initial commit

logging.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strings"
+)
+
+const (
+	ERROR = iota
+	WARNING
+	INFO
+	DEBUG
+	TRACE
+)
+
+const (
+	LoggerCreated       int = iota // return code if the logger creates a new logger
+	LoggerExists                   // retun cde in the case that there is already a logger
+	ErrorCreatingLogger            // in case of error creating the logger
+)
+
+var logLevelStringMap = map[string]int{
+	"error":   ERROR,
+	"warning": WARNING,
+	"info":    INFO,
+	"debug":   DEBUG,
+	"trace":   TRACE,
+}
+
+type logOutput interface {
+	Printf(format string, a ...interface{})
+	// Println(format string, a ...interface{})
+	init(m *io.Writer, s string, ll int)
+}
+
+type logStream struct {
+	s        *log.Logger
+	logLevel int
+}
+
+var (
+	Trace         logStream
+	Debug         logStream
+	Info          logStream
+	Warning       logStream
+	Error         logStream
+	DefaultLogger logStream
+	LogLevel      int
+)
+
+func (l *logStream) Printf(format string, a ...interface{}) {
+	// describe(a)
+	if LogLevel > l.logLevel {
+		return
+	}
+
+	if l.s == nil {
+		fmt.Printf(format, a...)
+		return
+	}
+
+	l.s.Printf(format, a...)
+}
+
+func (l *logStream) init(m io.Writer, s string, ll int) {
+	l.s = log.New(m, s, log.Ldate|log.Ltime|log.Lshortfile)
+	l.logLevel = ll
+}
+
+// function to parse string representation of log level into integer - if there
+// is no match of the string, it will return 0 which maps to error only
+// logging...perhaps this could be made more explicit
+func determineLogLevel(lstr string) int {
+
+	lstrLowerCase := strings.ToLower(lstr)
+	return logLevelStringMap[lstrLowerCase]
+}
+
+func initLogger(logFile string, logLevelStr string, logToConsole bool) {
+
+	LogLevel = determineLogLevel(logLevelStr)
+
+	file, err := os.OpenFile(logFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
+
+	var multi io.Writer
+
+	if err != nil {
+		log.Println("Failed to open log file:", logFile, ":", err)
+		multi = io.MultiWriter(os.Stdout)
+	} else {
+		if logToConsole {
+			multi = io.MultiWriter(file, os.Stdout)
+		} else {
+			multi = io.MultiWriter(file)
+		}
+	}
+
+	// Trace = log.New(multi, "  TRACE: ", log.Ldate|log.Ltime|log.Lshortfile)
+	// Debug = log.New(multi, "  DEBUG: ", log.Ldate|log.Ltime|log.Lshortfile)
+	// Info = log.New(multi, "   INFO: ", log.Ldate|log.Ltime|log.Lshortfile)
+	// Warning = log.New(multi, "WARNING: ", log.Ldate|log.Ltime|log.Lshortfile)
+	// Error = log.New(multi, "  ERROR: ", log.Ldate|log.Ltime|log.Lshortfile)
+	// Trace = logStream{}
+	Trace.init(multi, "   TRACE: ", TRACE)
+	Debug.init(multi, "  DEBUG: ", DEBUG)
+	Info.init(multi, "   INFO: ", INFO)
+	Warning.init(multi, "WARNING: ", WARNING)
+	Error.init(multi, "  ERROR: ", ERROR)
+}
+
+// Printf prints output to the logger if the DefaultLogger is non nil
+// - otherwise it does nothing
+func Printf(format string, a ...interface{}) {
+	// describe(a)
+	if DefaultLogger == nil {
+		fmt.Printf(format, a...)
+		return
+	}
+
+	DefaultLogger.Printf(format, a...)
+}