Implement authorization bearer token user prompt

If there is no saved token, we show the Spotify web site and intercept the user's login to grab the token and store it. Then we continue as usual. If the token is stored, we grab it from the disk cache and get right to business.

This doesn't solve for token expiration, which I will implement later most probably by extracting the token prompt logic to its own file and re-displaying the Spotify web page window so the user can login again and refresh the token.

.gitignore

@@ -2,3 +2,4 @@ node_modules
 bun.lockb
 lyrics/*
 !lyrics/.gitkeep
+token.json

index.js

@@ -4,6 +4,46 @@ import fs from 'fs';
 import askSpotify from './askSpotify.js';
 
 electron.app.on('ready', async () => {
+  /** @type {string} */
+  let authorization;
+
+  const path = `token.json`;
+  try {
+    await fs.promises.access(path);
+
+    console.log('Loading bearer token…');
+    authorization = JSON.parse(await fs.promises.readFile(path));
+    console.log('Loaded bearer token');
+  }
+  catch (error) {
+    if (error.code !== 'ENOENT') {
+      console.log(`Failed to load bearer token: ${error}`);
+    }
+
+    console.log('Obtaining bearer token…');
+    const window = new electron.BrowserWindow({ width: 800, height: 600 });
+    window.loadURL('https://open.spotify.com/');
+
+    authorization = await new Promise((resolve) => {
+      electron.session.defaultSession.webRequest.onSendHeaders(
+        { urls: ['https://gew4-spclient.spotify.com/*'] },
+        (details) => {
+          if (authorization) {
+            return;
+          }
+
+          if (details.requestHeaders['authorization']) {
+            resolve(details.requestHeaders['authorization']);
+          }
+        }
+      );
+    });
+
+    window.close();
+    await fs.promises.writeFile(path, JSON.stringify(authorization, null, 2));
+    console.log('Obtained bearer token');
+  }
+
   // Hide the Dock icon for the application
   electron.app.dock.hide();
 
@@ -31,7 +71,7 @@ electron.app.on('ready', async () => {
 
   /** @typedef {{ timeTag: string; words: string; }} Line */
 
-  /** @type {{ artist: string; song: string; error: boolean; message?: string; syncType: 'LINE_SYNCED' | 'UNSYNCED'; lines: Line[]; } | undefined} */
+  /** @type {({ artist: string; song: string; } & ({ error: string; } | { syncType: 'LINE_SYNCED' | 'UNSYNCED'; lines: Line[]; })) | undefined} */
   let lyrics;
 
   /** @type {Line | undefined} */
@@ -70,8 +110,7 @@ electron.app.on('ready', async () => {
         }
         case 'LINE_SYNCED': {
           {
-            const stamp = `${(~~(position / 60)).toString().padStart('00'.length, '0')}:${(position % 60).toFixed(2).toString().padStart('00.00'.length, '0')}`;
-            const index = lyrics.lines.findIndex(line => line.timeTag >= stamp);
+            const index = lyrics.lines.findIndex(line => line.startTimeMs >= position * 1000);
             const _line = lyrics.lines[index - 1];
             if (_line !== line) {
               line = _line;
@@ -152,18 +191,23 @@ electron.app.on('ready', async () => {
         console.log(`Downloading lyrics for ${artist} - ${song} (${id})…`);
 
         // Download LRC (timestamped) lyrics from the unofficial Spotify Lyrics API
-        // See https://github.com/akashrchandran/spotify-lyrics-api
-        const apiUrl = `https://spotify-lyric-api.herokuapp.com/?trackid=${id}&format=lrc`;
-        const apiJson = await fetch(apiUrl, { headers: { 'User-Agent': 'Firefox' } }).then(response => response.json());
+        // Inspect the `open.spotify.com` developer tools `lyrics` network call to maintain this 
+        const response = await fetch(`https://spclient.wg.spotify.com/color-lyrics/v2/track/${id}?format=json`, { headers: { authorization, 'app-platform': 'WebPlayer' } });
+        if (response.ok) {
+          const data = await response.json();
 
-        lyrics = { artist, song, ...apiJson };
-        await fs.promises.writeFile(path, JSON.stringify(lyrics, null, 2));
+          lyrics = { artist, song, ...data.lyrics };
+          await fs.promises.writeFile(path, JSON.stringify(lyrics, null, 2));
 
-        console.log(`Downloaded lyrics for ${artist} - ${song}`);
+          console.log(`Downloaded lyrics for ${artist} - ${song} (${id})`);
+        }
+        else {
+          lyrics = { artist, song, error: response.statusText };
+        }
       }
 
       if (lyrics.error) {
-        console.log(`Lyrics error for ${artist} - ${song}: ${lyrics.message ?? 'unknown error'}`);
+        console.log(`Lyrics error for ${artist} - ${song} (${id}): ${lyrics.error}`);
       }
     }