feat: support av

src/lib/server/av2bv.js

@@ -0,0 +1,32 @@
+// https://github.com/SocialSisterYi/bilibili-API-collect/blob/d4cb300051671443faee9493b57e6c35ef5bb526/docs/misc/bvid_desc.md?plain=1#L73-L105
+// Licensed under  CC-BY-NC 4.0
+
+const XOR_CODE = 23442827791579n;
+const MASK_CODE = 2251799813685247n;
+const MAX_AID = 1n << 51n;
+const BASE = 58n;
+
+const data = 'FcwAPNKTMug3GV5Lj7EJnHpWsx4tb8haYeviqBz6rkCy12mUSDQX9RdoZf';
+
+export function av2bv(aid) {
+  const bytes = ['B', 'V', '1', '0', '0', '0', '0', '0', '0', '0', '0', '0'];
+  let bvIndex = bytes.length - 1;
+  let tmp = (MAX_AID | BigInt(aid)) ^ XOR_CODE;
+  while (tmp > 0) {
+    bytes[bvIndex] = data[Number(tmp % BigInt(BASE))];
+    tmp = tmp / BASE;
+    bvIndex -= 1;
+  }
+  [bytes[3], bytes[9]] = [bytes[9], bytes[3]];
+  [bytes[4], bytes[7]] = [bytes[7], bytes[4]];
+  return bytes.join('');
+}
+
+export function bv2av(bvid) {
+  const bvidArr = Array.from(bvid);
+  [bvidArr[3], bvidArr[9]] = [bvidArr[9], bvidArr[3]];
+  [bvidArr[4], bvidArr[7]] = [bvidArr[7], bvidArr[4]];
+  bvidArr.splice(0, 3);
+  const tmp = bvidArr.reduce((pre, bvidChar) => pre * BASE + BigInt(data.indexOf(bvidChar)), 0n);
+  return Number((tmp & MASK_CODE) ^ XOR_CODE);
+}

src/lib/server/b23.ts

@@ -1,3 +1,5 @@
+import { av2bv } from './av2bv.js';
+
 const fetchRedirectUrl = async (url: URL | string): Promise<URL | null> => {
     try {
         const response = await fetch(url, { redirect: 'follow' });
@@ -19,6 +21,14 @@ const resolveB23 = async (str: string): Promise<string> => {
     let match: RegExpExecArray | null;
     let updatedString = str;
 
+    const avRegex = /\/av(\d+)/g;
+    if ((match = avRegex.exec(str)) !== null) {
+        let av = match[1];
+        const bv = av2bv(match[1]); 
+        console.info("av" + av + " -> " + bv);
+        updatedString = updatedString.replace("av" + av, bv);
+    }
+
     while ((match = urlRegex.exec(str)) !== null) {
         const originalUrl = match[0];
         const redirectedUrl = await fetchRedirectUrl(originalUrl);