refactor(Player.ts): Handle nsig failure gracefully

Preping for future changes.

src/core/Player.ts

@@ -8,16 +8,16 @@ const TAG = 'Player';
  * Represents YouTube's player script. This is required to decipher signatures.
  */
 export default class Player {
-  nsig_sc;
-  sig_sc;
-  sts;
-  player_id;
+  player_id: string;
+  sts: number;
+  nsig_sc?: string;
+  sig_sc?: string;
 
-  constructor(signature_timestamp: number, sig_sc: string, nsig_sc: string, player_id: string) {
+  constructor(player_id: string, signature_timestamp: number, sig_sc?: string, nsig_sc?: string) {
+    this.player_id = player_id;
+    this.sts = signature_timestamp;
     this.nsig_sc = nsig_sc;
     this.sig_sc = sig_sc;
-    this.sts = signature_timestamp;
-    this.player_id = player_id;
   }
 
   static async create(cache: ICache | undefined, fetch: FetchFunction = Platform.shim.fetch): Promise<Player> {
@@ -67,7 +67,7 @@ export default class Player {
 
     Log.info(TAG, `Got signature timestamp (${sig_timestamp}) and algorithms needed to decipher signatures.`);
 
-    return await Player.fromSource(cache, sig_timestamp, sig_sc, nsig_sc, player_id);
+    return await Player.fromSource(player_id, sig_timestamp, cache, sig_sc, nsig_sc);
   }
 
   decipher(url?: string, signature_cipher?: string, cipher?: string, this_response_nsig_cache?: Map<string, string>): string {
@@ -79,7 +79,7 @@ export default class Player {
     const args = new URLSearchParams(url);
     const url_components = new URL(args.get('url') || url);
 
-    if (signature_cipher || cipher) {
+    if (this.sig_sc && (signature_cipher || cipher)) {
       const signature = Platform.shim.eval(this.sig_sc, {
         sig: args.get('s')
       });
@@ -98,7 +98,7 @@ export default class Player {
 
     const n = url_components.searchParams.get('n');
 
-    if (n) {
+    if (this.nsig_sc && n) {
       let nsig;
 
       if (this_response_nsig_cache && this_response_nsig_cache.has(n)) {
@@ -174,17 +174,18 @@ export default class Player {
     const sig_sc = LZW.decompress(new TextDecoder().decode(sig_buf));
     const nsig_sc = LZW.decompress(new TextDecoder().decode(nsig_buf));
 
-    return new Player(sig_timestamp, sig_sc, nsig_sc, player_id);
+    return new Player(player_id, sig_timestamp, sig_sc, nsig_sc);
   }
 
-  static async fromSource(cache: ICache | undefined, sig_timestamp: number, sig_sc: string, nsig_sc: string, player_id: string): Promise<Player> {
-    const player = new Player(sig_timestamp, sig_sc, nsig_sc, player_id);
+  static async fromSource(player_id: string, sig_timestamp: number, cache?: ICache, sig_sc?: string, nsig_sc?: string): Promise<Player> {
+    const player = new Player(player_id, sig_timestamp, sig_sc, nsig_sc);
     await player.cache(cache);
     return player;
   }
 
   async cache(cache?: ICache): Promise<void> {
-    if (!cache) return;
+    if (!cache || !this.sig_sc || !this.nsig_sc)
+      return;
 
     const encoder = new TextEncoder();
 
@@ -219,13 +220,13 @@ export default class Player {
     return `function descramble_sig(a) { a = a.split(""); let ${obj_name}={${functions}}${calls} return a.join("") } descramble_sig(sig);`;
   }
 
-  static extractNSigSourceCode(data: string): string {
+  static extractNSigSourceCode(data: string): string | undefined {
     const match = data.match(/b=(?:a\.split\(|String\.prototype\.split\.call\(a,)""\).*?\}return (?:b\.join\(|Array\.prototype\.join\.call\(b,)""\)\}/s);
 
     // Don't throw an error here.
     if (!match) {
       Log.warn(TAG, 'Failed to extract nsig decipher algorithm.');
-      return 'function descramble_nsig(a) { return a } descramble_nsig(nsig);';
+      return;
     }
 
     return `function descramble_nsig(a) { let ${match[0]} descramble_nsig(nsig)`;