feat: add merge files api

Author: Azhovan

cmd/download.go

@@ -11,15 +11,17 @@ import (
 type downloadOptions struct {
 	remoteURL string
 	out       string
+	segSize   int64
+	segCount  int
 }
 
 func newDownloadCmd(output io.Writer) *cobra.Command {
 	var opts = &downloadOptions{}
 
 	var cmd = &cobra.Command{
 		Use:   "download --url [ADDRESS] --out [DIRECTORY]",
-		Short: "download remote file and store it in the output local directory",
-		Args:  cobra.MaximumNArgs(2),
+		Short: "download remote file and store it in a local directory",
+		Args:  cobra.MaximumNArgs(4),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			remoteFileURL, err := url.Parse(opts.remoteURL)
 			if err != nil {
@@ -35,8 +37,10 @@ func newDownloadCmd(output io.Writer) *cobra.Command {
 		},
 	}
 
-	cmd.Flags().StringVarP(&opts.remoteURL, "url", "u", "", "remote file address")
-	cmd.Flags().StringVarP(&opts.out, "out", "o", "", "local directory to save file")
+	cmd.Flags().StringVarP(&opts.remoteURL, "url", "u", "", "The remote file address to download.")
+	cmd.Flags().StringVarP(&opts.out, "out", "o", "", "The local target directory to save file.")
+	cmd.Flags().Int64VarP(&opts.segSize, "segment-size", "s", 0, "The size of each segment for download a file.")
+	cmd.Flags().IntVarP(&opts.segCount, "segment-count", "n", download.DefaultNumberOfSegments, "The number of segments for download a file.")
 
 	return cmd
 }

main.go

@@ -1,13 +1,13 @@
 package main
 
 import (
-	"log"
+	"os"
 
 	"github.com/azhovan/durable-resume/cmd"
 )
 
 func main() {
 	if err := cmd.Execute(); err != nil {
-		log.Fatalln(err)
+		os.Exit(1)
 	}
 }

pkg/download/client.go

@@ -49,7 +49,7 @@ func WithHTTPClient(httpClient *http.Client) ClientOption {
 	}
 }
 
-// WithAuth is an option function that allow the user to provide authentication method.
+// WithAuth is an option function that allows the user to provide authentication method.
 func WithAuth(auth AuthStrategy) ClientOption {
 	return func(client *Client) {
 		client.auth = auth

pkg/download/dl_manager.go

@@ -31,6 +31,7 @@ func NewDownloadManager(downloader *Downloader, retryPolicy *RetryPolicy) *Downl
 
 // Download initiates the download process.
 // It returns nil if the download completes successfully or an error if issues occur.
+// TODO(azhovan): not override existing files
 func (dm *DownloadManager) Download(ctx context.Context) error {
 	err := dm.Downloader.ValidateRangeSupport(ctx, dm.Downloader.UpdateRangeSupportState)
 	if err != nil {

pkg/download/segment.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -265,6 +266,9 @@ func (e *SegmentError) Error() string {
 	return fmt.Sprintf("%s, with error: %v", e.Details, e.Err)
 }
 
+// MergeFiles concatenates multiple segment files into one file with the specified filename.
+// The content type of the merged file is determined by reading the first 512 bytes of the first segment.
+// If there are no segments to merge, it returns an ErrNoContent error.
 func (sm *SegmentManager) MergeFiles(filename string) error {
 	if len(sm.Segments) == 0 {
 		return ErrNoContent
@@ -288,6 +292,7 @@ func (sm *SegmentManager) MergeFiles(filename string) error {
 		return err
 	}
 
+	wg := &sync.WaitGroup{}
 	// concatenate segment files
 	for i := 1; i < len(sm.Segments); i++ {
 		current := sm.Segments[i]
@@ -296,12 +301,23 @@ func (sm *SegmentManager) MergeFiles(filename string) error {
 			return err
 		}
 
+		wg.Add(1)
+
 		_, err = segment0.ReadFrom(f)
 		if err != nil {
 			return &SegmentError{Err: err, Details: fmt.Sprintf("reading segment %d failed", i)}
 		}
+
+		// remove the temporary segment file
+		go func(file *os.File) {
+			defer wg.Done()
+			_ = file.Close()
+			_ = os.Remove(file.Name())
+		}(f)
 	}
 
+	wg.Wait()
+
 	err = segment0.setDone(true)
 	if err != nil {
 		return &SegmentError{Err: err, Details: "closing the segment 0 failed"}