import type { GameWorld } from "../src/game/world/world";
import type { Direction } from "../src/game/world/types";

/** Drive a world through scenes the way a player would: acknowledge pages,
 * answer choices in order (default YES, the first weekday or menu item, or
 * the clock's shown value) and wait out timed
 * effects. Returns every page that was shown. */
/** RingTwice_StartCall's pages: the caller's name box and the cleared box
 * between rings. */
export const isRinging = (page: string) => page.startsWith("☎") || page === " ";

export function settle(
  world: GameWorld,
  answers: (number | string)[] = [],
): string[] {
  const shown: string[] = [];
  let lastHeld = "";
  for (let tick = 0; tick < 20_000; tick++) {
    const dialogue = world.dialogue;
    if (dialogue) {
      const page = dialogue.pages[dialogue.index];
      const last = dialogue.index === dialogue.pages.length - 1;
      if (last && dialogue.choice) {
        shown.push(page);
        // The naming screen waits for the caller unless a name is queued.
        if (dialogue.choice.kind === "name") {
          if (typeof answers[0] !== "string") return shown;
          world.choose(answers.shift()!);
          continue;
        }
        const answer = answers.shift();
        world.choose(
          typeof answer === "number"
            ? answer
            : dialogue.choice.kind === "yesno"
              ? 1
              : dialogue.choice.kind === "clock"
                ? dialogue.choice.selected
                : 0,
        );
      } else if (last && dialogue.holdTicks !== undefined) {
        // A received call's ringing (the caller's name box) is not text.
        if (page !== lastHeld && !isRinging(page)) shown.push(page);
        lastHeld = page;
        world.tick();
      } else {
        shown.push(page);
        world.advanceDialogue();
      }
      continue;
    }
    lastHeld = "";
    if (!world.busy) {
      // Scene scripts start on an idle tick.
      world.tick();
      if (!world.busy) return shown;
      continue;
    }
    world.tick();
  }
  throw new Error("The world did not settle.");
}

const DIRECTIONS = [
  ["up", 0, -1],
  ["down", 0, 1],
  ["left", -1, 0],
  ["right", 1, 0],
] as const;

/** .ledge_table's side-wall directions (GetMovementPermissions): side
 * walls ($b0) and buoys ($c0) block these directions. */
const EDGES: readonly (readonly Direction[])[] = [
  ["right"],
  ["left"],
  ["up"],
  ["down"],
  ["down", "right"],
  ["down", "left"],
  ["up", "right"],
  ["up", "left"],
];
const OPPOSITE = { up: "down", down: "up", left: "right", right: "left" } as const;
const edges = (tile: number): readonly Direction[] =>
  (tile & 0xf0) === 0xb0 || (tile & 0xf0) === 0xc0 ? EDGES[tile & 7] : [];

/** CheckWarpCollision's own two hazard nybbles ($6x pits, $7x doors/
 * stairs/carpets): a tile only needs avoiding here if stepping onto it
 * could actually trigger a warp. Burned Tower B1F's fall/ladder warps
 * (e.g. the coordinates `warpcheck` and a `changeblock`-revealed ladder
 * read) sit on ordinary $00 floor and never fire from an ordinary step,
 * so they are left walkable like any other floor tile. */
const isWarpHazard = (tile: number) =>
  (tile & 0xf0) === 0x60 || (tile & 0xf0) === 0x70;

/** COLL_WATER and the unused COLL_WATER_21: open water a surfer crosses
 * freely, unlike currents, waterfalls and whirlpools. */
const isOpenWater = (tile: number) => tile === 0x29 || tile === 0x21;
/** COLL_WHIRLPOOL and COLL_WHIRLPOOL_2C: water once Whirlpool clears it. */
export const isWhirlpool = (tile: number) => tile === 0x24 || tile === 0x2c;

/** COLL_ICE and COLL_ICE_2B: a step onto them keeps sliding (.CheckForced). */
const isIce = (tile: number) => tile === 0x23 || tile === 0x2b;

