0 +1,154 @@
+package flog
+
+
+import (
+	"testing"
+)
+
+
+func TestNewContext(t *testing.T) {
+
+	tests := []struct{
+		Cascade []interface{}
+		Expected map[string]interface{}
+	}{
+		{
+			Cascade: []interface{}{},
+			Expected: map[string]interface{}{},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				"apple",
+			},
+			Expected: map[string]interface{}{
+				"text":"apple",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				"apple",
+				"banana",
+			},
+			Expected: map[string]interface{}{
+				"text":"banana",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				"apple",
+				"banana",
+				"cherry",
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+				},
+			},
+			Expected: map[string]interface{}{},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+				map[string]string{
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD BE REPLACED",
+				},
+				map[string]string{
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+	}
+
+
+TestLoop:
+	for testNumber, test := range tests {
+
+		context := newContext(test.Cascade...)
+
+		if expected, actual := len(test.Expected), len(context); expected != actual {
+			t.Errorf("For test #%d, expected length to be %d but actually was %d.", testNumber, expected, actual)
+			continue TestLoop
+		}
+
+		for expectedKey, expectedValue := range test.Expected {
+			if _, ok := context[expectedKey]; !ok {
+				t.Errorf("For test #%d, expected key %q to be in resulting context but wasn't.", testNumber, expectedKey)
+				continue TestLoop
+			}
+
+			if expected, actual := expectedValue, context[expectedKey]; expected != actual {
+				t.Errorf("For test #%d, expected value for key %q to be %q in resulting context, but was actually %q.", testNumber, expectedKey, expected, actual)
+				continue TestLoop
+			}
+		}
+
+	}
+}

copying_router.go

@@ -0,0 +1,55 @@
+package flog
+
+
+// NewCopyingRouter returns an initialized CopyingRouter.
+func NewCopyingRouter(subrouter Router) *CopyingRouter {
+	copies  := make([]struct{Message string ; Context map[string]interface{}}, 0, 8)
+
+	router := CopyingRouter {
+		subrouter:subrouter,
+		copies:copies,
+	}
+
+	return &router
+}
+
+
+// CopyingRouter is a Router that copies a message (and its context) to memory, and then
+// re-routes a message (and its context) to a sub-router.
+//
+// This router is NOT designed to be used for an indefinite number of routings, and instead
+// should only be used for a limited amount of routings, as it stores all the copies in
+// memory.
+type CopyingRouter struct {
+	subrouter Router
+	copies []struct{Message string ; Context map[string]interface{}}
+}
+
+
+func (router *CopyingRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	copy := struct{Message string ; Context map[string]interface{}}{
+		Message: message,
+		Context: context,
+	}
+	router.copies = append(router.copies, copy)
+
+	return router.subrouter.Route(message, context)
+}
+
+
+func (router *CopyingRouter) Copies() <-chan struct{Message string ; Context map[string]interface{}} {
+	ch := make(chan struct{Message string ; Context map[string]interface{}})
+
+	go func() {
+		for _, copy := range router.copies {
+			ch <- copy
+		}
+		close(ch)
+	}()
+
+	return ch
+}

copying_router_test.go

@@ -0,0 +1,141 @@
+package flog
+
+
+import (
+	"testing"
+
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+
+func TestNewCopyingRouter(t *testing.T) {
+
+	randomness := rand.New(rand.NewSource( time.Now().UTC().UnixNano() ))
+
+
+	router := NewCopyingRouter(NewDiscardingRouter())
+	if nil == router {
+		t.Errorf("After trying to create a copying router, expected it to be not nil, but was: %v", router)
+	}
+
+
+	lenInitialCopies := 0
+	for range router.Copies() {
+		lenInitialCopies++
+	}
+	if expected, actual := 0, lenInitialCopies; expected != actual {
+		t.Errorf("After creating a copying router, expected copies to be length %d, but was actually %d,", expected, actual)
+	}
+
+
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
+
+	context := make(map[string]interface{})
+	limit := randomness.Int63n(30)
+	for i:=int64(0); i<limit; i++ {
+		context[ fmt.Sprintf("%x", randomness.Int63n(1000*limit)) ] = fmt.Sprintf("%x", randomness.Int63n(999999999999999))
+	}
+
+	router.Route(message, context) // Just make sure it doesn't panic or deadlok, by calling this.
+}
+
+
+func TestCopyingRouterRoute(t *testing.T) {
+
+	tests := []struct{
+		Data []struct{Message string ; Context map[string]interface{}}
+	}{
+		{
+			Data: []struct{Message string ; Context map[string]interface{}}{
+			},
+		},
+
+
+		{
+			Data: []struct{Message string ; Context map[string]interface{}}{
+				struct{Message string ; Context map[string]interface{}}{
+					Message: "apple banana cherry",
+					Context: map[string]interface{}{
+						"one":1,
+						"two":2,
+						"three":3,
+					},
+				},
+			},
+		},
+
+
+		{
+			Data: []struct{Message string ; Context map[string]interface{}}{
+				struct{Message string ; Context map[string]interface{}}{
+					Message: "apple",
+					Context: map[string]interface{}{
+						"one":1,
+					},
+				},
+				struct{Message string ; Context map[string]interface{}}{
+					Message: "banana",
+					Context: map[string]interface{}{
+						"two":2,
+					},
+				},
+				struct{Message string ; Context map[string]interface{}}{
+					Message: "cherry",
+					Context: map[string]interface{}{
+						"cherry":3,
+					},
+				},
+			},
+		},
+	}
+
+
+TLoop:	for testNumber, test := range tests {
+
+		router := NewCopyingRouter(NewDiscardingRouter())
+
+		for _, datum := range test.Data {
+			router.Route(datum.Message, datum.Context)
+		}
+
+
+		lenCopies := 0
+		for range router.Copies() {
+			lenCopies++
+		}
+		if expected, actual := len(test.Data), lenCopies; expected != actual {
+			t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected copies to be length %d, but was actually %d.", testNumber, expected, actual)
+			continue TLoop
+		}
+
+
+		datumNumber := 0
+		for actualDatum := range router.Copies() {
+			if expected, actual := test.Data[datumNumber].Message, actualDatum.Message; expected != actual {
+				t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected message for copies datum #%d to be %q, but was actually %q.", testNumber, datumNumber, expected, actual)
+				continue TLoop
+			}
+
+			if expected, actual := len(test.Data[datumNumber].Context), len(actualDatum.Context); expected != actual {
+				t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected length of context for copies datum #%d to be %d, but was actually %d.", testNumber, datumNumber, expected, actual)
+				continue TLoop
+			}
+
+			for expectedKey, expectedValue := range test.Data[datumNumber].Context {
+				if _, ok := actualDatum.Context[expectedKey]; !ok {
+					t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected context for copies datum #%d to have key %q, but didn't.", testNumber, datumNumber, expectedKey)
+					continue TLoop
+				}
+
+				if actualValue := actualDatum.Context[expectedKey]; expectedValue != actualValue {
+					t.Errorf("For test #%d, after creating a copying router and (potentially) doing some routing, expected value for context for copies datum #%d at key %q to have value [%v], but actually had [%v].", testNumber, datumNumber, expectedKey, expectedValue, actualValue)
+					continue TLoop
+				}
+			}
+
+			datumNumber++
+		}
+	}
+}

default.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"os"

