feat(users/Profpatsch/lyric): add vscode extension & helpers

* tap-bpm: simple CLI program that accepts key inputs and averages a
BPM value

* lyric-timing-mpv-script: If you press Ctrl+l, mpv attaches the
  current timestamp to a .lrc file named after the song.
  This is for manually timing missing songs for uploading them to
  https://lrclib.net/

* extension: vscode extension for `.lrc` files, currently with the
  following features:

    1. A “jump to LRC position” command which reads an .lrc timestamp
    from the current line and expects mpv to listen on
    `~/tmp/mpv-socket` (via `--input-ipc-server`), and will seek to
    the exact timestamp (down to the ms) in the currently playing
    song.

    2. Some initial linting warnings

      - A lint that warns if the difference to the next timestamp is
      more than 10s (which usually means there’s an instrumental and
      the previous line is stuck)

      - A lint that checks that timestamps are monotonically
      increasing

Change-Id: I32a4ac0e2c5bbe3d94e45ffcf647f81bc7c08aa0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12537
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/Profpatsch/lyric/src/index.ts

@@ -0,0 +1,16 @@
+import { tapBpm } from "./tap-bpm.js";
+
+async function main() {
+  // subcommand for tap-bpm
+  if (process.argv[2] === "tap-bpm") {
+    await tapBpm();
+  }
+}
+
+await main();
+
+// sleep in a loop to block nodejs
+console.log("Blocking event loop...");
+while (true) {
+  await new Promise((resolve) => setTimeout(resolve, 1000));
+}

users/Profpatsch/lyric/src/tap-bpm.ts

@@ -0,0 +1,79 @@
+// create a node command line listener that allows the user to press any key , and averages the distances between the key presses to determine the BPM (with a window of 4 key presses). If the user presses q, the program should exit and print the final BPM.
+
+// Import the necessary modules
+import * as readline from "readline";
+
+export function tapBpm() {
+  // Set up readline interface to listen for keypresses
+  readline.emitKeypressEvents(process.stdin);
+  process.stdin.setRawMode(true);
+  // accept SIGINT on stdin
+
+  // Array to store the time differences between the last 4 key presses
+  const timeDifferences: number[] = [];
+  let lastPressTime: number | null = null;
+
+  // Function to calculate BPM based on average time between keypresses
+  function calculateBPM() {
+    if (timeDifferences.length < 1) {
+      return 0;
+    }
+    const averageTimeDiff =
+      timeDifferences.reduce((acc, curr) => acc + curr, 0) /
+      timeDifferences.length;
+    return (60 * 1000) / averageTimeDiff;
+  }
+
+  // Handle the SIGINT (Ctrl+C) event manually
+  process.on("SIGINT", () => {
+    console.log(
+      "\nExiting via SIGINT (Ctrl+C)... Final BPM:",
+      calculateBPM().toFixed(2)
+    );
+    process.exit();
+  });
+
+  // Listen for keypress events
+  process.stdin.on("keypress", (str, key) => {
+    // Exit if 'q' is pressed
+    if (key.name === "q") {
+      console.log("Exiting... Final BPM:", calculateBPM().toFixed(2));
+      process.exit();
+    }
+
+    // Handle Ctrl+C (SIGINT)
+    if (key.sequence === "\u0003") {
+      // '\u0003' is the raw code for Ctrl+C
+      console.log(
+        "\nExiting via Ctrl+C... Final BPM:",
+        calculateBPM().toFixed(2)
+      );
+      process.exit();
+    }
+
+    // Capture the current time of the keypress
+    const currentTime = Date.now();
+
+    // If it's not the first keypress, calculate the time difference
+    if (lastPressTime !== null) {
+      const timeDiff = currentTime - lastPressTime;
+
+      // Add the time difference to the array (limit to last 10 key presses)
+      if (timeDifferences.length >= 10) {
+        timeDifferences.shift(); // Remove the oldest time difference
+      }
+      timeDifferences.push(timeDiff);
+
+      // Calculate and display the BPM
+      const bpm = calculateBPM();
+      console.log("Current BPM:", bpm.toFixed(2));
+    } else {
+      console.log("Waiting for more key presses to calculate BPM...");
+    }
+
+    // Update the lastPressTime to the current time
+    lastPressTime = currentTime;
+  });
+
+  console.log('Press any key to calculate BPM, press "q" to quit.');
+}