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 / first weekday) and wait out timed
 * effects. Returns every page that was shown. */
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
              : 0,
        );
      } else if (last && dialogue.holdTicks !== undefined) {
        if (page !== lastHeld) 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;

/** Shortest walkable path on the current map, avoiding other warps. */
export function findPath(
  world: GameWorld,
  targetX: number,
  targetY: number,
): Direction[] {
  const queue = [{ x: world.x, y: world.y, path: [] as Direction[] }];
  const visited = new Set<string>();
  for (let i = 0; i < queue.length; i++) {
    const node = queue[i],
      key = `${node.x},${node.y}`;
    if (visited.has(key)) continue;
    visited.add(key);
    if (node.x === targetX && node.y === targetY) return node.path;
    for (const [direction, dx, dy] of DIRECTIONS) {
      const x = node.x + dx,
        y = node.y + dy;
      if (x < 0 || y < 0 || x >= world.map.width || y >= world.map.height)
        continue;
      if (
        world.assets.permission(world.assets.collision(world.map, x, y)) !== 0
      )
        continue;
      if (world.objects().some((object) => object.x === x && object.y === y))
        continue;
      if (
        world.map.warps.some((warp) => warp.x === x && warp.y === y) &&
        (x !== targetX || y !== targetY)
      )
        continue;
      queue.push({ x, y, path: [...node.path, direction] });
    }
  }
  throw new Error(`No route to ${targetX},${targetY}`);
}

/** 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}`);
}