default_writing_router.go

@@ -0,0 +1,92 @@
+package flog
+
+import (
+	"github.com/reiver/go-dotquote"
+	"github.com/reiver/go-oi"
+
+	"fmt"
+	"io"
+	"time"
+)
+
+// NewDefaultWritingRouter returns an initialized DefaultWritingRouter
+func NewDefaultWritingRouter(writer io.Writer) *DefaultWritingRouter {
+	return NewDefaultWritingRouterWithPrefix(writer, nil)
+}
+
+// NewDefaultWritingRouterWithPrefix returns an initialized DefaultWritingRouter
+func NewDefaultWritingRouterWithPrefix(writer io.Writer, prefix map[string]interface{}) *DefaultWritingRouter {
+	var prefixBuffer []byte
+	if 0 < len(prefix) {
+		prefixBuffer = dotquote.AppendMap(prefixBuffer, prefix)
+		prefixBuffer = append(prefixBuffer, ' ')
+	}
+
+	router := DefaultWritingRouter{
+		writer:writer,
+		prefix:prefixBuffer,
+	}
+
+	return &router
+}
+
+// DefaultWritingRouter is a router that writes the log in a default format.
+//
+// A DefaultWritingRouter is appropriate for a production (i.e., "PROD")
+// deployment enviornment.
+type DefaultWritingRouter struct {
+	writer io.Writer
+	prefix []byte
+}
+
+func (router *DefaultWritingRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+
+	writer := router.writer
+	if nil == writer {
+		// Nothing to do, so just return silently.
+		return nil
+	}
+
+
+	var buffer [512]byte
+	p := buffer[:0]
+
+	if prefix := router.prefix; 0 < len(prefix) {
+		p = append(p, prefix...)
+	}
+
+
+	p = dotquote.AppendString(p, message, "text")
+	p = append(p, ' ')
+	p = dotquote.AppendString(p, time.Now().String(), "when")
+	if trace := calltrace(); nil != trace {
+		p = append(p, ' ')
+		p = dotquote.AppendStrings(p, trace, "calltrace")
+	}
+
+	// If we have an error, then get the error.Error() into the log too.
+	if errorFieldValue, ok := context["~error"]; ok {
+		if err, ok := errorFieldValue.(error); ok {
+			p = append(p, ' ')
+			p = dotquote.AppendString(p, fmt.Sprintf("%T", err), "error", "type")
+			p = append(p, ' ')
+			p = dotquote.AppendString(p, err.Error(), "error", "text")
+		}
+	}
+
+	if 0 < len(context) {
+		p = append(p, ' ')
+		p = dotquote.AppendMap(p, context, "ctx")
+	}
+
+	p = append(p, '\n')
+
+	_,_ = oi.LongWrite(router.writer, p)
+
+//@TODO: Should this be checking for errors from oi.LongWrite()?
+	return nil
+}

default_writing_router_test.go

@@ -0,0 +1,226 @@
+package flog
+
+
+import (
+	"bytes"
+	"errors"
+	"strings"
+
+	"testing"
+)
+
+
+func TestDefaultWritingRouterRoute(t *testing.T) {
+
+	tests := []struct{
+		Message string
+		Context map[string]interface{}
+		ExpectContains []string
+	}{
+		{
+			Message: "Hello world!",
+			Context: map[string]interface{}{
+				"apple": "one",
+				"banana": 2,
+				"cherry": 3.3,
+				"kiwi":   true,
+				"~error": errors.New("test error"),
+			},
+			ExpectContains: []string{
+				`"text"="Hello world!"`,
+				` "ctx"."apple"="one" "ctx"."banana"="2" "ctx"."cherry"="3.300000" "ctx"."kiwi"="true"`,
+				` "error"."type"="*errors.errorString" "error"."text"="test error" `,
+				` "when"="`,
+			},
+		},
+
+
+
+		{
+			Message: "Apple\tBANANA\nCherry",
+			Context: map[string]interface{}{
+				"apple": "one",
+				"banana": 2,
+				"cherry": 3.3,
+				"kiwi":   true,
+				"~error": errors.New("test error"),
+				"more": map[string]interface{}{
+					"ONE":   "1",
+					"TWO":   "2",
+					"THREE": "3",
+				},
+			},
+			ExpectContains: []string{
+				`"text"="Apple\tBANANA\nCherry"`,
+				` "ctx"."apple"="one" "ctx"."banana"="2" "ctx"."cherry"="3.300000" "ctx"."kiwi"="true"`,
+				` "error"."type"="*errors.errorString" "error"."text"="test error" `,
+				` "ctx"."more"."ONE"="1" "ctx"."more"."THREE"="3" "ctx"."more"."TWO"="2"`,
+				` "when"="`,
+			},
+		},
+
+
+
+		{
+			Message: "Apple\tBANANA\nCherry",
+			Context: map[string]interface{}{
+				"apple": "one",
+				"banana": 2,
+				"cherry": 3.3,
+				"kiwi":   true,
+				"~error": errors.New("test error"),
+				"more": map[string]interface{}{
+					"ONE":   "1",
+					"TWO":   "2",
+					"THREE": "3",
+					"FOUR":  map[string]interface{}{
+						"a": "1st",
+						"b": "2nd",
+						"c": []string{
+							"th",
+							"i",
+							"rd",
+						},
+					},
+				},
+			},
+			ExpectContains: []string{
+				`"text"="Apple\tBANANA\nCherry"`,
+				` "ctx"."apple"="one" "ctx"."banana"="2" "ctx"."cherry"="3.300000" "ctx"."kiwi"="true"`,
+				` "error"."type"="*errors.errorString" "error"."text"="test error" `,
+				` "ctx"."more"."FOUR"."a"="1st" "ctx"."more"."FOUR"."b"="2nd" "ctx"."more"."FOUR"."c"=["th","i","rd"] "ctx"."more"."ONE"="1" "ctx"."more"."THREE"="3" "ctx"."more"."TWO"="2"`,
+				` "when"="`,
+			},
+		},
+	}
+
+
+	for testNumber, test := range tests {
+
+		var buffer bytes.Buffer
+
+		var router Router = NewDefaultWritingRouter(&buffer)
+
+		ctx := map[string]interface{}{}
+		for n, v := range test.Context {
+			ctx[n] = v
+		}
+
+		if err := router.Route(test.Message, ctx); nil != err {
+			t.Errorf("For test #%d, did not expect an error, but actually got one: (%T) %v", testNumber, err, err)
+			continue
+		}
+
+		{
+			actual := buffer.String()
+			for expectedNumber, expectContains := range test.ExpectContains {
+
+				if !strings.Contains(actual, expectContains) {
+					t.Errorf("For test #%d and expected #%d, expect to contain, actual:\n==)>%s<(==\n==)>%s<(==", testNumber, expectedNumber, expectContains, actual)
+					continue
+				}
+			}
+		}
+	}
+}
+
+
+func TestDefaultWritingRouterWithPrefixRoute(t *testing.T) {
+
+	tests := []struct{
+		Message string
+		Context map[string]interface{}
+		Prefix map[string]interface{}
+		ExpectContains []string
+	}{
+		{
+			Message: "Hello world!",
+			Context: map[string]interface{}{
+				"apple": "one",
+				"banana": 2,
+				"cherry": 3.3,
+				"kiwi":   true,
+				"~error": errors.New("test error"),
+			},
+			Prefix: map[string]interface{}{
+				"name": "backendapi",
+				"number": "123",
+			},
+			ExpectContains: []string{
+				`"name"="backendapi" "number"="123" "text"="Hello world!" "when"="`,
+				` "ctx"."apple"="one" "ctx"."banana"="2" "ctx"."cherry"="3.300000" "ctx"."kiwi"="true"`,
+				` "error"."type"="*errors.errorString" "error"."text"="test error" `,
+			},
+		},
+
+
+		{
+			Message: "Apple\tBANANA\nCherry",
+			Context: map[string]interface{}{
+				"apple": "one",
+				"banana": 2,
+				"cherry": 3.3,
+				"kiwi":   true,
+				"~error": errors.New("test error"),
+				"more": map[string]interface{}{
+					"ONE":   "1",
+					"TWO":   "2",
+					"THREE": "3",
+					"FOUR":  map[string]interface{}{
+						"a": "1st",
+						"b": "2nd",
+						"c": []string{
+							"th",
+							"i",
+							"rd",
+						},
+					},
+				},
+			},
+			Prefix: map[string]interface{}{
+				"app": map[string]interface{}{
+					"name": "backendapi",
+					"build": map[string]interface{}{
+						"number": 123,
+						"hash":  "4a844b2",
+					},
+				},
+			},
+			ExpectContains: []string{
+				`"app"."build"."hash"="4a844b2" "app"."build"."number"="123" "app"."name"="backendapi" "text"="Apple\tBANANA\nCherry" "when"="`,
+				` "ctx"."apple"="one" "ctx"."banana"="2" "ctx"."cherry"="3.300000" "ctx"."kiwi"="true"`,
+				` "error"."type"="*errors.errorString" "error"."text"="test error" `,
+				` "ctx"."more"."FOUR"."a"="1st" "ctx"."more"."FOUR"."b"="2nd" "ctx"."more"."FOUR"."c"=["th","i","rd"] "ctx"."more"."ONE"="1" "ctx"."more"."THREE"="3" "ctx"."more"."TWO"="2"`,
+			},
+		},
+	}
+
+
+	for testNumber, test := range tests {
+
+		var buffer bytes.Buffer
+
+		var router Router = NewDefaultWritingRouterWithPrefix(&buffer, test.Prefix)
+
+		ctx := map[string]interface{}{}
+		for n, v := range test.Context {
+			ctx[n] = v
+		}
+
+		if err := router.Route(test.Message, ctx); nil != err {
+			t.Errorf("For test #%d, did not expect an error, but actually got one: (%T) %v", testNumber, err, err)
+			continue
+		}
+
+		{
+			actual := buffer.String()
+			for expectedNumber, expectContains := range test.ExpectContains {
+
+				if !strings.Contains(actual, expectContains) {
+					t.Errorf("For test #%d and expected #%d, expect to contain, actual:\n==)>%s<(==\n==)>%s<(==", testNumber, expectedNumber, expectContains, actual)
+					continue
+				}
+			}
+		}
+	}
+}

