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

package piecestore

import (
	"bytes"
	"context"
	"time"

	"github.com/golang/protobuf/ptypes"
	"github.com/golang/protobuf/ptypes/timestamp"
	"github.com/zeebo/errs"

	"storj.io/storj/internal/errs2"
	"storj.io/storj/pkg/auth/signing"
	"storj.io/storj/pkg/identity"
	"storj.io/storj/pkg/pb"
)

var (
	// ErrVerifyNotAuthorized is returned when the one submitting the action is not authorized to perform that action.
	ErrVerifyNotAuthorized = errs.Class("not authorized")
	// ErrVerifyUntrusted is returned when action is not trusted.
	ErrVerifyUntrusted = errs.Class("untrusted")
	// ErrVerifyDuplicateRequest is returned when serial number has been already used to submit an action.
	ErrVerifyDuplicateRequest = errs.Class("duplicate request")
)

// VerifyOrderLimit verifies that the order limit is properly signed and has sane values.
// It also verifies that the serial number has not been used.
func (endpoint *Endpoint) VerifyOrderLimit(ctx context.Context, limit *pb.OrderLimit) (err error) {
	defer mon.Task()(&ctx)(&err)

	// sanity checks
	switch {
	case limit.Limit < 0:
		return ErrProtocol.New("order limit is negative")
	case endpoint.signer.ID() != limit.StorageNodeId:
		return ErrProtocol.New("order intended for other storagenode: %v", limit.StorageNodeId)
	case limit.PieceExpiration != nil && endpoint.IsExpired(limit.PieceExpiration):
		return ErrProtocol.New("piece expired: %v", limit.PieceExpiration)
	case endpoint.IsExpired(limit.OrderExpiration):
		return ErrProtocol.New("order expired: %v", limit.OrderExpiration)

	case limit.SatelliteId.IsZero():
		return ErrProtocol.New("missing satellite id")
	case limit.UplinkId.IsZero():
		return ErrProtocol.New("missing uplink id")
	case len(limit.SatelliteSignature) == 0:
		return ErrProtocol.New("missing satellite signature")
	case limit.PieceId.IsZero():
		return ErrProtocol.New("missing piece id")
	}

	// either uplink or satellite can only make the request
	// TODO: should this check be based on the action?
	//       with macaroons we might not have either of them doing the action
	peer, err := identity.PeerIdentityFromContext(ctx)
	if err != nil || limit.UplinkId != peer.ID && limit.SatelliteId != peer.ID {
		return ErrVerifyNotAuthorized.New("uplink:%s satellite:%s sender %s", limit.UplinkId, limit.SatelliteId, peer.ID)
	}

	if err := endpoint.trust.VerifySatelliteID(ctx, limit.SatelliteId); err != nil {
		return ErrVerifyUntrusted.Wrap(err)
	}
	if err := endpoint.trust.VerifyUplinkID(ctx, limit.UplinkId); err != nil {
		return ErrVerifyUntrusted.Wrap(err)
	}

	if err := endpoint.VerifyOrderLimitSignature(ctx, limit); err != nil {
		if err == context.Canceled {
			return err
		}
		return ErrVerifyUntrusted.Wrap(err)
	}

	// TODO: use min of piece and order expiration instead
	serialExpiration, err := ptypes.Timestamp(limit.OrderExpiration)
	if err != nil {
		return ErrInternal.Wrap(err)
	}
	if err := endpoint.usedSerials.Add(ctx, limit.SatelliteId, limit.SerialNumber, serialExpiration); err != nil {
		return ErrVerifyDuplicateRequest.Wrap(err)
	}

	return nil
}

// VerifyOrder verifies that the order corresponds to the order limit and has all the necessary fields.
func (endpoint *Endpoint) VerifyOrder(ctx context.Context, peer *identity.PeerIdentity, limit *pb.OrderLimit, order *pb.Order, largestOrderAmount int64) (err error) {
	defer mon.Task()(&ctx)(&err)

	if order.SerialNumber != limit.SerialNumber {
		return ErrProtocol.New("order serial number changed during upload") // TODO: report grpc status bad message
	}
	// TODO: add check for minimum allocation step
	if order.Amount < largestOrderAmount {
		return ErrProtocol.New("order contained smaller amount=%v, previous=%v", order.Amount, largestOrderAmount) // TODO: report grpc status bad message
	}
	if order.Amount > limit.Limit {
		return ErrProtocol.New("order exceeded allowed amount=%v, limit=%v", order.Amount, limit.Limit) // TODO: report grpc status bad message
	}

	if err := signing.VerifyOrderSignature(ctx, signing.SigneeFromPeerIdentity(peer), order); err != nil {
		return ErrVerifyUntrusted.New("invalid order signature") // TODO: report grpc status bad message
	}

	return nil
}

// VerifyPieceHash verifies whether the piece hash is properly signed and matches the locally computed hash.
func (endpoint *Endpoint) VerifyPieceHash(ctx context.Context, peer *identity.PeerIdentity, limit *pb.OrderLimit, hash *pb.PieceHash, expectedHash []byte) (err error) {
	defer mon.Task()(&ctx)(&err)

	if peer == nil || limit == nil || hash == nil || len(expectedHash) == 0 {
		return ErrProtocol.New("invalid arguments")
	}
	if limit.PieceId != hash.PieceId {
		return ErrProtocol.New("piece id changed") // TODO: report grpc status bad message
	}
	if !bytes.Equal(hash.Hash, expectedHash) {
		return ErrProtocol.New("hashes don't match") // TODO: report grpc status bad message
	}

	if err := signing.VerifyPieceHashSignature(ctx, signing.SigneeFromPeerIdentity(peer), hash); err != nil {
		return ErrVerifyUntrusted.New("invalid hash signature: %v", err) // TODO: report grpc status bad message
	}

	return nil
}

// VerifyOrderLimitSignature verifies that the order limit signature is valid.
func (endpoint *Endpoint) VerifyOrderLimitSignature(ctx context.Context, limit *pb.OrderLimit) (err error) {
	defer mon.Task()(&ctx)(&err)

	signee, err := endpoint.trust.GetSignee(ctx, limit.SatelliteId)
	if err != nil {
		if errs2.IsCanceled(err) {
			return err
		}
		return ErrVerifyUntrusted.New("unable to get signee: %v", err) // TODO: report grpc status bad message
	}

	if err := signing.VerifyOrderLimitSignature(ctx, signee, limit); err != nil {
		return ErrVerifyUntrusted.New("invalid order limit signature: %v", err) // TODO: report grpc status bad message
	}

	return nil
}

// IsExpired checks whether the date has already expired (with a threshold) at the time of calling this function.
func (endpoint *Endpoint) IsExpired(expiration *timestamp.Timestamp) bool {
	if expiration == nil {
		return true
	}

	expirationTime, err := ptypes.Timestamp(expiration)
	if err != nil {
		// TODO: return error
		return true
	}

	// TODO: return specific error about either exceeding the expiration completely or just the grace period
	return expirationTime.Before(time.Now().Add(-endpoint.config.ExpirationGracePeriod))
}