using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 棋盘数据管理（普通类）：
/// 维护 9x10 棋子网格与全部棋子数据，负责落子/吃子/模拟回滚等纯数据操作
/// </summary>
public class ChessBoardManager
{
    /// <summary>网格数据 grid[x,y]（null = 空位）</summary>
    private ChessPieceData[,] grid = new ChessPieceData[ChessConst.BoardWidth, ChessConst.BoardHeight];

    /// <summary>全部棋子（含已被吃的，id 即添加顺序）</summary>
    public List<ChessPieceData> allPieces = new List<ChessPieceData>();

    public ChessPieceData GetPiece(int x, int y)
    {
        if (!ChessConst.InBoard(x, y)) return null;
        return grid[x, y];
    }

    public ChessPieceData GetPiece(Vector2Int p)
    {
        return GetPiece(p.x, p.y);
    }

    /// <summary>初始化一副标准开局棋子</summary>
    public void InitDefaultBoard()
    {
        grid = new ChessPieceData[ChessConst.BoardWidth, ChessConst.BoardHeight];
        allPieces.Clear();
        int id = 0;

        // 底线：车马象士将士士象马车
        var backRow = new[]
        {
            ChessPieceType.Ju, ChessPieceType.Ma, ChessPieceType.Xiang, ChessPieceType.Shi,
            ChessPieceType.Jiang, ChessPieceType.Shi, ChessPieceType.Xiang, ChessPieceType.Ma, ChessPieceType.Ju
        };

        // 红方（下方 y0~4）
        for (int x = 0; x < ChessConst.BoardWidth; x++)
            AddPiece(id++, backRow[x], ChessCamp.Red, x, 0);
        AddPiece(id++, ChessPieceType.Pao, ChessCamp.Red, 1, 2);
        AddPiece(id++, ChessPieceType.Pao, ChessCamp.Red, 7, 2);
        for (int x = 0; x < ChessConst.BoardWidth; x += 2)
            AddPiece(id++, ChessPieceType.Bing, ChessCamp.Red, x, 3);

        // 黑方（上方 y5~9）
        for (int x = 0; x < ChessConst.BoardWidth; x++)
            AddPiece(id++, backRow[x], ChessCamp.Black, x, 9);
        AddPiece(id++, ChessPieceType.Pao, ChessCamp.Black, 1, 7);
        AddPiece(id++, ChessPieceType.Pao, ChessCamp.Black, 7, 7);
        for (int x = 0; x < ChessConst.BoardWidth; x += 2)
            AddPiece(id++, ChessPieceType.Bing, ChessCamp.Black, x, 6);
    }

    private ChessPieceData AddPiece(int id, ChessPieceType type, ChessCamp camp, int x, int y)
    {
        var p = new ChessPieceData
        {
            id = id,
            pieceType = type,
            camp = camp,
            pos = new Vector2Int(x, y),
            isAlive = true
        };
        allPieces.Add(p);
        grid[x, y] = p;
        return p;
    }

    /// <summary>查找某方存活的将 / 帅</summary>
    public ChessPieceData FindKing(ChessCamp camp)
    {
        for (int i = 0; i < allPieces.Count; i++)
        {
            var p = allPieces[i];
            if (p.isAlive && p.camp == camp && p.pieceType == ChessPieceType.Jiang) return p;
        }
        return null;
    }

    /// <summary>
    /// 真正执行移动（被吃的棋子标记 isAlive=false）。不做任何规则校验，调用方负责校验。
    /// 返回被吃的棋子（没吃子返回 null）
    /// </summary>
    public ChessPieceData ApplyMove(ChessPieceData piece, Vector2Int to)
    {
        ChessPieceData captured = GetPiece(to);
        if (captured != null) captured.isAlive = false;
        grid[piece.pos.x, piece.pos.y] = null;
        piece.pos = to;
        grid[to.x, to.y] = piece;
        return captured;
    }

    /// <summary>
    /// 回退一步移动（配合悔棋 / 规则模拟）：
    /// 把 piece 移回 from，把 captured（可为 null）复活在原位置
    /// </summary>
    public void UndoMove(ChessPieceData piece, Vector2Int from, ChessPieceData captured)
    {
        Vector2Int to = piece.pos;
        grid[to.x, to.y] = captured;
        if (captured != null)
        {
            captured.isAlive = true;
            captured.pos = to;
        }
        piece.pos = from;
        grid[from.x, from.y] = piece;
    }
}