17 files changed, 452 insertions, 0 deletions
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e07f8e1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+public/main.js
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c939efb
--- /dev/null
+++ b/README.md
@@ -0,0 +1,14 @@
+# Getting started
+
+Having nix installed, run:
+
+```sh
+nix develop --command bin/watch.sh
+```
+
+Then, open your browser at `http://localhost:8000`.
+
+# Todo
+
+- [ ] Augment the BPM by X after Y cycles
+- [ ] Provide more drum sounds
diff --git a/bin/watch.sh b/bin/watch.sh
new file mode 100755
index 0000000..f93ce18
--- /dev/null
+++ b/bin/watch.sh
@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run server
+
+python -m http.server --directory public 8000 &
+trap "fuser -k 8000/tcp" EXIT
+
+# Watch TypeScript
+
+CHECK="echo Checking TypeScript… && tsc --checkJs"
+BUILD="esbuild --bundle src/main.ts --target=es2016 --outdir=public"
+watchexec \
+  --clear \
+  --watch src \
+  -- "$CHECK && $BUILD"
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..89217c5
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1653893745,
+        "narHash": "sha256-0jntwV3Z8//YwuOjzhV2sgJJPt+HY6KhU7VZUL0fKZQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "1ed9fb1935d260de5fe1c2f7ee0ebaae17ed2fa1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1654681126,
+        "narHash": "sha256-Y6uhgR3HjrHjxXk5k7Mlc9w2/DZSrS23y2gs7H/z8x8=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "543f9893c851909c59725556e327c722f56a6227",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..325ed60
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,21 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let pkgs = nixpkgs.legacyPackages.${system};
+        in { devShell = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            nodePackages.typescript
+            python3
+            psmisc # fuser
+            esbuild
+            watchexec
+          ];
+        }; }
+      );
+}
diff --git a/public/index.html b/public/index.html
new file mode 100644
index 0000000..5facb9e
--- /dev/null
+++ b/public/index.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<html lang="fr">
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width">
+<title>Metronome</title>
+<link rel="stylesheet" href="/main.css">
+
+<body></body>
+
+<script src="main.js"></script>
diff --git a/public/main.css b/public/main.css
new file mode 100644
index 0000000..fbc37c4
--- /dev/null
+++ b/public/main.css
@@ -0,0 +1,67 @@
+:root {
+  --color-block: lightgray;
+  --color-block-checked: lightgreen;
+
+  --spacing-mouse: 0.25rem;
+  --spacing-cat: 0.5rem;
+  --spacing-dog: 1rem;
+  --spacing-horse: 2rem;
+  --spacing-elephant: 4rem;
+}
+
+body {
+  margin: var(--spacing-dog);
+}
+
+.g-Bpm {
+  display: block;
+  margin-bottom: var(--spacing-dog);
+}
+
+.g-Input {
+  margin-left: var(--spacing-dog);
+}
+
+.g-PlayStop {
+  margin-bottom: var(--spacing-dog);
+}
+
+.g-Sequencer {
+  margin-top: var(--spacing-dog);
+}
+
+.g-Sequencer__Buttons {
+  margin-bottom: var(--spacing-dog);
+  display: flex;
+  gap: var(--spacing-dog);
+}
+
+.g-Sequencer__Blocks {
+  display: flex;
+  gap: var(--spacing-cat);
+}
+
+.g-Sequencer__Block {
+  width: var(--spacing-horse);
+  height: var(--spacing-horse);
+  background-color: lightgray;
+  cursor: pointer;
+}
+
+.g-Sequencer__Block:hover {
+  filter: brightness(110%);
+}
+
+.g-Sequencer__Block--Checked {
+  background-color: lightgreen;
+}
+
+.g-Sequencer__Block--Beat {
+  animation: beat 0.2s linear;
+}
+
+@keyframes beat {
+  0%   {transform: scale(100%);}
+  30%  {transform: scale(105%);}
+  100% {transform: scale(100%);}
+}
diff --git a/public/sounds/kick.opus b/public/sounds/kick.opus
new file mode 100644
index 0000000..40a8d60
--- /dev/null
+++ b/public/sounds/kick.opus
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
+          )
+        }
+      )
+    )
+  )
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..380eab3
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "module": "amd",
+    "target": "es2017",
+    "baseUrl": "src",
+    "outFile": "public/main.js",
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "removeComments": true,
+    "preserveConstEnums": true
+  },
+  "include": ["src/**/*"]
+}