1export interface WechatHttpInit {
2  method?: string;
3  headers?: Record<string, string>;
4  body?: string | Buffer;
5}
6 
7export interface WechatHttpResponse {
8  status: number;
9  statusText: string;
10  headers: Record<string, string | string[] | undefined>;
11  buffer(): Promise<Buffer>;
12  text(): Promise<string>;
13  json<T = unknown>(): Promise<T>;
14}
15 
16export type WechatClient = (
17  url: string,
18  init?: WechatHttpInit,
19) => Promise<WechatHttpResponse>;
20 
21export interface MultipartFilePart {
22  name: string;
23  filename: string;
24  contentType: string;
25  data: Buffer;
26}
27 
28export interface MultipartBody {
29  contentType: string;
30  body: Buffer;
31}
32 
33export function buildMultipart(parts: MultipartFilePart[]): MultipartBody {
34  const boundary = `----WebKitFormBoundary${Date.now().toString(16)}${Math.random().toString(16).slice(2, 10)}`;
35  const chunks: Buffer[] = [];
36 
37  for (const part of parts) {
38    const header =
39      `--${boundary}\r\n` +
40      `Content-Disposition: form-data; name="${part.name}"; filename="${part.filename}"\r\n` +
41      `Content-Type: ${part.contentType}\r\n\r\n`;
42    chunks.push(Buffer.from(header, "utf-8"));
43    chunks.push(part.data);
44    chunks.push(Buffer.from("\r\n", "utf-8"));
45  }
46  chunks.push(Buffer.from(`--${boundary}--\r\n`, "utf-8"));
47 
48  return {
49    contentType: `multipart/form-data; boundary=${boundary}`,
50    body: Buffer.concat(chunks),
51  };
52}
53 
54function headersToRecord(headers: Headers): Record<string, string | string[] | undefined> {
55  const out: Record<string, string | string[] | undefined> = {};
56  headers.forEach((value, key) => {
57    const existing = out[key];
58    if (existing === undefined) {
59      out[key] = value;
60    } else if (Array.isArray(existing)) {
61      existing.push(value);
62    } else {
63      out[key] = [existing, value];
64    }
65  });
66  return out;
67}
68 
69export const wechatHttp: WechatClient = async (url, init = {}) => {
70  const method = init.method ?? (init.body !== undefined ? "POST" : "GET");
71  const headers: Record<string, string> = { ...(init.headers ?? {}) };
72 
73  let body: BodyInit | undefined;
74  if (init.body !== undefined) {
75    body = Buffer.isBuffer(init.body)
76      ? new Uint8Array(init.body.buffer, init.body.byteOffset, init.body.byteLength)
77      : init.body;
78  }
79 
80  const res = await fetch(url, { method, headers, body });
81  const buf = Buffer.from(await res.arrayBuffer());
82 
83  return {
84    status: res.status,
85    statusText: res.statusText,
86    headers: headersToRecord(res.headers),
87    async buffer() {
88      return buf;
89    },
90    async text() {
91      return buf.toString("utf-8");
92    },
93    async json<T = unknown>() {
94      return JSON.parse(buf.toString("utf-8")) as T;
95    },
96  };
97};
98