/**
 * The map: one grid, and the geometry everything else asks questions of.
 *
 * Two sites (A left, B right), a mid corridor between the spawns, and a back
 * corridor along the bottom that links A main, spawn and B main — the flank.
 * Tiles are 80 units; a player is a circle of radius 16, so a one-tile
 * corridor is comfortably wide and a wall is never thin enough for a ray to
 * step over.
 *
 * Everything here is a pure function of the grid: collision, line of sight
 * and the walk distance a bot uses to path. No state.
 */

import { circleBlocked, slideCircle } from "./glide.ts";

export const TILE = 80;

// '#' wall · '.' floor · 'A'/'B' plant site · 'a' attacker spawn · 'd' defender spawn
const ROWS_SRC = [
  "##############################",
  "#........###.dddd.###........#",
  "#.AAAAA..###.dddd.###..BBBBB.#",
  "#.AAAAA..##........##..BBBBB.#",
  "#.AAAAA..##.#....#.##..BBBBB.#",
  "#.AAAAA..##........##..BBBBB.#",
  "#...##......#....#......##...#",
  "#..####....#......#....####..#",
  "#..####..###......###..####..#",
  "#..####..####....####..####..#",
  "#..####..####.##.####..####..#",
  "#........####.##.####........#",
  "#..####..####....####..####..#",
  "#..####..#####..#####..####..#",
  "#..####..#####..#####..####..#",
  "#..####..###......###..####..#",
  "#........##..aaaa..##........#",
  "#............aaaa............#",
  "##############################",
];

export const COLS = ROWS_SRC[0]!.length;
export const ROWS = ROWS_SRC.length;
export const WIDTH = COLS * TILE;
export const HEIGHT = ROWS * TILE;

export const grid: string[] = ROWS_SRC;
export const gridRows = (): string[] => ROWS_SRC.slice();

export type Site = "A" | "B";
export type Point = { x: number; y: number };

const at = (col: number, row: number): string =>
  row < 0 || row >= ROWS || col < 0 || col >= COLS ? "#" : ROWS_SRC[row]![col]!;

export const solidTile = (col: number, row: number): boolean => at(col, row) === "#";

export const tileOf = (x: number, y: number): { col: number; row: number } => ({
  col: Math.floor(x / TILE),
  row: Math.floor(y / TILE),
});

export const centreOf = (col: number, row: number): Point => ({
  x: col * TILE + TILE / 2,
  y: row * TILE + TILE / 2,
});

export const solidAt = (x: number, y: number): boolean => {
  const t = tileOf(x, y);
  return solidTile(t.col, t.row);
};

/** The site a point plants on, or null: the spike only arms inside a site. */
export const siteAt = (x: number, y: number): Site | null => {
  const t = tileOf(x, y);
  const c = at(t.col, t.row);
  return c === "A" || c === "B" ? c : null;
};

const cellsOf = (mark: string): Point[] => {
  const out: Point[] = [];
  for (let row = 0; row < ROWS; row++)
    for (let col = 0; col < COLS; col++) if (at(col, row) === mark) out.push(centreOf(col, row));
  return out;
};

export const spawnCells = (side: "atk" | "def"): Point[] => cellsOf(side === "atk" ? "a" : "d");
export const siteCells = (site: Site): Point[] => cellsOf(site);

export const siteCentre = (site: Site): Point => {
  const cells = siteCells(site);
  const sum = cells.reduce((a, p) => ({ x: a.x + p.x, y: a.y + p.y }), { x: 0, y: 0 });
  return { x: sum.x / cells.length, y: sum.y / cells.length };
};

/** Ult orbs: one on each half of mid, free for whoever walks over them. */
export const orbSpots = (): Point[] => [centreOf(4, 11), centreOf(25, 11)];

/**
 * Slide a circle through this grid. The maths is in `glide.ts`, which the
 * browser runs too; here it is bound to this map's tiles.
 */
export const moveCircle = (x: number, y: number, dx: number, dy: number, r: number): Point =>
  slideCircle(x, y, dx, dy, r, solidTile, TILE);

/** True when a circle at (x,y) overlaps any solid tile. */
export const blockedCircle = (x: number, y: number, r: number): boolean =>
  circleBlocked(x, y, r, solidTile, TILE);

/**
 * Does a wall stand between two points? Sampled every third of a tile: a
 * wall is a whole tile thick, so nothing is ever stepped over.
 */
export function wallBetween(a: Point, b: Point): boolean {
  const dx = b.x - a.x;
  const dy = b.y - a.y;
  const dist = Math.hypot(dx, dy);
  const steps = Math.ceil(dist / (TILE / 3));
  for (let i = 1; i < steps; i++) {
    const t = i / steps;
    if (solidAt(a.x + dx * t, a.y + dy * t)) return true;
  }
  return false;
}

