package client

import (
	"crypto/sha1"

	"storrent/bt"
)

type piece struct {
	hash    [20]byte
	size    int64
	data    []byte
	have    []bool
	reqs    []bool
	reqPeer []*bt.Peer
	done    bool
}

func (p *piece) put(begin int, data []byte) bool {
	if p.done {
		return false
	}
	block := begin / bt.BlockSize
	if block >= len(p.have) || p.have[block] {
		return false
	}
	copy(p.data[begin:], data)
	p.have[block] = true
	for _, got := range p.have {
		if !got {
			return false
		}
	}
	if sha1.Sum(p.data) != p.hash {
		for i := range p.have {
			p.have[i] = false
			p.reqs[i] = false
		}
		return false
	}
	p.done = true
	return true
}

func (p *piece) next(peer *bt.Peer) (begin, length int64, ok bool) {
	for i := range p.have {
		if p.have[i] || p.reqs[i] {
			continue
		}
		p.reqs[i] = true
		p.reqPeer[i] = peer
		begin = int64(i) * bt.BlockSize
		length = bt.BlockSize
		if begin+length > p.size {
			length = p.size - begin
		}
		return begin, length, true
	}
	return 0, 0, false
}

func (p *piece) resetPeer(peer *bt.Peer) {
	for i := range p.reqs {
		if p.reqs[i] && p.reqPeer[i] == peer {
			p.reqs[i] = false
			p.reqPeer[i] = nil
		}
	}
}