package task

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"log/slog"
	"os/exec"
	"sync"

	"git.lastassault.de/speatzle/morffix/config"
	"git.lastassault.de/speatzle/morffix/types"
)

type countReader struct {
	io.Reader
	n int
}

func (w *countReader) Read(p []byte) (int, error) {
	n, err := w.Reader.Read(p)
	w.n += n
	return n, err
}

// dropCR drops a terminal \r from the data.
func dropCR(data []byte) []byte {
	if len(data) > 0 && data[len(data)-1] == '\r' {
		return data[0 : len(data)-1]
	}
	return data
}

func scanLines(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	if i := bytes.IndexByte(data, '\n'); i >= 0 {
		// We have a full newline-terminated line.
		return i + 1, dropCR(data[0:i]), nil
	}
	if i := bytes.IndexByte(data, '\r'); i >= 0 {
		// We have a return line.
		return i + 1, dropCR(data[0:i]), nil
	}
	// If we're at EOF, we have a final, non-terminated line. Return it.
	if atEOF {
		return len(data), dropCR(data), nil
	}
	// Request more data.
	return 0, nil, nil
}

func runFfmpegCommand(ctx context.Context, l *slog.Logger, conf config.Config, command types.FFmpegCommand) error {
	l.InfoContext(ctx, "Running ffmpeg", "args", command.GetArgs())
	cmd := exec.CommandContext(ctx, conf.Worker.FFmpegPath, command.GetArgs()...)

	var wg sync.WaitGroup

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return fmt.Errorf("Error getting StdoutPipe: %w", err)
	}

	wg.Add(1)
	outScanner := bufio.NewScanner(stdout)
	outScanner.Split(scanLines)
	go func() {
		for outScanner.Scan() {
			l.InfoContext(ctx, outScanner.Text())
		}
		wg.Done()
	}()

	stderr, err := cmd.StderrPipe()
	if err != nil {
		return fmt.Errorf("Error getting StderrPipe: %w", err)
	}
	wg.Add(1)
	errScanner := bufio.NewScanner(stderr)
	errScanner.Split(scanLines)
	go func() {
		for errScanner.Scan() {
			l.InfoContext(ctx, errScanner.Text())
		}
		wg.Done()
	}()

	err = cmd.Start()
	if err != nil {
		l.ErrorContext(ctx, "Error Starting ffmpeg", "err", err)
		return fmt.Errorf("Error Starting ffmpeg: %w", err)
	}

	wg.Wait()

	err = cmd.Wait()
	if err != nil {
		l.ErrorContext(ctx, "Error Running ffmpeg", "err", err)
		return fmt.Errorf("Error Running ffmpeg: %w", err)
	}
	return nil
}