// Copyright 2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and

package pubsublite

import (
	"context"
	"errors"

	"cloud.google.com/go/pubsublite/internal/wire"
	"google.golang.org/api/option"

	vkit "cloud.google.com/go/pubsublite/apiv1"
	pb "cloud.google.com/go/pubsublite/apiv1/pubsublitepb"
	fmpb "google.golang.org/genproto/protobuf/field_mask"
)

var (
	errNoTopicFieldsUpdated        = errors.New("pubsublite: no fields updated for topic")
	errNoSubscriptionFieldsUpdated = errors.New("pubsublite: no fields updated for subscription")
	errNoReservationFieldsUpdated  = errors.New("pubsublite: no fields updated for reservation")
)

// AdminClient provides admin operations for Pub/Sub Lite resources within a
// Google Cloud region. The location (region or zone) component of resource
// paths must be within this region.
// See https://cloud.google.com/pubsub/lite/docs/locations for the list of
// regions and zones where Pub/Sub Lite is available.
//
// An AdminClient may be shared by multiple goroutines.
//
// Close must be called to release resources when an AdminClient is no longer
// required. If the client is available for the lifetime of the program, then
// Close need not be called at exit.
type AdminClient struct {
	admin *vkit.AdminClient
}

// NewAdminClient creates a new Pub/Sub Lite client to perform admin operations
// for resources within a given region.
func NewAdminClient(ctx context.Context, region string, opts ...option.ClientOption) (*AdminClient, error) {
	if err := wire.ValidateRegion(region); err != nil {
		return nil, err
	}
	admin, err := wire.NewAdminClient(ctx, region, opts...)
	if err != nil {
		return nil, err
	}
	return &AdminClient{admin: admin}, nil
}

// CreateTopic creates a new topic from the given config. If the topic already
// exists an error will be returned.
func (ac *AdminClient) CreateTopic(ctx context.Context, config TopicConfig) (*TopicConfig, error) {
	topicPath, err := wire.ParseTopicPath(config.Name)
	if err != nil {
		return nil, err
	}
	req := &pb.CreateTopicRequest{
		Parent:  topicPath.LocationPath().String(),
		Topic:   config.toProto(),
		TopicId: topicPath.TopicID,
	}
	topicpb, err := ac.admin.CreateTopic(ctx, req)
	if err != nil {
		return nil, err
	}
	return protoToTopicConfig(topicpb)
}

// UpdateTopic updates an existing topic from the given config and returns the
// new topic config. UpdateTopic returns an error if no fields were modified.
func (ac *AdminClient) UpdateTopic(ctx context.Context, config TopicConfigToUpdate) (*TopicConfig, error) {
	if _, err := wire.ParseTopicPath(config.Name); err != nil {
		return nil, err
	}
	req := config.toUpdateRequest()
	if len(req.GetUpdateMask().GetPaths()) == 0 {
		return nil, errNoTopicFieldsUpdated
	}
	topicpb, err := ac.admin.UpdateTopic(ctx, req)
	if err != nil {
		return nil, err
	}
	return protoToTopicConfig(topicpb)
}

// DeleteTopic deletes a topic. A valid topic path has the format:
// "projects/PROJECT_ID/locations/LOCATION/topics/TOPIC_ID".
func (ac *AdminClient) DeleteTopic(ctx context.Context, topic string) error {
	if _, err := wire.ParseTopicPath(topic); err != nil {
		return err
	}
	return ac.admin.DeleteTopic(ctx, &pb.DeleteTopicRequest{Name: topic})
}

// Topic retrieves the configuration of a topic. A valid topic path has the
// format: "projects/PROJECT_ID/locations/LOCATION/topics/TOPIC_ID".
func (ac *AdminClient) Topic(ctx context.Context, topic string) (*TopicConfig, error) {
	if _, err := wire.ParseTopicPath(topic); err != nil {
		return nil, err
	}
	topicpb, err := ac.admin.GetTopic(ctx, &pb.GetTopicRequest{Name: topic})
	if err != nil {
		return nil, err
	}
	return protoToTopicConfig(topicpb)
}

// TopicPartitionCount returns the number of partitions for a topic. A valid
// topic path has the format:
// "projects/PROJECT_ID/locations/LOCATION/topics/TOPIC_ID".
func (ac *AdminClient) TopicPartitionCount(ctx context.Context, topic string) (int, error) {
	if _, err := wire.ParseTopicPath(topic); err != nil {
		return 0, err
	}
	partitions, err := ac.admin.GetTopicPartitions(ctx, &pb.GetTopicPartitionsRequest{Name: topic})
	if err != nil {
		return 0, err
	}
	return int(partitions.GetPartitionCount()), nil
}

