wizwar6e/packages/engine/src/setups.ts

// Board configurations from the 6e rulebook's setup diagram. Sectors are
// shuffled and randomly rotated, then laid out per player count; each player
// gets the sector containing their home star.
//
// All five layouts are verified against the rulebook's Set-Up Diagram
// (research/images/6e-rules-setup-diagram.jpg): 2p crossed pairs, 3p stair
// with the Aisle Warp arc, 4p and 6p straight-across, 5p plus with corner
// warps at every notch. board.test.ts pins each pairing.

import {
  assembleBoard,
  type AssembledBoard,
  type Rotation,
  type SectorPlacement,
} from "./board";
import { layoutIds } from "./board";
import { shuffle, nextInt, type RngState } from "./rng";

export const SUPPORTED_PLAYER_COUNTS = [2, 3, 4, 5, 6] as const;

export interface SetupResult {
  board: AssembledBoard;
  rng: RngState;
}

export function setupBoard(playerCount: number, rng: RngState): SetupResult {
  const [shuffled, rng1] = shuffle(rng, layoutIds());
  let rngN = rng1;
  const pick = (n: number): { id: string; rotation: Rotation }[] => {
    const chosen: { id: string; rotation: Rotation }[] = [];
    for (let i = 0; i < n; i++) {
      const [r, next] = nextInt(rngN, 4);
      rngN = next;
      chosen.push({ id: shuffled[i]!, rotation: (r * 90) as Rotation });
    }
    return chosen;
  };

  if (playerCount === 2) {
    const picks = pick(2);
    const placements: SectorPlacement[] = [
      { boardId: picks[0]!.id, origin: { x: 0, y: 0 }, rotation: picks[0]!.rotation },
      { boardId: picks[1]!.id, origin: { x: 0, y: 5 }, rotation: picks[1]!.rotation },
    ];
    // Diagram: top {top A, left C, right B}, bottom {left B, right C, bottom A}
    // — A wraps vertically; the side openings pair CROSSED (top-left to
    // bottom-right and top-right to bottom-left).
    const board = assembleBoard(placements, {
      warpPairs: [
        [{ sector: 0, side: "N" }, { sector: 1, side: "S" }],
        [{ sector: 0, side: "W" }, { sector: 1, side: "E" }],
        [{ sector: 0, side: "E" }, { sector: 1, side: "W" }],
      ],
    });
    return { board, rng: rngN };
  }

  if (playerCount === 3) {
    // The rulebook's stair/L: one sector on the top row (offset right), two
    // on the bottom row. The two openings facing the concave notch join via
    // the AUTO WARP; the convex openings pair as below (interpretation of
    // the diagram's letters — geometrically matched pairs).
    const picks = pick(3);
    const placements: SectorPlacement[] = [
      { boardId: picks[0]!.id, origin: { x: 5, y: 0 }, rotation: picks[0]!.rotation },
      { boardId: picks[1]!.id, origin: { x: 0, y: 5 }, rotation: picks[1]!.rotation },
      { boardId: picks[2]!.id, origin: { x: 5, y: 5 }, rotation: picks[2]!.rotation },
    ];
    const board = assembleBoard(placements, {
      warpPairs: [
        [{ sector: 0, side: "W" }, { sector: 1, side: "N" }, "aisle"], // AUTO WARP corner
        [{ sector: 0, side: "N" }, { sector: 2, side: "S" }],
        [{ sector: 1, side: "W" }, { sector: 2, side: "E" }],
        [{ sector: 0, side: "E" }, { sector: 1, side: "S" }],
      ],
    });
    return { board, rng: rngN };
  }

  if (playerCount === 4) {
    const picks = pick(4);
    const placements: SectorPlacement[] = [
      { boardId: picks[0]!.id, origin: { x: 0, y: 0 }, rotation: picks[0]!.rotation },
      { boardId: picks[1]!.id, origin: { x: 5, y: 0 }, rotation: picks[1]!.rotation },
      { boardId: picks[2]!.id, origin: { x: 0, y: 5 }, rotation: picks[2]!.rotation },
      { boardId: picks[3]!.id, origin: { x: 5, y: 5 }, rotation: picks[3]!.rotation },
    ];
    // 4p square wraps straight across (left openings to right openings on the
    // same rows, top to bottom on the same columns) — the default pairing.
    const board = assembleBoard(placements);
    return { board, rng: rngN };
  }

  if (playerCount === 5) {
    // The plus/cross: four arms around a center. Opposite arm tips wrap to
    // each other; the notch-facing side openings warp around the corners.
    const picks = pick(5);
    const placements: SectorPlacement[] = [
      { boardId: picks[0]!.id, origin: { x: 5, y: 0 }, rotation: picks[0]!.rotation },  // N arm
      { boardId: picks[1]!.id, origin: { x: 0, y: 5 }, rotation: picks[1]!.rotation },  // W arm
      { boardId: picks[2]!.id, origin: { x: 5, y: 5 }, rotation: picks[2]!.rotation },  // center
      { boardId: picks[3]!.id, origin: { x: 10, y: 5 }, rotation: picks[3]!.rotation }, // E arm
      { boardId: picks[4]!.id, origin: { x: 5, y: 10 }, rotation: picks[4]!.rotation }, // S arm
    ];
    const board = assembleBoard(placements, {
      warpPairs: [
        [{ sector: 0, side: "N" }, { sector: 4, side: "S" }], // tip to tip
        [{ sector: 1, side: "W" }, { sector: 3, side: "E" }],
        [{ sector: 0, side: "W" }, { sector: 1, side: "N" }, "aisle"], // aisle-warp corners
        [{ sector: 0, side: "E" }, { sector: 3, side: "N" }, "aisle"],
        [{ sector: 4, side: "W" }, { sector: 1, side: "S" }, "aisle"],
        [{ sector: 4, side: "E" }, { sector: 3, side: "S" }, "aisle"],
      ],
    });
    return { board, rng: rngN };
  }

  if (playerCount === 6) {
    // 3x2 rectangle: straight-across wrap (the default pairing).
    const picks = pick(6);
    const placements: SectorPlacement[] = [
      { boardId: picks[0]!.id, origin: { x: 0, y: 0 }, rotation: picks[0]!.rotation },
      { boardId: picks[1]!.id, origin: { x: 5, y: 0 }, rotation: picks[1]!.rotation },
      { boardId: picks[2]!.id, origin: { x: 10, y: 0 }, rotation: picks[2]!.rotation },
      { boardId: picks[3]!.id, origin: { x: 0, y: 5 }, rotation: picks[3]!.rotation },
      { boardId: picks[4]!.id, origin: { x: 5, y: 5 }, rotation: picks[4]!.rotation },
      { boardId: picks[5]!.id, origin: { x: 10, y: 5 }, rotation: picks[5]!.rotation },
    ];
    const board = assembleBoard(placements);
    return { board, rng: rngN };
  }

  throw new Error(`unsupported player count: ${playerCount} (supported: 2-6)`);
}