| 1 | import { isBarrier, wallStacks, type WallProgress } from '../game/wall'; |
| 2 | import type { SeatId } from '../game/types'; |
| 3 | import type { Rect } from './physics'; |
| 4 | |
| 5 | /** |
| 6 | * Where everything on the table actually is, in pixels. |
| 7 | * |
| 8 | * The wall square's size lives entirely in CSS — `--ring`, `--ws`, `--wd` in |
| 9 | * styles.css work it out from the viewport and the strip depth — so rather than |
| 10 | * restate that arithmetic here and let the two drift apart, this *measures* it. |
| 11 | * `WallRing` renders every stack as a real element tagged with its index, so the |
| 12 | * colliders come from `getBoundingClientRect()` on the things already on screen. |
| 13 | * That is the whole mapping from the HTML to the physics. |
| 14 | * |
| 15 | * Measuring is one layout flush over ~74 elements. It happens when the window |
| 16 | * resizes and when the wall's shape changes, never per frame. |
| 17 | */ |
| 18 | |
| 19 | const SEATS: SeatId[] = [0, 1, 2, 3]; |
| 20 | |
| 21 | export interface TableGeometry { |
| 22 | /** Table size, world units — the world's origin is the table's top left. */ |
| 23 | size: { w: number; h: number }; |
| 24 | /** Inside the wall square: where a discard is aimed, and where a rebuilt pile |
| 25 | * is laid out. Not a fence — see `felt`. */ |
| 26 | pool: Rect; |
| 27 | /** |
| 28 | * The whole middle of the table, between the four strips. This is what |
| 29 | * actually stops a tile, because the square is not a box: it is eighteen |
| 30 | * stacks a side, and once they have been drawn there is nothing there. A tile |
| 31 | * is held in by the stacks still standing, and by the edge of the felt beyond |
| 32 | * them — so as the wall is eaten away the pool spills out through the gaps, |
| 33 | * exactly as it does on a table. |
| 34 | */ |
| 35 | felt: Rect; |
| 36 | /** Stacks of two still standing. Half stacks are low enough to throw over. */ |
| 37 | walls: Rect[]; |
| 38 | /** A tile in the pool is the same tile that was in the wall. */ |
| 39 | tile: { w: number; h: number }; |
| 40 | /** The middle of each seat's hand, if that seat's hand is on screen. */ |
| 41 | launch: Partial<Record<SeatId, Point>>; |
| 42 | /** The right-hand end of each seat's hand, which is where a tile is thrown |
| 43 | * from: the tile just drawn sits there, and that is the hand you throw with. */ |
| 44 | throwFrom: Partial<Record<SeatId, Point>>; |
| 45 | } |
| 46 | |
| 47 | export interface Point { |
| 48 | x: number; |
| 49 | y: number; |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Read the table. Returns null when there is no wall square to measure — the |
| 54 | * compact layout has none, and neither does a table that has not laid out yet. |
| 55 | */ |
| 56 | export function measure(table: HTMLElement, state: WallProgress): TableGeometry | null { |
| 57 | const ring = table.querySelector<HTMLElement>('.wall-ring'); |
| 58 | if (!ring) return null; |
| 59 | |
| 60 | const base = table.getBoundingClientRect(); |
| 61 | if (base.width === 0 || base.height === 0) return null; |
| 62 | const local = (r: DOMRect): Rect => ({ |
| 63 | x: r.left - base.left, |
| 64 | y: r.top - base.top, |
| 65 | w: r.width, |
| 66 | h: r.height, |
| 67 | }); |
| 68 | |
| 69 | const stacks = wallStacks(state); |
| 70 | const walls: Rect[] = []; |
| 71 | // A stack element is --ws by --wd (or the other way round on the left and |
| 72 | // right sides), which gives us both the tile size and the wall's thickness |
| 73 | // without knowing either number. |
| 74 | let short = 0; |
| 75 | let long = 0; |
| 76 | for (const el of ring.querySelectorAll<HTMLElement>('[data-stack]')) { |
| 77 | const i = Number(el.dataset.stack); |
| 78 | const r = local(el.getBoundingClientRect()); |
| 79 | short = Math.max(short, Math.min(r.w, r.h)); |
| 80 | long = Math.max(long, Math.max(r.w, r.h)); |
| 81 | const stack = stacks[i]; |
| 82 | if (stack && isBarrier(stack)) walls.push(r); |
| 83 | } |
| 84 | if (short === 0) return null; |
| 85 | |
| 86 | // The pool is the square the wall encloses, less the wall's own thickness. |
