package board

import (
	"strconv"
)

// Bitboard is defined as
type Bitboard uint64

// NewBitboard returns an initialized Bitboard.
func NewBitboard(m map[Square]bool) Bitboard {
	s := ""
	for sq := 0; sq < 64; sq++ {
		if m[Square(sq)] {
			s += "1"
		} else {
			s += "0"
		}
	}
	bb, err := strconv.ParseUint(s, 2, 64)
	if err != nil {
		panic(err)
	}
	return Bitboard(bb)
}

// Map returns a map[Square]bool representation of this Bitboard.
func (bb Bitboard) Map() map[Square]bool {
	m := map[Square]bool{}
	for sq := 0; sq < 64; sq++ {
		if bb&Square(sq).Bitboard() > 0 {
			m[Square(sq)] = true
		}
	}
	return m
}

// Squares returns a []Square of all bits in this Bitboard.
func (bb Bitboard) Squares() []Square {
	squares := []Square{}
	for sq := 0; sq < 64; sq++ {
		if bb&Square(sq).Bitboard() > 0 {
			squares = append(squares, Square(sq))
		}
	}
	return squares
}

// Occupied returns true if the given Square is occupied.
func (bb Bitboard) Occupied(sq Square) bool {
	return (uint64(bb) >> uint64(63-sq) & 1) == 1
}

// Draw returns visual representation of the bitboard useful for debugging.
func (bb Bitboard) Draw() string {
	s := "\n  A B C D E F G H\n"
	for r := 7; r >= 0; r-- {
		s += Rank(r).String()
		s += " "
		for f := 0; f < 8; f++ {
			sq := NewSquare(File(f), Rank(r))
			if bb.Occupied(sq) {
				s += "1"
			} else {
				s += "0"
			}
			s += " "
		}
		s += "\n"
	}
	return s
}

// Flip toggles the bit at the given square.
func (bb *Bitboard) Flip(sq Square) {
	if !sq.IsValid() {
		return
	}
	oldBB := *bb
	newBB := oldBB ^ sq.Bitboard()
	*bb = newBB
}