/** What one path search reads many times: the visible objects' tiles and
 * the map's warp tiles, taken once per search. */
interface Terrain {
  occupied: Set<string>;
  warps: Set<string>;
}
const terrainOf = (world: GameWorld): Terrain => ({
  occupied: new Set(world.objects().map((object) => `${object.x},${object.y}`)),
  warps: new Set(world.map.warps.map((warp) => `${warp.x},${warp.y}`)),
});
const VECTORS: Record<Direction, [number, number]> = {
  up: [0, -1],
  down: [0, 1],
  left: [-1, 0],
  right: [1, 0],
};

/** Whether a step from (fromX, fromY) onto the next tile in `direction`
 * is open: walkable (or open water for a surfer), no side wall, no object,
 * and no warp other than the target. */
function open(
  world: GameWorld,
  terrain: Terrain,
  fromX: number,
  fromY: number,
  direction: Direction,
  water: boolean,
  target?: { x: number; y: number },
  whirlpools = false,
) {
  const [dx, dy] = VECTORS[direction];
  const x = fromX + dx,
    y = fromY + dy;
  if (x < 0 || y < 0 || x >= world.map.width || y >= world.map.height) return false;
  const tile = world.assets.collision(world.map, x, y);
  if (
    world.assets.permission(tile) !== 0 &&
    !(water && (isOpenWater(tile) || (whirlpools && isWhirlpool(tile))))
  )
    return false;
  if (
    edges(world.assets.collision(world.map, fromX, fromY)).includes(direction) ||
    edges(tile).includes(OPPOSITE[direction])
  )
    return false;
  const key = `${x},${y}`;
  if (terrain.occupied.has(key)) return false;
  if (
    isWarpHazard(tile) &&
    terrain.warps.has(key) &&
    (x !== target?.x || y !== target?.y)
  )
    return false;
  return true;
}

/** .ledge_table: the directions each COLL_HOP_* tile jumps toward. */
const LEDGES: readonly (readonly Direction[])[] = [
  ["right"],
  ["left"],
  ["up"],
  ["down"],
  ["down", "right"],
  ["down", "left"],
  ["up", "right"],
  ["up", "left"],
];

interface PathOptions {
  water?: boolean;
  target?: { x: number; y: number };
  whirlpools?: boolean;
  ledges?: boolean;
}

/** Where a step in `direction` from (x, y) ends: the next tile, two tiles
 * on when standing on a ledge that jumps that way (.TryJump), or, on ice,
 * the last tile of the slide before something blocks it. Undefined when
 * the step is blocked. */
export function landing(
  world: GameWorld,
  x: number,
  y: number,
  direction: Direction,
  options: PathOptions = {},
  terrain = terrainOf(world),
): { x: number; y: number } | undefined {
  const { water = false, target, whirlpools = false, ledges = false } = options;
  const [dx, dy] = VECTORS[direction];
  if (ledges) {
    const standing = world.assets.collision(world.map, x, y);
    if ((standing & 0xf0) === 0xa0 && LEDGES[standing & 7].includes(direction)) {
      const lx = x + dx * 2,
        ly = y + dy * 2;
      const landingTile = world.assets.collision(world.map, lx, ly);
      if (
        lx >= 0 &&
        ly >= 0 &&
        lx < world.map.width &&
        ly < world.map.height &&
        world.assets.permission(landingTile) === 0 &&
        !terrain.occupied.has(`${x + dx},${y + dy}`) &&
        !terrain.occupied.has(`${lx},${ly}`) &&
        !(
          isWarpHazard(landingTile) &&
          terrain.warps.has(`${lx},${ly}`) &&
          (lx !== target?.x || ly !== target?.y)
        )
      )
        return { x: lx, y: ly };
    }
  }
  // COLL_WATERFALL: a surfer entering from above is carried down it.
  if (water && world.assets.collision(world.map, x + dx, y + dy) === 0x33) {
    if (direction !== "down") return undefined;
    let fy = y + 1;
    while (world.assets.collision(world.map, x, fy) === 0x33) fy++;
    if (!open(world, terrain, x, fy - 1, "down", water, target, whirlpools)) return undefined;
    return { x, y: fy };
  }
  if (!open(world, terrain, x, y, direction, water, target, whirlpools)) return undefined;
  x += dx;
  y += dy;
  while (
    isIce(world.assets.collision(world.map, x, y)) &&
    open(world, terrain, x, y, direction, water, target, whirlpools)
  ) {
    x += dx;
    y += dy;
  }
  return { x, y };
}

