package remote

import (
	"context"
	"fmt"
	"io"
	"net"

	stdgrpc "google.golang.org/grpc"
	"google.golang.org/protobuf/types/known/timestamppb"

	agateGrpc "gitea.unprism.ru/KRBL/Agate/grpc"
	"gitea.unprism.ru/KRBL/Agate/interfaces"
	"gitea.unprism.ru/KRBL/Agate/store"
)

// Server реализует gRPC-сервер для снапшотов.
type Server struct {
	agateGrpc.UnimplementedSnapshotServiceServer
	manager interfaces.SnapshotManager
	server  *stdgrpc.Server
}

// NewServer создает новый сервер снапшотов.
func NewServer(manager interfaces.SnapshotManager) *Server {
	return &Server{
		manager: manager,
	}
}

// Start запускает gRPC-сервер на указанном адресе.
func (s *Server) Start(ctx context.Context, address string) error {
	lis, err := net.Listen("tcp", address)
	if err != nil {
		return fmt.Errorf("failed to listen on %s: %w", address, err)
	}

	s.server = stdgrpc.NewServer()
	agateGrpc.RegisterSnapshotServiceServer(s.server, s)

	go func() {
		if err := s.server.Serve(lis); err != nil {
			fmt.Printf("Server error: %v\n", err)
		}
	}()

	fmt.Printf("Server started on %s\n", address)

	// Ждем отмены контекста для остановки сервера
	<-ctx.Done()
	s.Stop()
	return nil
}

// Stop изящно останавливает сервер.
func (s *Server) Stop() {
	if s.server != nil {
		s.server.GracefulStop()
		fmt.Println("Server stopped")
	}
}

// ListSnapshots реализует gRPC-метод ListSnapshots.
func (s *Server) ListSnapshots(ctx context.Context, req *agateGrpc.ListSnapshotsRequest) (*agateGrpc.ListSnapshotsResponse, error) {
	opts := store.ListOptions{}
	snapshots, err := s.manager.ListSnapshots(ctx, opts)
	if err != nil {
		return nil, fmt.Errorf("failed to list snapshots: %w", err)
	}

	response := &agateGrpc.ListSnapshotsResponse{
		Snapshots: make([]*agateGrpc.SnapshotInfo, 0, len(snapshots)),
	}

	for _, snapshot := range snapshots {
		response.Snapshots = append(response.Snapshots, convertToGrpcSnapshotInfo(snapshot))
	}

	return response, nil
}

// GetSnapshotDetails реализует gRPC-метод GetSnapshotDetails.
func (s *Server) GetSnapshotDetails(ctx context.Context, req *agateGrpc.GetSnapshotDetailsRequest) (*agateGrpc.SnapshotDetails, error) {
	snapshot, err := s.manager.GetSnapshotDetails(ctx, req.SnapshotId)
	if err != nil {
		return nil, fmt.Errorf("failed to get snapshot details: %w", err)
	}

	response := &agateGrpc.SnapshotDetails{
		Info: convertToGrpcSnapshotInfo(store.SnapshotInfo{
			ID:           snapshot.ID,
			Name:         snapshot.Name,
			ParentID:     snapshot.ParentID,
			CreationTime: snapshot.CreationTime,
		}),
		Files: make([]*agateGrpc.FileInfo, 0, len(snapshot.Files)),
	}

	for _, file := range snapshot.Files {
		response.Files = append(response.Files, &agateGrpc.FileInfo{
			Path:       file.Path,
			SizeBytes:  file.Size,
			Sha256Hash: file.SHA256,
			IsDir:      file.IsDir,
		})
	}

	return response, nil
}

// DownloadFile реализует gRPC-метод DownloadFile.
func (s *Server) DownloadFile(req *agateGrpc.DownloadFileRequest, stream agateGrpc.SnapshotService_DownloadFileServer) error {
	fileReader, err := s.manager.OpenFile(context.Background(), req.SnapshotId, req.FilePath)
	if err != nil {
		return fmt.Errorf("failed to open file: %w", err)
	}
	defer fileReader.Close()

	buffer := make([]byte, 64*1024)
	for {
		n, err := fileReader.Read(buffer)
		if err == io.EOF {
			break
		}
		if err != nil {
			return fmt.Errorf("failed to read file: %w", err)
		}
		if err := stream.Send(&agateGrpc.DownloadFileResponse{ChunkData: buffer[:n]}); err != nil {
			return fmt.Errorf("failed to send chunk: %w", err)
		}
	}
	return nil
}

// DownloadSnapshotDiff реализует gRPC-метод DownloadSnapshotDiff.
func (s *Server) DownloadSnapshotDiff(req *agateGrpc.DownloadSnapshotDiffRequest, stream agateGrpc.SnapshotService_DownloadSnapshotDiffServer) error {
	diffReader, err := s.manager.StreamSnapshotDiff(context.Background(), req.SnapshotId, req.LocalParentId, req.Offset)
	if err != nil {
		return fmt.Errorf("failed to stream snapshot diff: %w", err)
	}
	defer diffReader.Close()

	buffer := make([]byte, 64*1024)
	for {
		n, err := diffReader.Read(buffer)
		if err == io.EOF {
			break
		}
		if err != nil {
			return fmt.Errorf("failed to read from diff stream: %w", err)
		}
		if n > 0 {
			if err := stream.Send(&agateGrpc.DownloadFileResponse{ChunkData: buffer[:n]}); err != nil {
				return fmt.Errorf("failed to send diff chunk: %w", err)
			}
		}
	}
	return nil
}

// Вспомогательная функция для конвертации store.SnapshotInfo в grpc.SnapshotInfo
func convertToGrpcSnapshotInfo(info store.SnapshotInfo) *agateGrpc.SnapshotInfo {
	return &agateGrpc.SnapshotInfo{
		Id:           info.ID,
		Name:         info.Name,
		ParentId:     info.ParentID,
		CreationTime: timestamppb.New(info.CreationTime),
	}
}