feat(wechat): add image generation delivery policy

wechat-media.mjs

@@ -3,12 +3,15 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { fetch as undiciFetch } from 'undici';
+import sharp from 'sharp';
 import { buildPublicUrl, PUBLISH_ROOT_DIR, PUBLIC_ZONE_DIR } from './user-publish.mjs';
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
 const DEFAULT_WECHAT_MEDIA_URL = 'https://api.weixin.qq.com/cgi-bin/media/get';
+const DEFAULT_WECHAT_MEDIA_UPLOAD_URL = 'https://api.weixin.qq.com/cgi-bin/media/upload';
 const DEFAULT_MAX_IMAGE_BYTES = 10 * 1024 * 1024;
+const DEFAULT_MAX_OUTBOUND_IMAGE_BYTES = 2 * 1024 * 1024;
 const DEFAULT_MAX_ATTACHMENT_BYTES = 30 * 1024 * 1024;
 const ALLOWED_IMAGE_MIME_TYPES = new Map([
   ['image/jpeg', 'jpg'],
@@ -96,6 +99,93 @@ export async function downloadTemporaryMedia(accessToken, mediaId, { wechatFetch
   return { buffer, contentType };
 }
 
+async function normalizeWechatOutboundImage(buffer, maxBytes = DEFAULT_MAX_OUTBOUND_IMAGE_BYTES) {
+  ensureImageWithinLimit(buffer, DEFAULT_MAX_IMAGE_BYTES * 2);
+  const attempts = [
+    { width: 2048, quality: 86 },
+    { width: 1600, quality: 74 },
+    { width: 1280, quality: 62 },
+  ];
+  for (const attempt of attempts) {
+    const normalized = await sharp(buffer, { sequentialRead: true })
+      .rotate()
+      .resize({
+        width: attempt.width,
+        height: attempt.width,
+        fit: 'inside',
+        withoutEnlargement: true,
+      })
+      .flatten({ background: '#ffffff' })
+      .jpeg({ quality: attempt.quality, progressive: true, mozjpeg: true })
+      .toBuffer();
+    if (normalized.length <= maxBytes) {
+      return { buffer: normalized, contentType: 'image/jpeg', filename: 'memind-generated.jpg' };
+    }
+  }
+  throw new Error(`生成图片压缩后仍超过微信图片限制（${maxBytes} bytes）`);
+}
+
+export async function uploadWechatGeneratedImage(
+  accessToken,
+  publicUrl,
+  {
+    wechatFetch = undiciFetch,
+    publicBaseUrl = '',
+    uploadUrl = DEFAULT_WECHAT_MEDIA_UPLOAD_URL,
+    maxBytes = DEFAULT_MAX_OUTBOUND_IMAGE_BYTES,
+  } = {},
+) {
+  if (!accessToken) throw new Error('缺少微信 access_token');
+  if (!publicUrl) throw new Error('缺少生成图片公网地址');
+  const resolvedUrl = new URL(String(publicUrl), publicBaseUrl || undefined).toString();
+  if (publicBaseUrl && new URL(resolvedUrl).origin !== new URL(publicBaseUrl).origin) {
+    throw new Error('生成图片地址不属于当前 MindSpace 公网域名');
+  }
+  const sourceResponse = await wechatFetch(resolvedUrl, {
+    method: 'GET',
+    headers: { Accept: 'image/*,*/*;q=0.8' },
+  });
+  if (!sourceResponse.ok) {
+    const text = await sourceResponse.text().catch(() => '');
+    throw new Error(text || `生成图片下载失败 (${sourceResponse.status})`);
+  }
+  const declaredBytes = Number(sourceResponse.headers.get('content-length') ?? 0);
+  if (Number.isFinite(declaredBytes) && declaredBytes > DEFAULT_MAX_IMAGE_BYTES * 2) {
+    throw new Error('生成图片下载体积超过安全限制');
+  }
+  const sourceBuffer = Buffer.from(await sourceResponse.arrayBuffer());
+  const normalized = await normalizeWechatOutboundImage(sourceBuffer, maxBytes);
+  const form = new FormData();
+  form.append(
+    'media',
+    new Blob([normalized.buffer], { type: normalized.contentType }),
+    normalized.filename,
+  );
+  const endpoint = new URL(uploadUrl);
+  endpoint.searchParams.set('access_token', accessToken);
+  endpoint.searchParams.set('type', 'image');
+  const response = await wechatFetch(endpoint.toString(), {
+    method: 'POST',
+    body: form,
+  });
+  const text = await response.text().catch(() => '');
+  let payload = {};
+  try {
+    payload = text ? JSON.parse(text) : {};
+  } catch {
+    payload = {};
+  }
+  if (!response.ok || Number(payload?.errcode ?? 0) !== 0 || !String(payload?.media_id ?? '').trim()) {
+    const detail = String(payload?.errmsg ?? text ?? '').trim() || `HTTP ${response.status}`;
+    throw new Error(`微信生成图片素材上传失败：${detail}`);
+  }
+  return {
+    mediaId: String(payload.media_id),
+    bytes: normalized.buffer.length,
+    contentType: normalized.contentType,
+  };
+}
+
 export function buildWechatImagePublicUrl({
   publicBaseUrl,
   publishKey,