move core repl + add package

packages/webaudio/clockworker.mjs

@@ -0,0 +1,69 @@
+// helpers to create a worker dynamically without needing a server / extra file
+const stringifyFunction = (func) => '(' + func + ')();';
+const urlifyFunction = (func) => URL.createObjectURL(new Blob([stringifyFunction(func)], { type: 'text/javascript' }));
+const createWorker = (func) => new Worker(urlifyFunction(func));
+
+// this class is basically the tale of two clocks
+class ClockWorker {
+  worker;
+  audioContext;
+  interval = 0.2; // query span
+  lastEnd = 0;
+  constructor(audioContext, callback, interval = this.interval) {
+    this.audioContext = audioContext;
+    this.interval = interval;
+    this.worker = createWorker(() => {
+      // we cannot use closures here!
+      let interval;
+      let timerID = null; // this is clock #1 (the sloppy js clock)
+      const clear = () => {
+        if (timerID) {
+          clearInterval(timerID);
+          timerID = null;
+        }
+      };
+      const start = () => {
+        clear();
+        if (!interval) {
+          throw new Error('no interval set! call worker.postMessage({interval}) before starting.');
+        }
+        timerID = setInterval(() => postMessage('tick'), interval * 1000);
+      };
+      self.onmessage = function (e) {
+        if (e.data == 'start') {
+          start();
+        } else if (e.data.interval) {
+          interval = e.data.interval;
+          if (timerID) {
+            start();
+          }
+        } else if (e.data == 'stop') {
+          clear();
+        }
+      };
+    });
+    this.worker.postMessage({ interval });
+    // const round = (n, d) => Math.round(n * d) / d;
+    const precision = 100;
+    this.worker.onmessage = (e) => {
+      if (e.data === 'tick') {
+        const begin = this.lastEnd || this.audioContext.currentTime;
+        const end = this.audioContext.currentTime + this.interval; // DONT reference begin here!
+        this.lastEnd = end;
+        // callback with query span, using clock #2 (the audio clock)
+        callback(begin, end);
+      }
+    };
+  }
+  start() {
+    console.log('start...');
+    this.audioContext.resume();
+    this.worker.postMessage('start');
+  }
+  stop() {
+    console.log('stop...');
+    this.worker.postMessage('stop');
+  }
+}
+
+export default ClockWorker;