package main

import (
	// Standard
	"flag"
	"fmt"
	"os"
	"os/exec"
	"path"
	"regexp"
	"slices"
	"strconv"
	"time"
)

var (
	fromHour     int
	toHour       int
	startDir     string
	outFilename  string
	framerate    string
	rxpFilename  *regexp.Regexp
	rxpTimestamp *regexp.Regexp
)

func parseCommandLine() {
	workDir, err := os.Getwd()
	if err != nil {
		panic(err)
	}
	flag.IntVar(&fromHour, "from", 0, "Hour each day to start picking images from")
	flag.IntVar(&toHour, "to", 24, "Hour each day to start picking images up to")
	flag.StringVar(&startDir, "dir", workDir, "Directory to find date folders in")
	flag.StringVar(&outFilename, "out", "timelapse.mp4", "path and filename for the final timelapse video")
	flag.StringVar(&framerate, "framerate", "60", "Framerate")
	flag.Parse()

	rxpFilename = regexp.MustCompile(`(?i)^(\d+)\.(?:jpg|png)$`)
	rxpTimestamp = regexp.MustCompile(`/(\d+)\.(?:\S{3})$`)
}

func findFiles(dir string) (files []string) { // {{{
	entries, err := os.ReadDir(dir)
	if err != nil {
		return
	}

	for _, entry := range entries {
		if entry.IsDir() {
			files = append(
				files,
				findFiles(path.Join(dir, entry.Name()))...,
			)
		} else {
			if validateFilename(entry.Name()) {
				files = append(files, path.Join(dir, entry.Name()))
			}
		}
	}

	return
} // }}}
func validateFilename(fname string) bool { // {{{
	// fname is just a bunch of numbers with a .png or .jpg postfix.
	if !rxpFilename.MatchString(fname) {
		return false
	}

	t := filenameToTime(fname, false)
	return t.Hour() >= fromHour && t.Hour() <= toHour
} // }}}
func filenameToTime(fname string, fnameWithPath bool) time.Time { // {{{
	var tp []string
	if fnameWithPath {
		tp = rxpTimestamp.FindStringSubmatch(fname)
	} else {
		tp = rxpFilename.FindStringSubmatch(fname)
	}
	tsi, _ := strconv.Atoi(tp[1])
	ts := int64(tsi)
	t := time.Unix(int64(ts), 0)
	sweden, _ := time.LoadLocation("Europe/Stockholm")
	t = t.In(sweden)
	return t
} // }}}
func sortFiles(a, b string) int { // {{{
	as := rxpTimestamp.FindStringSubmatch(a)
	bs := rxpTimestamp.FindStringSubmatch(b)
	an, _ := strconv.Atoi(as[1])
	bn, _ := strconv.Atoi(bs[1])
	switch {
	case an < bn:
		return -1
	case an > bn:
		return 1
	}
	return 0
} // }}}

func separateDays(files []string) *map[string][]string { // {{{
	days := make(map[string][]string, 128)

	var t time.Time
	var date string
	var fnames []string
	var found bool
	for _, f := range files {
		t = filenameToTime(f, true)
		date = t.Format("2006-01-02")

		fnames, found = days[date]
		if !found {
			fnames = []string{}
		}
		fnames = append(fnames, f)
		days[date] = fnames
	}

	return &days
} // }}}
func filesToSequenceFile(fname string, files []string) { // {{{
	out, err := os.OpenFile(fname, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	defer out.Close()

	for _, f := range files {
		_, err = out.WriteString(
			fmt.Sprintf("file '%s'\n", f),
		)
		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}
	}
} // }}}
func timelapse(date string, files []string) { // {{{
	sequenceFile := fmt.Sprintf("/tmp/timelapse/sequence_%s", date)
	videoFile := fmt.Sprintf("/tmp/timelapse/video_%s.mp4", date)
	text := fmt.Sprintf("drawtext=text='%s':fontsize=30:x=10:y=10:fontcolor=#71b045:bordercolor=black:borderw=1", date)

	filesToSequenceFile(sequenceFile, files)
	os.Remove(videoFile)
	ffmpeg := exec.Command("ffmpeg", "-safe", "0", "-f", "concat", "-i", sequenceFile, "-filter_complex", text, "-framerate", framerate, "-c:v", "libx264", "-crf", "23", videoFile)
	out, err := ffmpeg.CombinedOutput()
	if err != nil {
		fmt.Printf("%s\n", out)
		panic(err)
	}
} // }}}
func concatVideos(unsortedDates []string) { // {{{
	fname := "/tmp/timelapse/sequence_all"
	var videos []string

	for _, date := range unsortedDates {
		videos = append(videos, "/tmp/timelapse/video_"+date+".mp4")
	}
	slices.Sort(videos)

	filesToSequenceFile(fname, videos)
	os.Remove(outFilename)
	ffmpeg := exec.Command("ffmpeg", "-safe", "0", "-f", "concat", "-i", fname, "-c", "copy", outFilename)
	out, err := ffmpeg.CombinedOutput()
	if err != nil {
		fmt.Printf("%s\n", out)
		panic(err)
	}
} // }}}

func main() {
	parseCommandLine()
	files := findFiles(startDir)
	slices.SortStableFunc(files, sortFiles)
	sortedDays := separateDays(files)

	os.Mkdir("/tmp/timelapse", 0755)
	var dates []string
	for date, files := range *sortedDays {
		fmt.Printf("Create timelapse for %s\n", date)
		dates = append(dates, date)
		timelapse(date, files)
	}

	fmt.Println("Assemble day videos to complete timelapse")
	concatVideos(dates)
}