// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package bitvector

import (
	"errors"
)

var errInvalidLength = errors.New("invalid length")

type BitVector struct {
	len int
	b   []byte
}

func New(l int) (bv *BitVector, err error) {
	return NewFromBytes(make([]byte, l/8+1), l)
}

func NewFromBytes(b []byte, l int) (bv *BitVector, err error) {
	if l <= 0 {
		return nil, errInvalidLength
	}
	if len(b)*8 < l {
		return nil, errInvalidLength
	}
	return &BitVector{
		len: l,
		b:   b,
	}, nil
}

func (bv *BitVector) Get(i int) bool {
	bi := i / 8
	return bv.b[bi]&(0x1<<uint(i%8)) != 0
}

func (bv *BitVector) Set(i int, v bool) {
	bi := i / 8
	cv := bv.Get(i)
	if cv != v {
		bv.b[bi] ^= 0x1 << uint8(i%8)
	}
}

func (bv *BitVector) Bytes() []byte {
	return bv.b
}

func (bv *BitVector) Length() int {
	return bv.len
}