// Board assembly: sector layouts from data/boards.json are rotated and placed
// into one global grid. Cells are {x, y}, 0-indexed, x → east, y → south.
// Edges between cells are 'open', 'wall', or 'door'; sector perimeters become
// walls except the mid-edge openings, which either join two sectors or become
// wraparound warp connections at the outer boundary.

import boardsData from "../data/boards.json";

export type Cell = { readonly x: number; readonly y: number };
export type Side = "N" | "S" | "E" | "W";
export type EdgeState = "open" | "wall" | "door" | "firewall";
export type Rotation = 0 | 90 | 180 | 270;

export interface SectorPlacement {
  boardId: string;
  /** Top-left cell of the sector in global coordinates (multiples of 5). */
  origin: Cell;
  rotation: Rotation;
}

export interface Warp {
  /** Leaving this cell through this side of the map... */
  from: { cell: Cell; side: Side };
  /** ...you arrive at this cell (entering through `side`). */
  to: { cell: Cell; side: Side };
}

export interface AssembledBoard {
  width: number;
  height: number;
  placements: SectorPlacement[];
  /** Edge states keyed by edgeKey(). Only non-open edges are stored. */
  edges: Record<string, EdgeState>;
  /** Cells that are part of the map (all cells inside placed sectors). */
  cells: Record<string, true>;
  warps: Warp[];
  /** Per player-sector info, in placement order. */
  homes: Cell[];
  treasureSpaces: Cell[][];
}

const SECTOR = 5;

export function cellKey(c: Cell): string {
  return `${c.x},${c.y}`;
}

/**
 * Canonical key for the edge between cell c and its neighbor on `side`.
 * Every edge is expressed from its north/west cell so both cells agree.
 */
export function edgeKey(c: Cell, side: Side): string {
  switch (side) {
    case "E": return `V:${c.x},${c.y}`;
    case "W": return `V:${c.x - 1},${c.y}`;
    case "S": return `H:${c.x},${c.y}`;
    case "N": return `H:${c.x},${c.y - 1}`;
  }
}

export function neighbor(c: Cell, side: Side): Cell {
  switch (side) {
    case "N": return { x: c.x, y: c.y - 1 };
    case "S": return { x: c.x, y: c.y + 1 };
    case "E": return { x: c.x + 1, y: c.y };
    case "W": return { x: c.x - 1, y: c.y };
  }
}

export const SIDES: readonly Side[] = ["N", "S", "E", "W"];

interface LayoutData {
  id: string;
  homeSpace: number[];
  treasureSpaces: number[][];
  walls: { cell: number[]; side: string }[];
  doors: { cell: number[]; side: string }[];
}

const layouts: Map<string, LayoutData> = new Map(
  (boardsData as { boards: LayoutData[] }).boards.map((b) => [b.id, b]),
);

export function layoutIds(): string[] {
  return [...layouts.keys()];
}

/** Rotate a sector-local cell (1-indexed [row, col]) within a 5x5 grid. */
function rotateCell(row: number, col: number, rotation: Rotation): [number, number] {
  switch (rotation) {
    case 0: return [row, col];
    case 90: return [col, SECTOR + 1 - row]; // clockwise
    case 180: return [SECTOR + 1 - row, SECTOR + 1 - col];
    case 270: return [SECTOR + 1 - col, row];
  }
}

function rotateSide(side: Side, rotation: Rotation): Side {
  const order: Side[] = ["N", "E", "S", "W"];
  const idx = order.indexOf(side);
  return order[(idx + rotation / 90) % 4]!;
}

/** Convert sector-local (1-indexed [row, col]) to a global cell. */
function toGlobal(origin: Cell, row: number, col: number): Cell {
  return { x: origin.x + col - 1, y: origin.y + row - 1 };
}

/** An outer-boundary opening, identified by placement index and map side. */
export type OpeningRef = { sector: number; side: Side };

export interface AssemblyOptions {
  /**
   * Explicit wraparound pairings (each pair is bidirectional). When omitted,
   * openings pair straight across the map — correct for the 4p square; the
   * standard 2p column crosses its side openings and must pass pairs.
   */
  warpPairs?: [OpeningRef, OpeningRef][];
}