discarding_router.go

@@ -0,0 +1,24 @@
+package flog
+
+
+var (
+	singltonDiscardingRouter = DiscardingRouter{}
+)
+
+
+// NewDiscardingRouter returns an initialized DiscardingRouter.
+func NewDiscardingRouter() *DiscardingRouter {
+	return &singltonDiscardingRouter
+}
+
+
+// DiscardingRouter is a Router that discards any message (and its context)
+// it is asked to route.
+//
+// Conceptually it is similar to /dev/null
+type DiscardingRouter struct{}
+
+
+func (router *DiscardingRouter) Route(message string, context map[string]interface{}) error {
+	return nil
+}

discarding_router_test.go

@@ -0,0 +1,33 @@
+package flog
+
+
+import (
+	"testing"
+
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+
+func TestNewDiscardingRouter(t *testing.T) {
+
+	randomness := rand.New(rand.NewSource( time.Now().UTC().UnixNano() ))
+
+
+	router := NewDiscardingRouter()
+	if nil == router {
+		t.Errorf("After trying to create a discard router, expected it to be not nil, but was: %v", router)
+	}
+
+
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
+
+	context := make(map[string]interface{})
+	limit := randomness.Int63n(30)
+	for i:=int64(0); i<limit; i++ {
+		context[ fmt.Sprintf("%x", randomness.Int63n(1000*limit)) ] = fmt.Sprintf("%x", randomness.Int63n(999999999999999))
+	}
+
+	router.Route(message, context) // Just make sure it doesn't panic or deadlok, by calling this.
+}

doc.go

@@ -0,0 +1,104 @@
+/*
+Package flog provides structured and formatted logging.
+
+Basic Usage
+
+Basic usage of the flogger looks like this:
+
+	router := flog.NewPrettyWritingRouter(os.Stdout)
+	
+	flogger := flog.New(router)
+
+Once you have the flogger, you can do things such as:
+
+	flogger.Print("Hello world!")
+	flogger.Println("Hello world!")
+	flogger.Printf("Hello %s!", name)
+	
+	flogger.Panic("Uh oh!")
+	flogger.Panicln("Uh oh!")
+	flogger.Panicf("Uh oh, had a problem happen: %s.", problemDescription)
+	
+	flogger.Fatal("Something really bad happened!")
+	flogger.Fatalln("Something really bad happened!")
+	flogger.Fatalf("Something really bad happened: %s.", problemDescription)
+
+BTW, if the PrettyWritingRouter was being used, then this:
+
+	flogger.Print("Hello world!")
+
+Would generate output like the following:
+
+	Hello world!	(2015-10-10 17:28:49.397356044 -0700 PDT)
+
+(Although note that in actual usage this would have color.)
+
+(Note that for for other routers the actual output would look very different!
+What the output looks like is router dependent.)
+
+Structured Logging
+
+But those method calls all generated unstructure data.
+
+To include structured data the flogger's With method needs to be used.
+For example:
+
+	newFlogger := flogger.With(map[string]interface{}{
+		"method":"Toil",
+		"secret_note":"Hi there! How are you?",
+	})
+
+Then if the PrettyWritingRouter was being used, then this:
+
+	newFlogger.Print("Hello world!")
+
+Would generate output like the following:
+
+	Hello world!	(2015-10-10 17:28:49.397356044 -0700 PDT)	method="Toil"	secret_note="Hi there! How are you?"
+
+(Again, note that in actual usage this would have color.)
+
+Deployment Environment
+
+Of course in a real application system you should (probably) create a different kind
+of flogger for each deployment environment.
+
+Even though the PrettyWritingRouter is great for a development deployment environment
+(i.e., "DEV") it is probably not appropriate for a production deployment environment
+(i.e., "PROD").
+
+For example:
+
+	var flogger flog.Flogger
+	
+	switch deploymentEnvironment {
+	case "DEV":
+		router := flog.NewPrettyWritingRouter(os.Stdout)
+		
+		flogger = flog.New(router)
+	case "PROD":
+		verboseRouter = flog.NewDiscardingRouter()
+		if isVerboseMode {
+			verboseRouter = NewCustomVerboseRouter()
+		}
+
+		panicDetectionRouter := flog.NewFilteringRouter(NewCustomerPanicRecordingRouter(), filterOnlyPanicsFunc)
+
+		errorDetectionRouter := flog.NewFilteringRouter(NewCustomerPanicRecordingRouter(), filterOnlyErrorsFunc)
+
+		router := NewFanoutRouter(verboseRouter, panicDetectionRouter, errorDetectionRouter)
+		
+		flogger = flog.New(router)
+	}
+
+More Routers
+
+In addition to the builtin routers that go-flog comes with, other external
+routers are also available. These include:
+
+go-slackchannelrouter:
+Makes it so log messages get posted to a Slack channel.
+https://github.com/reiver/go-slackchannelrouter
+
+*/
+package flog

error_test.go

@@ -0,0 +1,198 @@
+package flog
+
+
+import (
+	"errors"
+	"reflect"
+
+	"testing"
+)
+
+
+func TestNewErrorContext(t *testing.T) {
+
+	err1 := errors.New("error 1")
+	err2 := errors.New("error 2")
+	err3 := errors.New("error 3")
+	err4 := errors.New("error 4")
+	err5 := errors.New("error 5")
+
+
+	tests := []struct{
+		BaseContext map[string]interface{}
+		V                    []interface{}
+		Expected    map[string]interface{}
+	}{
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				// Nothing here.
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+			},
+		},
+
+
+
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				1,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				1, "two",
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				1, "two", 3.0,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+			},
+		},
+
+
+
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				1, "two", 3.0,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+			},
+		},
+
+
+
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				err1,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1,
+				},
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				err1, err2,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1, err2,
+				},
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				err1, err2, err3,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1, err2, err3,
+				},
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				err1, err2, err3, err4,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1, err2, err3, err4,
+				},
+			},
+		},
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				err1, err2, err3, err4, err5,
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1, err2, err3, err4, err5,
+				},
+			},
+		},
+
+
+
+		{
+			BaseContext: map[string]interface{}{
+				"~type":"error",
+			},
+			V: []interface{}{
+				1, err1, "two", err2, 3.0, err3, '4',
+			},
+			Expected: map[string]interface{}{
+				"~type":"error",
+				"~errors": []error{
+					err1, err2, err3,
+				},
+			},
+		},
+	}
+
+
+	for testNumber, test := range tests {
+
+		actualContext := newErrorContext(test.BaseContext, test.V...)
+		if actual := actualContext; nil == actual {
+			t.Errorf("For test #%d, did not expected nil, but actually got %v", testNumber, actual)
+			continue
+		}
+
+		if expected, actual := len(test.Expected), len(actualContext); expected != actual  {
+			t.Errorf("For test #%d, expected %d, but actually got %d.", testNumber, expected, actual)
+			continue
+		}
+
+		if expected, actual := test.Expected, actualContext; !reflect.DeepEqual(expected, actual) {
+			t.Errorf("For test #%d, expected...\n%#v\nbut actually got...\n%#v", testNumber, expected, actual)
+			continue
+		}
+	}
+}

errors.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 
 import (
@@ -8,4 +8,5 @@ import (
 
 var (
 	errNilReceiver = errors.New("Nil Receiver")
+	errNilRouter   = errors.New("Nil Router")
 )

fanout_router.go

@@ -0,0 +1,44 @@
+package flog
+
+
+import (
+	"github.com/reiver/go-manyerrors"
+)
+
+
+// NewFanoutRouter returns an initialized FanoutRouter.
+func NewFanoutRouter(subrouters ...Router) *FanoutRouter {
+	router := FanoutRouter{
+		subrouters:subrouters,
+	}
+
+	return &router
+}
+
+
+// FanoutRouter is a Router that re-routes any message (and its context) it
+// receives to all of its sub-routers.
+type FanoutRouter struct {
+	subrouters []Router
+}
+
+
+func (router *FanoutRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	errors := []error{}
+
+	for _, subrouter := range router.subrouters {
+		if err := subrouter.Route(message, context); nil != err {
+			errors = append(errors, err)
+		}
+	}
+
+	if 0 < len(errors) {
+		return manyerrors.New(errors...)
+	}
+
+	return nil
+}

