chess/planning/implementation/code-templates/js/models/Piece.js

/**
 * @file Piece.js
 * @description Base class for all chess pieces
 * @author Implementation Team
 */

import { PIECE_TYPES } from '../utils/Constants.js';

/**
 * @class Piece
 * @description Abstract base class for chess pieces
 * All specific piece classes (Pawn, Rook, etc.) inherit from this
 *
 * @example
 * // Don't instantiate directly, use subclasses
 * const pawn = new Pawn('white', {row: 6, col: 4});
 */
class Piece {
  /**
   * @param {string} color - Piece color ('white' or 'black')
   * @param {Object} position - Initial position {row, col}
   * @param {string} type - Piece type (from PIECE_TYPES)
   */
  constructor(color, position, type) {
    /**
     * @property {string} color - Piece color
     */
    this.color = color;

    /**
     * @property {Object} position - Current position {row, col}
     */
    this.position = position;

    /**
     * @property {string} type - Piece type
     */
    this.type = type;

    /**
     * @property {boolean} hasMoved - Whether piece has moved (for castling, pawn two-square)
     */
    this.hasMoved = false;

    /**
     * @property {string} id - Unique identifier for the piece
     */
    this.id = `${color}-${type}-${Date.now()}`;
  }

  /**
   * Moves the piece to a new position
   *
   * @param {Object} newPosition - Target position {row, col}
   *
   * @example
   * piece.move({row: 4, col: 4});
   */
  move(newPosition) {
    // TODO: Implement move
    // 1. Update position
    // 2. Set hasMoved to true
  }

  /**
   * Gets all valid moves for this piece
   * Must be implemented by subclasses
   *
   * @abstract
   * @param {Board} board - Current board state
   * @returns {Array<Object>} Array of valid positions {row, col}
   *
   * @example
   * const validMoves = piece.getValidMoves(board);
   */
  getValidMoves(board) {
    // TODO: Override in subclasses
    throw new Error('getValidMoves must be implemented by subclass');
  }

  /**
   * Checks if this piece can move to a specific position
   *
   * @param {Object} position - Target position {row, col}
   * @param {Board} board - Current board state
   * @returns {boolean} True if move is valid
   *
   * @example
   * if (piece.canMoveTo({row: 4, col: 4}, board)) {
   *   // Move is valid
   * }
   */
  canMoveTo(position, board) {
    // TODO: Implement can move to
    // Get valid moves and check if position is in the list
    return false;
  }

  /**
   * Creates a copy of this piece
   *
   * @returns {Piece} Cloned piece
   *
   * @example
   * const pieceCopy = piece.clone();
   */
  clone() {
    // TODO: Implement clone
    // Create new instance of same class with same properties
    // Note: This is tricky because we need to know the actual subclass
    return null;
  }

  /**
   * Gets the piece's symbol for display
   *
   * @returns {string} Unicode symbol for the piece
   *
   * @example
   * console.log(piece.getSymbol());  // → '♙'
   */
  getSymbol() {
    // TODO: Implement get symbol
    // Use PIECE_SYMBOLS from Constants
    return '';
  }

  /**
   * Gets the piece's value for AI evaluation
   *
   * @returns {number} Piece value
   *
   * @example
   * const value = piece.getValue();  // → 3 for knight
   */
  getValue() {
    // TODO: Implement get value
    // Use PIECE_VALUES from Constants
    return 0;
  }

  /**
   * Checks if this piece is white
   *
   * @returns {boolean} True if piece is white
   */
  get isWhite() {
    // TODO: Implement is white
    return false;
  }

  /**
   * Checks if this piece is black
   *
   * @returns {boolean} True if piece is black
   */
  get isBlack() {
    // TODO: Implement is black
    return false;
  }

  /**
   * Gets a string representation of the piece
   *
   * @returns {string} String representation
   *
   * @example
   * console.log(piece.toString());  // → "White Pawn at e2"
   */
  toString() {
    // TODO: Implement toString
    // Format: "[Color] [Type] at [algebraic notation]"
    return '';
  }

  /**
   * Helper method to check if a position is occupied by an enemy
   *
   * @protected
   * @param {Object} position - Position to check {row, col}
   * @param {Board} board - Current board state
   * @returns {boolean} True if position has enemy piece
   */
  _isEnemyAt(position, board) {
    // TODO: Implement enemy check
    // Get piece at position and compare colors
    return false;
  }

  /**
   * Helper method to check if a position is occupied by friendly piece
   *
   * @protected
   * @param {Object} position - Position to check {row, col}
   * @param {Board} board - Current board state
   * @returns {boolean} True if position has friendly piece
   */
  _isFriendlyAt(position, board) {
    // TODO: Implement friendly check
    return false;
  }

  /**
   * Helper method to check if a position is empty
   *
   * @protected
   * @param {Object} position - Position to check {row, col}
   * @param {Board} board - Current board state
   * @returns {boolean} True if position is empty
   */
  _isEmptyAt(position, board) {
    // TODO: Implement empty check
    return false;
  }
}

export default Piece;