/**
 * Created by IntelliJ IDEA.
 * User: Ar.M
 * Date: 2020-05-10
 * Time: 22:13
 */
package main

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"google.golang.org/grpc"
	"io"
	"log"
	"net"
	"os"
	"path/filepath"
	transportpb "yunlian-file-v2/proto"
)

var filesDir string

func init() {
	str, _ := os.Getwd()
	filesDir = filepath.Join(str, "/files")
}

type server struct{}

func (s *server) GetFileInfo(ctx context.Context, req *transportpb.FileInfoRequest) (*transportpb.FileInfoResponse, error) {

	fileName := req.GetFileName()

	path := filepath.Join(filesDir, fileName)

	file, err := os.Open(path)
	defer file.Close()
	if err != nil {
		return nil, err
	}
	hash := sha256.New()
	if _, err := io.Copy(hash, file); err != nil {
		fmt.Println(err)
	}
	fileSha256 := hex.EncodeToString(hash.Sum(nil))

	fileInfo, err := file.Stat()
	if err != nil {
		return nil, err
	}

	resp := &transportpb.FileInfoResponse{
		FileName:   fileName,
		FileSize:   fileInfo.Size(),
		FileSha256: fileSha256,
	}

	return resp, nil
}

func (s *server) Download(req *transportpb.FileRequest, stream transportpb.FileService_DownloadServer) error {
	fileName := req.GetFileName()
	fileRangeStart := req.GetFileRangeStart()
	fileRangeEnd := req.GetFileRangeEnd()

	path := filepath.Join(filesDir, fileName)

	fileInfo, err := os.Stat(path)
	if err != nil {
		return err
	}
	fileSize := fileInfo.Size()

	f, err := os.Open(path)
	if err != nil {
		return err
	}
	defer f.Close()

	_, err = f.Seek(fileRangeStart, 0)
	if err != nil {
		return err
	}
	log.Printf("开始读取区块: %d-%d\n", fileRangeStart, fileRangeEnd)

	var totalBytesStreamed int64
	var packageLen int64 = 1024

	for totalBytesStreamed < fileRangeEnd-fileRangeStart {
		block := make([]byte, packageLen)
		if totalBytesStreamed+packageLen > fileRangeEnd-fileRangeStart {
			block = make([]byte, fileRangeEnd-fileRangeStart-totalBytesStreamed)
		}

		bytesRead, err := f.Read(block)
		if err == io.EOF {
			break
		}

		if err != nil {
			return err
		}

		if err := stream.Send(&transportpb.FileResponse{
			Block:    block,
			FileSize: fileSize,
		}); err != nil {
			return err
		}
		totalBytesStreamed += int64(bytesRead)
	}
	return nil
}

func main() {
	lis, err := net.Listen("tcp", "0.0.0.0:10086")
	if err != nil {
		log.Fatalf("Failed to listen on 10086 : %v\n", err)
	}

	s := grpc.NewServer()
	transportpb.RegisterFileServiceServer(s, &server{})

	fmt.Println("Starting server on 10086")
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to start server : %v\n", err)
	}
}