fanout_router_test.go

@@ -0,0 +1,350 @@
+package flog
+
+
+import (
+	"testing"
+
+	"github.com/reiver/go-manyerrors"
+
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+
+func TestNewFanoutRouter(t *testing.T) {
+
+	randomness := rand.New(rand.NewSource( time.Now().UTC().UnixNano() ))
+
+
+	router := NewFanoutRouter()
+	if nil == router {
+		t.Errorf("After trying to create a discard router, expected it to be not nil, but was: %v", router)
+	}
+
+
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
+
+	context := make(map[string]interface{})
+	limit := randomness.Int63n(30)
+	for i:=int64(0); i<limit; i++ {
+		context[ fmt.Sprintf("%x", randomness.Int63n(1000*limit)) ] = fmt.Sprintf("%x", randomness.Int63n(999999999999999))
+	}
+
+	router.Route(message, context) // Just make sure it doesn't panic or deadlok, by calling this.
+}
+
+
+func TestFanoutRouterRoute(t *testing.T) {
+
+	numApples   := 0
+	numBananas  := 0
+	numCherries := 0
+	numFigs     := 0
+	numKiwis    := 0
+	numApplesOrFigs := 0
+
+	appleRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "apple" == message {
+			numApples++
+			return true
+		}
+
+		return false
+	})
+	bananaRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "banana" == message {
+			numBananas++
+			return true
+		}
+
+		return false
+	})
+	cherryRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "cherry" == message {
+			numCherries++
+			return true
+		}
+
+		return false
+	})
+	figRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "fig" == message {
+			numFigs++
+			return true
+		}
+
+		return false
+	})
+	kiwiRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "kiwi" == message {
+			numKiwis++
+			return true
+		}
+
+		return false
+	})
+	appleOrFigRouter := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		if "apple" == message || "fig" == message {
+			numApplesOrFigs++
+			return true
+		}
+
+		return false
+	})
+
+
+	router := NewFanoutRouter(appleRouter, bananaRouter, cherryRouter, figRouter, kiwiRouter, appleOrFigRouter)
+
+	if expected, actual := 0, numApples; expected != actual {
+		t.Errorf("Initially expected numApples to be %d, but actually was %d.", expected, actual)
+		return
+	}
+	if expected, actual := 0, numBananas; expected != actual {
+		t.Errorf("Initially expected numBananas to be %d, but actually was %d.", expected, actual)
+		return
+	}
+	if expected, actual := 0, numCherries; expected != actual {
+		t.Errorf("Initially expected numCherries to be %d, but actually was %d.", expected, actual)
+		return
+	}
+	if expected, actual := 0, numFigs; expected != actual {
+		t.Errorf("Initially expected numFigs to be %d, but actually was %d.", expected, actual)
+		return
+	}
+	if expected, actual := 0, numKiwis; expected != actual {
+		t.Errorf("Initially expected numKiwis to be %d, but actually was %d.", expected, actual)
+		return
+	}
+	if expected, actual := 0, numApplesOrFigs; expected != actual {
+		t.Errorf("Initially expected numApplesOrFigs to be %d, but actually was %d.", expected, actual)
+		return
+	}
+
+
+
+	var message string
+	var context map[string]interface{} = map[string]interface{}{}
+
+
+
+	message = "apple"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+
+
+
+	message = "banana"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+
+
+
+	message = "cherry"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+
+
+
+	message = "fig"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 0, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 2, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+
+
+
+	message = "kiwi"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 2, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+
+
+
+	message = "fig"
+	if err := router.Route(message, context); nil != err {
+		switch errs := err.(type) {
+		case manyerrors.Errors:
+			t.Errorf("Received many error when trying to send message %q: %#v", message, errs.Errors())
+		default:
+			t.Errorf("Received error when trying to send message %q: %v", message, err)
+		}
+	}
+
+	if expected, actual := 1, numApples; expected != actual {
+		t.Errorf("After sending message %q expected numApples to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numBananas; expected != actual {
+		t.Errorf("After sending message %q expected numBananas to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numCherries; expected != actual {
+		t.Errorf("After sending message %q expected numCherries to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 2, numFigs; expected != actual {
+		t.Errorf("After sending message %q expected numFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 1, numKiwis; expected != actual {
+		t.Errorf("After sending message %q expected numKiwis to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+	if expected, actual := 3, numApplesOrFigs; expected != actual {
+		t.Errorf("After sending message %q expected numApplesOrFigs to be %d, but actually was %d.", message, expected, actual)
+		return
+	}
+}

filtering_router.go

@@ -0,0 +1,86 @@
+package flog
+
+
+// NewFilteringRouter returns an initialized FilteringRouter.
+//
+// 'subrouter' is the sub-router that a FilteringRouter will
+// re-Route a 'message' (and 'context') to, but only on the
+// condition that 'filterFn' returns 'true' for the 'message'
+// and 'context' passed to it.
+//
+// An example for 'filterFn' is the following.
+//
+//	func filterError(message string, context map[string]interface{})bool) bool {
+//		if datum, ok := context["error"]; !ok {
+//			return false
+//		} else if _, ok := datum.(error); !ok {
+//			return false
+//		} else {
+//			return true
+//		}
+//	}
+//
+// This func will cause the router it only re-route messages whose context #1 has the
+// key "error" and #2 where the value of the context at key "key" fits the builtin Go
+// 'error' interface.
+//
+// So, for example, for 'filterError' this would pass:
+//
+//	context := map[string]interface{}{
+//		"apple":1,
+//		"banana":2,
+//		"cherry":3,
+//		"error": errors.New("Something bad happened :-("),
+//	}
+//
+// But, again for 'filterError', this would NOT pass:
+//
+//	context := map[string]interface{}{
+//		"apple":1,
+//		"banana":2,
+//		"cherry":3,
+//	}
+//
+// Also, a rather useless example, but a 'filterFn' that would reject all messages (and
+// contexts) is:
+//
+//	func filterRejectAll(message string, context map[string]interface{})bool) bool {
+//		return false
+//	}
+//
+//
+// And also, another rather useless example, but a 'filterFn' that would allow all messages
+// (and contexts) is:
+//
+//	func filterAcceptAll(message string, context map[string]interface{})bool) bool {
+//		return true
+//	}
+//
+func NewFilteringRouter(subrouter Router, filterFn func(string, map[string]interface{})bool) *FilteringRouter {
+	router := FilteringRouter{
+		subrouter:subrouter,
+		filterFn:filterFn,
+	}
+
+	return &router
+}
+
+
+// FilteringRouter is a Router that conditionally re-routes or discards a message (and its context).
+type FilteringRouter struct {
+	subrouter Router
+	filterFn func(string, map[string]interface{})bool
+}
+
+
+func (router *FilteringRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	if router.filterFn(message, context) {
+		return router.subrouter.Route(message, context)
+	}
+
+	return nil
+}

filtering_router_test.go

@@ -0,0 +1,91 @@
+package flog
+
+
+import (
+	"testing"
+
+	"fmt"
+	"math/rand"
+	"time"
+)
+
+
+func TestFilteringRouterJustCreated(t *testing.T) {
+
+	randomness := rand.New(rand.NewSource( time.Now().UTC().UnixNano() ))
+
+
+	router := NewFilteringRouter(NewDiscardingRouter(), func(string, map[string]interface{}) bool {
+		return false
+	})
+	if nil == router {
+		t.Errorf("After trying to create a filtering router, expected it to be not nil, but was: %v", router)
+	}
+
+
+	message := fmt.Sprintf("%x", randomness.Int63n(9999999999))
+
+	context := make(map[string]interface{})
+	limit := randomness.Int63n(30)
+	for i:=int64(0); i<limit; i++ {
+		context[ fmt.Sprintf("%x", randomness.Int63n(1000*limit)) ] = fmt.Sprintf("%x", randomness.Int63n(999999999999999))
+	}
+
+	router.Route(message, context) // Just make sure it doesn't panic or deadlok, by calling this.
+}
+
+
+func TestFilteringRouterJustFilterParameters(t *testing.T) {
+
+	randomness := rand.New(rand.NewSource( time.Now().UTC().UnixNano() ))
+
+
+	var filterMessage string
+	var filterContext map[string] interface{}
+	var filterResult = false
+
+	router := NewFilteringRouter(NewDiscardingRouter(), func(message string, context map[string]interface{}) bool {
+		filterMessage = message
+		filterContext = context
+
+		filterResult = !filterResult
+
+		return filterResult
+	})
+
+	const NUM_TESTS = 20
+TLoop:	for testNumber:=0; testNumber<NUM_TESTS; testNumber++ {
+		msg := fmt.Sprintf("string with random numbers: %d", randomness.Int63n(9999999999))
+
+		ctx := make(map[string]interface{})
+		lenCtx := randomness.Int63n(30)
+		for i:=int64(0); i<lenCtx; i++ {
+			ctx[ fmt.Sprintf("%x", randomness.Int63n(1000*lenCtx)) ] = fmt.Sprintf("%x", randomness.Int63n(999999999999999))
+		}
+
+
+		router.Route(msg, ctx)
+
+		if expected, actual := msg, filterMessage; expected != actual {
+			t.Errorf("For test #%d, expected message passed to filter func to be %q, but actually was %q.", testNumber, expected, actual)
+			continue TLoop
+		}
+
+		if expected, actual := len(ctx), len(filterContext); expected != actual {
+			t.Errorf("For test #%d, expected context passed to filter func to be len %d, but actually was %d.", testNumber, expected, actual)
+			continue TLoop
+		}
+
+		for expectedKey, expectedValue := range ctx {
+			if _, ok := filterContext[expectedKey]; !ok {
+				t.Errorf("For test #%d, expected context passed to filter func to have key %q, but didn't.", testNumber, expectedKey)
+				continue TLoop
+			}
+
+			if expected, actual := expectedValue.(string), filterContext[expectedKey].(string); expected != actual {
+				t.Errorf("For test #%d, expected context passed to filter func for key %q to have value %q, but actuall had %q.", testNumber, expectedKey, expected, actual)
+				continue TLoop
+			}
+		}
+	}
+}