| 87 | const ringRect = local(ring.getBoundingClientRect()); |
| 88 | const pool: Rect = { |
| 89 | x: ringRect.x + long, |
| 90 | y: ringRect.y + long, |
| 91 | w: Math.max(short, ringRect.w - long * 2), |
| 92 | h: Math.max(short, ringRect.h - long * 2), |
| 93 | }; |
| 94 | |
| 95 | const launch: Partial<Record<SeatId, Point>> = {}; |
| 96 | const throwFrom: Partial<Record<SeatId, Point>> = {}; |
| 97 | for (const seat of SEATS) { |
| 98 | const hand = table.querySelector<HTMLElement>(`[data-seat="${seat}"] .hand`); |
| 99 | if (!hand) continue; |
| 100 | const r = hand.getBoundingClientRect(); |
| 101 | if (r.width === 0 && r.height === 0) continue; |
| 102 | // A rotated element's bounding box is still centred on the element, so this |
| 103 | // is the right point whichever edge the seat is sitting at. |
| 104 | launch[seat] = { x: r.left + r.width / 2 - base.left, y: r.top + r.height / 2 - base.top }; |
| 105 | |
| 106 | // The end of the row rather than the middle of it. That is where the tile |
| 107 | // just drawn is sitting and which hand it is in, so it is where a throw |
| 108 | // comes from — measured off the last cell, so it is the right end of the |
| 109 | // *row* whichever way round the seat is turned. |
| 110 | const end = hand.querySelector<HTMLElement>('.hand-cell:last-child'); |
| 111 | const er = end?.getBoundingClientRect(); |
| 112 | throwFrom[seat] = er |
| 113 | ? { x: er.left + er.width / 2 - base.left, y: er.top + er.height / 2 - base.top } |
| 114 | : launch[seat]; |
| 115 | } |
| 116 | |
| 117 | // The felt is the centre element's own box — the area the four strips leave. |
| 118 | const centre = table.querySelector<HTMLElement>('.center'); |
| 119 | const felt = centre ? local(centre.getBoundingClientRect()) : ringRect; |
| 120 | |
| 121 | return { |
| 122 | size: { w: base.width, h: base.height }, |
| 123 | pool, |
| 124 | felt, |
| 125 | walls, |
| 126 | tile: poolTile(table, short), |
| 127 | launch, |
| 128 | throwFrom, |
| 129 | }; |
| 130 | } |
| 131 | |
| 132 | /** |
| 133 | * How big a tile in the middle is drawn: the same size as the tiles being |
| 134 | * played with. |
| 135 | * |
| 136 | * It used to be the size of a tile in the wall, which is much smaller, and that |
| 137 | * was a mistake you could see rather than measure — a tile thrown from a hand |
| 138 | * shrank as it crossed the table, so it read as being dropped away from you into |
| 139 | * the distance rather than skidded across a flat one. They are the same tiles, |
| 140 | * so they are the same size. |
| 141 | * |
| 142 | * A seat's strip is rotated by a right angle, which swaps its bounding box, and |
| 143 | * a tile is always taller than it is wide — so the narrower side is the width |
| 144 | * whichever edge is measured. Falls back to the wall's own tile if no hand has |
| 145 | * been dealt yet. |
| 146 | */ |
| 147 | function poolTile(table: HTMLElement, fallback: number): { w: number; h: number } { |
| 148 | const el = table.querySelector<HTMLElement>('.hand .tile'); |
| 149 | const r = el?.getBoundingClientRect(); |
| 150 | const w = r && r.width > 0 ? Math.min(r.width, r.height) : fallback; |
| 151 | return { w, h: w * 1.375 }; |
| 152 | } |
| 153 | |
| 154 | export const centreOf = (r: Rect): Point => ({ x: r.x + r.w / 2, y: r.y + r.h / 2 }); |
| 155 | |
| 156 | /** |
| 157 | * Whether a seat has a clear line into the middle — the throw gate. |
| 158 | * |
| 159 | * Not a rule bolted on beside the physics; it *is* the physics, asked ahead of |
| 160 | * time. While a standing stack of two is between a seat and the pool, a tile |
| 161 | * flicked from there would hit it, so the seat cannot throw and has to place the |
| 162 | * tile over the wall instead (tap-tap, or 打出). As the hand eats the square, |
| 163 | * gaps open and seats come good one at a time. |
| 164 | * |
| 165 | * Aim is not just dead ahead: a fan of lines spread across the pool means a gap |
| 166 | * off to one side counts, which is how you would actually throw it. |
| 167 | */ |
