Moved all download related stuff to downloader.go and fixed some errors in it

format.go

@@ -1,18 +1,7 @@
 package crunchyroll
 
 import (
-	"bufio"
-	"bytes"
-	"context"
-	"fmt"
 	"github.com/grafov/m3u8"
-	"io/ioutil"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"sort"
-	"strconv"
-	"strings"
 )
 
 type FormatType string
@@ -56,144 +45,7 @@ func (f *Format) InitVideo() error {
 	return nil
 }
 
+// Download downloads the Format with the via Downloader specified options
 func (f *Format) Download(downloader Downloader) error {
-	if _, err := os.Stat(downloader.Filename); err == nil && !downloader.IgnoreExisting {
-		return fmt.Errorf("file %s already exists", downloader.Filename)
-	}
-	if _, err := os.Stat(downloader.TempDir); err != nil {
-		if os.IsNotExist(err) {
-			err = os.Mkdir(downloader.TempDir, 0755)
-		}
-		if err != nil {
-			return err
-		}
-	} else if !downloader.IgnoreExisting {
-		content, err := os.ReadDir(downloader.TempDir)
-		if err != nil {
-			return err
-		}
-		if len(content) > 0 {
-			return fmt.Errorf("directory %s is not empty", downloader.Filename)
-		}
-	}
-
-	if downloader.DeleteTempAfter {
-		defer os.RemoveAll(downloader.TempDir)
-	}
-	if err := download(downloader.Context, f, downloader.TempDir, downloader.Goroutines, downloader.LockOnSegmentDownload, downloader.OnSegmentDownload); err != nil {
-		return err
-	}
-
-	if downloader.FFmpegOpts != nil {
-		return mergeSegmentsFFmpeg(downloader.Context, downloader.TempDir, downloader.Filename, downloader.FFmpegOpts)
-	} else {
-		return mergeSegments(downloader.Context, downloader.TempDir, downloader.Filename)
-	}
-}
-
-// mergeSegments reads every file in tempDir and writes their content to the outputFile.
-// The given output file gets created or overwritten if already existing
-func mergeSegments(context context.Context, tempDir string, outputFile string) error {
-	dir, err := os.ReadDir(tempDir)
-	if err != nil {
-		return err
-	}
-	file, err := os.OpenFile(outputFile, os.O_CREATE|os.O_WRONLY, 0755)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-	writer := bufio.NewWriter(file)
-	defer writer.Flush()
-
-	// sort the directory files after their numeric names
-	sort.Slice(dir, func(i, j int) bool {
-		iNum, err := strconv.Atoi(strings.Split(dir[i].Name(), ".")[0])
-		if err != nil {
-			return false
-		}
-		jNum, err := strconv.Atoi(strings.Split(dir[j].Name(), ".")[0])
-		if err != nil {
-			return false
-		}
-		return iNum < jNum
-	})
-
-	for _, file := range dir {
-		select {
-		case <-context.Done():
-			return context.Err()
-		default:
-		}
-
-		bodyAsBytes, err := ioutil.ReadFile(filepath.Join(tempDir, file.Name()))
-		if err != nil {
-			return err
-		}
-		if _, err = writer.Write(bodyAsBytes); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-// mergeSegmentsFFmpeg reads every file in tempDir and merges their content to the outputFile
-// with ffmpeg (https://ffmpeg.org/).
-// The given output file gets created or overwritten if already existing
-func mergeSegmentsFFmpeg(context context.Context, tempDir string, outputFile string, opts []string) error {
-	dir, err := os.ReadDir(tempDir)
-	if err != nil {
-		return err
-	}
-	f, err := os.Create(filepath.Join(tempDir, "list.txt"))
-	if err != nil {
-		return err
-	}
-	// -1 is the list.txt file
-	for i := 0; i < len(dir)-1; i++ {
-		fmt.Fprintf(f, "file '%s.ts'\n", filepath.Join(tempDir, strconv.Itoa(i)))
-	}
-	f.Close()
-
-	// predefined options ... custom options ... predefined output filename
-	command := []string{
-		"-y",
-		"-f", "concat",
-		"-safe", "0",
-		"-i", f.Name(),
-		"-c", "copy",
-	}
-	if opts != nil {
-		command = append(command, opts...)
-	}
-	command = append(command, outputFile)
-
-	var errBuf bytes.Buffer
-	cmd := exec.Command("ffmpeg",
-		command...)
-	cmd.Stderr = &errBuf
-
-	if err := cmd.Start(); err != nil {
-		return err
-	}
-
-	cmdChan := make(chan error, 1)
-	go func() {
-		cmdChan <- cmd.Wait()
-	}()
-
-	select {
-	case err = <-cmdChan:
-		if err != nil {
-			if errBuf.Len() > 0 {
-				return fmt.Errorf(errBuf.String())
-			} else {
-				return err
-			}
-		}
-		return nil
-	case <-context.Done():
-		cmd.Process.Kill()
-		return context.Err()
-	}
+	return downloader.download(f)
 }