// TopicSubscriptions retrieves the list of subscription paths for a topic.
// A valid topic path has the format:
// "projects/PROJECT_ID/locations/LOCATION/topics/TOPIC_ID".
func (ac *AdminClient) TopicSubscriptions(ctx context.Context, topic string) *SubscriptionPathIterator {
	if _, err := wire.ParseTopicPath(topic); err != nil {
		return &SubscriptionPathIterator{err: err}
	}
	return &SubscriptionPathIterator{
		it: ac.admin.ListTopicSubscriptions(ctx, &pb.ListTopicSubscriptionsRequest{Name: topic}),
	}
}

// Topics retrieves the list of topic configs for a given project and location
// (region or zone). A valid parent path has the format:
// "projects/PROJECT_ID/locations/LOCATION".
func (ac *AdminClient) Topics(ctx context.Context, parent string) *TopicIterator {
	if _, err := wire.ParseLocationPath(parent); err != nil {
		return &TopicIterator{err: err}
	}
	return &TopicIterator{
		it: ac.admin.ListTopics(ctx, &pb.ListTopicsRequest{Parent: parent}),
	}
}

type createSubscriptionSettings struct {
	target SeekTarget
}

// CreateSubscriptionOption is an option for AdminClient.CreateSubscription.
type CreateSubscriptionOption interface {
	apply(*createSubscriptionSettings)
}

type targetLocation struct {
	target SeekTarget
}

func (tl targetLocation) apply(settings *createSubscriptionSettings) {
	settings.target = tl.target
}

// StartingOffset specifies the offset at which a newly created subscription
// will start receiving messages.
//
// Deprecated. This is equivalent to calling AtTargetLocation with a
// BacklogLocation and will be removed in the next major version.
func StartingOffset(location BacklogLocation) CreateSubscriptionOption {
	return targetLocation{location}
}

// AtTargetLocation specifies the target location within the message backlog
// that a new subscription should be initialized to.
//
// An additional seek request is initiated if the target location is a publish
// or event time. If the seek fails, the created subscription is not deleted.
func AtTargetLocation(target SeekTarget) CreateSubscriptionOption {
	return targetLocation{target}
}

// CreateSubscription creates a new subscription from the given config. If the
// subscription already exists an error will be returned.
//
// By default, a new subscription will only receive messages published after
// the subscription was created. Use AtTargetLocation to initialize the
// subscription to another location within the message backlog.
func (ac *AdminClient) CreateSubscription(ctx context.Context, config SubscriptionConfig, opts ...CreateSubscriptionOption) (*SubscriptionConfig, error) {
	settings := createSubscriptionSettings{
		target: End,
	}
	for _, opt := range opts {
		opt.apply(&settings)
	}

	subsPath, err := wire.ParseSubscriptionPath(config.Name)
	if err != nil {
		return nil, err
	}
	if _, err := wire.ParseTopicPath(config.Topic); err != nil {
		return nil, err
	}

	var skipBacklog, requiresSeek, requiresUpdate bool
	switch settings.target.(type) {
	case PublishTime, EventTime:
		requiresSeek = true
	case BacklogLocation:
		skipBacklog = settings.target.(BacklogLocation) == End
	}

	// Request 1 - create the subscription.
	createReq := &pb.CreateSubscriptionRequest{
		Parent:         subsPath.LocationPath().String(),
		Subscription:   config.toProto(),
		SubscriptionId: subsPath.SubscriptionID,
		SkipBacklog:    skipBacklog,
	}
	if requiresSeek && createReq.Subscription.GetExportConfig().GetDesiredState() == pb.ExportConfig_ACTIVE {
		// Export subscriptions must be paused while seeking. The state is later
		// updated to active.
		requiresUpdate = true
		createReq.Subscription.ExportConfig.DesiredState = pb.ExportConfig_PAUSED
	}
	subspb, err := ac.admin.CreateSubscription(ctx, createReq)
	if err != nil {
		return nil, err
	}

	// Request 2 (optional) - seek the subscription.
	if requiresSeek {
		if _, err = ac.SeekSubscription(ctx, subsPath.String(), settings.target); err != nil {
			return nil, err
		}
	}

	// Request 3 (optional) - make the export subscription active.
	if requiresUpdate {
		updateReq := &pb.UpdateSubscriptionRequest{
			Subscription: &pb.Subscription{
				Name:         subsPath.String(),
				ExportConfig: &pb.ExportConfig{DesiredState: pb.ExportConfig_ACTIVE},
			},
			UpdateMask: &fmpb.FieldMask{Paths: []string{"export_config.desired_state"}},
		}
		if subspb, err = ac.admin.UpdateSubscription(ctx, updateReq); err != nil {
			return nil, err
		}
	}
	return protoToSubscriptionConfig(subspb), nil
}

