package grpc

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

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

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

// SnapshotServer implements the gRPC server for snapshots
type SnapshotServer struct {
	UnimplementedSnapshotServiceServer
	manager interfaces.SnapshotManager
	server  *grpc.Server
}

// NewSnapshotServer creates a new snapshot server
func NewSnapshotServer(manager interfaces.SnapshotManager) *SnapshotServer {
	return &SnapshotServer{
		manager: manager,
	}
}

// Start starts the gRPC server on the specified address
func (s *SnapshotServer) 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 = grpc.NewServer()
	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)
	return nil
}

// Stop gracefully stops the server
func (s *SnapshotServer) Stop(ctx context.Context) error {
	if s.server != nil {
		s.server.GracefulStop()
		fmt.Println("Server stopped")
	}
	return nil
}

// ListSnapshots implements the gRPC ListSnapshots method
func (s *SnapshotServer) ListSnapshots(ctx context.Context, req *ListSnapshotsRequest) (*ListSnapshotsResponse, error) {
	snapshots, err := s.manager.ListSnapshots(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to list snapshots: %w", err)
	}

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

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

	return response, nil
}

// GetSnapshotDetails implements the gRPC GetSnapshotDetails method
func (s *SnapshotServer) GetSnapshotDetails(ctx context.Context, req *GetSnapshotDetailsRequest) (*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 := &SnapshotDetails{
		Info: convertToGrpcSnapshotInfo(store.SnapshotInfo{
			ID:           snapshot.ID,
			Name:         snapshot.Name,
			ParentID:     snapshot.ParentID,
			CreationTime: snapshot.CreationTime,
		}),
		Files: make([]*FileInfo, 0, len(snapshot.Files)),
	}

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

	return response, nil
}

// DownloadFile implements the gRPC DownloadFile method
func (s *SnapshotServer) DownloadFile(req *DownloadFileRequest, stream grpc.ServerStreamingServer[DownloadFileResponse]) error {
	// Open the file from the snapshot
	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()

	// Read the file in chunks and send them to the client
	buffer := make([]byte, 64*1024) // 64KB chunks
	for {
		n, err := fileReader.Read(buffer)
		if err == io.EOF {
			break
		}
		if err != nil {
			return fmt.Errorf("failed to read file: %w", err)
		}

		// Send the chunk to the client
		if err := stream.Send(&DownloadFileResponse{
			ChunkData: buffer[:n],
		}); err != nil {
			return fmt.Errorf("failed to send chunk: %w", err)
		}
	}

	return nil
}

// Helper function to convert store.SnapshotInfo to grpc.SnapshotInfo
func convertToGrpcSnapshotInfo(info store.SnapshotInfo) *SnapshotInfo {
	return &SnapshotInfo{
		Id:           info.ID,
		Name:         info.Name,
		ParentId:     info.ParentID,
		CreationTime: timestamppb.New(info.CreationTime),
	}
}

// RunServer is a helper function to create and start a snapshot server
func RunServer(ctx context.Context, manager interfaces.SnapshotManager, address string) (*SnapshotServer, error) {
	server := NewSnapshotServer(manager)
	if err := server.Start(ctx, address); err != nil {
		return nil, err
	}
	return server, nil
}