package main

import (
	"os"
	"sync"

	"github.com/anacrolix/torrent/metainfo"
	"github.com/anacrolix/torrent/storage"
)

type BFPieceCompletion struct {
	sync.Mutex
}

func NewBFPieceCompletion() *BFPieceCompletion {
	return &BFPieceCompletion{}
}

func (self *BFPieceCompletion) Get(pk metainfo.PieceKey) (c storage.Completion, rerr error) {
	self.Lock()
	defer self.Unlock()
	fd, err := os.OpenFile(pk.InfoHash.HexString()+".bf", os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		rerr = err
		return
	}
	defer fd.Close()
	b := []byte{0}
	_, err = fd.ReadAt(b, int64(pk.Index))
	if err != nil {
		return
	}
	c.Ok = true
	switch string(b) {
	case "0":
		c.Complete = false
	case "1":
		c.Complete = true
	default:
		c.Ok = false
	}
	return
}

func (self *BFPieceCompletion) Set(pk metainfo.PieceKey, complete bool) error {
	if c, err := self.Get(pk); err == nil && c.Ok && c.Complete == complete {
		return nil
	}
	self.Lock()
	defer self.Unlock()
	fd, err := os.OpenFile(pk.InfoHash.HexString()+".bf", os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		return err
	}
	defer fd.Close()
	b := []byte{'1'}
	if !complete {
		b[0] = '0'
	}
	if _, err = fd.WriteAt(b, int64(pk.Index)); err != nil {
		return err
	}
	return nil
}

func (self *BFPieceCompletion) Close() error {
	return nil
}