using System;
using System.Collections.Generic;
using Vector2I = Vector.Vector2I;

using static IBoard;
public abstract class AbstractBoard : IBoard {
    private readonly int rows;
    private readonly int cols;
    protected readonly IPiece[,] pieces;
    protected readonly List<MoveRecord> moveRecords = new();
    protected readonly int MAX_RECORDS;

    public int Rows => rows;
    public int Cols => cols;

    public event EventHandler<SetPieceEventArgs> OnSetPiece;
    public event EventHandler<IPiece> OnInsert;
    public event EventHandler<IPiece> OnRemove;
    public event EventHandler<MoveEventArgs> OnMove;

    public event EventHandler<MoveRecord> OnAddRecord;
    public event EventHandler<MoveRecord> OnUndoRecord;

    public AbstractBoard(int rows, int cols, int maxRecords = int.MaxValue) {
        this.rows = rows;
        this.cols = cols;
        pieces = new IPiece[rows, cols];
        MAX_RECORDS = maxRecords;
    }

    public virtual bool IsPosOutOfRange(Vector2I arrayPos) {
        return arrayPos.X < 0 || arrayPos.X >= Rows || arrayPos.Y < 0 || arrayPos.Y >= Cols;
    }

    public virtual IPiece GetPiece(Vector2I arrayPos) {
        if (IsPosOutOfRange(arrayPos)) return null;
        return pieces[arrayPos.X, arrayPos.Y];
    }

    public virtual IPiece SetPiece(IPiece piece, Vector2I pos) {
        if (IsPosOutOfRange(pos)) return null;
        
        IPiece oldPiece = pieces[pos.X, pos.Y];
        pieces[pos.X, pos.Y] = piece;
        if (piece != null) piece.Pos = pos;
        // if (oldPiece != null) oldPiece.Pos = Vector2I.Zero;

        OnSetPiece?.Invoke(this, new SetPieceEventArgs { OldPiece = oldPiece, NewPiece = piece, Pos = pos });        
        return oldPiece;
    }

    public virtual bool InsertPiece(IPiece piece, Vector2I pos) {
        if (GetPiece(pos) != null && piece == null) {
            return false;
        }

        OnInsert?.Invoke(this, piece);
        SetPiece(piece, pos);
        return true;
    }

    public virtual bool MovePiece(Vector2I from, Vector2I to) {
        if (IsPosOutOfRange(to) || IsPosOutOfRange(from)) {
            return false;
        }

        IPiece piece = GetPiece(from);
        if (GetPiece(to) != null && piece == null) {
            return false;
        }

        OnMove?.Invoke(this, new MoveEventArgs { From = from, To = to, Piece = piece });
        SetPiece(null, from);
        SetPiece(piece, to);
        return true;
    }

    public virtual IPiece RemovePiece(Vector2I pos) {
        IPiece piece = GetPiece(pos);
        OnRemove?.Invoke(this, piece);
        return SetPiece(null, pos);
    }

    public virtual void Clear() { Clear(true); }

    public virtual void Clear(bool clearRecords) {
        for (int i = 0; i < Rows; i++) {
            for (int j = 0; j < Cols; j++) {
                RemovePiece(new Vector2I(i, j));
            }
        }
        if (clearRecords) ClearRecords();
    }

    public virtual void ClearRecords() {
        moveRecords.Clear();
    }

    public virtual void AddRecord(IPiece From, IPiece To, Vector2I FromPos, Vector2I ToPos) {
        if (moveRecords.Count >= MAX_RECORDS) {
            moveRecords.RemoveAt(0);
        }
        MoveRecord record = new(From, To, FromPos, ToPos);

        OnAddRecord?.Invoke(this, record);
        moveRecords.Add(record);
    }
    
    public virtual void UndoRecord() {
        if (moveRecords.Count == 0) return;
        MoveRecord record = moveRecords[^1];
        moveRecords.RemoveAt(moveRecords.Count - 1);

        // 恢复新位置的棋子，order is very inmportant
        if (record.From != null) {
            MovePiece(record.ToPos, record.FromPos);
        }
        
        // 恢复旧位置的棋子
        if (record.To != null) {
            InsertPiece(record.To, record.ToPos);
        }

        OnUndoRecord?.Invoke(this, record);
    }

    public class MoveRecord {
        public IPiece From { get; }
        public IPiece To { get; }
        public Vector2I FromPos { get; }
        public Vector2I ToPos { get; }

        public MoveRecord(IPiece From, IPiece To, Vector2I FromPos, Vector2I ToPos) {
            this.From = From;
            this.To = To;
            this.ToPos = ToPos;
            this.FromPos = FromPos;
        }
    }
}