/**
 * Assemble sectors into one board. Interior walls and doors come from the
 * layout data; sector perimeters become walls except the centered mid-edge
 * opening on each side. Openings between two adjacent sectors line up (they
 * are always centered) and stay open; openings on the outer boundary become
 * wraparound warps ("leave at A, re-enter at A").
 */
export function assembleBoard(
  placements: SectorPlacement[],
  options: AssemblyOptions = {},
): AssembledBoard {
  const edges: Record<string, EdgeState> = {};
  const cells: Record<string, true> = {};
  const homes: Cell[] = [];
  const treasureSpaces: Cell[][] = [];

  let width = 0;
  let height = 0;

  for (const p of placements) {
    const layout = layouts.get(p.boardId);
    if (!layout) throw new Error(`unknown board layout: ${p.boardId}`);
    if (p.origin.x % SECTOR !== 0 || p.origin.y % SECTOR !== 0) {
      throw new Error("sector origins must be multiples of 5");
    }
    width = Math.max(width, p.origin.x + SECTOR);
    height = Math.max(height, p.origin.y + SECTOR);

    for (let r = 1; r <= SECTOR; r++) {
      for (let c = 1; c <= SECTOR; c++) {
        cells[cellKey(toGlobal(p.origin, r, c))] = true;
      }
    }

    const [hr, hc] = rotateCell(layout.homeSpace[0]!, layout.homeSpace[1]!, p.rotation);
    homes.push(toGlobal(p.origin, hr, hc));
    treasureSpaces.push(
      layout.treasureSpaces.map((t) => {
        const [tr, tc] = rotateCell(t[0]!, t[1]!, p.rotation);
        return toGlobal(p.origin, tr, tc);
      }),
    );

    const place = (cellRC: number[], side: string, state: EdgeState) => {
      // Rotating a cell+side pair: rotate the cell, rotate the side.
      const [r0, c0] = cellRC as [number, number];
      const [r, c] = rotateCell(r0, c0, p.rotation);
      const s = rotateSide(side as Side, p.rotation);
      edges[edgeKey(toGlobal(p.origin, r, c), s)] = state;
    };
    for (const w of layout.walls) place(w.cell, w.side, "wall");
    for (const d of layout.doors) place(d.cell, d.side, "door");

    // Perimeter: wall everywhere except the centered opening (position 3) on
    // each side. Openings are rotation-invariant because they are centered.
    for (let i = 1; i <= SECTOR; i++) {
      if (i !== 3) {
        edges[edgeKey(toGlobal(p.origin, 1, i), "N")] = "wall";
        edges[edgeKey(toGlobal(p.origin, SECTOR, i), "S")] = "wall";
        edges[edgeKey(toGlobal(p.origin, i, 1), "W")] = "wall";
        edges[edgeKey(toGlobal(p.origin, i, SECTOR), "E")] = "wall";
      }
    }
  }

  // Wraparound warps. An opening that faces another sector is a corridor, not
  // a warp. The remaining outer-boundary openings pair per options.warpPairs
  // (from the setup diagram's letters) or, by default, straight across the
  // map. (L-shaped 3p aisle-warp corners are TODO.)
  const warps: Warp[] = [];
  const inMap = (c: Cell) => cells[cellKey(c)] === true;
  const openingCell = (sectorIndex: number, side: Side): Cell => {
    const origin = placements[sectorIndex]!.origin;
    switch (side) {
      case "N": return toGlobal(origin, 1, 3);
      case "S": return toGlobal(origin, SECTOR, 3);
      case "W": return toGlobal(origin, 3, 1);
      case "E": return toGlobal(origin, 3, SECTOR);
    }
  };
  const opposite = (s: Side): Side => (s === "N" ? "S" : s === "S" ? "N" : s === "E" ? "W" : "E");

  if (options.warpPairs) {
    for (const [a, b] of options.warpPairs) {
      const ca = openingCell(a.sector, a.side);
      const cb = openingCell(b.sector, b.side);
      warps.push({ from: { cell: ca, side: a.side }, to: { cell: cb, side: b.side } });
      warps.push({ from: { cell: cb, side: b.side }, to: { cell: ca, side: a.side } });
    }
  } else {
    for (let i = 0; i < placements.length; i++) {
      for (const side of SIDES) {
        const cell = openingCell(i, side);
        if (inMap(neighbor(cell, side))) continue; // joins an adjacent sector
        let probe = cell;
        while (inMap(neighbor(probe, opposite(side)))) probe = neighbor(probe, opposite(side));
        warps.push({ from: { cell, side }, to: { cell: probe, side: opposite(side) } });
      }
    }
  }

  return { width, height, placements, edges, cells, warps, homes, treasureSpaces };
}

export function edgeState(board: AssembledBoard, c: Cell, side: Side): EdgeState {
  return board.edges[edgeKey(c, side)] ?? "open";
}

export function findWarp(board: AssembledBoard, c: Cell, side: Side): Warp | undefined {
  return board.warps.find((w) => cellKey(w.from.cell) === cellKey(c) && w.from.side === side);
}

