From 94ae50b2f20fbe413175e9ee6efab4ba117d19b1 Mon Sep 17 00:00:00 2001
From: Be <be@mixxx.org>
Date: Sun, 14 Jun 2020 15:43:41 -0500
Subject: [PATCH] add MidiDispatcher module in new res/controllers/lib folder

---
 res/controllers/lib/mididispatcher.mjs | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 res/controllers/lib/mididispatcher.mjs

diff --git a/res/controllers/lib/mididispatcher.mjs b/res/controllers/lib/mididispatcher.mjs
new file mode 100644
index 000000000000..367a247d54b6
--- /dev/null
+++ b/res/controllers/lib/mididispatcher.mjs
@@ -0,0 +1,24 @@
+export class MidiDispatcher {
+    constructor(noteOff) {
+        this.noteOff = noteOff;
+        this.inputMap = new Map();
+    }
+    registerInputCallback(midiBytes, callback) {
+        // JavaScript is broken and believes [1,2] === [1,2] is false, so
+        // JSONify the Array to make it usable as a Map key.
+        const key = JSON.stringify(midiBytes);
+        this.inputMap.set(key, callback);
+        if (this.noteOff === true && ((midiBytes[0] & 0xF0) === 0x90)) {
+            const noteOffBytes = [midiBytes[0] - 0x10, midiBytes[1]];
+            const noteOffKey = JSON.stringify(noteOffBytes);
+            this.inputMap.set(noteOffKey, callback);
+        }
+    }
+    receiveData(data, timestamp) {
+        const key = JSON.stringify([data[0], data[1]]);
+        const callback = this.inputMap.get(key);
+        if (typeof callback === 'function') {
+            callback(data, timestamp);
+        }
+    }
+}