faet: add support of xmly android (#1)

src/decrypt-worker/crypto/xmly/xmly_android.ts

@@ -0,0 +1,29 @@
+import { transformBlob } from '~/decrypt-worker/util/transformBlob';
+import type { CryptoBase } from '../CryptoBase.js';
+import { XimalayaAndroidKey, XimalayaX2MKey, XimalayaX3MKey } from './xmly_android.key.js';
+
+export class XimalayaAndroidCrypto implements CryptoBase {
+  cryptoName = 'Ximalaya/Android';
+  checkByDecryptHeader = true;
+  constructor(private key: XimalayaAndroidKey) {}
+
+  async decrypt(buffer: ArrayBuffer): Promise<Blob> {
+    const { contentKey, init, step } = this.key;
+    return transformBlob(buffer, (p) => {
+      const transformer = p.make.XimalayaAndroid(init, step, contentKey);
+      if (!transformer) {
+        throw new Error('could not make xmly transformer, is key invalid?');
+      }
+
+      return transformer;
+    });
+  }
+
+  public static makeX2M() {
+    return new XimalayaAndroidCrypto(XimalayaX2MKey);
+  }
+
+  public static makeX3M() {
+    return new XimalayaAndroidCrypto(XimalayaX3MKey);
+  }
+}