Add kick sequencer

1 files changed, 68 insertions, 0 deletions

diff --git a/src/view/sequencer/play.ts b/src/view/sequencer/play.ts
new file mode 100644
index 0000000..9ff9c81
--- /dev/null
+++ b/src/view/sequencer/play.ts
@@ -0,0 +1,68 @@
+import h, { classNames } from 'lib/h'
+import * as time from 'lib/time'
+import * as soundsLib from 'sounds'
+
+const MIN_BPM: number = 1
+const MAX_BPM: number = 1000
+
+interface Params {
+  onNextStep: (sounds: soundsLib.Sounds) => void,
+  onStop: () => void
+}
+
+export function view({ onNextStep, onStop }: Params) {
+  let bpm = 60
+  let isPlaying = false
+  let lastBeat: undefined | number = undefined
+
+  return h('div', {},
+    h('button',
+      { className: 'g-PlayStop',
+        onclick: async (e: Event) => {
+          const target = e.target as HTMLButtonElement
+          isPlaying = !isPlaying
+          target.innerText = isPlaying ? '■' : '▶'
+
+          let sounds = await soundsLib.load()
+          let step = (timestamp: number) => {
+            if (lastBeat === undefined || timestamp - lastBeat > 1000 * 60 / bpm) {
+              lastBeat = timestamp
+              onNextStep(sounds)
+            }
+
+            if (isPlaying) window.requestAnimationFrame(step)
+          }
+
+          if (isPlaying) {
+            window.requestAnimationFrame(step)
+          } else {
+            onStop()
+          }
+        }
+      },
+      '▶'
+    )
+    , h('label', 
+      { className: 'g-Bpm' },
+      'BPM',
+      h('input', 
+        { className: 'g-Input', 
+          type: 'number', 
+          value: bpm,
+          min: MIN_BPM,
+          max: MAX_BPM,
+          oninput: time.debounce(
+            (e: Event) => {
+              const target = e.target as HTMLInputElement
+              const n = parseInt(target.value)
+              if (n >= MIN_BPM && n <= MAX_BPM) {
+                bpm = n
+              }
+            },
+            1000
+          )
+        }
+      )
+    )
+  )
+}