add trading in the rain post

1 files changed, 70 insertions, 0 deletions

diff --git a/assets/trading-in-the-rain/MusicBox.js b/assets/trading-in-the-rain/MusicBox.js
new file mode 100644
index 0000000..a30074c
--- /dev/null
+++ b/assets/trading-in-the-rain/MusicBox.js
@@ -0,0 +1,70 @@
+var midiLoaded = false;
+function loadMIDI() {
+  MIDI.loadPlugin({
+    soundfontUrl: "/assets/trading-in-the-rain/soundfont/",
+    instrument: "acoustic_grand_piano",
+    onprogress: (state, progress) => {
+      console.log("MIDI loading...", progress*100, "%");
+    },
+    onsuccess: () => {
+      console.log("MIDI is ready to be used");
+      MIDI.setVolume(0, 127);
+      midiLoaded = true;
+    },
+  });
+}
+
+function MusicBox(priceDist, volumeDist) {
+  this.priceDist = priceDist;
+  this.volumeDist = volumeDist;
+
+  // clamp the keyboard so we're not using the very low notes, they don't sound
+  // good.
+  const noteRange = {
+    //low: 21,
+    //low: 36, // C2
+    low: 60, // C4, middle C
+    high: 108
+  };
+
+
+  function makeScale(tpl) {
+    tplObj = {};
+    for (i in tpl) {
+      tplObj[tpl[i]] = true;
+    }
+  
+    let scale = [];
+    for (let note=noteRange.low; note<=noteRange.high; note++) {
+      let key = MIDI.noteToKey[note].replace(/\d+$/, "");
+      if (tplObj[key]) {
+        scale.push(note);
+      }
+    }
+    return scale;
+  }
+
+  //this.scale = makeScale(["C", "D", "E", "F", "G", "A", "B"]); // cMajor
+  //this.scale = makeScale(["D", "E", "Gb", "G", "A", "Db"]); //dMajor
+  //this.scale = makeScale(["C", "D", "E", "G", "A"]); // cMajor pentatonic
+  this.scale = makeScale(["F", "G", "A", "C", "D"]); // fMajor pentatonic
+
+  this.playNote = (note, holdFor) => {
+    if (!midiLoaded) return;
+    let velocity = 127;
+    MIDI.noteOn(0, note, velocity, 0);
+    MIDI.noteOff(0, note, holdFor);
+  };
+
+  this.playTrades = (trades) => {
+    if (this.priceDist.length == 0) return;
+    for (let i in trades) {
+      let noteIdx = this.priceDist.distribute(trades[i].price, 0, this.scale.length-1);
+      noteIdx = Math.round(noteIdx);
+
+      let holdFor = 0.25 + this.volumeDist.distribute(trades[i].volume, 0, 1.75);
+      let note = this.scale[noteIdx];
+      this.playNote(note, holdFor);
+    }
+  };
+}