package main

import (
	"bufio"
	"bytes"
	"fmt"
	"go/format"
	"log"
	"os"
	"os/exec"
	"strings"
)

func must(err error) {
	if err == nil {
		return
	}
	log.Fatal(err)
}

func main() {
	cmd := exec.Command("ffmpeg", "-muxers")
	outputBytes, err := cmd.Output()
	must(err)

	code := `package formats

var (
`

	bufreader := bufio.NewScanner(bytes.NewReader(outputBytes))

	/*File formats:
	D. = Demuxing supported
	.E = Muxing supported
	--
	 E 3g2             3GP2 (3GPP2 file format)
	 E 3gp             3GP (3GPP file format)*/

	waitingForList := true
	for bufreader.Scan() && waitingForList {
		text := bufreader.Text()
		if text == " --" {
			waitingForList = false
		}
	}

	for bufreader.Scan() {
		text := bufreader.Text()
		demuxingSupported := text[1] == 'D'
		muxingSupported := text[2] == 'E'
		text = text[4:]
		cols := strings.Fields(text)
		id := cols[0]
		name := strings.Join(cols[1:], " ")
		code += fmt.Sprintf(`
	// %s
	Format_%s = %q
`, name, strings.ToUpper(id), id)
		if demuxingSupported {
			code += fmt.Sprintf(`	// %s
	Demux_Format_%s = Format_%s
`, name, strings.ToUpper(id), strings.ToUpper(id))
		}
		if muxingSupported {
			code += fmt.Sprintf(`	// %s
	Mux_Format_%s = Format_%s
`, name, strings.ToUpper(id), strings.ToUpper(id))
		}
	}

	code += `
)
`

	codeBytes, err := format.Source([]byte(code))
	must(err)

	f, err := os.Create("gen_formats.go")
	must(err)
	defer f.Close()
	_, err = f.Write(codeBytes)
	must(err)
}