/** 주사위판 위를 이동하는 말. */
export class Chessman {
  private index: number;
  private readonly boardLength: number;
  /** 1: 시계방향, -1: 반시계방향 */
  private direction: 1 | -1 = 1;
  /** 무인도: 남은 대기 턴, 탈출 가능 눈 */
  private island: { turnsLeft: number; escapeOn: number } | null = null;

  constructor(boardLength: number, startIndex = 0) {
    if (boardLength <= 0) {
      throw new Error('Chessman boardLength must be positive');
    }
    this.boardLength = boardLength;
    this.index = ((startIndex % boardLength) + boardLength) % boardLength;
  }

  get position(): number {
    return this.index;
  }

  get facing(): 1 | -1 {
    return this.direction;
  }

  get isOnIsland(): boolean {
    return this.island != null;
  }

  get islandTurnsLeft(): number {
    return this.island?.turnsLeft ?? 0;
  }

  reverseDirection(): 1 | -1 {
    this.direction = this.direction === 1 ? -1 : 1;
    return this.direction;
  }

  enterIsland(turns: number, escapeOn = 6) {
    this.island = { turnsLeft: Math.max(1, Math.trunc(turns)), escapeOn };
  }

  clearIsland() {
    this.island = null;
  }

  /**
   * 무인도 상태에서의 주사위 처리.
   * - escape: escapeOn(기본 6)이 한 면이라도 나오면 탈출 → 이후 정상 이동
   * - wait: 턴 소모 후 대기 (turnsLeft 0이면 자동 해제, 이번 턴은 이동 없음)
   * - free: 이미 무인도 아님
   */
  resolveIslandRoll(roll: number, faces?: number[]): 'escape' | 'wait' | 'free' {
    if (!this.island) return 'free';

    const values = faces && faces.length > 0 ? faces : [roll];
    if (values.some((value) => value === this.island!.escapeOn)) {
      this.island = null;
      return 'escape';
    }

    this.island.turnsLeft -= 1;
    if (this.island.turnsLeft <= 0) {
      this.island = null;
    }
    return 'wait';
  }

  teleport(index: number): number {
    this.index = ((index % this.boardLength) + this.boardLength) % this.boardLength;
    return this.index;
  }

  moveOne(): number {
    return this.move(1);
  }

  /** steps칸만큼 현재 방향으로 이동 */
  move(steps: number): number {
    const amount = Math.trunc(steps);
    if (amount === 0) return this.index;
    const delta = amount * this.direction;
    this.index = (this.index + delta) % this.boardLength;
    if (this.index < 0) this.index += this.boardLength;
    return this.index;
  }

  reset(startIndex = 0): number {
    this.index = ((startIndex % this.boardLength) + this.boardLength) % this.boardLength;
    this.direction = 1;
    this.island = null;
    return this.index;
  }
}