package main

import (
	"flag"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

const DEFAULT_PRESET = "slow"
const DEFAULT_CRF = "20"

func scanArgFromConsole(text string, v *string) error {
	fmt.Print(text)
	if _, err := fmt.Scanln(v); err != nil && err.Error() == "EOF" {
		return err
	}
	return nil
}

func pressEnterToExit(code int) {
	fmt.Print("\npress enter to exit... ")
	_, _ = fmt.Scanln()
	os.Exit(code)
}

func main() {
	var err error
	var debug bool
	var vfArgs []string
	var audioFilters []string
	var videoFilters []string
	var inputVideo, ss, to, an, crf, preset, mergeAudioStreams, speedUp string

	ffmpegExecutable := "ffmpeg"
	ffmpegArgs := append(make([]string, 0, 30), "-hide_banner")
	inputArgs := []string{
		"-hwaccel", "nvdec",
		"-threads", "1",
	}
	postArgs := []string{
		"-c:v", "h264",
		"-profile:v", "high",
		"-pix_fmt", "yuv420p",
		"-tune", "film",
		"-movflags", "+faststart",
		"-r", "60",
	}

	flag.StringVar(&inputVideo, "i", "", "input video path")
	flag.BoolVar(&debug, "debug", false, "debug mode (default params)")
	flag.Parse()

	// check video exists
	if _, err := os.Stat(inputVideo); err != nil {
		fmt.Println(err)
		pressEnterToExit(1)
	}

	stat, err := ffprobe(inputVideo)
	if err != nil {
		fmt.Println(err)
		return
	}

	if !debug {
		err = func() error {
			if err = scanArgFromConsole("ss > ", &ss); err != nil {
				return err
			}
			if err = scanArgFromConsole("to > ", &to); err != nil {
				return err
			}
			if err = scanArgFromConsole("an > ", &an); err != nil {
				return err
			}
			if err = scanArgFromConsole(fmt.Sprintf("crf [%v] > ", DEFAULT_CRF), &crf); err != nil {
				return err
			}
			if err = scanArgFromConsole("speed up > ", &speedUp); err != nil {
				return err
			}
			if err = scanArgFromConsole(fmt.Sprintf("preset [%v] > ", DEFAULT_PRESET), &preset); err != nil {
				return err
			}
			if err = scanArgFromConsole("merge audio streams > ", &mergeAudioStreams); err != nil {
				return err
			}
			return nil
		}()
		if err != nil {
			os.Exit(0)
		}
	}

	for _, v := range []*string{&ss, &to, &an, &crf, &preset, &mergeAudioStreams, &speedUp} {
		*v = strings.ToLower(strings.TrimSpace(*v))
	}

	if len(ss) != 0 {
		inputArgs = append(inputArgs, "-ss", ss)
	}

	if len(to) != 0 {
		inputArgs = append(inputArgs, "-to", to)
	}

	if len(an) != 0 {
		postArgs = append(postArgs, "-an")
	} else {
		audioFilters = append(audioFilters, "amix=inputs=2:normalize=0")
	}

	if len(crf) == 0 {
		crf = DEFAULT_CRF
	}

	if len(preset) == 0 {
		preset = DEFAULT_PRESET
	}

	postArgs = append(postArgs, "-preset", preset)
	postArgs = append(postArgs, "-crf", crf)

	// speed up video and audio(?)
	if len(speedUp) != 0 {
		videoFilters = append(videoFilters, fmt.Sprintf("setpts=1/%s*PTS", speedUp))
		if len(an) == 0 {
			audioFilters = append(audioFilters, fmt.Sprintf("atempo=%s", speedUp))
		}
	}

	if len(videoFilters) != 0 {
		vfArgs = append(vfArgs, "[0:v:0]"+strings.Join(videoFilters, ",")+"[v]")
		postArgs = append(postArgs, "-map", "[v]")
	} else {
		postArgs = append(postArgs, "-map", "0:v:0")
	}

	if len(audioFilters) != 0 {
		vfArgs = append(vfArgs, "[0:a]"+strings.Join(audioFilters, ",")+"[a]")
		postArgs = append(postArgs, "-map", "[a]")
	} else {
		postArgs = append(postArgs, "-map", "0:a")
	}

	// merge filter complex args
	if len(vfArgs) != 0 {
		postArgs = append(postArgs, "-filter_complex", strings.Join(vfArgs, ";"))
	}

	// out file name
	outDir, _ := filepath.Split(inputVideo)
	outFile := filepath.Join(outDir, strconv.FormatInt(time.Now().Unix(), 10)+".mp4")

	// merge args to one slice
	ffmpegArgs = append(ffmpegArgs, inputArgs...)
	ffmpegArgs = append(ffmpegArgs, "-i", inputVideo)
	ffmpegArgs = append(ffmpegArgs, postArgs...)
	ffmpegArgs = append(ffmpegArgs, outFile)

	fmt.Printf("
running %v: %v

", ffmpegExecutable, strings.Join(ffmpegArgs, " "))

	proc := exec.Command(ffmpegExecutable, ffmpegArgs...)
	proc.Stderr = os.Stderr
	err = proc.Start()
	if err != nil {
		fmt.Println(err)
		pressEnterToExit(1)
	}
	err = proc.Wait()
	if err != nil {
		fmt.Println(err)
		pressEnterToExit(1)
	}
	if proc.ProcessState.ExitCode() != 0 {
		fmt.Println(err)
		pressEnterToExit(1)
	}
}