import { z } from "zod";

const MAZE_CHARS = new Set(["#", ".", "S", "E", "*", "O", "G"]);
const MAX_GHOSTS = 4;

// Pac-Man-flavored timing/scoring — fixed, not hand-authored (same
// "curve is fixed" precedent as the quiz money ladder / clicker HP curve).
export const PLAYER_STEP_MS = 180;
export const GHOST_STEP_MS = 220; // slightly slower than the player — keeps it beatable.
export const FRIGHTEN_DURATION_MS = 7000;
export const GHOST_RESPAWN_DELAY_MS = 3000;
export const DOT_SCORE = 10;
export const PELLET_SCORE = 50;
export const GHOST_EAT_SCORE = 200;

/** BFS from S — used both to find the exit and to prove every collectible tile is reachable. '#' is the only impassable tile. */
function reachableFrom(grid: string[], start: [number, number]): Set<string> {
  const rows = grid.length;
  const cols = grid[0]?.length ?? 0;
  const visited = new Set<string>([`${start[0]},${start[1]}`]);
  const queue: [number, number][] = [start];
  while (queue.length > 0) {
    const [r, c] = queue.shift()!;
    for (const [dr, dc] of [
      [-1, 0],
      [1, 0],
      [0, -1],
      [0, 1],
    ]) {
      const nr = r + dr;
      const nc = c + dc;
      if (nr < 0 || nr >= rows || nc < 0 || nc >= cols) continue;
      const key = `${nr},${nc}`;
      if (visited.has(key) || grid[nr][nc] === "#") continue;
      visited.add(key);
      queue.push([nr, nc]);
    }
  }
  return visited;
}

function findStart(grid: string[]): [number, number] | null {
  for (let r = 0; r < grid.length; r++) {
    const c = grid[r].indexOf("S");
    if (c !== -1) return [r, c];
  }
  return null;
}

/** Every dot, power pellet, and the exit must be reachable — win condition requires collecting them all. */
function allCollectiblesReachable(grid: string[]): boolean {
  const start = findStart(grid);
  if (!start) return false;
  const reachable = reachableFrom(grid, start);

  for (let r = 0; r < grid.length; r++) {
    for (let c = 0; c < grid[r].length; c++) {
      const ch = grid[r][c];
      if ((ch === "*" || ch === "O" || ch === "E") && !reachable.has(`${r},${c}`)) return false;
    }
  }
  return true;
}

export const mazeDefinitionSchema = z
  .object({
    // Each string is one row. '#' wall, '.' floor, 'S' start, 'E' exit,
    // '*' dot, 'O' power pellet, 'G' ghost spawn (0-4 of them).
    grid: z.array(z.string().min(1)).min(3).max(30),
    // 0 = no limit.
    timeLimitSec: z.number().int().min(0).max(600).default(0),
    lives: z.number().int().min(1).max(9).default(3),
  })
  .refine((def) => def.grid.every((row) => row.length === def.grid[0].length), {
    message: "All grid rows must be the same length",
    path: ["grid"],
  })
  .refine((def) => def.grid.every((row) => [...row].every((c) => MAZE_CHARS.has(c))), {
    message: "Grid may only contain the characters # . S E * O G",
    path: ["grid"],
  })
  .refine((def) => def.grid.flatMap((row) => [...row]).filter((c) => c === "S").length === 1, {
    message: "Grid must contain exactly one S (start)",
    path: ["grid"],
  })
  .refine((def) => def.grid.some((row) => row.includes("E")), {
    message: "Grid must contain at least one E (exit)",
    path: ["grid"],
  })
  .refine((def) => def.grid.flatMap((row) => [...row]).filter((c) => c === "G").length <= MAX_GHOSTS, {
    message: `Grid may contain at most ${MAX_GHOSTS} G (ghost spawns)`,
    path: ["grid"],
  })
  .refine((def) => allCollectiblesReachable(def.grid), {
    message: "Every dot (*), power pellet (O), and the exit (E) must be reachable from the start (S)",
    path: ["grid"],
  });

export type MazeDefinition = z.infer<typeof mazeDefinitionSchema>;

export const DEFAULT_MAZE_DEFINITION: MazeDefinition = {
  grid: [
    "#############",
    "#O****#****O#",
    "#*###*#*###*#",
    "#*#*******#*#",
    "#*#*#####*#*#",
    "#****GGG****#",
    "#*#*#####*#*#",
    "#*#*******#*#",
    "#*###*#*###*#",
    "#S****#****E#",
    "#############",
  ],
  timeLimitSec: 0,
  lives: 3,
};

export const mazeProgressSchema = z.object({
  playerRow: z.number().int().min(0),
  playerCol: z.number().int().min(0),
  collectedKeys: z.array(z.string()).default([]),
  remainingMs: z.number().int().min(0),
  lives: z.number().int().min(0),
});

export type MazeProgress = z.infer<typeof mazeProgressSchema>;