Break out logger as a reusable component

Godeps/_workspace/src/github.com/calmh/logger/LICENSE

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+Copyright (C) 2013 Jakob Borg
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+- The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Godeps/_workspace/src/github.com/calmh/logger/README.md

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+logger
+======
+
+A small wrapper around `log` to provide log levels.
+
+Documentation
+-------------
+
+http://godoc.org/github.com/calmh/logger
+
+License
+-------
+
+MIT

Godeps/_workspace/src/github.com/calmh/logger/logger.go

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+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// Package logger implements a standardized logger with callback functionality
+package logger
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"sync"
+)
+
+type LogLevel int
+
+const (
+	LevelDebug LogLevel = iota
+	LevelInfo
+	LevelOK
+	LevelWarn
+	LevelFatal
+	NumLevels
+)
+
+// A MessageHandler is called with the log level and message text.
+type MessageHandler func(l LogLevel, msg string)
+
+type Logger struct {
+	logger   *log.Logger
+	handlers [NumLevels][]MessageHandler
+	mut      sync.Mutex
+}
+
+// The default logger logs to standard output with a time prefix.
+var DefaultLogger = New()
+
+func New() *Logger {
+	return &Logger{
+		logger: log.New(os.Stdout, "", log.Ltime),
+	}
+}
+
+// AddHandler registers a new MessageHandler to receive messages with the
+// specified log level or above.
+func (l *Logger) AddHandler(level LogLevel, h MessageHandler) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	l.handlers[level] = append(l.handlers[level], h)
+}
+
+// See log.SetFlags
+func (l *Logger) SetFlags(flag int) {
+	l.logger.SetFlags(flag)
+}
+
+// See log.SetPrefix
+func (l *Logger) SetPrefix(prefix string) {
+	l.logger.SetPrefix(prefix)
+}
+
+func (l *Logger) callHandlers(level LogLevel, s string) {
+	for _, h := range l.handlers[level] {
+		h(level, strings.TrimSpace(s))
+	}
+}
+
+// Debugln logs a line with a DEBUG prefix.
+func (l *Logger) Debugln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "DEBUG: "+s)
+	l.callHandlers(LevelDebug, s)
+}
+
+// Debugf logs a formatted line with a DEBUG prefix.
+func (l *Logger) Debugf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "DEBUG: "+s)
+	l.callHandlers(LevelDebug, s)
+}
+
+// Infoln logs a line with an INFO prefix.
+func (l *Logger) Infoln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "INFO: "+s)
+	l.callHandlers(LevelInfo, s)
+}
+
+// Infof logs a formatted line with an INFO prefix.
+func (l *Logger) Infof(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "INFO: "+s)
+	l.callHandlers(LevelInfo, s)
+}
+
+// Okln logs a line with an OK prefix.
+func (l *Logger) Okln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "OK: "+s)
+	l.callHandlers(LevelOK, s)
+}
+
+// Okf logs a formatted line with an OK prefix.
+func (l *Logger) Okf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "OK: "+s)
+	l.callHandlers(LevelOK, s)
+}
+
+// Warnln logs a formatted line with a WARNING prefix.
+func (l *Logger) Warnln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "WARNING: "+s)
+	l.callHandlers(LevelWarn, s)
+}
+
+// Warnf logs a formatted line with a WARNING prefix.
+func (l *Logger) Warnf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "WARNING: "+s)
+	l.callHandlers(LevelWarn, s)
+}
+
+// Fatalln logs a line with a FATAL prefix and exits the process with exit
+// code 1.
+func (l *Logger) Fatalln(vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintln(vals...)
+	l.logger.Output(2, "FATAL: "+s)
+	l.callHandlers(LevelFatal, s)
+	os.Exit(1)
+}
+
+// Fatalf logs a formatted line with a FATAL prefix and exits the process with
+// exit code 1.
+func (l *Logger) Fatalf(format string, vals ...interface{}) {
+	l.mut.Lock()
+	defer l.mut.Unlock()
+	s := fmt.Sprintf(format, vals...)
+	l.logger.Output(2, "FATAL: "+s)
+	l.callHandlers(LevelFatal, s)
+	os.Exit(1)
+}

Godeps/_workspace/src/github.com/calmh/logger/logger_test.go

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+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+package logger
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestAPI(t *testing.T) {
+	l := New()
+	l.SetFlags(0)
+	l.SetPrefix("testing")
+
+	debug := 0
+	l.AddHandler(LevelDebug, checkFunc(t, LevelDebug, "test 0", &debug))
+	info := 0
+	l.AddHandler(LevelInfo, checkFunc(t, LevelInfo, "test 1", &info))
+	warn := 0
+	l.AddHandler(LevelWarn, checkFunc(t, LevelWarn, "test 2", &warn))
+	ok := 0
+	l.AddHandler(LevelOK, checkFunc(t, LevelOK, "test 3", &ok))
+
+	l.Debugf("test %d", 0)
+	l.Debugln("test", 0)
+	l.Infof("test %d", 1)
+	l.Infoln("test", 1)
+	l.Warnf("test %d", 2)
+	l.Warnln("test", 2)
+	l.Okf("test %d", 3)
+	l.Okln("test", 3)
+
+	if debug != 2 {
+		t.Errorf("Debug handler called %d != 2 times", debug)
+	}
+	if info != 2 {
+		t.Errorf("Info handler called %d != 2 times", info)
+	}
+	if warn != 2 {
+		t.Errorf("Warn handler called %d != 2 times", warn)
+	}
+	if ok != 2 {
+		t.Errorf("Ok handler called %d != 2 times", ok)
+	}
+}
+
+func checkFunc(t *testing.T, expectl LogLevel, expectmsg string, counter *int) func(LogLevel, string) {
+	return func(l LogLevel, msg string) {
+		*counter++
+		if l != expectl {
+			t.Errorf("Incorrect message level %d != %d", l, expectl)
+		}
+		if !strings.HasSuffix(msg, expectmsg) {
+			t.Errorf("%q does not end with %q", msg, expectmsg)
+		}
+	}
+}