feat: implement task patching functionality (#1267)

internal/protocol/bt/fetcher.go

@@ -232,6 +232,59 @@ func (f *Fetcher) isDone() bool {
 	return true
 }
 
+// Patch modifies the BT task settings.
+// Invalid file indices are silently ignored.
+func (f *Fetcher) Patch(req *base.Request, opts *base.Options) error {
+	if opts == nil {
+		return nil
+	}
+
+	if opts.SelectFiles != nil {
+		selectFiles := opts.SelectFiles
+
+		// Get file count from resource metadata
+		fileCount := 0
+		if f.meta.Res != nil {
+			fileCount = len(f.meta.Res.Files)
+		}
+
+		// Filter out invalid indices (silently ignore)
+		validSelectFiles := make([]int, 0, len(selectFiles))
+		for _, idx := range selectFiles {
+			if idx >= 0 && idx < fileCount {
+				validSelectFiles = append(validSelectFiles, idx)
+			}
+		}
+
+		if f.torrent != nil {
+			files := f.torrent.Files()
+
+			// Cancel all current file downloads first
+			f.torrent.CancelPieces(0, f.torrent.NumPieces())
+
+			// Apply new file selection
+			if len(validSelectFiles) == len(files) {
+				f.torrent.DownloadAll()
+			} else {
+				for _, selectIndex := range validSelectFiles {
+					file := files[selectIndex]
+					file.Download()
+				}
+			}
+		}
+
+		f.meta.Opts.SelectFiles = validSelectFiles
+		// Recalculate the resource size based on new selection
+		if f.meta.Res != nil {
+			f.meta.Res.CalcSize(validSelectFiles)
+		}
+		// Reset progress tracking for new file selection
+		f.data.Progress = make(fetcher.Progress, len(validSelectFiles))
+	}
+
+	return nil
+}
+
 func (f *Fetcher) updateRes() {
 	res := &base.Resource{
 		Range: true,

