52 lines
1.6 KiB
JavaScript
52 lines
1.6 KiB
JavaScript
// m02 model: the data the whole game is built from. Plain objects, never mutated.
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/** @typedef {{x: number, y: number}} Point */
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/** @typedef {'Up'|'Down'|'Left'|'Right'} Direction */
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/** @typedef {'Playing'|'Paused'|'GameOver'|'Won'} Status */
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/** @typedef {{width: number, height: number, snake: Point[], dir: Direction, nextDir: Direction,
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* apple: Point|null, seed: number, score: number, status: Status, frame: number}} GameState */
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/** A grid cell. */
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export const point = (x, y) => ({ x, y })
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/** Structural equality: same x and same y. */
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export const pointEquals = (a, b) => a.x === b.x && a.y === b.y
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const deltas = {
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Up: point(0, -1),
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Down: point(0, 1),
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Left: point(-1, 0),
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Right: point(1, 0),
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}
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/** The unit step for a direction (y grows downward). */
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export const delta = (dir) => deltas[dir]
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const opposites = { Up: 'Down', Down: 'Up', Left: 'Right', Right: 'Left' }
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/** The direction pointing the other way. */
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export const opposite = (dir) => opposites[dir]
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/** Everything that can happen to the game, as data. `Turn` is a function because it carries a direction. */
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export const Action = {
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Tick: { tag: 'Tick' },
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Turn: (dir) => ({ tag: 'Turn', dir }),
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TogglePause: { tag: 'TogglePause' },
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Restart: { tag: 'Restart' },
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Frame: { tag: 'Frame' },
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}
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/** A fresh 20x20 game: 3-segment snake heading Right, no apple yet. */
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export const initialState = (seed) => ({
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width: 20,
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height: 20,
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snake: [point(10, 10), point(9, 10), point(8, 10)],
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dir: 'Right',
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nextDir: 'Right',
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apple: null,
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seed,
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score: 0,
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status: 'Playing',
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frame: 0,
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})
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