flogger.go

@@ -0,0 +1,36 @@
+package flog
+
+
+type Flogger interface {
+	Debug(...interface{})
+	Debugf(string, ...interface{})
+	Debugln(...interface{})
+
+	Error(...interface{})
+	Errorf(string, ...interface{})
+	Errorfe(error, string, ...interface{})
+	Errorln(...interface{})
+
+	Fatal(...interface{})
+	Fatalf(string, ...interface{})
+	Fatalln(...interface{})
+
+	Panic(...interface{})
+	Panicf(string, ...interface{})
+	Panicfv(interface{}, string, ...interface{})
+	Panicln(...interface{})
+
+	Print(...interface{})
+	Printf(string, ...interface{})
+	Println(...interface{})
+
+	Trace(...interface{})
+	Tracef(string, ...interface{})
+	Traceln(...interface{})
+
+	Warn(...interface{})
+	Warnf(string, ...interface{})
+	Warnln(...interface{})
+
+	With(...interface{}) Flogger
+}

internal_flogger.go

@@ -0,0 +1,37 @@
+package flog
+
+
+type internalFlogger struct {
+	context map[string]interface{}
+	router       Router
+}
+
+
+// New returns an initialized Flogger.
+func New(router Router, cascade ...interface{}) Flogger {
+	context := newContext(cascade...)
+
+	flogger := internalFlogger{
+		context:context,
+		router:router,
+	}
+
+	return &flogger
+}
+
+
+
+func (flogger *internalFlogger) route(message string, moreContext map[string]interface{}) error {
+	if nil == flogger {
+		return errNilReceiver
+	}
+
+	context := newContext(flogger.context, moreContext)
+
+	router := flogger.router
+	if nil == router {
+		return errNilRouter
+	}
+
+	return router.Route(message, context)
+}

internal_flogger_debug.go

@@ -0,0 +1,35 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	debugContext = map[string]interface{}{
+		"~type":"debug",
+	}
+)
+
+
+func (flogger *internalFlogger) Debug(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, debugContext)
+}
+
+func (flogger *internalFlogger) Debugf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, debugContext)
+}
+
+func (flogger *internalFlogger) Debugln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, debugContext)
+}

internal_flogger_error.go

@@ -0,0 +1,86 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	errorContext = map[string]interface{}{
+		"~type":"error",
+	}
+)
+
+
+func (flogger *internalFlogger) Error(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	errCtx := newErrorContext(errorContext, v...)
+
+	flogger.route(msg, errCtx)
+}
+
+func (flogger *internalFlogger) Errorf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	errCtx := newErrorContext(errorContext, v...)
+
+	flogger.route(msg, errCtx)
+}
+
+func (flogger *internalFlogger) Errorfe(err error, format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	context := map[string]interface{}{}
+	for k,v := range errorContext {
+		context[k] = v
+	}
+	context["~error"] = err
+
+	flogger.route(msg, context)
+}
+
+func (flogger *internalFlogger) Errorln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	errCtx := newErrorContext(errorContext, v...)
+
+	flogger.route(msg, errCtx)
+}
+
+
+func newErrorContext(baseContext map[string]interface{}, v ...interface{}) map[string]interface{} {
+
+
+	// Collect any errors.
+	errs := []error{}
+	for _, datum := range v {
+		if err, ok := datum.(error); ok {
+			errs = append(errs, err)
+		}
+	}
+
+
+	if 0 == len(errs) {
+		return baseContext
+	}
+
+
+	// Copy the base context.
+	context := map[string]interface{}{}
+	for k,v := range baseContext {
+		context[k] = v
+	}
+
+
+	// Put the collected errors in this new context.
+	context["~errors"] = errs
+
+
+	return context
+}

internal_flogger_fatal.go

@@ -0,0 +1,39 @@
+package flog
+
+
+import (
+	"fmt"
+	"os"
+)
+
+
+var (
+	fatalContext = map[string]interface{}{
+		"~type":"fatal",
+	}
+)
+
+
+func (flogger *internalFlogger) Fatal(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, fatalContext)
+	os.Exit(1)
+}
+
+func (flogger *internalFlogger) Fatalf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, fatalContext)
+	os.Exit(1)
+}
+
+func (flogger *internalFlogger) Fatalln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, fatalContext)
+	os.Exit(1)
+}

internal_flogger_panic.go

@@ -0,0 +1,46 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	panicContext = map[string]interface{}{
+		"~type":"panic",
+	}
+)
+
+
+func (flogger *internalFlogger) Panic(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, panicContext)
+	panic(msg)
+}
+
+func (flogger *internalFlogger) Panicf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, panicContext)
+	panic(msg)
+}
+
+func (flogger *internalFlogger) Panicfv(panicValue interface{}, format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, panicContext)
+	panic(panicValue)
+}
+
+func (flogger *internalFlogger) Panicln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, panicContext)
+	panic(msg)
+}

internal_flogger_print.go

@@ -0,0 +1,35 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	printContext = map[string]interface{}{
+		"~type":"print",
+	}
+)
+
+
+func (flogger *internalFlogger) Print(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, printContext)
+}
+
+func (flogger *internalFlogger) Printf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, printContext)
+}
+
+func (flogger *internalFlogger) Println(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, printContext)
+}

