feat(regen): per-slide regeneration dialog with block toggles and title editing

app/api/generate/media-prompt/route.ts

@@ -0,0 +1,59 @@
+/**
+ * Auto-generates a media generation prompt from a slide indication text.
+ * Used when the user picks a media type not present in the original slide.
+ */
+import { NextRequest } from 'next/server';
+import { createLogger } from '@/lib/logger';
+import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { callLLM } from '@/lib/ai/llm';
+import { resolveModelFromHeaders } from '@/lib/server/resolve-model';
+
+const log = createLogger('MediaPrompt API');
+
+export const maxDuration = 30;
+
+export async function POST(req: NextRequest) {
+  try {
+    const body = await req.json();
+    const { indicationText, mediaType, language } = body as {
+      indicationText: string;
+      mediaType: 'image' | 'video';
+      language?: string;
+    };
+
+    if (!indicationText || !indicationText.trim()) {
+      return apiError('MISSING_REQUIRED_FIELD', 400, 'indicationText is required');
+    }
+    if (!mediaType) {
+      return apiError('MISSING_REQUIRED_FIELD', 400, 'mediaType is required');
+    }
+    if (mediaType !== 'image' && mediaType !== 'video') {
+      return apiError('INVALID_REQUEST', 400, 'mediaType must be "image" or "video"');
+    }
+
+    const { model: languageModel } = await resolveModelFromHeaders(req);
+
+    const mediaLabel = mediaType === 'image' ? 'image' : 'short video loop';
+    const langHint = language ? ` The course language is ${language}.` : '';
+
+    const result = await callLLM(
+      {
+        model: languageModel,
+        system: `You are a visual media prompt writer. Given a slide description, write a concise prompt (1–2 sentences, max 30 words) for generating a ${mediaLabel} that visually represents the slide content. Respond with ONLY the prompt text — no quotes, no explanation.${langHint}`,
+        prompt: indicationText,
+        maxOutputTokens: 150,
+      },
+      'media-prompt',
+    );
+
+    const prompt = result.text.trim();
+    log.info(
+      `Generated media prompt for ${mediaType}: "${prompt.length > 60 ? prompt.slice(0, 60) + '...' : prompt}"`,
+    );
+
+    return apiSuccess({ data: { prompt } });
+  } catch (error) {
+    log.error('media-prompt generation failed:', error);
+    return apiError('INTERNAL_ERROR', 500, error instanceof Error ? error.message : String(error));
+  }
+}

app/api/generate/narration-text/route.ts

@@ -0,0 +1,54 @@
+/**
+ * Generates narration text for a slide from its indication (description + key points).
+ * Used by the "Regenerate narration" AI button in the slide regeneration dialog.
+ */
+import { NextRequest } from 'next/server';
+import { createLogger } from '@/lib/logger';
+import { apiError, apiSuccess, requireAuth } from '@/lib/server/api-response';
+import { callLLM } from '@/lib/ai/llm';
+import { resolveModelFromHeaders } from '@/lib/server/resolve-model';
+
+const log = createLogger('NarrationText API');
+
+export const maxDuration = 30;
+
+export async function POST(req: NextRequest) {
+  const user = await requireAuth(req);
+  if ('status' in user && user instanceof Response) return user;
+
+  try {
+    const body = await req.json();
+    const { indicationText, language } = body as {
+      indicationText: string;
+      language?: string;
+    };
+
+    if (!indicationText || !indicationText.trim()) {
+      return apiError('MISSING_REQUIRED_FIELD', 400, 'indicationText is required');
+    }
+
+    const { model: languageModel } = await resolveModelFromHeaders(req);
+
+    const langHint = language
+      ? ` The narration MUST be written in ${language} (match the language of the key points).`
+      : '';
+
+    const result = await callLLM(
+      {
+        model: languageModel,
+        system: `You are an expert educational narrator. Given a slide's description and key points, write a natural spoken narration for a teacher to deliver while presenting the slide. The narration should:\n- Be conversational and engaging, as if speaking directly to students\n- Cover the key points clearly without reading them verbatim\n- Be 2-4 sentences long (suitable for a 15-30 second voiceover)\n- NOT include stage directions, quotes, or explanations — only the spoken text itself${langHint}`,
+        prompt: indicationText,
+        maxOutputTokens: 300,
+      },
+      'narration-text',
+    );
+
+    const text = result.text.trim();
+    log.info(`Generated narration text (${text.length} chars)`);
+
+    return apiSuccess({ data: { text } });
+  } catch (error) {
+    log.error('narration-text generation failed:', error);
+    return apiError('INTERNAL_ERROR', 500, error instanceof Error ? error.message : String(error));
+  }
+}

app/api/generate/scene-content-only/route.ts

@@ -0,0 +1,83 @@
+/**
+ * Synchronous slide content generation — returns raw PPTElements without persisting a scene.
+ * Used by the per-slide regeneration flow.
+ */
+import { NextRequest } from 'next/server';
+import { createLogger } from '@/lib/logger';
+import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { generateSceneContentFromInput } from '@/lib/server/scene-content-generation';
+import { getStorageBackend } from '@/lib/server/storage';
+import { resolveModelFromHeaders } from '@/lib/server/resolve-model';
+import type { SceneOutline, GeneratedSlideContent } from '@/lib/types/generation';
+import type { AgentInfo } from '@/lib/generation/generation-pipeline';
+
+const log = createLogger('SceneContentOnly API');
+
+export const maxDuration = 60;
+
+export async function POST(req: NextRequest) {
+  try {
+    const body = await req.json();
+    const { outline, stageId, agents, themeId } = body as {
+      outline: SceneOutline;
+      stageId: string;
+      agents?: AgentInfo[];
+      themeId?: string;
+    };
+
+    if (!outline) {
+      return apiError('MISSING_REQUIRED_FIELD', 400, 'outline is required');
+    }
+    if (!stageId) {
+      return apiError('MISSING_REQUIRED_FIELD', 400, 'stageId is required');
+    }
+
+    if (outline.type !== 'slide') {
+      return apiError('INVALID_REQUEST', 400, 'Only slide-type outlines are supported');
+    }
+
+    // Load stage metadata and outlines from server storage
+    const backend = getStorageBackend();
+    const [stageData, savedOutlines] = await Promise.all([
+      backend.loadStage(stageId),
+      backend.loadOutlines(stageId),
+    ]);
+
+    if (!stageData) {
+      return apiError('NOT_FOUND', 404, 'Stage not found');
+    }
+
+    const allOutlines = savedOutlines ?? [outline];
+    const stageInfo = {
+      name: stageData.stage.name ?? '',
+      description: stageData.stage.description,
+      language: stageData.stage.language,
+      style: stageData.stage.style,
+      themeId,
+    };
+
+    // ── Model resolution from request headers ──
+    const { modelString } = await resolveModelFromHeaders(req);
+
+    const result = await generateSceneContentFromInput({
+      outline,
+      allOutlines,
+      stageId,
+      stageInfo,
+      agents,
+      modelConfig: { modelString },
+    });
+
+    // Return only the slide content fields (elements + background)
+    const slideContent = result.content as GeneratedSlideContent;
+    return apiSuccess({
+      data: {
+        elements: slideContent.elements ?? [],
+        background: slideContent.background,
+      },
+    });
+  } catch (error) {
+    log.error('scene-content-only failed:', error);
+    return apiError('INTERNAL_ERROR', 500, error instanceof Error ? error.message : String(error));
+  }
+}