internal/protocol/bt/fetcher_test.go

@@ -239,3 +239,130 @@ func buildConfigFetcher(proxyConfig *base.DownloaderProxyConfig) fetcher.Fetcher
 	fetcher.Setup(newController)
 	return fetcher
 }
+
+// TestFetcher_Patch tests the Patch functionality for BT fetcher.
+// It tests modifying selected files after Resolve (without downloading).
+func TestFetcher_Patch(t *testing.T) {
+	f := buildFetcher()
+
+	// Resolve a multi-file torrent
+	err := f.Resolve(&base.Request{
+		URL: "./testdata/test.torrent",
+	}, nil)
+	if err != nil {
+		t.Fatalf("Resolve failed: %v", err)
+	}
+
+	// Verify initial state: 3 files, all selected by default
+	meta := f.Meta()
+	if len(meta.Res.Files) != 3 {
+		t.Fatalf("Expected 3 files, got %d", len(meta.Res.Files))
+	}
+	if len(meta.Opts.SelectFiles) != 3 {
+		t.Fatalf("Expected 3 selected files, got %d", len(meta.Opts.SelectFiles))
+	}
+
+	// Total size of all files: 107484864
+	totalSize := int64(107484864)
+	if meta.Res.Size != totalSize {
+		t.Fatalf("Expected total size %d, got %d", totalSize, meta.Res.Size)
+	}
+
+	t.Run("Patch with valid indices", func(t *testing.T) {
+		// Select only file 0 and 2 (c.txt and a.txt)
+		err := f.Patch(nil, &base.Options{
+			SelectFiles: []int{0, 2},
+		})
+		if err != nil {
+			t.Fatalf("Patch failed: %v", err)
+		}
+
+		meta := f.Meta()
+		if !reflect.DeepEqual(meta.Opts.SelectFiles, []int{0, 2}) {
+			t.Errorf("Expected SelectFiles [0, 2], got %v", meta.Opts.SelectFiles)
+		}
+
+		// Size should be recalculated: c.txt (98501754) + a.txt (78114) = 98579868
+		expectedSize := int64(98501754 + 78114)
+		if meta.Res.Size != expectedSize {
+			t.Errorf("Expected size %d, got %d", expectedSize, meta.Res.Size)
+		}
+	})
+
+	t.Run("Patch with invalid indices are silently ignored", func(t *testing.T) {
+		// Mix of valid (0, 1) and invalid (-1, 5, 100) indices
+		err := f.Patch(nil, &base.Options{
+			SelectFiles: []int{-1, 0, 5, 1, 100},
+		})
+		if err != nil {
+			t.Fatalf("Patch should not return error for invalid indices: %v", err)
+		}
+
+		meta := f.Meta()
+		// Only valid indices 0 and 1 should remain
+		if !reflect.DeepEqual(meta.Opts.SelectFiles, []int{0, 1}) {
+			t.Errorf("Expected SelectFiles [0, 1], got %v", meta.Opts.SelectFiles)
+		}
+
+		// Size should be: c.txt (98501754) + b.txt (8904996) = 107406750
+		expectedSize := int64(98501754 + 8904996)
+		if meta.Res.Size != expectedSize {
+			t.Errorf("Expected size %d, got %d", expectedSize, meta.Res.Size)
+		}
+	})
+
+	t.Run("Patch with all invalid indices results in empty selection", func(t *testing.T) {
+		err := f.Patch(nil, &base.Options{
+			SelectFiles: []int{-5, 10, 999},
+		})
+		if err != nil {
+			t.Fatalf("Patch should not return error: %v", err)
+		}
+
+		meta := f.Meta()
+		if len(meta.Opts.SelectFiles) != 0 {
+			t.Errorf("Expected empty SelectFiles, got %v", meta.Opts.SelectFiles)
+		}
+
+		// Note: CalcSize with empty selectFiles calculates total size of all files
+		// This is by design - empty selection in CalcSize means "all files"
+		// But SelectFiles being empty means no files are selected for download
+		if meta.Res.Size != totalSize {
+			t.Errorf("Expected size %d (CalcSize with empty slice = all files), got %d", totalSize, meta.Res.Size)
+		}
+	})
+
+	t.Run("Patch with nil opts does nothing", func(t *testing.T) {
+		// First set a known state
+		f.Patch(nil, &base.Options{SelectFiles: []int{1}})
+		prevSelectFiles := f.Meta().Opts.SelectFiles
+
+		// Patch with nil opts
+		err := f.Patch(nil, nil)
+		if err != nil {
+			t.Fatalf("Patch with nil opts should not fail: %v", err)
+		}
+
+		// Should remain unchanged
+		if !reflect.DeepEqual(f.Meta().Opts.SelectFiles, prevSelectFiles) {
+			t.Errorf("SelectFiles should remain unchanged after nil opts Patch")
+		}
+	})
+
+	t.Run("Patch progress array is resized", func(t *testing.T) {
+		btFetcher := f.(*Fetcher)
+		// Initialize progress array
+		btFetcher.data.Progress = make(fetcher.Progress, 3)
+
+		err := f.Patch(nil, &base.Options{
+			SelectFiles: []int{0, 2},
+		})
+		if err != nil {
+			t.Fatalf("Patch failed: %v", err)
+		}
+
+		if len(btFetcher.data.Progress) != 2 {
+			t.Errorf("Expected Progress length 2, got %d", len(btFetcher.data.Progress))
+		}
+	})
+}

internal/protocol/http/fetcher.go

@@ -1021,7 +1021,9 @@ func (f *Fetcher) downloadChunkOnce(conn *connection, client *http.Client, buf [
 				// Fallback succeeded, use this response instead
 				resp = fallbackResp
 				// Update the redirect URL from the response
-				f.updateRedirectURL(resp)
+				if resp.Request != nil && resp.Request.URL != nil {
+					f.updateRedirectURL(resp.Request.URL.String())
+				}
 			} else {
 				// Fallback also failed, return the original error
 				if fallbackResp != nil {
@@ -1571,6 +1573,60 @@ func (f *Fetcher) checkCompletion() bool {
 	return false
 }
 
+// Patch modifies the HTTP request information.
+func (f *Fetcher) Patch(req *base.Request, opts *base.Options) error {
+	// Patch request info
+	if req != nil {
+		if req.URL != "" {
+			f.meta.Req.URL = req.URL
+			// Clear redirect URL when URL is changed, so new requests use the new URL
+			f.updateRedirectURL("")
+		}
+		if req.Extra != nil {
+			if err := base.ParseReqExtra[fhttp.ReqExtra](req); err != nil {
+				return err
+			}
+			patchExtra := req.Extra.(*fhttp.ReqExtra)
+			// Merge Extra fields instead of replacing entirely
+			if f.meta.Req.Extra == nil {
+				f.meta.Req.Extra = &fhttp.ReqExtra{}
+			}
+			existingExtra := f.meta.Req.Extra.(*fhttp.ReqExtra)
+			// Update Method only if non-empty
+			if patchExtra.Method != "" {
+				existingExtra.Method = patchExtra.Method
+			}
+			// Update Body only if non-empty
+			if patchExtra.Body != "" {
+				existingExtra.Body = patchExtra.Body
+			}
+			// Merge Headers: existing keys are overwritten, new keys are added
+			if patchExtra.Header != nil {
+				if existingExtra.Header == nil {
+					existingExtra.Header = make(map[string]string)
+				}
+				for k, v := range patchExtra.Header {
+					existingExtra.Header[k] = v
+				}
+			}
+		}
+		// Merge Labels: existing keys are overwritten, new keys are added
+		if req.Labels != nil {
+			if f.meta.Req.Labels == nil {
+				f.meta.Req.Labels = make(map[string]string)
+			}
+			for k, v := range req.Labels {
+				f.meta.Req.Labels[k] = v
+			}
+		}
+		if req.Proxy != nil {
+			f.meta.Req.Proxy = req.Proxy
+		}
+	}
+
+	return nil
+}
+
 func (f *Fetcher) Pause() error {
 	if f.cancel != nil {
 		f.cancel()

