// Production build: go build -ldflags="-w" -o gelf-reader_release gelf-reader
package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"

	"gopkg.in/Graylog2/go-gelf.v2/gelf"
)

const (
	VERSION = "0.1.2"
)

func main() {
	var (
		listenAddr  string
		outputFile  string
		showVersion bool
		outWriter   io.Writer
	)

	flag.StringVar(&listenAddr, "listen", "0.0.0.0:12201", "listen address")
	flag.StringVar(&outputFile, "output", "", "Output file (stdout if empty)")
	flag.BoolVar(&showVersion, "version", false, "Show version and exit")
	flag.Parse()

	fmt.Printf("GELF reader server %v\n", VERSION)
	if showVersion {
		return
	}

	if len(outputFile) > 0 {
		outFile, err := os.OpenFile(outputFile, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0755)
		if err != nil {
			log.Fatalf("Error opening output file\n%s", err)
		}

		outWriter = outFile
		defer outFile.Close()
	} else {
		outWriter = os.Stdout
	}

	gelfReader, err := gelf.NewReader(listenAddr)
	if err != nil {
		log.Fatalf("Error creating GELF network reader\n%s", err)
	}

	fmt.Printf("Listening on %v\n", gelfReader.Addr())

	for {
		msg, err := gelfReader.ReadMessage()
		if err != nil {
			log.Printf("Error reading message\n%s\n", err)
		} else {
			fmt.Fprintf(outWriter, "%f %v: %v\n", msg.TimeUnix, msg.Host, msg.Short)
		}
	}
}