From 53631ad1ef5497017f00f56608649e9bee90b264 Mon Sep 17 00:00:00 2001
From: Brian Cully <bjc@spork.org>
Date: Sun, 9 Mar 2025 16:50:07 -0400
Subject: add display for available chords in the key

---
 index.html     | 18 +++++++++++++++++-
 key-picker.mjs | 25 ++++++++++++++++++++++++-
 main.css       | 11 +++++++++++
 scale.mjs      |  1 -
 4 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/index.html b/index.html
index aa2c60a..055fdcb 100644
--- a/index.html
+++ b/index.html
@@ -101,12 +101,17 @@
         <label for='tonic'>tonic:</label>
         <select id='tonic' name='tonic'>
           <option value='A'>A</option>
+          <option value='A#'>A#</option>
           <option value='B'>B</option>
           <option value='C' selected>C</option>
+          <option value='C#'>C#</option>
           <option value='D'>D</option>
+          <option value='D#'>D#</option>
           <option value='E'>E</option>
           <option value='F'>F</option>
+          <option value='F#'>F#</option>
           <option value='G'>G</option>
+          <option value='G#'>G#</option>
         </select>
         <label for='diatonic'>diatonic:</label>
         <select id='diatonic' name='diatonic'>
@@ -117,7 +122,7 @@
         <hr>
 
         <ol class='notes'>
-          <li class='first'>C</li>
+          <li class='tonic'>C</li>
           <li class='second'>D</li>
           <li class='third'>E</li>
           <li class='fourth'>F</li>
@@ -125,6 +130,17 @@
           <li class='sixth'>A</li>
           <li class='seventh'>B</li>
         </ol>
+        <hr>
+
+        <p>Available chords:</p>
+        <ul class='chords'>
+          <li>Amin</li>
+          <li>C</li>
+          <li>Dmin</li>
+          <li>Emin</li>
+          <li>F</li>
+          <li>G</li>
+        </ul>
       </fieldset>
     </form>
 
diff --git a/key-picker.mjs b/key-picker.mjs
index bd6482a..fc6b4ed 100644
--- a/key-picker.mjs
+++ b/key-picker.mjs
@@ -14,9 +14,32 @@ function scaleFrom(tonic, diatonic) {
 function formChanged(form) {
     const formData = new FormData(form);
     const scale = scaleFrom(formData.get('tonic'), formData.get('diatonic'));
-    ['first', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh'].forEach((c, i) => {
+    ['tonic', 'second', 'third', 'fourth', 'fifth', 'sixth', 'seventh'].forEach((c, i) => {
         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)];
+    })
+
+    const availableScales =
+        allScales.reduce((acc, s, i) => {
+            const suffix = i % 2 == 0 ? '' : 'min';
+            if (scale.includes(s.tonic) && scale.includes(s.third) && scale.includes(s.fifth)) {
+                return acc.concat(`${s.tonic}${suffix}`);
+            }
+            return acc;
+        }, []);
+    Array.from(form.getElementsByClassName('chords')).forEach(list => {
+        const items = availableScales.map(s => {
+            const elt = document.createElement('li');
+            elt.innerText = s;
+            return elt;
+        });
+        list.replaceChildren();
+        items.forEach(item => list.appendChild(item));
+    });
 }
 
 function handleFormChanged(e) {
diff --git a/main.css b/main.css
index 77b282a..49f3ba3 100644
--- a/main.css
+++ b/main.css
@@ -67,3 +67,14 @@ body {
     counter-increment: notes;
     text-align: center;
 }
+
+#key-picker .chords {
+    display: grid;
+    grid-template-rows: 1;
+    grid-template-columns: 4em 4em 4em 4em 4em 4em;
+    padding-left: 0;
+}
+
+#key-picker .chords li {
+    display: grid;
+}
diff --git a/scale.mjs b/scale.mjs
index 045265b..9e0e122 100644
--- a/scale.mjs
+++ b/scale.mjs
@@ -61,7 +61,6 @@ class Scale {
     }
 
     get length() {
-        console.debug(`get length`, this.scale.length);
         return this.scale.length;
     }
 
-- 
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