feat: change external storage CLI output to JSON format

storage.go

@@ -1,12 +1,11 @@
 package deck
 
 import (
-	"bufio"
 	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
 	"os"
-	"strings"
 	"time"
 
 	"github.com/k1LoW/deck/template"
@@ -15,6 +14,12 @@ import (
 	"google.golang.org/api/drive/v3"
 )
 
+// uploadResult represents the JSON output from the external upload command.
+type uploadResult struct {
+	URL string `json:"url"`
+	ID  string `json:"id"`
+}
+
 // Storage is the interface for image upload/delete operations.
 type Storage interface {
 	Upload(ctx context.Context, data []byte, mimeType string) (publicURL, uploadedID string, err error)
@@ -111,7 +116,7 @@ func newExternalStorage(uploadCmd, deleteCmd string) *externalStorage {
 // Upload uploads an image using the external upload command.
 // It passes image data via stdin and sets the environment variable DECK_UPLOAD_MIME.
 // The command also supports template variables: {{mime}} and {{env.XXX}}.
-// The command should output the public URL on the first line and uploaded ID on the second line.
+// The command should output JSON: {"url":"...","id":"..."}
 func (u *externalStorage) Upload(ctx context.Context, data []byte, mimeType string) (publicURL, uploadedID string, err error) {
 	const envUploadMIME = "DECK_UPLOAD_MIME"
 
@@ -149,26 +154,20 @@ func (u *externalStorage) Upload(ctx context.Context, data []byte, mimeType stri
 		return "", "", fmt.Errorf("failed to run upload command: %w\nstderr: %s", err, stderr.String())
 	}
 
-	// Parse stdout: first line is public URL, second line is uploaded ID
-	scanner := bufio.NewScanner(&stdout)
-	if !scanner.Scan() {
-		return "", "", fmt.Errorf("upload command did not output public URL")
+	// Parse JSON output
+	var result uploadResult
+	if err := json.Unmarshal(stdout.Bytes(), &result); err != nil {
+		return "", "", fmt.Errorf("failed to parse upload command output as JSON: %w\nstdout: %s", err, stdout.String())
 	}
-	publicURL = strings.TrimSpace(scanner.Text())
 
-	if !scanner.Scan() {
-		return "", "", fmt.Errorf("upload command did not output uploaded ID")
+	if result.URL == "" {
+		return "", "", fmt.Errorf("upload command returned empty URL")
 	}
-	uploadedID = strings.TrimSpace(scanner.Text())
-
-	if publicURL == "" {
-		return "", "", fmt.Errorf("upload command returned empty public URL")
-	}
-	if uploadedID == "" {
-		return "", "", fmt.Errorf("upload command returned empty uploaded ID")
+	if result.ID == "" {
+		return "", "", fmt.Errorf("upload command returned empty ID")
 	}
 
-	return publicURL, uploadedID, nil
+	return result.URL, result.ID, nil
 }
 
 // Delete deletes an uploaded image using the external delete command.