// © 2025 A.M. Rowsell <amr@frzn.dev>

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as
// defined by the Mozilla Public License, v. 2.0.

#include "Piece.hpp"

Piece::~Piece() {
    return;
}

// because the Piece class is instantiated in another class using
// unique_ptr, non-pure virtual functions apparently *must*
// have definitions, or the linker freaks out
// so this is just a stub that does nothing. it doesn't matter
// because only the derived class versions should be called.

std::vector<Move> Piece::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    return moveList;
}

std::vector<Move> King::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[8][2] = {
        {-1, 0}, // Up
        {-1, -1}, // up-left
        {-1, 1}, // up-right
        {1, 0}, // Down
        {1, -1}, // down-left
        {1, 1}, // down-right
        {0, -1}, // Left
        {0, 1} // Right
    };
    for(auto &dir : directions) {
        // establish r/f for square to check
        int r = from.rank + dir[0];
        int f = from.file + dir[1];
        if(r >= 0 && r < 8 && f >= 0 && f < 8) {
            const auto &target = board.boardGrid[r][f]; // examine the target square
            auto ra = static_cast<Rank>(r);
            auto fi = static_cast<File>(f);
            Square targetSquare = {ra, fi};
            if(!target) { // if square is empty (NULL)
                moveList.push_back({from, targetSquare}); // then it's potentially a legal move
            } else if(target && target->getColour() != this->getColour()) { // if it's occupied with a piece of opposite colour
                moveList.push_back({from, targetSquare}); // then again it's potentially legal
                break;
            } else {
                // otherwise it's one of our pieces
                break;
            }
        }
    }
    // How to check for check:
    // go through moveList.to, then check all directions to see if an enemy piece is threatening
    // If a piece of opposite colour is detected:
    // - Determine the piece type
    // - Determine the direction we are looking at (diagonal or not)
    // - If that piece can attack in that direction, it would be check, so remove this move from moveList
    for(auto &moves : moveList) {
        Square startSquare = moves.to; // get the potential move to square
        for(auto &dir : directions) { // now go through all directions
            int r = startSquare.rank + dir[0];
            int f = startSquare.file + dir[1];
            bool diagonal = (abs(dir[0]) + abs(dir[1]) == 2) ? 1 : 0; // check if diagonal
            while(r >= 0 && r < 8 && f >= 0 && f < 8) {
                auto &target = board.boardGrid[r][f]; // check what's at the square we're examining
                if(target && target->getColour() != this->getColour()) { // is it occupied & an enemy?
                    if((target->getPieceType() == QUEEN || target->getPieceType() == BISHOP) && diagonal) {
                        // we are being attacked diagonally on this square, so remove it
                        //moves.to.rank = 255; moves.to.file = 255; // mark as invalid???
                    }
                }
            }
        }
    
    }
    return moveList;
}

std::vector<Move> Rook::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[4][2] = {
        {-1, 0}, // Up
        {1, 0}, // Down
        {0, -1}, // Left
        {0, 1} // Right
    };
    for(auto& dir : directions) {
        int r = from.rank + dir[0];
        int f = from.file + dir[1];
        while(r >= 0 && r < 8 && f >= 0 && f < 8) {
            const auto& target = board.boardGrid[r][f];
            auto ra = static_cast<Rank>(r);
            auto fi = static_cast<File>(f);
            Square targetSquare = {ra, fi};
            if(!target) {
                moveList.push_back({from, targetSquare});
            } else if(target && target->getColour() != this->getColour()) {
                moveList.push_back({from, targetSquare});
                break;
            } else
                break;
            r += dir[0];
            f += dir[1];
        }
    }
    return moveList;
}

std::vector<Move> Queen::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    return moveList;
}

std::vector<Move> Knight::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    return moveList;
}

std::vector<Move> Bishop::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    return moveList;
}

std::vector<Move> Pawn::getLegalMoves(const Square &from, const Board &board) const {
    std::vector<Move> moveList;
    const int directions[2][4][2] = {
        {
            // black
            {-1, 0}, // Up
            {-2, 0}, // 2up first move
            {-1, 1}, // attack to right
            {-1, -1} // attack to left
        },
        {
            // white
            {1, 0}, // down
            {2, 0}, // 2down first move
            {1, 1}, // attack to right
            {1, -1} // attack to left
        }
    };
    if(this->getColour() == PIECE_BLACK) {
        // go through black options
        for(auto &dir : directions[0]) {
            int r = from.rank + dir[0];
            int f = from.file + dir[1];
            if(r >= 0 && r < 8 && f >= 0 && f < 8) { // no need for a while loop as we only have finite moves in limited directions
                const auto& target = board.boardGrid[r][f];
                auto ra = static_cast<Rank>(r);
                auto fi = static_cast<File>(f);
                Square targetSquare = {ra, fi};
                if(dir[0] == -2 && !this->checkIfMoved()) {
                    // then 2 is potentially legal
                    if(!target && !(board.boardGrid[r + 1][f])) // check both squares for pieces of any colour
                        moveList.push_back({from, targetSquare});
                    else
                        continue;
                } else if(abs(dir[1]) == 1) { // attempted capture (diagonal)
                    if(target && target->getColour() != this->getColour()) {
                        // legal capture
                        moveList.push_back({from, targetSquare});
                    } else
                        continue;
                } else { // normal one square forward
                    if(!target)
                        moveList.push_back({from, targetSquare});
                }
                // now check if we are on 8th rank, for promotion
            }
        }
    } else if(this->getColour() == PIECE_WHITE) {
        for(auto &dir : directions[1]) {
            // go through white options
            int r = from.rank + dir[0];
            int f = from.file + dir[1];
            if(r >= 0 && r < 8 && f >= 0 && f < 8) { // no need for a while loop as we only have finite moves in limited directions
                const auto& target = board.boardGrid[r][f];
                auto ra = static_cast<Rank>(r);
                auto fi = static_cast<File>(f);
                Square targetSquare = {ra, fi};
                if(dir[0] == 2 && !this->checkIfMoved()) {
                    // then 2 is potentially legal
                    if(!target && !(board.boardGrid[r - 1][f]))
                        moveList.push_back({from, targetSquare});
                    else
                        continue;
                } else if(abs(dir[1]) == 1) { // attempted capture (diagonal)
                    if(target && target->getColour() != this->getColour()) { // can only move there if it's a capture
                        // legal capture
                        moveList.push_back({from, targetSquare});
                    } else
                        continue;
                } else { // normal one square forward
                    if(!target)
                        moveList.push_back({from, targetSquare});
                }
                // now check if we are on 8th rank, for promotion
            }
        }
    }
    return moveList;
}