/** Where a shot stops: the first wall along the ray, or its full range. */
export function rayHitWall(from: Point, angle: number, range: number): Point {
  const dx = Math.cos(angle);
  const dy = Math.sin(angle);
  const step = TILE / 4;
  for (let d = step; d <= range; d += step) {
    const x = from.x + dx * d;
    const y = from.y + dy * d;
    if (solidAt(x, y)) return { x: from.x + dx * (d - step), y: from.y + dy * (d - step) };
  }
  return { x: from.x + dx * range, y: from.y + dy * range };
}

/** Closest approach of a segment to a point, as distance and travel along it. */
export function segmentPoint(a: Point, b: Point, p: Point): { dist: number; travel: number } {
  const dx = b.x - a.x;
  const dy = b.y - a.y;
  const len2 = dx * dx + dy * dy;
  const t = len2 === 0 ? 0 : Math.max(0, Math.min(1, ((p.x - a.x) * dx + (p.y - a.y) * dy) / len2));
  const cx = a.x + dx * t;
  const cy = a.y + dy * t;
  return { dist: Math.hypot(p.x - cx, p.y - cy), travel: t * Math.sqrt(len2) };
}

export const segmentHitsCircle = (a: Point, b: Point, c: Point, r: number): boolean =>
  segmentPoint(a, b, c).dist <= r;

// Walk distance from a goal tile, breadth-first over floor. Bots ask for it
// every few ticks; the field for a goal is built once and kept for the round.
const fields = new Map<number, Int32Array>();

export const clearPaths = (): void => void fields.clear();

function field(goalCol: number, goalRow: number): Int32Array {
  const key = goalRow * COLS + goalCol;
  const cached = fields.get(key);
  if (cached) return cached;
  const dist = new Int32Array(COLS * ROWS).fill(-1);
  if (!solidTile(goalCol, goalRow)) {
    dist[key] = 0;
    const queue: number[] = [key];
    for (let head = 0; head < queue.length; head++) {
      const here = queue[head]!;
      const col = here % COLS;
      const row = (here - col) / COLS;
      const d = dist[here]!;
      for (const [dc, dr] of [
        [1, 0],
        [-1, 0],
        [0, 1],
        [0, -1],
      ] as const) {
        const nc = col + dc;
        const nr = row + dr;
        if (nc < 0 || nc >= COLS || nr < 0 || nr >= ROWS) continue;
        const nk = nr * COLS + nc;
        if (dist[nk] !== -1 || solidTile(nc, nr)) continue;
        dist[nk] = d + 1;
        queue.push(nk);
      }
    }
  }
  if (fields.size > 64) fields.clear();
  fields.set(key, dist);
  return dist;
}

/** Walk distance in tiles between two points, or -1 when unreachable. */
export function walkDistance(from: Point, to: Point): number {
  const f = tileOf(from.x, from.y);
  const g = tileOf(to.x, to.y);
  return field(g.col, g.row)[f.row * COLS + f.col] ?? -1;
}

/**
 * The next point to walk toward on the way to a goal: the centre of the
 * neighbouring tile that is one step closer, so bots round corners instead
 * of grinding into them.
 */
export function pathStep(from: Point, to: Point): Point {
  const f = tileOf(from.x, from.y);
  const g = tileOf(to.x, to.y);
  if (f.col === g.col && f.row === g.row) return to;
  const dist = field(g.col, g.row);
  const here = dist[f.row * COLS + f.col] ?? -1;
  if (here <= 0) return to;
  let best: Point | null = null;
  let bestD = here;
  for (const [dc, dr] of [
    [1, 0],
    [-1, 0],
    [0, 1],
    [0, -1],
  ] as const) {
    const nc = f.col + dc;
    const nr = f.row + dr;
    if (nc < 0 || nc >= COLS || nr < 0 || nr >= ROWS) continue;
    const d = dist[nr * COLS + nc] ?? -1;
    if (d !== -1 && d < bestD) {
      bestD = d;
      best = centreOf(nc, nr);
    }
  }
  // Straight to the goal when nothing stands in the way — smoother than
  // walking tile centre to tile centre down an open corridor.
  if (best && !wallBetween(from, to) && (walkDistance(from, to) ?? 99) < 6) return to;
  return best ?? to;
}