bridge functionality for midi

packages/midi/midibridge.mjs

@@ -0,0 +1,58 @@
+import { invoke } from '@tauri-apps/api/tauri';
+import { noteToMidi } from '@strudel.cycles/core';
+
+const ON_MESSAGE = 0x90;
+const OFF_MESSAGE = 0x80;
+
+export function playNote(hap, offset, output) {
+  const { note, nrpnn, nrpv, ccn, ccv } = hap.value;
+  const velocity = Math.floor((hap.context?.velocity ?? 0.9) * 100); // TODO: refactor velocity
+  const duration = Math.floor(hap.duration.valueOf() * 1000 - 10);
+  const roundedOffset = Math.round(offset);
+  const midichan = (hap.value.midichan ?? 1) - 1;
+  const requestedport = output ?? 'IAC';
+  const messagesfromjs = [];
+  if (note != null) {
+    const midiNumber = typeof note === 'number' ? note : noteToMidi(note);
+
+    messagesfromjs.push({
+      requestedport,
+      message: [ON_MESSAGE + midichan, midiNumber, velocity],
+      offset: roundedOffset,
+    });
+
+    messagesfromjs.push({
+      requestedport,
+      message: [OFF_MESSAGE + midichan, midiNumber, velocity],
+      offset: roundedOffset + duration,
+    });
+  }
+
+  if (ccv && ccn) {
+    if (typeof ccv !== 'number' || ccv < 0 || ccv > 1) {
+      throw new Error('expected ccv to be a number between 0 and 1');
+    }
+    if (!['string', 'number'].includes(typeof ccn)) {
+      throw new Error('expected ccn to be a number or a string');
+    }
+    const scaled = Math.round(ccv * 127);
+    messagesfromjs.push({
+      requestedport,
+      message: [ON_MESSAGE + midichan, ccn, scaled],
+      offset: roundedOffset,
+    });
+
+    messagesfromjs.push({
+      requestedport,
+      message: [OFF_MESSAGE + midichan, ccn, scaled],
+      offset: roundedOffset + duration,
+    });
+  }
+
+  // invoke is temporarily blocking, run in an async process
+  if (messagesfromjs.length) {
+    setTimeout(() => {
+      invoke('sendmidi', { messagesfromjs });
+    });
+  }
+}