internal_flogger_test.go

@@ -0,0 +1,352 @@
+package flog
+
+
+import (
+	"testing"
+)
+
+
+func TestNew(t *testing.T) {
+
+	flogger := New(NewDiscardingRouter())
+	if nil == flogger {
+		t.Errorf("Expected created flogger to not be nil, but was: %v", flogger)
+	}
+}
+
+
+func TestNewForContext(t *testing.T) {
+
+	tests := []struct{
+		Cascade     []interface{}
+		Expected map[string]interface{}
+	}{
+		{
+			Cascade: []interface{}{},
+			Expected: map[string]interface{}{},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				"apple",
+			},
+			Expected: map[string]interface{}{
+				"text":"apple",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				"apple",
+				"banana",
+			},
+			Expected: map[string]interface{}{
+				"text":"banana",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				"apple",
+				"banana",
+				"cherry",
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+				},
+			},
+			Expected: map[string]interface{}{
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+			},
+		},
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+				map[string]string{
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+
+
+		{
+			Cascade: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD BE REPLACED",
+				},
+				map[string]string{
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+	}
+
+
+TestLoop:
+	for testNumber, test := range tests {
+
+		flogger := New(NewDiscardingRouter(), test.Cascade...)
+
+		context := flogger.(*internalFlogger).context
+
+		if expected, actual := len(test.Expected), len(context); expected != actual {
+			t.Errorf("For test #%d, expected length to be %d but actually was %d.", testNumber, expected, actual)
+	               continue TestLoop
+		}
+
+		for expectedKey, expectedValue := range test.Expected {
+			if _, ok := context[expectedKey]; !ok {
+				t.Errorf("For test #%d, expected key %q to be in resulting context but wasn't.", testNumber, expectedKey)
+				continue TestLoop
+			}
+
+			if expected, actual := expectedValue, context[expectedKey]; expected != actual {
+				t.Errorf("For test #%d, expected value for key %q to be %q in resulting context, but was actually %q.", testNumber, expectedKey, expected, actual)
+				continue TestLoop
+			}
+		}
+	}
+}
+
+
+func TestInternalFloggerRouteNilReceiver(t *testing.T) {
+
+	tests := []struct{
+		Message string
+		MoreContext map[string]interface{}
+	}{
+		{
+			Message: "",
+			MoreContext: nil,
+		},
+		{
+			Message: "",
+			MoreContext: map[string]interface{}{},
+		},
+		{
+			Message: "",
+			MoreContext: map[string]interface{}{
+				"apple":  "one",
+				"banana": 2,
+				"cherry": '3',
+				"kiwi":   4.0,
+			},
+		},
+
+
+
+		{
+			Message: "Hello world!",
+			MoreContext: nil,
+		},
+		{
+			Message: "Hello world!",
+			MoreContext: map[string]interface{}{},
+		},
+		{
+			Message: "Hello world!",
+			MoreContext: map[string]interface{}{
+				"apple":  "one",
+				"banana": 2,
+				"cherry": '3',
+				"kiwi":   4.0,
+			},
+		},
+
+
+
+		{
+			Message: " ",
+			MoreContext: nil,
+		},
+		{
+			Message: " ",
+			MoreContext: map[string]interface{}{},
+		},
+		{
+			Message: " ",
+			MoreContext: map[string]interface{}{
+				"apple":  "one",
+				"banana": 2,
+				"cherry": '3',
+				"kiwi":   4.0,
+			},
+		},
+
+
+
+		{
+			Message: "one\ntwo\tthree\r\n",
+			MoreContext: nil,
+		},
+		{
+			Message: "one\ntwo\tthree\r\n",
+			MoreContext: map[string]interface{}{},
+		},
+		{
+			Message: "one\ntwo\tthree\r\n",
+			MoreContext: map[string]interface{}{
+				"apple":  "one",
+				"banana": 2,
+				"cherry": '3',
+				"kiwi":   4.0,
+			},
+		},
+	}
+
+
+
+	for testNumber, test := range tests {
+
+		var flogger *internalFlogger = nil
+
+		err := flogger.route(test.Message, test.MoreContext)
+		if nil == err {
+			t.Errorf("For test #%d, expected an error, but did not actually get one: %v", testNumber, err)
+			continue
+		}
+		if expected, actual := errNilReceiver, err; expected != actual {
+			t.Errorf("For test #%d, expected an error (%T) %q, but actually got (%T) %q", testNumber, expected, expected, actual, actual)
+			continue
+		}
+
+	}
+}
+
+
+func TestInternalFloggerRouteNilRouter(t *testing.T) {
+
+	moreContexts := []map[string]interface{}{
+		nil,
+		map[string]interface{}{},
+		map[string]interface{}{
+			"apple":  "one",
+			"banana": 2,
+			"cherry": '3',
+			"kiwi":   4.0,
+		},
+	}
+
+
+	messages := []string{
+		"",
+		"Hello world!",
+		" ",
+		"one\ntwo\tthree\r\n",
+	}
+
+
+	tests := []struct{
+		Context map[string]interface{}
+	}{
+		{
+			Context: nil,
+		},
+		{
+			Context: map[string]interface{}{},
+		},
+
+
+
+		{
+			Context: map[string]interface{}{
+				"apple":  "one",
+				"banana": 2,
+				"cherry": '3',
+				"kiwi":   4.0,
+			},
+		},
+	}
+
+
+	for testNumber, test := range tests {
+		var flogger internalFlogger
+
+		flogger.context = test.Context
+		flogger.router  = nil
+
+		for messageNumber, message := range messages {
+			for moreContextNumber, moreContext := range moreContexts {
+				err := flogger.route(message, moreContext)
+				if nil == err {
+					t.Errorf("For test #%d and message #%d and more context #%d, expected an error, but did not actually get one: %v", testNumber, messageNumber, moreContextNumber, err)
+					continue
+				}
+				if expected, actual := errNilRouter, err; expected != actual {
+					t.Errorf("For test #%d and message #%d and more context #%d, expected an error (%T) %q, but actually got (%T) %q", testNumber, messageNumber, moreContextNumber, expected, expected, actual, actual)
+					continue
+				}
+			}
+		}
+	}
+}

internal_flogger_trace.go

@@ -0,0 +1,35 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	traceContext = map[string]interface{}{
+		"~type":"trace",
+	}
+)
+
+
+func (flogger *internalFlogger) Trace(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, traceContext)
+}
+
+func (flogger *internalFlogger) Tracef(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, traceContext)
+}
+
+func (flogger *internalFlogger) Traceln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, traceContext)
+}

internal_flogger_warn.go

@@ -0,0 +1,35 @@
+package flog
+
+
+import (
+	"fmt"
+)
+
+
+var (
+	warnContext = map[string]interface{}{
+		"~type":"warn",
+	}
+)
+
+
+func (flogger *internalFlogger) Warn(v ...interface{}) {
+
+	msg := fmt.Sprint(v...)
+
+	flogger.route(msg, warnContext)
+}
+
+func (flogger *internalFlogger) Warnf(format string, v ...interface{}) {
+
+	msg := fmt.Sprintf(format, v...)
+
+	flogger.route(msg, warnContext)
+}
+
+func (flogger *internalFlogger) Warnln(v ...interface{}) {
+
+	msg := fmt.Sprintln(v...)
+
+	flogger.route(msg, warnContext)
+}

internal_flogger_with.go

@@ -0,0 +1,14 @@
+package flog
+
+
+func (flogger *internalFlogger)  With(cascade ...interface{}) Flogger {
+
+	var x    interface{} = flogger.context
+	var xs []interface{} = []interface{}{x}
+
+	newCascade := append(xs, cascade...)
+
+	newFlogger := New(flogger.router, newCascade...)
+
+	return newFlogger
+}

internal_flogger_with_test.go

@@ -0,0 +1,329 @@
+package flog
+
+
+import (
+	"testing"
+)
+
+
+func TestWith(t *testing.T) {
+
+	tests := []struct{
+		Cascade1    []interface{}
+		Cascade2    []interface{}
+		Expected map[string]interface{}
+	}{
+		{
+			Cascade1: []interface{}{},
+			Cascade2: []interface{}{},
+			Expected: map[string]interface{}{},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				"apple",
+			},
+			Cascade2: []interface{}{
+			},
+			Expected: map[string]interface{}{
+				"text":"apple",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+			},
+			Cascade2: []interface{}{
+				"apple",
+			},
+			Expected: map[string]interface{}{
+				"text":"apple",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				"apple",
+			},
+			Cascade2: []interface{}{
+				"apple",
+			},
+			Expected: map[string]interface{}{
+				"text":"apple",
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				"apple",
+			},
+			Cascade2: []interface{}{
+				"banana",
+			},
+			Expected: map[string]interface{}{
+				"text":"banana",
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				"apple",
+				"banana",
+				"cherry",
+			},
+			Cascade2: []interface{}{
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				"apple",
+				"banana",
+			},
+			Cascade2: []interface{}{
+				"cherry",
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				"apple",
+			},
+			Cascade2: []interface{}{
+				"banana",
+				"cherry",
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+			},
+			Cascade2: []interface{}{
+				"apple",
+				"banana",
+				"cherry",
+			},
+			Expected: map[string]interface{}{
+				"text":"cherry",
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+				},
+			},
+			Expected: map[string]interface{}{
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"cherry":"three",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+			},
+		},
+
+
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+
+		{
+			Cascade1: []interface{}{
+				map[string]string{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD BE REPLACED",
+				},
+			},
+			Cascade2: []interface{}{
+				map[string]string{
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+				},
+			},
+			Expected: map[string]interface{}{
+					"apple":"one",
+					"banana":"two",
+					"cherry":"three",
+					"fig":"THIS SHOULD REMAIN",
+					"kiwi":"four",
+					"watermelon":"five",
+			},
+		},
+	}
+
+
+TestLoop:
+	for testNumber, test := range tests {
+
+		flogger1 := New(NewDiscardingRouter(), test.Cascade1...)
+
+		flogger2 := flogger1.With(test.Cascade2...)
+
+		context := flogger2.(*internalFlogger).context
+
+		if expected, actual := len(test.Expected), len(context); expected != actual {
+			t.Errorf("For test #%d, expected length to be %d but actually was %d.", testNumber, expected, actual)
+	               continue TestLoop
+		}
+
+		for expectedKey, expectedValue := range test.Expected {
+			if _, ok := context[expectedKey]; !ok {
+				t.Errorf("For test #%d, expected key %q to be in resulting context but wasn't.", testNumber, expectedKey)
+				continue TestLoop
+			}
+
+			if expected, actual := expectedValue, context[expectedKey]; expected != actual {
+                                t.Errorf("For test #%d, expected value for key %q to be %q in resulting context, but was actually %q.", testNumber, expectedKey, expected, actual)
+				continue TestLoop
+			}
+		}
+	}
+}

