feat(app): support local screenshot actions

internal/application/capture_actions.go

@@ -0,0 +1,88 @@
+package application
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/mmmy/snapgo/internal/infrastructure/clipboard"
+)
+
+// CaptureActionsService handles non-upload actions on already-produced PNG
+// screenshots. Keeping these actions here makes save/copy available across
+// overlay implementations without binding them to Wails or a specific OS.
+type CaptureActionsService struct {
+	Clipboard clipboard.Writer
+	Notifier  Notifier
+}
+
+func (s *CaptureActionsService) CopyImage(_ context.Context, pngBytes []byte) error {
+	if len(pngBytes) == 0 {
+		err := fmt.Errorf("empty screenshot")
+		s.notifyFailure(err.Error())
+		return err
+	}
+	if s.Clipboard == nil {
+		err := fmt.Errorf("clipboard is not configured")
+		s.notifyFailure(err.Error())
+		return err
+	}
+	if err := s.Clipboard.WriteImage(pngBytes); err != nil {
+		s.notifyFailure("clipboard write failed: " + err.Error())
+		return err
+	}
+	if s.Notifier != nil {
+		s.Notifier.NotifySuccess("image copied to clipboard")
+	}
+	return nil
+}
+
+func (s *CaptureActionsService) SaveImage(_ context.Context, pngBytes []byte, dir string) (string, error) {
+	if len(pngBytes) == 0 {
+		err := fmt.Errorf("empty screenshot")
+		s.notifyFailure(err.Error())
+		return "", err
+	}
+	dir = strings.TrimSpace(dir)
+	if dir == "" {
+		err := fmt.Errorf("save directory is empty")
+		s.notifyFailure(err.Error())
+		return "", err
+	}
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		s.notifyFailure("create save directory failed: " + err.Error())
+		return "", err
+	}
+	path := uniquePNGPath(dir, time.Now())
+	if err := os.WriteFile(path, pngBytes, 0o644); err != nil {
+		s.notifyFailure("save failed: " + err.Error())
+		return "", err
+	}
+	if s.Notifier != nil {
+		s.Notifier.NotifySuccess(path)
+	}
+	return path, nil
+}
+
+func (s *CaptureActionsService) notifyFailure(reason string) {
+	if s.Notifier != nil {
+		s.Notifier.NotifyFailure(reason)
+	}
+}
+
+func uniquePNGPath(dir string, now time.Time) string {
+	base := now.Format("20060102-150405")
+	path := filepath.Join(dir, base+".png")
+	for i := 1; fileExists(path); i++ {
+		path = filepath.Join(dir, fmt.Sprintf("%s-%02d.png", base, i))
+	}
+	return path
+}
+
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
+}