// fen.cpp

// includes

#include <cctype>
#include <cstdlib>
#include "fen.h"

// "constants"

const char *const start_fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";

// functions

// board_from_fen()

void board_from_fen(board_t *board, const char fen [])
    {
    int pos;
    int file, rank, sq;
    int c;
    int i, len;
    int piece;
    int pawn;

    board_clear(board);

    pos = 0;
    c = fen[pos];

    // piece placement

    for ( rank = (0xB); rank >= (0x4); rank-- )
        {
        for ( file = (0x4); file <= (0xB); )
            {
            if(c >= '1' && c <= '8')
                { // empty square(s)

                len = c - '0';

                for ( i = 0; i < len; i++ )
                    {
                    board->square[SQUARE_MAKE(file, rank)] = 0;
                    file++;
                    }
                }
            else
                { // piece

                piece = piece_from_char(c);
                board->square[SQUARE_MAKE(file, rank)] = piece;
                file++;
                }

            c = fen[++pos];
            }

        if(rank > (0x4))
            {
            c = fen[++pos];
            }
        }

    // active color

    c = fen[++pos];

    switch(c)
        {
        case 'w':
            board->turn = 0;
            break;

        case 'b':
            board->turn = 1;
            break;

        default:
            break;
        }

    c = fen[++pos];

    // castling

    c = fen[++pos];

    board->flags = 0;

    if(c == '-')
        { // no castling rights

        c = fen[++pos];
        }
    else
        {
        if(c == 'K')
            {
            if(board->square[(0x48)] == ((1 << 7) | (1 << 0)) && board->square[(0x4B)] == ((1 << 6) | (1 << 0)))
                board->flags |= (1 << 0);
            c = fen[++pos];
            }

        if(c == 'Q')
            {
            if(board->square[(0x48)] == ((1 << 7) | (1 << 0)) && board->square[(0x44)] == ((1 << 6) | (1 << 0)))
                board->flags |= (1 << 1);
            c = fen[++pos];
            }

        if(c == 'k')
            {
            if(board->square[(0xB8)] == ((1 << 7) | (1 << 1)) && board->square[(0xBB)] == ((1 << 6) | (1 << 1)))
                board->flags |= (1 << 2);
            c = fen[++pos];
            }

        if(c == 'q')
            {
            if(board->square[(0xB8)] == ((1 << 7) | (1 << 1)) && board->square[(0xB4)] == ((1 << 6) | (1 << 1)))
                board->flags |= (1 << 3);
            c = fen[++pos];
            }
        }

    // en-passant

    c = fen[++pos];

    if(c == '-')
        { // no en-passant

        sq = 0;
        c = fen[++pos];
        }
    else
        {
        file = file_from_char(c);
        c = fen[++pos];

        rank = rank_from_char(c);
        c = fen[++pos];

        sq = SQUARE_MAKE(file, rank);
        pawn = SQUARE_EP_DUAL(sq);

        if(board->square[sq] != 0 || board->square[pawn] != PAWN_MAKE(COLOUR_OPP(board->turn))
            || (board->square[pawn - 1] != PAWN_MAKE(board->turn) && board->square[pawn + 1] != PAWN_MAKE(board->turn)))
            {
            sq = 0;
            }
        }

    board->ep_square = sq;

    // halfmove clock

    board->ply_nb = 0;

    if(c != ' ')
        {
        goto update;
        }
    c = fen[++pos];

    if(!isdigit(c))
        {
        goto update;
        }

    board->ply_nb = atoi(&fen[pos]);

    // board update

    update:
    board_init_list(board);
    }

// end of fen.cpp