internal_logger.go

@@ -1,19 +1,15 @@
-package log
+package flog
 
 import (
 	"io"
-	"time"
 )
 
 type internalLogger struct {
 	prefix string
 	style  string
 
-	begin time.Time
-
 	writer io.Writer
 
-	mutedAlert      bool
 	mutedDebug      bool
 	mutedError      bool
 	mutedFatal      bool

internal_logger_alert.go

@@ -1,62 +0,0 @@
-package log
-
-import (
-	"fmt"
-	"io"
-	"strings"
-)
-
-func (receiver internalLogger) AlertMuted() bool {
-	return receiver.mutedAlert
-}
-
-func (receiver internalLogger) Alert(a ...interface{}) error {
-	s := fmt.Sprint(a...)
-
-	return receiver.Alertf("%s", s)
-}
-
-func (receiver internalLogger) Alertf(format string, a ...interface{}) error {
-	err := fmt.Errorf(format, a...)
-
-	if receiver.AlertMuted() {
-		return err
-	}
-
-	var writer io.Writer = receiver.writer
-	if nil == writer {
-		return err
-	}
-
-	var newformat string
-	{
-		var buffer strings.Builder
-
-		switch receiver.style{
-		case"color":
-			buffer.WriteString("☣️☣️☣️☣️☣️ ")
-			buffer.WriteString("\x1b[48;2;0;43;54m")
-			buffer.WriteString("\x1b[38;2;220;50;47m")
-		case "":
-			buffer.WriteString("[ALERT] ")
-		}
-
-		buffer.WriteString(receiver.prefix)
-		buffer.WriteString(format)
-
-		switch receiver.style {
-		case "color":
-			buffer.WriteString("\x1b[0m")
-			buffer.WriteString(" ☣️☣️☣️☣️☣️")
-			buffer.WriteRune('\n')
-		case "":
-			buffer.WriteRune('\n')
-		}
-
-		newformat = buffer.String()
-	}
-
-	fmt.Fprintf(receiver.writer, newformat, a...)
-
-	return err
-}

internal_logger_alert_test.go

@@ -1,70 +0,0 @@
-package log
-
-import (
-	"bytes"
-
-	"testing"
-)
-
-func TestInternalLogger_Alertf(t *testing.T) {
-
-	tests := []struct{
-		Format string
-		Array []interface{}
-		Expected string
-	}{
-		{
-			Format: "",
-			Array: []interface{}(nil),
-			Expected: "[ALERT] \n",
-		},
-		{
-			Format: "",
-			Array: []interface{}{},
-			Expected: "[ALERT] \n",
-		},
-
-
-
-		{
-			Format: "hello world",
-			Array: []interface{}(nil),
-			Expected: "[ALERT] hello world\n",
-		},
-		{
-			Format: "hello world",
-			Array: []interface{}{},
-			Expected: "[ALERT] hello world\n",
-		},
-
-
-
-		{
-			Format: "hello %s",
-			Array: []interface{}{"Joe"},
-			Expected: "[ALERT] hello Joe\n",
-		},
-		{
-			Format: "hello %s %s",
-			Array: []interface{}{"Joe", "Blow"},
-			Expected: "[ALERT] hello Joe Blow\n",
-		},
-	}
-
-	for testNumber, test := range tests {
-
-		var buffer bytes.Buffer
-
-		logger := NewLogger(&buffer)
-
-		logger.Alertf(test.Format, test.Array...)
-
-		if expected, actual := test.Expected, buffer.String(); expected != actual {
-			t.Errorf("For tst #%d, the actual result is not what was expected.", testNumber)
-			t.Logf("EXPECTED: %q", expected)
-			t.Logf("ACTUAL:   %q", actual)
-			t.Logf("ACTUAL:   %s", actual)
-			continue
-		}
-	}
-}

internal_logger_begin.go

@@ -1,30 +0,0 @@
-package log
-
-import (
-	"runtime"
-	"time"
-)
-
-func (receiver internalLogger) Begin(a ...interface{}) Logger {
-
-	var funcName string = "<([-UNKNOWN-])>"
-	{
-		pc, _, _, ok := runtime.Caller(1)
-		if ok {
-			fn := runtime.FuncForPC(pc)
-			funcName = fn.Name()
-		}
-	}
-
-	logger := receiver.Prefix(funcName)
-	switch casted := logger.(type) {
-	case *internalLogger:
-		casted.begin = time.Now()
-	}
-
-	a = append([]interface{}{"BEGIN "}, a...)
-
-	logger.Debug(a...)
-
-	return logger
-}

internal_logger_debug.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -45,7 +45,6 @@ func (receiver internalLogger) Debugf(format string, a ...interface{}) {
 			buffer.WriteString("[debug] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_debug_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

internal_logger_end.go

@@ -1,17 +0,0 @@
-package log
-
-import (
-	"fmt"
-	"time"
-)
-
-func (receiver internalLogger) End(a ...interface{}) {
-	diff := time.Now().Sub(receiver.begin)
-
-	msg := fmt.Sprintf(" δt=%s", diff)
-
-	a = append([]interface{}{"END "}, a...)
-	a = append(a, msg)
-
-	receiver.Debug(a...)
-}

internal_logger_error.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -40,7 +40,6 @@ func (receiver internalLogger) Errorf(format string, a ...interface{}) error {
 			buffer.WriteString("[ERROR] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_error_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

internal_logger_fatal.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -41,7 +41,6 @@ func (receiver internalLogger) Fatalf(format string, a ...interface{}) {
 			buffer.WriteString("[PANIC] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_highlight.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -45,7 +45,6 @@ func (receiver internalLogger) Highlightf(format string, a ...interface{}) {
 			buffer.WriteString("[HIGHLIGHT] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_highlight_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

internal_logger_inform.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -45,7 +45,6 @@ func (receiver internalLogger) Informf(format string, a ...interface{}) {
 			buffer.WriteString("[inform] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_inform_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

internal_logger_mute.go

@@ -1,8 +1,4 @@
-package log
+package flog
-
-func (receiver *internalLogger) MuteAlert() {
-	receiver.mutedDebug = true
-}
 
 func (receiver *internalLogger) MuteDebug() {
 	receiver.mutedDebug = true

internal_logger_panic.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -40,7 +40,6 @@ func (receiver internalLogger) Panicf(format string, a ...interface{}) {
 			buffer.WriteString("[PANIC] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_prefix.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"strings"
@@ -17,7 +17,7 @@ func (receiver internalLogger) Prefix(newprefix ...string) Logger {
 	prefix := buffer.String()
 
 	var logger internalLogger = receiver
-	logger.prefix = prefix
+	logger.prefix += prefix
 
 	return &logger
 }

internal_logger_prefix_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"
@@ -66,7 +66,7 @@ func TestLoggerPrefix(t *testing.T) {
 
 		newInternalLogger, casted := newLogger.(*internalLogger)
 		if !casted {
-			t.Errorf("For test #%d, could not cast to log.internalLogger.", testNumber)
+			t.Errorf("For test #%d, could not cast to flog.internalLogger.", testNumber)
 			t.Logf("TYPE: %T", newLogger)
 			continue
 		}
@@ -101,20 +101,14 @@ func TestLoggerPrefix_inform(t *testing.T) {
 	log.Debug("hello DEBUG")
 	log.Trace("hello TRACE")
 
-
+	const expected = "[PANIC] hello PANIC"       + "\n" +
-	log = log.Prefix("four")
-	log.Highlight("new prefix FOUR")
-
-
-	const expected = "[PANIC] one: two: three: hello PANIC"              + "\n" +
 	                  "RECOVER:hello PANIC"       + "\n" +
-	                "[inform] one: two: three: hello INFORM"             + "\n" +
+	                "[inform] hello INFORM"       + "\n" +
-	                "[HIGHLIGHT] one: two: three: hello HIGHLIGHT"       + "\n" +
+	                "[HIGHLIGHT] hello HIGHLIGHT" + "\n" +
-	                "[ERROR] one: two: three: hello ERROR"               + "\n" +
+	                "[ERROR] hello ERROR"         + "\n" +
-	                "[warn] one: two: three: hello WARN"                 + "\n" +
+	                "[warn] hello WARN"           + "\n" +
-	                "[debug] one: two: three: hello DEBUG"               + "\n" +
+	                "[debug] hello DEBUG"         + "\n" +
-	                "[trace] one: two: three: hello TRACE"               + "\n" +
+	                "[trace] hello TRACE"         + "\n"
-	                "[HIGHLIGHT] one: two: three: four: new prefix FOUR" + "\n"
 
 	if actual := buffer.String(); expected != actual {
 		t.Error("The actual logs is not what was expected.")