/** Breadth first from the player: each reached tile's path, in the order
 * the search reaches them. Stops at `target` when one is given. */
function search(world: GameWorld, options: PathOptions) {
  const terrain = terrainOf(world);
  const paths = new Map<string, Direction[]>();
  const queue = [{ x: world.x, y: world.y, path: [] as Direction[] }];
  for (let i = 0; i < queue.length; i++) {
    const node = queue[i],
      key = `${node.x},${node.y}`;
    if (paths.has(key)) continue;
    paths.set(key, node.path);
    if (node.x === options.target?.x && node.y === options.target?.y) break;
    for (const [direction] of DIRECTIONS) {
      const end = landing(world, node.x, node.y, direction, options, terrain);
      if (end) queue.push({ ...end, path: [...node.path, direction] });
    }
  }
  return paths;
}

/** Shortest walkable path on the current map, avoiding other warps.
 * `water` also crosses open water, for a player who can Surf, and
 * `whirlpools` the whirlpools a player with Whirlpool can clear; `ledges`
 * takes ledge jumps; a step onto ice slides on until blocked. */
export function findPath(
  world: GameWorld,
  targetX: number,
  targetY: number,
  { water = false, whirlpools = false, ledges = false } = {},
): Direction[] {
  const path = search(world, {
    water,
    whirlpools,
    ledges,
    target: { x: targetX, y: targetY },
  }).get(`${targetX},${targetY}`);
  if (!path) throw new Error(`No route to ${targetX},${targetY}`);
  return path;
}

/** Every tile the player can reach (not stepping onto warps), with its
 * shortest path's length: one search for many candidate targets. */
export function pathLengths(
  world: GameWorld,
  { water = false, ledges = false } = {},
): Map<string, number> {
  const lengths = new Map<string, number>();
  for (const [key, path] of search(world, { water, ledges })) lengths.set(key, path.length);
  return lengths;
}

/** Walk to a tile, settling any scene that a step triggers. A roaming NPC
 * that steps into the way is waited out, then the route is planned again. */
export function walkTo(
  world: GameWorld,
  targetX: number,
  targetY: number,
  answers: (number | string)[] = [],
): string[] {
  // Finish anything in progress first, such as the tick after a warp.
  const shown: string[] = settle(world, answers);
  for (let attempt = 0; attempt < 20; attempt++) {
    let blocked = false;
    for (const direction of findPath(world, targetX, targetY)) {
      if (!world.move(direction)) {
        const [, dx, dy] = DIRECTIONS.find(([name]) => name === direction)!;
        const blocker = world
          .objects()
          .some((object) => object.x === world.x + dx && object.y === world.y + dy);
        if (!blocker)
          throw new Error(
            `Blocked moving ${direction} at ${world.x},${world.y}: ${world.notice}`,
          );
        for (let tick = 0; tick < 64; tick++) world.tick();
        blocked = true;
        break;
      }
      shown.push(...settle(world, answers));
    }
    // A warp target leaves the map, so a completed path is the success test.
    if (!blocked) return shown;
  }
  throw new Error(`Could not reach ${targetX},${targetY}`);
}

/** A save without the play time, which keeps counting while refused or
 * rolled-back actions leave everything else unchanged. */
export function withoutPlayTime<T extends { gameTime?: unknown }>(save: T) {
  const { gameTime: _, ...rest } = save;
  return rest;
}

/** Restoring a save always moves the roam-mon bookkeeping to the map just
 * loaded (Continue's own farcall JumpRoamMons, then _BackUpMapIndices),
 * even before any roaming Pokémon has been released; a round-trip
 * comparison needs `reloaded`'s own `roamMons`/`roamMonsMap` in place of
 * `saved`'s to still match everything else exactly. */
export function afterRestore<
  T extends { roamMons?: unknown; roamMonsMap?: unknown },
>(saved: T, reloaded: T) {
  return { ...saved, roamMons: reloaded.roamMons, roamMonsMap: reloaded.roamMonsMap };
}