// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package vouchers

import (
	"context"
	"time"

	"github.com/zeebo/errs"
	"go.uber.org/zap"
	"golang.org/x/sync/errgroup"
	monkit "gopkg.in/spacemonkeygo/monkit.v2"

	"storj.io/storj/internal/sync2"
	"storj.io/storj/pkg/kademlia"
	"storj.io/storj/pkg/pb"
	"storj.io/storj/pkg/storj"
	"storj.io/storj/pkg/transport"
	"storj.io/storj/storagenode/trust"
)

var (
	// VoucherError represents errors with vouchers
	VoucherError = errs.Class("voucher")

	mon = monkit.Package()
)

// DB implements storing and retrieving vouchers
type DB interface {
	// Put inserts or updates a voucher from a satellite
	Put(context.Context, *pb.Voucher) error
	// GetValid returns one valid voucher from the list of approved satellites
	GetValid(context.Context, []storj.NodeID) (*pb.Voucher, error)
	// NeedVoucher returns true if a voucher from a particular satellite is expired, about to expire, or does not exist
	NeedVoucher(context.Context, storj.NodeID, time.Duration) (bool, error)
}

// Config defines configuration for requesting vouchers.
type Config struct {
	Interval time.Duration `help:"interval between voucher service iterations" default:"168h0m0s"`
}

// Service is a service for requesting vouchers
type Service struct {
	log *zap.Logger

	kademlia  *kademlia.Kademlia
	transport transport.Client

	vouchersdb DB
	trust      *trust.Pool

	expirationBuffer time.Duration

	Loop sync2.Cycle
}

// NewService creates a new voucher service
func NewService(log *zap.Logger, kad *kademlia.Kademlia, transport transport.Client, vouchersdb DB, trust *trust.Pool, interval, expirationBuffer time.Duration) *Service {
	return &Service{
		log:              log,
		kademlia:         kad,
		transport:        transport,
		vouchersdb:       vouchersdb,
		trust:            trust,
		expirationBuffer: expirationBuffer,
		Loop:             *sync2.NewCycle(interval),
	}
}

// Run sends requests to satellites for vouchers
func (service *Service) Run(ctx context.Context) (err error) {
	defer mon.Task()(&ctx)(&err)
	return service.Loop.Run(ctx, service.RunOnce)
}

// RunOnce runs one iteration of the voucher request service
func (service *Service) RunOnce(ctx context.Context) (err error) {
	defer mon.Task()(&ctx)(&err)
	service.log.Info("Checking vouchers")

	trustedSatellites := service.trust.GetSatellites((ctx))

	if len(trustedSatellites) == 0 {
		service.log.Debug("No trusted satellites configured. No vouchers to request")
		return nil
	}

	var group errgroup.Group
	ctx, cancel := context.WithTimeout(ctx, time.Hour)
	defer cancel()
	for _, satellite := range trustedSatellites {
		satellite := satellite
		needVoucher, err := service.vouchersdb.NeedVoucher(ctx, satellite, service.expirationBuffer)
		if err != nil {
			service.log.Error("getting voucher status", zap.Error(err))
			return nil
		}
		if needVoucher {
			group.Go(func() error {
				service.Request(ctx, satellite)
				return nil
			})
		}
	}
	_ = group.Wait() // doesn't return errors

	return nil
}

// Request makes a voucher request to a satellite
func (service *Service) Request(ctx context.Context, satelliteID storj.NodeID) {
	service.log.Info("Requesting voucher", zap.String("satellite", satelliteID.String()))
	err := service.request(ctx, satelliteID)
	if err != nil {
		service.log.Error("Error requesting voucher", zap.String("satellite", satelliteID.String()), zap.Error(err))
	}
}

func (service *Service) request(ctx context.Context, satelliteID storj.NodeID) (err error) {
	defer mon.Task()(&ctx)(&err)

	satellite, err := service.kademlia.FindNode(ctx, satelliteID)
	if err != nil {
		return VoucherError.New("unable to find satellite on the network: %v", err)
	}

	conn, err := service.transport.DialNode(ctx, &satellite)
	if err != nil {
		return VoucherError.New("unable to connect to the satellite: %v", err)
	}
	defer func() {
		if cerr := conn.Close(); cerr != nil {
			err = errs.Combine(err, VoucherError.New("failed to close connection: %v", err))
		}
	}()

	resp, err := pb.NewVouchersClient(conn).Request(ctx, &pb.VoucherRequest{})
	if err != nil {
		return VoucherError.New("failed to start request: %v", err)
	}

	// TODO: separate status for disqualified nodes?
	switch resp.GetStatus() {
	case pb.VoucherResponse_REJECTED:
		service.log.Info("Voucher request denied. Vetting process not yet complete")
	case pb.VoucherResponse_ACCEPTED:
		voucher := resp.GetVoucher()

		if err := service.VerifyVoucher(ctx, satelliteID, voucher); err != nil {
			return err
		}

		err = service.vouchersdb.Put(ctx, voucher)
		if err != nil {
			return err
		}
		service.log.Info("Voucher received", zap.String("satellite", voucher.SatelliteId.String()))
	default:
		service.log.Warn("Unknown voucher response status")
	}

	return err
}

// Close stops the voucher service
func (service *Service) Close() error {
	service.Loop.Close()
	return nil
}