package main

import (
	"context"
	"flag"
	"github.com/golang/glog"
	"github.com/lib/pq"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	"io"
	"time"

	"code.hackerspace.pl/hscloud/bgpwtf/cccampix/pgpencryptor/gpg"
	"code.hackerspace.pl/hscloud/bgpwtf/cccampix/pgpencryptor/hkp"
	"code.hackerspace.pl/hscloud/bgpwtf/cccampix/pgpencryptor/model"
	pb "code.hackerspace.pl/hscloud/bgpwtf/cccampix/proto"
	"code.hackerspace.pl/hscloud/go/mirko"
)

var (
	flagMaxClients     int
	flagChunkSize      int
	flagHkpMaxWaitTime time.Duration
	flagDSN            string
)

type service struct {
	hkpClient        hkp.Client
	encryptorFactory gpg.EncryptorFactory
	clients          chan (struct{})
	model            model.Model
}

func (s *service) KeyInfo(ctx context.Context, req *pb.KeyInfoRequest) (*pb.KeyInfoResponse, error) {
	var data []byte
	var err error

	switch req.Caching {
	case pb.KeyInfoRequest_CACHING_AUTO:
		_, err := s.model.GetKey(ctx, req.Fingerprint)
		if err != nil {
			data, err = s.hkpClient.GetKeyRing(ctx, req.Fingerprint)
			switch err {
			case nil:
				break
			case hkp.ErrKeyNotFound:
				return nil, status.Errorf(codes.NotFound, "key not found: %v", err)
			default:
				return nil, status.Errorf(codes.Unavailable, "failed to get key from HKP servers: %v", err)
			}
		}
	case pb.KeyInfoRequest_CACHING_FORCE_REMOTE:
		data, err = s.hkpClient.GetKeyRing(ctx, req.Fingerprint)
		switch err {
		case nil:
			break
		case hkp.ErrKeyNotFound:
			return nil, status.Errorf(codes.NotFound, "key not found: %v", err)
		default:
			return nil, status.Errorf(codes.Unavailable, "failed to get key from HKP servers: %v", err)
		}
	case pb.KeyInfoRequest_CACHING_FORCE_LOCAL:
		_, err := s.model.GetKey(ctx, req.Fingerprint)
		switch err {
		case nil:
			break
		case model.ErrKeyNotFound:
			return nil, status.Errorf(codes.NotFound, "key not found: %v", err)
		default:
			return nil, status.Errorf(codes.Unavailable, "failed to read key from local db: %v", err)
		}
	default:
		return nil, status.Errorf(codes.InvalidArgument, "caching field value is invalid")
	}

	// successfully read fresh key from hkp, update db
	if data != nil {
		err := s.model.PutKey(ctx, &model.PgpKey{
			Fingerprint: req.Fingerprint,
			KeyData:     data,
			Okay:        true,
		})

		if err != nil {
			return nil, status.Errorf(codes.Unavailable, "failed to cache key received from HKP: %v", err)
		}
	}

	return &pb.KeyInfoResponse{}, nil
}

func (s *service) Encrypt(stream pb.PGPEncryptor_EncryptServer) error {
	select {
	case s.clients <- struct{}{}:
		break
	case <-stream.Context().Done():
		return status.Errorf(codes.ResourceExhausted, "PGPEncryptor to many sessions running, try again later")
	}

	defer func() {
		<-s.clients
	}()

	ctx, _ := context.WithTimeout(context.Background(), flagHkpMaxWaitTime)
	initialMessage, err := stream.Recv()
	if err != nil {
		return status.Errorf(codes.Canceled, "failed to read data from the client: %v", err)
	}

	key, err := s.model.GetKey(ctx, initialMessage.Fingerprint)
	if err != nil {
		if err != nil {
			switch err {
			case model.ErrKeyNotFound:
				return status.Errorf(codes.NotFound, "recipient key not found: %v", err)
			default:
				return status.Errorf(codes.Unavailable, "error when getting keyring: %v", err)
			}
		}
	}

	if key.Okay == false {
		return status.Errorf(codes.InvalidArgument, "cached key is invalid, call PGPEncryptor.KeyInfo with caching=FORCE_REMOTE to refresh")
	}

