package main

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

func main() {
	pkg := flag.String("p", "", "package")
	name := flag.String("n", "", "const name")
	inputfn := flag.String("i", "", "input file")
	outputfn := flag.String("o", "", "output file")
	flag.Parse()

	if *pkg == "" {
		log.Fatal("pkg required")
	}

	if *name == "" {
		log.Fatal("name required")
	}

	if *inputfn == "" {
		log.Fatal("input file required")
	}

	if *outputfn == "" {
		*outputfn = *inputfn + ".go"
	}

	omod := fmod(*outputfn)
	imod := fmod(*inputfn)
	if omod.After(imod) {
		log.Printf("Refusing to update %s\n", *outputfn)
		return
	}

	ifile, err := os.Open(*inputfn)
	if err != nil {
		log.Fatal(err)
	}
	defer ifile.Close()

	ofile, err := os.OpenFile(*outputfn, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0660)
	if err != nil {
		log.Fatal(err)
	}
	defer ofile.Close()

	fmt.Fprintf(ofile, "package %s\n\nvar %s = []byte{", *pkg, *name)

	buf := make([]byte, 4096)
	for c := 0; ; {
		i, err := ifile.Read(buf)
		if err != nil {
			if err != io.EOF {
				log.Fatal(err)
			}
			break
		}

		for j := 0; j < i; j++ {
			if (c % 13) == 0 {
				fmt.Fprintf(ofile, "\n\t")
			} else {
				fmt.Fprintf(ofile, " ")
			}
			fmt.Fprintf(ofile, "0x%02x,", buf[j])
			c++
		}
	}
	fmt.Fprintf(ofile, "\n}\n")
}

func fmod(fn string) time.Time {
	fi, err := os.Stat(fn)
	if err != nil {
		if os.IsNotExist(err) {
			return time.Time{}
		}
		log.Fatal(err)
	}
	return fi.ModTime()
}