41 lines
1.7 KiB
JavaScript
41 lines
1.7 KiB
JavaScript
// m05 game: one `update` function turns every action into a new state; replay is a fold over actions.
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// m10 adds pause, restart and a frame clock that speeds up as the score grows.
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import { turn } from './rules.js'
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import { tick, newGame } from './spawn.js'
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/** How many frames pass between game steps: 8 at first, one fewer every 3 points, never fewer than 2. */
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export const movesEvery = (score) => Math.max(2, 8 - Math.floor(score / 3))
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// One animation frame: count it, and every `movesEvery(score)`-th frame run a game step.
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const frame = (state) => {
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if (state.status !== 'Playing') return state
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const counted = { ...state, frame: state.frame + 1 }
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return counted.frame % movesEvery(counted.score) === 0 ? tick(counted) : counted
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}
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// Pause and resume only make sense in those two statuses; a finished game stays finished.
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const togglePause = (state) =>
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state.status === 'Playing' ? { ...state, status: 'Paused' }
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: state.status === 'Paused' ? { ...state, status: 'Playing' }
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: state
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export const update = (state, action) => {
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switch (action.tag) {
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case 'Tick': return tick(state)
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case 'Turn': return turn(state, action.dir)
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case 'TogglePause': return togglePause(state)
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case 'Restart': return newGame(state.seed)
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case 'Frame': return frame(state)
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default: return state
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}
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}
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/** Fold the actions over the state, left to right. */
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export const replay = (state, actions) => actions.reduce(update, state)
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/** Like replay, but keeps each intermediate state. Recursion instead of mutation: no array is ever pushed to. */
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export const history = (state, actions) =>
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actions.length === 0
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? [state]
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: [state, ...history(update(state, actions[0]), actions.slice(1))]
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