Carry out MIDI input wrapper into dedicated file

packages/midi/util.mjs

@@ -0,0 +1,38 @@
+import { Input, Output } from 'webmidi';
+
+/**
+ * Get a string listing device names for error messages.
+ * @param {Input[] | Output[]} devices
+ * @returns {string}
+ */
+export function getMidiDeviceNamesString(devices) {
+  return devices.map((o) => `'${o.name}'`).join(' | ');
+}
+
+/**
+ * Look up a device by index or name. Otherwise return a default device, or fail if none are connected.
+ *
+ * @param {string | number} indexOrName
+ * @param {Input[] | Output[]} devices
+ * @returns {Input | Output | undefined}
+ */
+export function getDevice(indexOrName, devices) {
+  if (typeof indexOrName === 'number') {
+    return devices[indexOrName];
+  }
+  const byName = (name) => devices.find((output) => output.name.includes(name));
+  if (typeof indexOrName === 'string') {
+    return byName(indexOrName);
+  }
+  // attempt to default to first IAC device if none is specified
+  const IACOutput = byName('IAC');
+  const device = IACOutput ?? devices[0];
+  if (!device) {
+    if (!devices.length) {
+      throw new Error(`🔌 No MIDI devices found. Connect a device or enable IAC Driver.`);
+    }
+    throw new Error(`🔌 Default MIDI device not found. Use one of ${getMidiDeviceNamesString(devices)}`);
+  }
+
+  return device;
+}