debug.go

package stf

import (
	"fmt"
	"io"
	"log"
	"os"
	"strconv"
	"strings"
)

func init() {
	dbgEnabled := false

	dbgOutput := os.Stderr
	if dbg := os.Getenv("STF_DEBUG"); dbg != "" {
		// STF_DEBUG='1:path/to/log'
		if strings.Index(dbg, ":") > -1 {
			list := strings.Split(dbg, ":")
			dbg = list[0]
			if len(list) > 1 {
				file, err := os.OpenFile(list[1], os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0755)
				if err != nil {
					log.Fatalf("Failed to open debug log output %s: %s", list[1], err)
				}
				dbgOutput = file
			}
		}
		x, err := strconv.ParseBool(dbg)
		if err == nil {
			dbgEnabled = x
		}
	}

	if dbgEnabled {
		global = NewDebugLog()
		global.SetOutput(dbgOutput)
	}
}

const INDENT_PATTERN string = "  "

type DebugLog struct {
	Prefix string
	Indent string
	out    io.Writer
}

func NewDebugLog() *DebugLog {
	return &DebugLog{
		"",
		"",
		os.Stderr,
	}
}

var global *DebugLog

func (self *DebugLog) SetOutput(out io.Writer) {
	self.out = out
}

func (self *DebugLog) Printf(format string, args ...interface{}) {
	message := fmt.Sprintf(format, args...)
	log.Printf("%s %s %s", self.Prefix, self.Indent, message)
}

func (self *DebugLog) LogIndent() func() {
	self.Indent = INDENT_PATTERN + self.Indent
	return func() {
		self.Indent = strings.TrimPrefix(self.Indent, INDENT_PATTERN)
	}
}

func Debugf(format string, args ...interface{}) {
	if global != nil {
		global.Printf(format, args...)
	}
}

func LogIndent() {
	if global != nil {
		global.LogIndent()
	}
}

func LogMark(format string, args ...interface{}) func() {
	if global == nil {
		return func() {}
	}

	return global.LogMark(format, args...)
}

func DebugEnabled() bool {
	return global != nil
}

func (self *DebugLog) LogMark(format string, args ...interface{}) func() {
	marker := fmt.Sprintf(format, args...)

	self.Printf("%s START", marker)
	closer := self.LogIndent()
	return func() {
		err := recover()
		if err != nil {
			self.Printf("Encoundered panic during '%s': %s", marker, err)
		}
		closer()
		self.Printf("%s END", marker)
		if err != nil {
			panic(err)
		}
	}
}