package erasure_coding

import (
	"fmt"
	"os"
	"path"
	"strconv"

	"github.com/chrislusf/seaweedfs/weed/storage/needle"
)

type ShardId uint8

type EcVolumeShard struct {
	VolumeId    needle.VolumeId
	ShardId     ShardId
	Collection  string
	dir         string
	ecdFile     *os.File
	ecdFileSize int64
}

func NewEcVolumeShard(dirname string, collection string, id needle.VolumeId, shardId ShardId) (v *EcVolumeShard, e error) {

	v = &EcVolumeShard{dir: dirname, Collection: collection, VolumeId: id, ShardId: shardId}

	baseFileName := v.FileName()

	// open ecd file
	if v.ecdFile, e = os.OpenFile(baseFileName+ToExt(int(shardId)), os.O_RDONLY, 0644); e != nil {
		return nil, fmt.Errorf("cannot read ec volume shard %s.%s: %v", baseFileName, ToExt(int(shardId)), e)
	}
	ecdFi, statErr := v.ecdFile.Stat()
	if statErr != nil {
		return nil, fmt.Errorf("can not stat ec volume shard %s.%s: %v", baseFileName, ToExt(int(shardId)), statErr)
	}
	v.ecdFileSize = ecdFi.Size()

	return
}

func (shard *EcVolumeShard) Size() int64 {
	return shard.ecdFileSize
}

func (shard *EcVolumeShard) String() string {
	return fmt.Sprintf("ec shard %v:%v, dir:%s, Collection:%s", shard.VolumeId, shard.ShardId, shard.dir, shard.Collection)
}

func (shard *EcVolumeShard) FileName() (fileName string) {
	return EcShardFileName(shard.Collection, shard.dir, int(shard.VolumeId))
}

func EcShardFileName(collection string, dir string, id int) (fileName string) {
	idString := strconv.Itoa(id)
	if collection == "" {
		fileName = path.Join(dir, idString)
	} else {
		fileName = path.Join(dir, collection+"_"+idString)
	}
	return
}

func EcShardBaseFileName(collection string, id int) (baseFileName string) {
	baseFileName = strconv.Itoa(id)
	if collection != "" {
		baseFileName = collection+"_"+baseFileName
	}
	return
}

func (shard *EcVolumeShard) Close() {
	if shard.ecdFile != nil {
		_ = shard.ecdFile.Close()
		shard.ecdFile = nil
	}
}

func (shard *EcVolumeShard) Destroy() {
	os.Remove(shard.FileName() + ToExt(int(shard.ShardId)))
}

func (shard *EcVolumeShard) ReadAt(buf []byte, offset int64) (int, error) {

	return shard.ecdFile.ReadAt(buf, offset)

}