From 7928e4a7d3311cc1325d413c53ff349e5ef816b5 Mon Sep 17 00:00:00 2001
From: Brian Cully <bjc@spork.org>
Date: Mon, 10 Mar 2025 16:23:07 -0400
Subject: scale: calculate diatonic scales

---
 key-picker.mjs | 18 +++++++++++-------
 scale.mjs      |  8 ++++++++
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/key-picker.mjs b/key-picker.mjs
index fe344ae..6d2efbe 100644
--- a/key-picker.mjs
+++ b/key-picker.mjs
@@ -1,4 +1,4 @@
-import { MajorScale, MinorScale, Note, chromaticScale } from "./scale.mjs";
+import { AugmentedScale, DiminishedScale, MajorScale, MinorScale, Note, allDiatonicScales } from "./scale.mjs";
 
 function scaleFrom(tonic, scale) {
     switch (scale) {
@@ -70,14 +70,18 @@ function formChanged(form) {
         Array.from(form.getElementsByClassName(c)).forEach(elt => elt.innerText = scale[i]);
     });
 
-    // todo: memoize this or put it in the scales module.
-    const allScales = chromaticScale.flatMap(tonic => {
-        return [MajorScale(tonic), MinorScale(tonic)];
-    })
+    function suffixFromIndex(i) {
+        switch (i % 2) {
+        case 0:
+            return '';
+        case 1:
+            return 'm';
+        }
+    }
 
     const availableScales =
-        allScales.reduce((acc, s, i) => {
-            const suffix = i % 2 == 0 ? '' : 'm';
+        allDiatonicScales.reduce((acc, s, i) => {
+            const suffix = suffixFromIndex(i);
             if (scale.includes(s.tonic) && scale.includes(s.third) && scale.includes(s.fifth)) {
                 return acc.concat(`${s.tonic}${suffix}`);
             }
diff --git a/scale.mjs b/scale.mjs
index 9bec03b..d33a5c3 100644
--- a/scale.mjs
+++ b/scale.mjs
@@ -182,3 +182,11 @@ export function MinorScale(tonic) {
     const intervals = [2, 1, 2, 2, 1, 2];
     return new Scale(tonic, intervals);
 }
+
+// well, a lot of them.
+export const allDiatonicScales = chromaticScale.flatMap(tonic => {
+    return [
+        MajorScale(tonic),
+        MinorScale(tonic)
+    ];
+})
-- 
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