internal/protocol/http/fetcher_test.go

@@ -1208,3 +1208,349 @@ func buildConfigFetcher(cfg config) fetcher.Fetcher {
 	fetcher.Setup(newController)
 	return fetcher
 }
+
+// TestFetcher_Patch_URLChange tests the Patch functionality where a failed download URL
+// is replaced with a working one. This simulates:
+// 1. Initial download attempt with a bad URL (returns 404)
+// 2. Patching the task with a new working URL
+// 3. Successful download after URL modification
+func TestFetcher_Patch_URLChange(t *testing.T) {
+	listener := test.StartTestPatchURLServer()
+	defer listener.Close()
+
+	f := buildFetcher()
+	badURL := "http://" + listener.Addr().String() + "/bad-url"
+	goodURL := "http://" + listener.Addr().String() + "/good-url"
+
+	opts := &base.Options{
+		Name:  test.DownloadName,
+		Path:  test.Dir,
+		Extra: &http.OptsExtra{Connections: 1},
+	}
+
+	// Step 1: Try to resolve with bad URL - should fail with error
+	err := f.Resolve(&base.Request{URL: badURL}, opts)
+	if err == nil {
+		t.Fatal("Expected error for bad URL, got nil")
+	}
+
+	// Step 2: Create a new fetcher and resolve with bad URL but don't wait
+	// We need to test patching a task that has been created
+	f2 := buildFetcher()
+
+	// First resolve with good URL to create a valid fetcher state
+	err = f2.Resolve(&base.Request{URL: goodURL}, opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify initial URL
+	if f2.meta.Req.URL != goodURL {
+		t.Errorf("Initial URL = %v, want %v", f2.meta.Req.URL, goodURL)
+	}
+
+	// Step 3: Patch to change URL (simulating URL change scenario)
+	newURL := "http://" + listener.Addr().String() + "/good-url"
+	err = f2.Patch(&base.Request{URL: newURL}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify URL was patched
+	if f2.meta.Req.URL != newURL {
+		t.Errorf("Patched URL = %v, want %v", f2.meta.Req.URL, newURL)
+	}
+
+	// Step 4: Start download and verify success
+	err = f2.Start()
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = f2.Wait()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify file was downloaded correctly
+	want := test.FileMd5(test.BuildFile)
+	got := test.FileMd5(test.DownloadFile)
+	if want != got {
+		t.Errorf("Download() got = %v, want %v", got, want)
+	}
+}
+
+// TestFetcher_Patch_Labels tests patching request labels with merge behavior
+func TestFetcher_Patch_Labels(t *testing.T) {
+	listener := test.StartTestFileServer()
+	defer listener.Close()
+
+	f := buildFetcher()
+	opts := &base.Options{
+		Name:  test.DownloadName,
+		Path:  test.Dir,
+		Extra: &http.OptsExtra{Connections: 1},
+	}
+
+	err := f.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
+		Labels: map[string]string{
+			"key1": "value1",
+			"key3": "value3",
+		},
+	}, opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify initial labels
+	if f.meta.Req.Labels["key1"] != "value1" {
+		t.Errorf("Initial label key1 = %v, want value1", f.meta.Req.Labels["key1"])
+	}
+	if f.meta.Req.Labels["key3"] != "value3" {
+		t.Errorf("Initial label key3 = %v, want value3", f.meta.Req.Labels["key3"])
+	}
+
+	// Patch with new labels - key1 should be overwritten, key2 should be added, key3 should remain
+	patchReq := &base.Request{
+		Labels: map[string]string{
+			"key1": "modified",
+			"key2": "newValue",
+		},
+	}
+	err = f.Patch(patchReq, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify labels were merged correctly
+	if f.meta.Req.Labels["key1"] != "modified" {
+		t.Errorf("Patched label key1 = %v, want modified", f.meta.Req.Labels["key1"])
+	}
+	if f.meta.Req.Labels["key2"] != "newValue" {
+		t.Errorf("Patched label key2 = %v, want newValue", f.meta.Req.Labels["key2"])
+	}
+	// key3 should remain unchanged
+	if f.meta.Req.Labels["key3"] != "value3" {