internal_logger_trace.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -45,7 +45,6 @@ func (receiver internalLogger) Tracef(format string, a ...interface{}) {
 			buffer.WriteString("[trace] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_trace_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

internal_logger_unmute.go

@@ -1,8 +1,4 @@
-package log
+package flog
-
-func (receiver *internalLogger) UnmuteAlert() {
-	receiver.mutedAlert = false
-}
 
 func (receiver *internalLogger) UnmuteDebug() {
 	receiver.mutedDebug = false

internal_logger_warn.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"fmt"
@@ -45,7 +45,6 @@ func (receiver internalLogger) Warnf(format string, a ...interface{}) {
 			buffer.WriteString("[warn] ")
 		}
 
-		buffer.WriteString(receiver.prefix)
 		buffer.WriteString(format)
 
 		switch receiver.style {

internal_logger_warn_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"bytes"

logger.go

@@ -1,22 +1,12 @@
-package log
+package flog
 
 type Logger interface {
-	Alert(...interface{}) error
-	Alertf(string, ...interface{}) error
-	MuteAlert()
-	UnmuteAlert()
-	AlertMuted() bool
-
-	Begin(...interface{}) Logger
-
 	Debug(...interface{})
 	Debugf(string, ...interface{})
 	MuteDebug()
 	UnmuteDebug()
 	DebugMuted() bool
 
-	End(...interface{})
-
 	Error(...interface{}) error
 	Errorf(string, ...interface{}) error
 	MuteError()

logger_test.go

@@ -1,4 +1,4 @@
-package log
+package flog
 
 import (
 	"testing"

mapping_router.go

@@ -0,0 +1,32 @@
+package flog
+
+
+// NewMappingRouter returns an initialized MappingRouter.
+func NewMappingRouter(subrouter Router, fn func(string, map[string]interface{})(string, map[string]interface{})) *MappingRouter {
+	router := MappingRouter{
+		subrouter:subrouter,
+		fn:fn,
+	}
+
+	return &router
+}
+
+
+// MappingRouter is a Router that can modify the message and context before
+// re-routing it to its sub-router.
+//
+// Conceptually this is somewhat similar to "map" functions in functional
+// programming.
+type MappingRouter struct {
+	subrouter Router
+	fn func(string, map[string]interface{})(string, map[string]interface{})
+}
+
+
+func (router *MappingRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	return router.subrouter.Route(router.fn(message, context))
+}

non_blocking_router.go

@@ -0,0 +1,34 @@
+package flog
+
+
+// NewNonBlockingRouter returns an initialized NonBlockingRouter.
+func NewNonBlockingRouter(subrouter Router) *NonBlockingRouter {
+	router := NonBlockingRouter{
+		subrouter:subrouter,
+	}
+
+	return &router
+}
+
+
+// NonBlockingRouter is a Router when its Route method is call its does not
+// block and dealing with the routing in parallel.
+//
+// Note that this means that if the application could terminate before this
+// completes.
+type NonBlockingRouter struct {
+	subrouter Router
+}
+
+
+func (router *NonBlockingRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	go func() {
+		router.subrouter.Route(message, context)
+	}()
+
+	return nil
+}

pretty_writing_router.go

@@ -0,0 +1,117 @@
+package flog
+
+import (
+	"fmt"
+	"io"
+	"sort"
+	"time"
+)
+
+// PrettyWritingRouter returns an initialized PrettyWritingRouter
+func NewPrettyWritingRouter(writer io.Writer) *PrettyWritingRouter {
+	router := PrettyWritingRouter{
+		writer:writer,
+	}
+
+	return &router
+}
+
+// PrettyWritingRouter is a router that writes a pretty version of
+// the log it was give (including COLORS!) to the writer it was
+// given when it was created.
+//
+// A PrettyWritingRouter is appropriate for a development (i.e., "DEV")
+// deployment enviornment. (And  probably not appropriate a production
+// (i.e., "PROD") deployment environment.)
+type PrettyWritingRouter struct {
+	writer io.Writer
+}
+
+func (router *PrettyWritingRouter) Route(message string, context map[string]interface{}) error {
+	if nil == router {
+		return errNilReceiver
+	}
+
+	const STYLE_FATAL     = "\x1b[40;33;1m" // BG BLACK,  FG YELLOW, BOLD
+	const STYLE_PANIC     = "\x1b[40;31;1m" // BG BLACK,  FG RED,    BOLD
+	const STYLE_ERROR     = "\x1b[41;37;1m" // BG RED,    FG WHITE,  BOLD
+	const STYLE_WARNING   = "\x1b[43;37;1m" // BG YELLOW, FG WHITE,  BOLD
+	const STYLE_NOTICE    = "\x1b[42;33;1m" // BG GREEN,  FG YELLOW, BOLD
+	const STYLE_TIMESTAMP = "\x1b[2m"       // FAINT
+	const STYLE_MESSAGE   = "\x1b[44;37;1m" // BG BLUE,   FG WHITE,  BOLD
+	const STYLE_DEFAULT   = "\033[95m"      // HEADER
+	const STYLE_RESET     = "\033[0m"       // RESET
+	const STYLE_CALLTRACE = "\033[40;36;1m" // BG BLACK,  FG CYAN,   BOLD
+
+	str := ""
+
+	if nil != context {
+		if _, ok := context["~fatal"]; ok {
+			str = fmt.Sprintf("%s 💀 💀 💀 💀 💀 %s\t%s", STYLE_FATAL, STYLE_RESET, str)
+		} else if _, ok := context["~panic"]; ok {
+			str = fmt.Sprintf("%s ☠ ☠ ☠ ☠ ☠ %s\t%s", STYLE_PANIC, STYLE_RESET, str)
+		} else if _, ok := context["~error"]; ok {
+			str = fmt.Sprintf("%s 😨 😨 😨 😨 😨 %s\t%s", STYLE_ERROR, STYLE_RESET, str)
+		} else if _, ok := context["~warn"]; ok {
+			str = fmt.Sprintf("%s 😟 😟 😟 😟 😟 %s\t%s", STYLE_WARNING, STYLE_RESET, str)
+		} else if _, ok := context["~print"]; ok {
+			str = fmt.Sprintf("%s 😮 😮 😮 😮 😮 %s\t%s", STYLE_NOTICE, STYLE_RESET, str)
+		}
+	}
+
+	str = fmt.Sprintf("%s%s%s%s\t(%s%v%s)", str, STYLE_MESSAGE, message, STYLE_RESET, STYLE_TIMESTAMP, time.Now(), STYLE_RESET)
+
+	// If we have an error, then get the error.Error() into the log too.
+	if errorFieldValue, ok := context["~error"]; ok {
+		if err, ok := errorFieldValue.(error); ok {
+			context["~~error"] = fmt.Sprintf("%s, {{%T}}", err.Error(), err)
+		}
+	}
+
+
+//@TODO: This is a potential heavy operation. Is there a better way
+//       to get the ultimate result this is trying to archive?
+//
+	sortedKeys := make([]string, len(context))
+	i := 0
+	for key, _ := range context {
+		sortedKeys[i] = key
+		i++
+	}
+	sort.Strings(sortedKeys)
+
+	for _, key := range sortedKeys {
+
+		value := context[key]
+
+		style := STYLE_DEFAULT
+
+		switch key {
+                case "~fatal", "~fatals":
+                        style = STYLE_FATAL
+		case "~panic", "~panics":
+			style = STYLE_PANIC
+		case "~error", "~errors", "~~error":
+			style = STYLE_ERROR
+		case "~warning", "~warnings":
+			style = STYLE_WARNING
+		case "~print", "~prints":
+			style = STYLE_NOTICE
+		}
+
+		str = fmt.Sprintf("%s\t%s%s%s=%s%#v%s", str, style, key, STYLE_RESET, style, value, STYLE_RESET)
+	}
+
+	if trace := calltrace(); nil != trace {
+		str = fmt.Sprintf("%s\t⟨⟨", str)
+		for _, s := range trace {
+			str = fmt.Sprintf("%s %s%s%s,", str, STYLE_CALLTRACE, s, STYLE_RESET)
+		}
+		str = fmt.Sprintf("%s ⟩⟩", str)
+	}
+
+	fmt.Fprintln(router.writer, str)
+
+//@TODO: Should this be checking for errors from fmt.Fprintln()?
+	return nil
+}

router.go

@@ -0,0 +1,6 @@
+package flog
+
+
+type Router interface {
+	Route(message string, context map[string]interface{}) error
+}