package pipes

import (
	"bufio"
	"errors"
	"io"
	"log/slog"
	"os/exec"
	"strings"
)

type Transcoder struct {
	Args []string
}

func (t *Transcoder) Name() string { return "ffmpeg-transcoder" }

func (t *Transcoder) Connect(r io.Reader) (io.Reader, error) {
	cmd := exec.Command("ffmpeg",
		append([]string{"-i", "pipe:0"}, append(t.Args, "-f", "webm", "pipe:1")...)...,
	)

	stdin, err := cmd.StdinPipe()
	if err != nil {
		return nil, err
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return nil, err
	}
	stderr, err := cmd.StderrPipe()
	if err != nil {
		return nil, err
	}

	go func() {
		reader := bufio.NewReader(stderr)
		var line string

		for {
			part, err := reader.ReadString('\r')
			line += part
			if err != nil {
				break
			}

			line = strings.TrimRight(line, "\r\n")
			slog.Info("ffmpeg transcoder", slog.String("log", line))
			line = ""
		}
	}()

	go func() {
		defer stdin.Close()
		_, err := io.Copy(stdin, r)
		if err != nil && !errors.Is(err, io.EOF) {
			slog.Error("transcoder stdin error", slog.Any("err", err))
		}
	}()

	if err := cmd.Start(); err != nil {
		return nil, err
	}

	return stdout, nil
}