"""Bitboard utilities (square index: a1=0, h8=63)."""

from __future__ import annotations

RANK_1 = 0x00000000000000FF
RANK_2 = 0x000000000000FF00
RANK_3 = 0x0000000000FF0000
RANK_4 = 0x00000000FF000000
RANK_5 = 0x000000FF00000000
RANK_6 = 0x0000FF0000000000
RANK_7 = 0x00FF000000000000
RANK_8 = 0xFF00000000000000

FILE_A = 0x0101010101010101
FILE_B = 0x0202020202020202
FILE_C = 0x0404040404040404
FILE_D = 0x0808080808080808
FILE_E = 0x1010101010101010
FILE_F = 0x2020202020202020
FILE_G = 0x4040404040404040
FILE_H = 0x8080808080808080

WHITE_SQUARES = 0x55AA55AA55AA55AA
BLACK_SQUARES = 0xAA55AA55AA55AA55
LONG_DIAGONALS = 0x8142241818244281
CENTER_SQUARES = 0x0000001818000000
CENTER_BIG = 0x00003C3C3C3C0000
LEFT_FLANK = FILE_A | FILE_B | FILE_C | FILE_D
RIGHT_FLANK = FILE_E | FILE_F | FILE_G | FILE_H

FILES = [FILE_A, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_H]
RANKS = [RANK_1, RANK_2, RANK_3, RANK_4, RANK_5, RANK_6, RANK_7, RANK_8]

MIRROR_FILE = (0, 1, 2, 3, 3, 2, 1, 0)


def file_of(sq: int) -> int:
    return sq % 8


def rank_of(sq: int) -> int:
    return sq // 8


def square(rank: int, file: int) -> int:
    return rank * 8 + file


def relative_rank_of(colour: int, sq: int) -> int:
    return rank_of(sq) if colour == 0 else 7 - rank_of(sq)


def relative_square(colour: int, sq: int) -> int:
    return square(relative_rank_of(colour, sq), file_of(sq))


def relative_square32(colour: int, sq: int) -> int:
    return 4 * relative_rank_of(colour, sq) + MIRROR_FILE[file_of(sq)]


def squares_of_matching_colour(sq: int) -> int:
    return WHITE_SQUARES if (WHITE_SQUARES >> sq) & 1 else BLACK_SQUARES


def popcount(bb: int) -> int:
    return bb.bit_count()


def getlsb(bb: int) -> int:
    return (bb & -bb).bit_length() - 1


def getmsb(bb: int) -> int:
    return bb.bit_length() - 1


def poplsb(bb: int) -> tuple[int, int]:
    sq = getlsb(bb)
    return sq, bb & (bb - 1)


def several(bb: int) -> bool:
    return bb & (bb - 1) != 0


def only_one(bb: int) -> bool:
    return bb != 0 and not several(bb)


def test_bit(bb: int, sq: int) -> bool:
    return (bb >> sq) & 1 != 0


def set_bit(bb: int, sq: int) -> int:
    return bb | (1 << sq)


def backmost(colour: int, bb: int) -> int:
    return getlsb(bb) if colour == 0 else getmsb(bb)


def frontmost(colour: int, bb: int) -> int:
    return getmsb(bb) if colour == 0 else getlsb(bb)