	senderDone := make(chan struct{})
	errors := make(chan error)
	enc, err := s.encryptorFactory.Get(key.Fingerprint, key.KeyData)
	defer enc.Close()

	if err != nil {
		return status.Errorf(codes.Unavailable, "PGPEncryptor error while creating encryptor: %v", err)
	}

	err = enc.WritePlainText(initialMessage.Data)
	if err != nil {
		return err
	}

	// keep reading incoming messages and pass them to the encryptor
	go func() {
		defer enc.Finish()

		for {
			in, err := stream.Recv()

			if err != nil {
				if err == io.EOF {
					return
				}

				errors <- status.Errorf(codes.Unavailable, "PGPEncryptor error while receiving message: %v", err)
				return
			}

			err = enc.WritePlainText(in.Data)
			if err != nil {
				errors <- status.Errorf(codes.Unavailable, "PGPEncryptor error while writing data to encryptor: %v", err)
				return
			}

			if in.Info == pb.EncryptRequest_CHUNK_LAST {
				return
			}
		}
	}()

	// start sender routine
	go func() {
		defer close(senderDone)

		for {
			data, err := enc.ReadCipherText(flagChunkSize)
			if err != nil && err != io.EOF {
				errors <- status.Errorf(codes.Unavailable, "PGPEncryptor error while reading cipher stream: %v", err)
				return
			}

			info := pb.EncryptResponse_CHUNK_INFO_MORE
			if err == io.EOF {
				info = pb.EncryptResponse_CHUNK_LAST
			}

			res := &pb.EncryptResponse{
				Data: data,
				Info: info,
			}

			err = stream.Send(res)
			if err != nil {
				errors <- status.Errorf(codes.Unavailable, "PGPEncryptor error while sending data to client: %v", err)
				return
			}

			if info == pb.EncryptResponse_CHUNK_LAST {
				return
			}
		}
	}()

	// sync with sender routine
	select {
	case <-senderDone:
		return nil
	case err := <-errors:
		return err
	}
}

func main() {
	flag.IntVar(&flagMaxClients, "maxClients", 20, "maximum number of concurrent encryption sessions")
	flag.IntVar(&flagChunkSize, "chunkSize", 1024*8, "maximum size of chunk sent back to client")
	flag.DurationVar(&flagHkpMaxWaitTime, "hkpMaxWaitTime", 10*time.Second, "maximum time awaiting reply from HKP")
	flag.StringVar(&flagDSN, "dsn", "", "PostrgreSQL connection string")

	flag.DurationVar(&gpg.ExecutionTimeLimit, "gpgExecutionTimeLimit", 30*time.Second, "execution time limit for gpg commands")
	flag.StringVar(&gpg.BinaryPath, "gpgPath", "gpg", "path to gpg binary")

	flag.DurationVar(&hkp.PerServerTimeLimit, "hkpPerServerTimeLimit", 5*time.Second, "time for HKP server to reply with key")
	flag.IntVar(&hkp.PerServerRetryCount, "hkpPerServerRetryCount", 3, "retry count per HKP server")
	flag.Parse()

	// Picking an existing postgres-like driver for sqlx.BindType to work
	// See: https://github.com/jmoiron/sqlx/blob/ed7c52c43ee1e12a35efbcfea8dbae2d62a90370/bind.go#L24
	mirko.TraceSQL(&pq.Driver{}, "pgx")
	mi := mirko.New()

	m, err := model.Connect(mi.Context(), "pgx", flagDSN)
	if err != nil {
		glog.Exitf("Failed to create model: %v", err)
	}

	err = m.MigrateUp()
	if err != nil {
		glog.Exitf("Failed to migrate up: %v", err)
	}

	if err := mi.Listen(); err != nil {
		glog.Exitf("Listen failed: %v", err)
	}

	s := &service{
		hkpClient:        hkp.NewClient(),
		encryptorFactory: gpg.CLIEncryptorFactory{},
		clients:          make(chan struct{}, flagMaxClients),
		model:            m,
	}
	pb.RegisterPGPEncryptorServer(mi.GRPC(), s)

	if err := mi.Serve(); err != nil {
		glog.Exitf("Serve failed: %v", err)
	}

	<-mi.Done()
}