/**
 * data-structure-typed
 *
 * @author Pablo Zeng
 * @copyright Copyright (c) 2022 Pablo Zeng <zrwusa@gmail.com>
 * @license MIT License
 */
import type { Direction, NavigatorParams, Turning } from '../../types';

export class Character {
  direction: Direction;
  turn: () => Character;

  /**
   * The constructor function takes in a direction and turning object and sets the direction and turn properties of the
   * Character class.
   * @param {Direction} direction - The direction parameter is used to specify the current direction of the character. It
   * can be any value that represents a direction, such as "north", "south", "east", or "west".
   * @param {Turning} turning - The `turning` parameter is an object that maps each direction to the corresponding
   * turning direction. It is used to determine the new direction when the character turns.
   */
  constructor(direction: Direction, turning: Turning) {
    this.direction = direction;
    this.turn = () => new Character(turning[direction], turning);
  }
}

/**
 *
 */
export class Navigator<T = number> {
  onMove: (cur: [number, number]) => void;
  protected readonly _matrix: T[][];
  protected readonly _cur: [number, number];
  protected _character: Character;
  protected readonly _VISITED: T;

  /**
   * The constructor initializes the Navigator object with the given parameters and sets the current position as visited
   * in the matrix.
   * @param  - - `matrix`: a 2D array representing the grid or map
   */
  constructor({ matrix, turning, onMove, init: { cur, charDir, VISITED } }: NavigatorParams<T>) {
    this._matrix = matrix;
    this._cur = cur;
    this._character = new Character(charDir, turning);
    this.onMove = onMove;
    if (this.onMove) this.onMove(this._cur);
    this._VISITED = VISITED;
    this._matrix[this._cur[0]][this._cur[1]] = this._VISITED;
  }

  /**
   * The "start" function moves the character in its current direction until it encounters an obstacle, then it turns the
   * character and repeats the process.
   */
  start() {
    while (this.check(this._character.direction) || this.check(this._character.turn().direction)) {
      const { direction } = this._character;
      if (this.check(direction)) {
        this.move(direction);
      } else if (this.check(this._character.turn().direction)) {
        this._character = this._character.turn();
      }
    }
  }

  /**
   * The function checks if there is a valid move in the specified direction in a matrix.
   * @param {Direction} direction - The direction parameter is a string that represents the direction in which to check.
   * It can be one of the following values: 'up', 'right', 'down', or 'left'.
   * @returns a boolean value.
   */
  check(direction: Direction) {
    let forward: T | undefined, row: T[] | undefined;
    const matrix = this._matrix;
    const [i, j] = this._cur;
    switch (direction) {
      case 'up':
        row = matrix[i - 1];
        if (!row) return false;
        forward = row[j];
        break;
      case 'right':
        forward = matrix[i][j + 1];
        break;
      case 'down':
        row = matrix[i + 1];
        if (!row) return false;
        forward = row[j];
        break;
      case 'left':
        forward = matrix[i][j - 1];
        break;
    }
    return forward !== undefined && forward !== this._VISITED;
  }

  /**
   * The `move` function updates the current position based on the given direction and updates the matrix accordingly.
   * @param {Direction} direction - The `direction` parameter is a string that represents the direction in which to move.
   * It can have one of the following values: 'up', 'right', 'down', or 'left'.
   */
  move(direction: Direction) {
    switch (direction) {
      case 'up':
        this._cur[0]--;
        break;
      case 'right':
        this._cur[1]++;
        break;
      case 'down':
        this._cur[0]++;
        break;
      case 'left':
        this._cur[1]--;
        break;
    }

    const [i, j] = this._cur;
    this._matrix[i][j] = this._VISITED;
    if (this.onMove) this.onMove(this._cur);
  }
}