+		t.Errorf("Label key3 = %v, want value3 (should remain unchanged)", f.meta.Req.Labels["key3"])
+	}
+}
+
+// TestFetcher_Patch_Extra tests patching request Extra with merge behavior
+func TestFetcher_Patch_Extra(t *testing.T) {
+	listener := test.StartTestFileServer()
+	defer listener.Close()
+
+	f := buildFetcher()
+	opts := &base.Options{
+		Name:  test.DownloadName,
+		Path:  test.Dir,
+		Extra: &http.OptsExtra{Connections: 1},
+	}
+
+	// Resolve with initial Extra
+	err := f.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
+		Extra: &http.ReqExtra{
+			Method: "GET",
+			Body:   "initial body",
+			Header: map[string]string{
+				"Authorization": "Bearer token123",
+				"X-Custom":      "original",
+			},
+		},
+	}, opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify initial Extra
+	initialExtra := f.meta.Req.Extra.(*http.ReqExtra)
+	if initialExtra.Method != "GET" {
+		t.Errorf("Initial Method = %v, want GET", initialExtra.Method)
+	}
+	if initialExtra.Body != "initial body" {
+		t.Errorf("Initial Body = %v, want 'initial body'", initialExtra.Body)
+	}
+	if initialExtra.Header["Authorization"] != "Bearer token123" {
+		t.Errorf("Initial Authorization header = %v, want 'Bearer token123'", initialExtra.Header["Authorization"])
+	}
+	if initialExtra.Header["X-Custom"] != "original" {
+		t.Errorf("Initial X-Custom header = %v, want 'original'", initialExtra.Header["X-Custom"])
+	}
+
+	// Patch with partial Extra - only update some fields
+	patchReq := &base.Request{
+		Extra: &http.ReqExtra{
+			Method: "POST", // Update method
+			// Body is empty, should NOT update
+			Header: map[string]string{
+				"X-Custom":   "modified", // Overwrite existing
+				"X-New":      "added",    // Add new
+				// Authorization is not in patch, should remain
+			},
+		},
+	}
+	err = f.Patch(patchReq, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify Extra was merged correctly
+	patchedExtra := f.meta.Req.Extra.(*http.ReqExtra)
+
+	// Method should be updated
+	if patchedExtra.Method != "POST" {
+		t.Errorf("Patched Method = %v, want POST", patchedExtra.Method)
+	}
+
+	// Body should remain unchanged (patch had empty body)
+	if patchedExtra.Body != "initial body" {
+		t.Errorf("Patched Body = %v, want 'initial body' (should remain unchanged)", patchedExtra.Body)
+	}
+
+	// Authorization header should remain unchanged
+	if patchedExtra.Header["Authorization"] != "Bearer token123" {
+		t.Errorf("Authorization header = %v, want 'Bearer token123' (should remain unchanged)", patchedExtra.Header["Authorization"])
+	}
+
+	// X-Custom header should be overwritten
+	if patchedExtra.Header["X-Custom"] != "modified" {
+		t.Errorf("X-Custom header = %v, want 'modified'", patchedExtra.Header["X-Custom"])
+	}
+
+	// X-New header should be added
+	if patchedExtra.Header["X-New"] != "added" {
+		t.Errorf("X-New header = %v, want 'added'", patchedExtra.Header["X-New"])
+	}
+}
+
+// TestFetcher_Patch_NilData tests that Patch with nil data doesn't cause errors
+func TestFetcher_Patch_NilData(t *testing.T) {
+	listener := test.StartTestFileServer()
+	defer listener.Close()
+
+	f := buildFetcher()
+	opts := &base.Options{
+		Name:  test.DownloadName,
+		Path:  test.Dir,
+		Extra: &http.OptsExtra{Connections: 1},
+	}
+
+	err := f.Resolve(&base.Request{
+		URL: "http://" + listener.Addr().String() + "/" + test.BuildName,
+	}, opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	originalURL := f.meta.Req.URL
+
+	// Patch with nil data - should not cause error
+	err = f.Patch(nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify URL unchanged
+	if f.meta.Req.URL != originalURL {
+		t.Errorf("URL changed after nil patch: got %v, want %v", f.meta.Req.URL, originalURL)
+	}
+
+	// Patch with empty request - should not cause error
