From 7f7445eb64d8e0b46fafa9e55e6cf55ac046239d Mon Sep 17 00:00:00 2001
From: Nicolas Mafra <nickmafra@hotmail.com>
Date: Wed, 31 Jan 2024 18:54:10 -0300
Subject: [PATCH] feat: add PitchParser

---
 theory/PitchParser.mjs | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 theory/PitchParser.mjs

diff --git a/theory/PitchParser.mjs b/theory/PitchParser.mjs
new file mode 100644
index 0000000..c511829
--- /dev/null
+++ b/theory/PitchParser.mjs
@@ -0,0 +1,27 @@
+const notes = [ 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B' ];
+
+export default {
+    chromaToText(chroma) {
+        return notes[chroma];
+    },
+    textToChroma(text) {
+        const letter = text.substring(0, 1);
+        let chroma = notes.indexOf(letter);
+        if (text.includes('#')) chroma++;
+        if (text.includes('b')) chroma--;
+        return (chroma + 12) % 12;
+    },
+    pitchToText(midiNumber) {
+        const chroma = midiNumber % 12;
+        const octave = Math.floor(midiNumber / 12) - 1;
+
+        return this.chromaToText(chroma) + octave;
+    },
+    textToPitch(text) {
+        const chroma = this.textToChroma(text);
+        text = text.substring(1);
+        if (text.startsWith('#') || text.startsWith('b')) text = text.substring(1);
+        const octave = parseInt(text);
+        return 12 * (octave + 1) + chroma;
+    },
+};