Add kick sequencer

8 files changed, 268 insertions, 0 deletions

diff --git a/src/lib/h.ts b/src/lib/h.ts
new file mode 100644
index 0000000..8b1abf3
--- /dev/null
+++ b/src/lib/h.ts
@@ -0,0 +1,34 @@
+type Child = Element | Text | string | number
+
+export default function h(
+  tagName: string,
+  attrs: object,
+  ...children: Child[]
+): Element {
+  const isSvg = tagName === 'svg' || tagName === 'path'
+
+  let elem = isSvg
+    ? document.createElementNS('http://www.w3.org/2000/svg', tagName)
+    : document.createElement(tagName)
+
+  if (isSvg) {
+    Object.entries(attrs).forEach(([key, value]) => {
+      elem.setAttribute(key, value)
+    })
+  } else {
+    elem = Object.assign(elem, attrs)
+  }
+
+  for (const child of children) {
+    if (typeof child === 'number')
+      elem.append(child.toString())
+    else
+      elem.append(child)
+  }
+
+  return elem
+}
+
+export function classNames(obj: {[key: string]: boolean }): string {
+  return Object.keys(obj).filter(k => obj[k]).join(' ')
+}
diff --git a/src/lib/time.ts b/src/lib/time.ts
new file mode 100644
index 0000000..d85e935
--- /dev/null
+++ b/src/lib/time.ts
@@ -0,0 +1,8 @@
+export function debounce<A extends any[]>(f: (...args: A) => void, timeout: number): (...args: A) => void {
+  let interval: number | undefined = undefined
+
+  return (...args: A) => {
+    clearTimeout(interval)
+    interval = setTimeout(() => f.apply(this, args), timeout)
+  }
+}
diff --git a/src/main.ts b/src/main.ts
new file mode 100644
index 0000000..16d4bb5
--- /dev/null
+++ b/src/main.ts
@@ -0,0 +1,9 @@
+import h from 'lib/h'
+import * as sequencer from 'view/sequencer'
+
+let view = h('main', {},
+  h('h1', { className: 'g-Title' }, 'Metronome'),
+  sequencer.view()
+)
+
+document.body.appendChild(view)
diff --git a/src/sounds.ts b/src/sounds.ts
new file mode 100644
index 0000000..9ce8d2e
--- /dev/null
+++ b/src/sounds.ts
@@ -0,0 +1,29 @@
+export interface Sounds {
+  kick: AudioBuffer
+}
+
+const audioContext = new AudioContext()
+let lazy: undefined | Sounds = undefined
+
+export async function load(): Promise<Sounds> {
+  if (lazy !== undefined) {
+    return lazy
+  } else {
+
+    const kick = await fetch('/sounds/kick.opus')
+      .then(res => res.arrayBuffer())
+      .then(ArrayBuffer => audioContext.decodeAudioData(ArrayBuffer))
+
+    lazy = {
+      kick
+    }
+    return lazy
+  }
+}
+
+export function playKick(sounds: Sounds) {
+  const source = audioContext.createBufferSource()
+  source.buffer = sounds.kick
+  source.connect(audioContext.destination)
+  source.start()
+}
diff --git a/src/view/sequencer.ts b/src/view/sequencer.ts
new file mode 100644
index 0000000..150f89b
--- /dev/null
+++ b/src/view/sequencer.ts
@@ -0,0 +1,60 @@
+import h, { classNames } from 'lib/h'
+import * as soundsLib from 'sounds'
+import * as play from 'view/sequencer/play'
+import * as addRemoveBeat from 'view/sequencer/addRemoveBeat'
+import * as block from 'view/sequencer/block'
+
+export function view() {
+  let index = -1
+  let blocks = [true]
+  let blocksNode = h('div', 
+    { className: 'g-Sequencer__Blocks' }, 
+    block.view({ 
+      checked: true,
+      onCheck: checked => blocks[0] = checked
+    })
+  )
+
+  let onNextStep = (sounds: soundsLib.Sounds) => {
+    let oldIndex = index
+    let newIndex = (index + 1) % blocks.length
+    index = newIndex
+
+    let oldBlock = blocksNode.childNodes[oldIndex] as HTMLElement
+    if (oldBlock !== undefined) oldBlock.classList.remove('g-Sequencer__Block--Beat')
+
+    let newBlock = blocksNode.childNodes[newIndex] as HTMLElement
+    newBlock.classList.add('g-Sequencer__Block--Beat')
+
+    if (blocks[newIndex]) soundsLib.playKick(sounds)
+  }
+
+  let sequencer = h('div', { className: 'g-Sequencer' },
+    play.view({
+      onNextStep,
+      onStop: () => {
+        let block = blocksNode.childNodes[index] as HTMLElement
+        block.classList.remove('g-Sequencer__Block--Beat')
+        index = -1
+      }
+    }),
+    addRemoveBeat.view({
+      initBeats: 1,
+      onRemove: index => {
+        let lastBlock = blocksNode.childNodes[index]
+        blocksNode.removeChild(lastBlock)
+        blocks.pop()
+      },
+      onAdd: index => {
+        blocks.push(false)
+        blocksNode.appendChild(block.view({ 
+          checked: false,
+          onCheck: checked => blocks[index] = checked
+        })) 
+      }
+    }),
+    blocksNode
+  )
+
+  return sequencer
+}
diff --git a/src/view/sequencer/addRemoveBeat.ts b/src/view/sequencer/addRemoveBeat.ts
new file mode 100644
index 0000000..e991d3f
--- /dev/null
+++ b/src/view/sequencer/addRemoveBeat.ts
@@ -0,0 +1,32 @@
+import h, { classNames } from 'lib/h'
+
+interface Params {
+  initBeats: number,
+  onRemove: (index: number) => void,
+  onAdd: (index: number) => void
+}
+
+export function view({ initBeats, onRemove, onAdd }: Params) {
+  let beats = initBeats
+
+  return h('div', { className: 'g-Sequencer__Buttons' },
+    h('button', 
+      { onclick: () => {
+          if (beats > 1) {
+            beats -= 1
+            onRemove(beats)
+          }
+        }
+      },
+      'Remove Beat'
+    ),
+    h('button', 
+      { onclick: () => {
+          onAdd(beats)
+          beats += 1
+        }
+      },
+      'Add Beat'
+    )
+  )
+}
diff --git a/src/view/sequencer/block.ts b/src/view/sequencer/block.ts
new file mode 100644
index 0000000..5776120
--- /dev/null
+++ b/src/view/sequencer/block.ts
@@ -0,0 +1,28 @@
+import h, { classNames } from 'lib/h'
+
+interface Params {
+  checked: boolean,
+  onCheck: (checked: boolean) => void
+}
+
+export function view({ checked, onCheck }: Params) {
+  return h('div', 
+    { className: classNames({
+        'g-Sequencer__Block': true,
+        'g-Sequencer__Block--Checked': checked
+      }),
+      onclick: (e: Event) => {
+        checked = !checked
+        onCheck(checked)
+        let target = e.target as HTMLElement
+        if (target !== undefined) {
+          if (checked) {
+            target.classList.add('g-Sequencer__Block--Checked')
+          } else {
+            target.classList.remove('g-Sequencer__Block--Checked')
+          }
+        }
+      }
+    }
+  )
+}
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
+          )
+        }
+      )
+    )
+  )
+}