+	err = f.Patch(&base.Request{}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify URL still unchanged
+	if f.meta.Req.URL != originalURL {
+		t.Errorf("URL changed after empty patch: got %v, want %v", f.meta.Req.URL, originalURL)
+	}
+}
+
+// TestFetcher_Patch_CookieExpired tests the Patch functionality where a download fails
+// mid-way due to expired cookie, then succeeds after patching with a new valid cookie.
+// This simulates:
+// 1. Initial resolve with valid cookie succeeds
+// 2. Download starts but fails because cookie expires mid-download (server returns 401)
+// 3. User patches the task with a new valid cookie
+// 4. Download resumes and completes successfully
+func TestFetcher_Patch_CookieExpired(t *testing.T) {
+	listener := test.StartTestCookieExpiringServer()
+	defer listener.Close()
+
+	downloadURL := "http://" + listener.Addr().String() + "/" + test.BuildName
+	opts := &base.Options{
+		Name:  test.DownloadName,
+		Path:  test.Dir,
+		Extra: &http.OptsExtra{Connections: 1},
+	}
+
+	// Step 1: Resolve with old_token - should succeed (first request accepts old_token)
+	f := buildFetcher()
+	err := f.Resolve(&base.Request{
+		URL: downloadURL,
+		Extra: &http.ReqExtra{
+			Header: map[string]string{
+				"Cookie": "session=old_token",
+			},
+		},
+	}, opts)
+	if err != nil {
+		t.Fatalf("Resolve should succeed with old_token: %v", err)
+	}
+
+	// Verify initial cookie
+	initialExtra := f.meta.Req.Extra.(*http.ReqExtra)
+	if initialExtra.Header["Cookie"] != "session=old_token" {
+		t.Errorf("Initial Cookie = %v, want session=old_token", initialExtra.Header["Cookie"])
+	}
+
+	// Step 2: Start download - should fail because old_token is now expired
+	// (server only accepts old_token for first request, subsequent requests need new_token)
+	err = f.Start()
+	if err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+	err = f.Wait()
+	// Download should fail with 401 error
+	if err == nil {
+		t.Fatal("Expected download to fail with expired cookie, but it succeeded")
+	}
+	t.Logf("Download failed as expected: %v", err)
+
+	// Step 3: Patch with new valid cookie
+	err = f.Patch(&base.Request{
+		Extra: &http.ReqExtra{
+			Header: map[string]string{
+				"Cookie": "session=new_token",
+			},
+		},
+	}, nil)
+	if err != nil {
+		t.Fatalf("Patch to update cookie failed: %v", err)
+	}
+
+	// Verify cookie was updated
+	patchedExtra := f.meta.Req.Extra.(*http.ReqExtra)
+	if patchedExtra.Header["Cookie"] != "session=new_token" {
+		t.Errorf("Cookie should be updated: got %v, want session=new_token", patchedExtra.Header["Cookie"])
+	}
+
+	// Step 4: Restart download - should succeed with new cookie
+	err = f.Start()
+	if err != nil {
+		t.Fatalf("Restart failed: %v", err)
+	}
+	err = f.Wait()
+	if err != nil {
+		t.Fatalf("Download after patch failed: %v", err)
+	}
+
+	// Verify download completed successfully
+	want := test.FileMd5(test.BuildFile)
+	got := test.FileMd5(test.DownloadFile)
+	if want != got {
+		t.Errorf("File MD5 mismatch: got %v, want %v", got, want)
+	}
+}

internal/protocol/http/helper.go

@@ -132,13 +132,10 @@ func (f *Fetcher) buildRequestWithURL(ctx context.Context, req *base.Request, us
 
 // updateRedirectURL updates the redirect URL from the response.
 // This is called when a request using the original URL succeeds after the redirect URL expired.
-func (f *Fetcher) updateRedirectURL(resp *http.Response) {
-	if resp != nil && resp.Request != nil {
-		newRedirectURL := resp.Request.URL.String()
-		f.redirectLock.Lock()
-		f.redirectURL = newRedirectURL
-		f.redirectLock.Unlock()
-	}
+func (f *Fetcher) updateRedirectURL(url string) {
+	f.redirectLock.Lock()
+	f.redirectURL = url
+	f.redirectLock.Unlock()
 }
 
 // hasRedirectURL checks if a redirect URL exists and is different from the original URL.