Split param processor and tighten Volces frame validation

apps/api/internal/clients/volces.go

@@ -76,6 +76,9 @@ func (c VolcesClient) runVideo(ctx context.Context, request Request, apiKey stri
 	upstreamTaskID := strings.TrimSpace(request.RemoteTaskID)
 	if upstreamTaskID == "" {
 		body := volcesVideoBody(request)
+		if err := validateVolcesVideoTaskBody(body); err != nil {
+			return Response{}, err
+		}
 		submitResult, requestID, err := c.postJSON(ctx, request, request.Candidate.BaseURL, "/contents/generations/tasks", apiKey, body)
 		submitRequestID = requestID
 		if err != nil {
@@ -297,6 +300,39 @@ func volcesVideoTaskBody(body map[string]any, content []map[string]any) map[stri
 	return out
 }
 
+func validateVolcesVideoTaskBody(body map[string]any) error {
+	firstFrameCount := 0
+	lastFrameCount := 0
+	for _, item := range contentItems(body["content"]) {
+		if stringFromAny(item["type"]) != "image_url" {
+			continue
+		}
+		switch stringFromAny(item["role"]) {
+		case "first_frame":
+			firstFrameCount++
+		case "last_frame":
+			lastFrameCount++
+		}
+	}
+	if firstFrameCount > 1 {
+		return &ClientError{
+			Code:       "invalid_parameter",
+			Message:    fmt.Sprintf("content contains %d first_frame image items; expected at most one first frame image content", firstFrameCount),
+			StatusCode: 400,
+			Retryable:  false,
+		}
+	}
+	if lastFrameCount > 1 {
+		return &ClientError{
+			Code:       "invalid_parameter",
+			Message:    fmt.Sprintf("content contains %d last_frame image items; expected at most one last frame image content", lastFrameCount),
+			StatusCode: 400,
+			Retryable:  false,
+		}
+	}
+	return nil
+}
+
 func addVolcesVideoTaskParams(out map[string]any, body map[string]any) {
 	copyVolcesStringParam(out, "callback_url", body, "callback_url", "callbackUrl")
 	copyVolcesBoolParam(out, "return_last_frame", body, "return_last_frame", "returnLastFrame")