fix(ai): add VIP98K expansion fallback

lib/ai/extend/service.ts

@@ -16,6 +16,9 @@ type ExtendConfig = {
   yScale?: number;
 };
 
+const VIP98K_EXPANSION_FALLBACK_MODEL = "google/nano-banana-pro/edit";
+const VIP98K_SOURCE_DOWNLOAD_TIMEOUT_MS = 120_000;
+
 export interface ExecuteExtendJobParams {
   userId: string;
   imageUrl?: string | null;
@@ -123,6 +126,97 @@ async function uploadImageToS3ForAPI(imageBase64: string): Promise<string> {
   }
 }
 
+function isTemporaryVip98kExpansionError(error: unknown) {
+  const message = error instanceof Error ? error.message : String(error || "");
+  return /HTTP\s+(?:429|5\d\d)|temporar(?:y|ily)|timeout|timed out|unavailable/i.test(
+    message,
+  );
+}
+
+async function createVip98kExpansionCanvas(
+  imageUrl: string,
+  xScale: number,
+  yScale: number,
+) {
+  const response = await fetch(imageUrl, {
+    cache: "no-store",
+    redirect: "follow",
+    signal: AbortSignal.timeout(VIP98K_SOURCE_DOWNLOAD_TIMEOUT_MS),
+  });
+  if (!response.ok) {
+    throw new ExtendServiceError(
+      "下载待拓展图片失败",
+      502,
+      `${response.status} ${response.statusText}`,
+    );
+  }
+
+  const sourceBuffer = Buffer.from(await response.arrayBuffer());
+  const sharp = await import("sharp");
+  const image = sharp.default(sourceBuffer, { failOn: "none" });
+  const metadata = await image.metadata();
+  const width = Number(metadata.width || 0);
+  const height = Number(metadata.height || 0);
+  if (!width || !height) {
+    throw new ExtendServiceError("无法识别待拓展图片尺寸", 422);
+  }
+
+  const targetWidth = Math.max(width, Math.round(width * xScale));
+  const targetHeight = Math.max(height, Math.round(height * yScale));
+  const left = Math.floor((targetWidth - width) / 2);
+  const top = Math.floor((targetHeight - height) / 2);
+  const canvas = await image
+    .ensureAlpha()
+    .extend({
+      left,
+      right: targetWidth - width - left,
+      top,
+      bottom: targetHeight - height - top,
+      background: { r: 0, g: 0, b: 0, alpha: 0 },
+    })
+    .png()
+    .toBuffer();
+  const arrayBuffer = canvas.buffer.slice(
+    canvas.byteOffset,
+    canvas.byteOffset + canvas.byteLength,
+  ) as ArrayBuffer;
+  const uploaded = await uploadFile(
+    `extend-vip98k-canvas-${Date.now()}-${Math.random().toString(36).slice(2, 8)}.png`,
+    arrayBuffer,
+  );
+  return {
+    imageUrl: uploaded.url,
+    width,
+    height,
+    targetWidth,
+    targetHeight,
+  };
+}
+
+async function extendImageWithVip98kEditFallback(
+  imageUrl: string,
+  xScale: number,
+  yScale: number,
+) {
+  const canvas = await createVip98kExpansionCanvas(imageUrl, xScale, yScale);
+  const result = await executeConfiguredVip98kTask({
+    modelId: VIP98K_EXPANSION_FALLBACK_MODEL,
+    kind: "image",
+    prompt: [
+      "Outpaint only the transparent regions of this image.",
+      "Keep every original pixel, subject, scale, position, perspective, lighting and style unchanged.",
+      `Complete the ${canvas.targetWidth}x${canvas.targetHeight} canvas naturally from the centered ${canvas.width}x${canvas.height} source.`,
+      "Do not crop, zoom, move, replace or redraw the original content.",
+    ].join(" "),
+    imageUrls: [canvas.imageUrl],
+  });
+  const outputUrl = result.outputUrls[0];
+  if (!outputUrl) {
+    throw new ExtendServiceError("VIP98K 生成式扩图未返回图片", 502);
+  }
+  return outputUrl;
+}
+
 async function extendImage(
   imageUrl: string,
   config: ExtendConfig,
@@ -130,18 +224,27 @@ async function extendImage(
   yScale: number,
 ): Promise<string> {
   if (config.provider === "vip98k") {
-    const result = await executeConfiguredVip98kTask({
-      modelId: "image-expansion",
-      kind: "image-tool",
-      prompt: `Expand the image canvas naturally to ${xScale}x width and ${yScale}x height. Preserve the original subject, perspective, lighting and style.`,
-      imageUrls: [imageUrl],
-      imageParams: { xScale, yScale },
-    });
-    const outputUrl = result.outputUrls[0];
-    if (!outputUrl) {
-      throw new ExtendServiceError("VIP98K 图像拓展未返回图片", 502);
+    try {
+      const result = await executeConfiguredVip98kTask({
+        modelId: "image-expansion",
+        kind: "image-tool",
+        prompt: `Expand the image canvas naturally to ${xScale}x width and ${yScale}x height. Preserve the original subject, perspective, lighting and style.`,
+        imageUrls: [imageUrl],
+        imageParams: { xScale, yScale },
+      });
+      const outputUrl = result.outputUrls[0];
+      if (!outputUrl) {
+        throw new ExtendServiceError("VIP98K 图像拓展未返回图片", 502);
+      }
+      return outputUrl;
+    } catch (error) {
+      if (!isTemporaryVip98kExpansionError(error)) throw error;
+      console.warn(
+        "[Extend Service] VIP98K expansion tool is temporarily unavailable; using VIP98K generative outpainting fallback",
+        error instanceof Error ? error.message : String(error),
+      );
+      return extendImageWithVip98kEditFallback(imageUrl, xScale, yScale);
     }
-    return outputUrl;
   }
 
   if (!config.apiKey) {

scripts/test-vip98k-capability.ts

@@ -145,8 +145,11 @@ async function fetchVip98kCatalog(params: { baseURL: string; apiKey: string }) {
   ).flatMap((section: any) => (Array.isArray(section?.models) ? section.models : []));
   if (authorized.length === 0) throw new Error("VIP98K authorized model catalog is empty");
   if (publicModels.length === 0) throw new Error("VIP98K public invocation catalog is empty");
-  const publicById = new Map(
-    publicModels.map((model: Vip98kCatalogModel) => [getModelId(model).toLowerCase(), model]),
+  const publicById = new Map<string, Vip98kCatalogModel>(
+    publicModels.map((model: Vip98kCatalogModel) => [
+      getModelId(model).toLowerCase(),
+      model,
+    ]),
   );
   return authorized.map((model: Vip98kCatalogModel) => ({
     ...(publicById.get(getModelId(model).toLowerCase()) || {}),