| 168 | export function canThrow(geo: TableGeometry, seat: SeatId): boolean { |
| 169 | const from = geo.launch[seat]; |
| 170 | return !!from && canThrowFrom(geo, from); |
| 171 | } |
| 172 | |
| 173 | /** |
| 174 | * The same question asked from a particular point rather than from a seat. |
| 175 | * |
| 176 | * This is the one that matters for a tile somebody is holding: they have picked |
| 177 | * it up and can carry it anywhere, so what decides whether it can be slid in is |
| 178 | * the line from wherever they let go of it — not the line from the hand it came |
| 179 | * out of. Judging a throw released out over the square by the view from the |
| 180 | * player's own edge called almost everything a lob. |
| 181 | */ |
| 182 | export function canThrowFrom(geo: TableGeometry, from: Point): boolean { |
| 183 | if (inRect(geo.pool, from)) return true; |
| 184 | return aimPoints(geo).some((to) => clearLine(geo.walls, from, to)); |
| 185 | } |
| 186 | |
| 187 | export const inRect = (r: Rect, p: Point) => |
| 188 | p.x >= r.x && p.x <= r.x + r.w && p.y >= r.y && p.y <= r.y + r.h; |
| 189 | |
| 190 | /** Somewhere in the pool this seat could actually get a tile to, or null. */ |
| 191 | export function aimAt(geo: TableGeometry, seat: SeatId): Point | null { |
| 192 | const from = geo.launch[seat]; |
| 193 | if (!from) return null; |
| 194 | const open = aimPoints(geo).filter((to) => clearLine(geo.walls, from, to)); |
| 195 | if (open.length === 0) return null; |
| 196 | // The most central thing reachable, so a tile lands among the others rather |
| 197 | // than hugging whichever edge it squeezed past. |
| 198 | const c = centreOf(geo.pool); |
| 199 | return open.reduce((best, p) => |
| 200 | Math.hypot(p.x - c.x, p.y - c.y) < Math.hypot(best.x - c.x, best.y - c.y) ? p : best, |
| 201 | ); |
| 202 | } |
| 203 | |
| 204 | /** |
| 205 | * Landing spots to try for: a grid over the whole pool, not a line through its |
| 206 | * middle. |
| 207 | * |
| 208 | * A throw only has to *get inside* the square — once past the wall the tile |
| 209 | * slides to a stop wherever it ends up. So the near corners matter as much as |
| 210 | * the centre, and they matter more: they sit much closer to the seat, which is |
| 211 | * what makes a gap well off to one side worth aiming through at all. Aiming |
| 212 | * only at the middle would call a seat walled in when it plainly is not. |
| 213 | */ |
| 214 | function aimPoints(geo: TableGeometry): Point[] { |
| 215 | const { x, y, w, h } = geo.pool; |
| 216 | // Fine rather than coarse, and it costs nothing: this runs once when a tile |
| 217 | // is let go of, not per frame. A sparse grid missed narrow gaps and called a |
| 218 | // throw impossible when a tile would plainly have gone through, and sliding is |
| 219 | // what a discard should be whenever it can be. |
| 220 | const steps = [0.06, 0.2, 0.35, 0.5, 0.65, 0.8, 0.94]; |
| 221 | const out: Point[] = []; |
| 222 | for (const u of steps) for (const v of steps) out.push({ x: x + w * u, y: y + h * v }); |
| 223 | return out; |
| 224 | } |
| 225 | |
| 226 | /** Segment against every standing stack, by the slab method. */ |
| 227 | function clearLine(walls: Rect[], from: Point, to: Point): boolean { |
| 228 | return !walls.some((w) => segmentHitsRect(from, to, w)); |
| 229 | } |
| 230 | |
| 231 | export function segmentHitsRect(a: Point, b: Point, r: Rect): boolean { |
| 232 | const dx = b.x - a.x; |
| 233 | const dy = b.y - a.y; |
| 234 | let t0 = 0; |
| 235 | let t1 = 1; |
| 236 | |
| 237 | // Each axis clips the span of the segment that could still be inside. |
| 238 | const slab = (p: number, d: number, lo: number, hi: number): boolean => { |
| 239 | if (Math.abs(d) < 1e-9) return p >= lo && p <= hi; |
| 240 | const near = (lo - p) / d; |
| 241 | const far = (hi - p) / d; |
| 242 | t0 = Math.max(t0, Math.min(near, far)); |
| 243 | t1 = Math.min(t1, Math.max(near, far)); |
| 244 | return t1 >= t0; |
| 245 | }; |
| 246 | |
| 247 | if (!slab(a.x, dx, r.x, r.x + r.w)) return false; |
| 248 | if (!slab(a.y, dy, r.y, r.y + r.h)) return false; |
| 249 | return t1 >= t0; |
| 250 | } |