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// Copyright © 2016 Steve Francia <spf@spf13.com>.
//
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
package jwalterweatherman
import (
"fmt"
"io"
"io/ioutil"
"log"
)
type Threshold int
func (t Threshold) String() string {
return prefixes[t]
}
const (
LevelTrace Threshold = iota
LevelDebug
LevelInfo
LevelWarn
LevelError
LevelCritical
LevelFatal
)
var prefixes map[Threshold]string = map[Threshold]string{
LevelTrace: "TRACE",
LevelDebug: "DEBUG",
LevelInfo: "INFO",
LevelWarn: "WARN",
LevelError: "ERROR",
LevelCritical: "CRITICAL",
LevelFatal: "FATAL",
}
// Notepad is where you leave a note!
type Notepad struct {
TRACE *log.Logger
DEBUG *log.Logger
INFO *log.Logger
WARN *log.Logger
ERROR *log.Logger
CRITICAL *log.Logger
FATAL *log.Logger
LOG *log.Logger
FEEDBACK *Feedback
loggers [7]**log.Logger
logHandle io.Writer
outHandle io.Writer
logThreshold Threshold
stdoutThreshold Threshold
prefix string
flags int
logListeners []LogListener
}
// A LogListener can ble supplied to a Notepad to listen on log writes for a given
// threshold. This can be used to capture log events in unit tests and similar.
// Note that this function will be invoked once for each log threshold. If
// the given threshold is not of interest to you, return nil.
// Note that these listeners will receive log events for a given threshold, even
// if the current configuration says not to log it. That way you can count ERRORs even
// if you don't print them to the console.
type LogListener func(t Threshold) io.Writer
// NewNotepad creates a new Notepad.
func NewNotepad(
outThreshold Threshold,
logThreshold Threshold,
outHandle, logHandle io.Writer,
prefix string, flags int,
logListeners ...LogListener,
) *Notepad {
n := &Notepad{logListeners: logListeners}
n.loggers = [7]**log.Logger{&n.TRACE, &n.DEBUG, &n.INFO, &n.WARN, &n.ERROR, &n.CRITICAL, &n.FATAL}
n.outHandle = outHandle
n.logHandle = logHandle
n.stdoutThreshold = outThreshold
n.logThreshold = logThreshold
if len(prefix) != 0 {
n.prefix = "[" + prefix + "] "
} else {
n.prefix = ""
}
n.flags = flags
n.LOG = log.New(n.logHandle,
"LOG: ",
n.flags)
n.FEEDBACK = &Feedback{out: log.New(outHandle, "", 0), log: n.LOG}
n.init()
return n
}
// init creates the loggers for each level depending on the notepad thresholds.
func (n *Notepad) init() {
logAndOut := io.MultiWriter(n.outHandle, n.logHandle)
for t, logger := range n.loggers {
threshold := Threshold(t)
prefix := n.prefix + threshold.String() + " "
switch {
case threshold >= n.logThreshold && threshold >= n.stdoutThreshold:
*logger = log.New(n.createLogWriters(threshold, logAndOut), prefix, n.flags)
case threshold >= n.logThreshold:
*logger = log.New(n.createLogWriters(threshold, n.logHandle), prefix, n.flags)
case threshold >= n.stdoutThreshold:
*logger = log.New(n.createLogWriters(threshold, n.outHandle), prefix, n.flags)
default:
*logger = log.New(n.createLogWriters(threshold, ioutil.Discard), prefix, n.flags)
}
}
}
func (n *Notepad) createLogWriters(t Threshold, handle io.Writer) io.Writer {
if len(n.logListeners) == 0 {
return handle
}
writers := []io.Writer{handle}
for _, l := range n.logListeners {
w := l(t)
if w != nil {
writers = append(writers, w)
}
}
if len(writers) == 1 {
return handle
}
return io.MultiWriter(writers...)
}
// SetLogThreshold changes the threshold above which messages are written to the
// log file.
func (n *Notepad) SetLogThreshold(threshold Threshold) {
n.logThreshold = threshold
n.init()
}
// SetLogOutput changes the file where log messages are written.
func (n *Notepad) SetLogOutput(handle io.Writer) {
n.logHandle = handle
n.init()
}
// GetStdoutThreshold returns the defined Treshold for the log logger.
func (n *Notepad) GetLogThreshold() Threshold {
return n.logThreshold
}
// SetStdoutThreshold changes the threshold above which messages are written to the
// standard output.
func (n *Notepad) SetStdoutThreshold(threshold Threshold) {
n.stdoutThreshold = threshold
n.init()
}
// GetStdoutThreshold returns the Treshold for the stdout logger.
func (n *Notepad) GetStdoutThreshold() Threshold {
return n.stdoutThreshold
}
// SetPrefix changes the prefix used by the notepad. Prefixes are displayed between
// brackets at the beginning of the line. An empty prefix won't be displayed at all.
func (n *Notepad) SetPrefix(prefix string) {
if len(prefix) != 0 {
n.prefix = "[" + prefix + "] "
} else {
n.prefix = ""
}
n.init()
}
// SetFlags choose which flags the logger will display (after prefix and message
// level). See the package log for more informations on this.
func (n *Notepad) SetFlags(flags int) {
n.flags = flags
n.init()
}
// Feedback writes plainly to the outHandle while
// logging with the standard extra information (date, file, etc).
type Feedback struct {
out *log.Logger
log *log.Logger
}
func (fb *Feedback) Println(v ...interface{}) {
fb.output(fmt.Sprintln(v...))
}
func (fb *Feedback) Printf(format string, v ...interface{}) {
fb.output(fmt.Sprintf(format, v...))
}
func (fb *Feedback) Print(v ...interface{}) {
fb.output(fmt.Sprint(v...))
}
func (fb *Feedback) output(s string) {
if fb.out != nil {
fb.out.Output(2, s)
}
if fb.log != nil {
fb.log.Output(2, s)
}
}
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