feat(wails): add native file dialogs and video streaming

FileService exposes open/save dialogs for video, project JSON, and WAV
export. User-selected videos stream from disk at /localmedia/video with
range request support for seeking in the webview.

Co-authored-by: Cursor <cursoragent@cursor.com>

fileservice.go

@@ -0,0 +1,161 @@
+package main
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"github.com/wailsapp/wails/v3/pkg/application"
+)
+
+const localMediaVideoPath = "/localmedia/video"
+
+// VideoResult is returned when the user opens a video file.
+type VideoResult struct {
+	URL  string `json:"url"`
+	Name string `json:"name"`
+}
+
+// FileService exposes native file dialogs and streams the current video.
+type FileService struct {
+	app *application.App
+
+	mu         sync.RWMutex
+	videoPath  string
+	videoMod   os.FileInfo
+}
+
+func NewFileService(app *application.App) *FileService {
+	return &FileService{app: app}
+}
+
+func (s *FileService) OpenVideo() (VideoResult, error) {
+	path, err := s.app.Dialog.OpenFile().
+		SetTitle("Open Video").
+		CanChooseFiles(true).
+		AddFilter("Video", "*.mp4;*.mov;*.webm;*.mkv").
+		AddFilter("All Files", "*").
+		PromptForSingleSelection()
+	if err != nil {
+		return VideoResult{}, err
+	}
+	if path == "" {
+		return VideoResult{}, nil
+	}
+
+	info, err := os.Stat(path)
+	if err != nil {
+		return VideoResult{}, err
+	}
+
+	s.mu.Lock()
+	s.videoPath = path
+	s.videoMod = info
+	s.mu.Unlock()
+
+	return VideoResult{
+		URL:  localMediaVideoPath,
+		Name: filepath.Base(path),
+	}, nil
+}
+
+func (s *FileService) OpenProject() (string, error) {
+	path, err := s.app.Dialog.OpenFile().
+		SetTitle("Open Project").
+		CanChooseFiles(true).
+		AddFilter("JSON", "*.json").
+		AddFilter("All Files", "*").
+		PromptForSingleSelection()
+	if err != nil {
+		return "", err
+	}
+	if path == "" {
+		return "", nil
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
+func (s *FileService) SaveProject(content string, defaultName string) error {
+	if defaultName == "" {
+		defaultName = "project.json"
+	}
+
+	path, err := s.app.Dialog.SaveFile().
+		SetMessage("Save Project").
+		SetFilename(defaultName).
+		AddFilter("JSON", "*.json").
+		AddFilter("All Files", "*").
+		PromptForSingleSelection()
+	if err != nil {
+		return err
+	}
+	if path == "" {
+		return nil
+	}
+
+	return os.WriteFile(path, []byte(content), 0o644)
+}
+
+func (s *FileService) SaveAudio(data []byte, defaultName string) error {
+	if defaultName == "" {
+		defaultName = "keyboard_track.wav"
+	}
+
+	path, err := s.app.Dialog.SaveFile().
+		SetMessage("Export Audio").
+		SetFilename(defaultName).
+		AddFilter("WAV", "*.wav").
+		AddFilter("All Files", "*").
+		PromptForSingleSelection()
+	if err != nil {
+		return err
+	}
+	if path == "" {
+		return nil
+	}
+
+	return os.WriteFile(path, data, 0o644)
+}
+
+func (s *FileService) serveVideo(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	s.mu.RLock()
+	path := s.videoPath
+	modTime := s.videoMod
+	s.mu.RUnlock()
+
+	if path == "" {
+		http.NotFound(w, r)
+		return
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		http.Error(w, "video unavailable", http.StatusNotFound)
+		return
+	}
+	defer file.Close()
+
+	info, err := file.Stat()
+	if err != nil {
+		http.Error(w, "video unavailable", http.StatusNotFound)
+		return
+	}
+	if modTime != nil && !info.ModTime().Equal(modTime.ModTime()) {
+		s.mu.Lock()
+		s.videoMod = info
+		s.mu.Unlock()
+	}
+
+	http.ServeContent(w, r, info.Name(), info.ModTime(), file)
+}