/**
 * Where does one step from `c` toward `side` lead?
 * - blocked: a wall or (locked) door is in the way
 * - normal step to the adjacent cell
 * - warp step through a map-edge opening
 */
export function stepTarget(
  board: AssembledBoard,
  c: Cell,
  side: Side,
): { kind: "blocked"; by: EdgeState } | { kind: "step" | "warp"; to: Cell } {
  const e = edgeState(board, c, side);
  if (e !== "open") return { kind: "blocked", by: e };
  const n = neighbor(c, side);
  if (board.cells[cellKey(n)]) return { kind: "step", to: n };
  const warp = findWarp(board, c, side);
  if (warp) return { kind: "warp", to: warp.to.cell };
  return { kind: "blocked", by: "wall" };
}

/**
 * Line of sight from the center of `from` to the center of `to`, blocked by
 * wall/door/firewall edges the segment crosses and by any `blockedCells`
 * (solid stone, thornbushes) it passes through. Grazing a wall endpoint
 * (passing exactly through a corner adjacent to a wall) counts as blocked —
 * strict reading; revisit against FAQ rulings if needed. LOS through
 * wraparound openings is not yet modeled (TODO).
 */
export function hasLineOfSight(
  board: AssembledBoard,
  from: Cell,
  to: Cell,
  blockedCells?: Record<string, true>,
): boolean {
  if (cellKey(from) === cellKey(to)) return true;
  // Centers of cells: (x + 0.5, y + 0.5).
  const x0 = from.x + 0.5, y0 = from.y + 0.5;
  const x1 = to.x + 0.5, y1 = to.y + 0.5;

  if (blockedCells) {
    for (const key of Object.keys(blockedCells)) {
      const [bx, by] = key.split(",").map(Number) as [number, number];
      if ((bx === from.x && by === from.y) || (bx === to.x && by === to.y)) continue;
      // The sight line is blocked if it crosses any side of the solid cell.
      const sides: [number, number, number, number][] = [
        [bx, by, bx + 1, by],
        [bx, by + 1, bx + 1, by + 1],
        [bx, by, bx, by + 1],
        [bx + 1, by, bx + 1, by + 1],
      ];
      if (sides.some(([ax, ay, cx, cy]) => segmentsIntersect(x0, y0, x1, y1, ax, ay, cx, cy))) {
        return false;
      }
    }
  }

  for (const [key, state] of Object.entries(board.edges)) {
    if (state === "open") continue;
    // Reconstruct the wall segment for this edge.
    const [kind, coords] = key.split(":") as [string, string];
    const [ex, ey] = coords.split(",").map(Number) as [number, number];
    // V:x,y = edge between (x,y) and (x+1,y): vertical segment at x+1 from y to y+1.
    // H:x,y = edge between (x,y) and (x,y+1): horizontal segment at y+1 from x to x+1.
    const [ax, ay, bx, by] =
      kind === "V" ? [ex + 1, ey, ex + 1, ey + 1] : [ex, ey + 1, ex + 1, ey + 1];
    if (segmentsIntersect(x0, y0, x1, y1, ax, ay, bx, by)) return false;
  }
  return true;
}

/** Segment intersection where touching (colinear overlap or endpoint contact) counts. */
function segmentsIntersect(
  p0x: number, p0y: number, p1x: number, p1y: number,
  p2x: number, p2y: number, p3x: number, p3y: number,
): boolean {
  const d1 = cross(p2x, p2y, p3x, p3y, p0x, p0y);
  const d2 = cross(p2x, p2y, p3x, p3y, p1x, p1y);
  const d3 = cross(p0x, p0y, p1x, p1y, p2x, p2y);
  const d4 = cross(p0x, p0y, p1x, p1y, p3x, p3y);
  if (((d1 > 0 && d2 < 0) || (d1 < 0 && d2 > 0)) && ((d3 > 0 && d4 < 0) || (d3 < 0 && d4 > 0))) {
    return true;
  }
  if (d1 === 0 && onSegment(p2x, p2y, p3x, p3y, p0x, p0y)) return true;
  if (d2 === 0 && onSegment(p2x, p2y, p3x, p3y, p1x, p1y)) return true;
  if (d3 === 0 && onSegment(p0x, p0y, p1x, p1y, p2x, p2y)) return true;
  if (d4 === 0 && onSegment(p0x, p0y, p1x, p1y, p3x, p3y)) return true;
  return false;
}

function cross(ax: number, ay: number, bx: number, by: number, px: number, py: number): number {
  return (bx - ax) * (py - ay) - (by - ay) * (px - ax);
}

function onSegment(ax: number, ay: number, bx: number, by: number, px: number, py: number): boolean {
  return (
    Math.min(ax, bx) <= px && px <= Math.max(ax, bx) &&
    Math.min(ay, by) <= py && py <= Math.max(ay, by)
  );
}