// UpdateSubscription updates an existing subscription from the given config and
// returns the new subscription config. UpdateSubscription returns an error if
// no fields were modified.
func (ac *AdminClient) UpdateSubscription(ctx context.Context, config SubscriptionConfigToUpdate) (*SubscriptionConfig, error) {
	if _, err := wire.ParseSubscriptionPath(config.Name); err != nil {
		return nil, err
	}
	req := config.toUpdateRequest()
	if len(req.GetUpdateMask().GetPaths()) == 0 {
		return nil, errNoSubscriptionFieldsUpdated
	}
	subspb, err := ac.admin.UpdateSubscription(ctx, req)
	if err != nil {
		return nil, err
	}
	return protoToSubscriptionConfig(subspb), nil
}

// SeekSubscription initiates an out-of-band seek for a subscription to a
// specified target, which may be timestamps or named positions within the
// message backlog. A valid subscription path has the format:
// "projects/PROJECT_ID/locations/LOCATION/subscriptions/SUBSCRIPTION_ID".
//
// See https://cloud.google.com/pubsub/lite/docs/seek for more information.
func (ac *AdminClient) SeekSubscription(ctx context.Context, subscription string, target SeekTarget, opts ...SeekSubscriptionOption) (*SeekSubscriptionOperation, error) {
	if _, err := wire.ParseSubscriptionPath(subscription); err != nil {
		return nil, err
	}
	req := &pb.SeekSubscriptionRequest{Name: subscription}
	target.setRequest(req)
	op, err := ac.admin.SeekSubscription(ctx, req)
	if err != nil {
		return nil, err
	}
	return &SeekSubscriptionOperation{op}, err
}

// DeleteSubscription deletes a subscription. A valid subscription path has the
// format: "projects/PROJECT_ID/locations/LOCATION/subscriptions/SUBSCRIPTION_ID".
func (ac *AdminClient) DeleteSubscription(ctx context.Context, subscription string) error {
	if _, err := wire.ParseSubscriptionPath(subscription); err != nil {
		return err
	}
	return ac.admin.DeleteSubscription(ctx, &pb.DeleteSubscriptionRequest{Name: subscription})
}

// Subscription retrieves the configuration of a subscription. A valid
// subscription name has the format:
// "projects/PROJECT_ID/locations/LOCATION/subscriptions/SUBSCRIPTION_ID".
func (ac *AdminClient) Subscription(ctx context.Context, subscription string) (*SubscriptionConfig, error) {
	if _, err := wire.ParseSubscriptionPath(subscription); err != nil {
		return nil, err
	}
	subspb, err := ac.admin.GetSubscription(ctx, &pb.GetSubscriptionRequest{Name: subscription})
	if err != nil {
		return nil, err
	}
	return protoToSubscriptionConfig(subspb), nil
}

// Subscriptions retrieves the list of subscription configs for a given project
// and location (region or zone). A valid parent path has the format:
// "projects/PROJECT_ID/locations/LOCATION".
func (ac *AdminClient) Subscriptions(ctx context.Context, parent string) *SubscriptionIterator {
	if _, err := wire.ParseLocationPath(parent); err != nil {
		return &SubscriptionIterator{err: err}
	}
	return &SubscriptionIterator{
		it: ac.admin.ListSubscriptions(ctx, &pb.ListSubscriptionsRequest{Parent: parent}),
	}
}

// CreateReservation creates a new reservation from the given config. If the
// reservation already exists an error will be returned.
func (ac *AdminClient) CreateReservation(ctx context.Context, config ReservationConfig) (*ReservationConfig, error) {
	reservationPath, err := wire.ParseReservationPath(config.Name)
	if err != nil {
		return nil, err
	}
	req := &pb.CreateReservationRequest{
		Parent:        reservationPath.Location().String(),
		Reservation:   config.toProto(),
		ReservationId: reservationPath.ReservationID,
	}
	reservationpb, err := ac.admin.CreateReservation(ctx, req)
	if err != nil {
		return nil, err
	}
	return protoToReservationConfig(reservationpb), nil
}

// UpdateReservation updates an existing reservation from the given config and
// returns the new reservation config. UpdateReservation returns an error if no
// fields were modified.
func (ac *AdminClient) UpdateReservation(ctx context.Context, config ReservationConfigToUpdate) (*ReservationConfig, error) {
	if _, err := wire.ParseReservationPath(config.Name); err != nil {
		return nil, err
	}
	req := config.toUpdateRequest()
	if len(req.GetUpdateMask().GetPaths()) == 0 {
		return nil, errNoReservationFieldsUpdated
	}
	respb, err := ac.admin.UpdateReservation(ctx, req)
	if err != nil {
		return nil, err
	}
	return protoToReservationConfig(respb), nil
}

// DeleteReservation deletes a reservation. A valid reservation path has the
// format: "projects/PROJECT_ID/locations/REGION/reservations/RESERVATION_ID".
func (ac *AdminClient) DeleteReservation(ctx context.Context, reservation string) error {
	if _, err := wire.ParseReservationPath(reservation); err != nil {
		return err
	}
	return ac.admin.DeleteReservation(ctx, &pb.DeleteReservationRequest{Name: reservation})
}

// Reservation retrieves the configuration of a reservation. A valid reservation
// name has the format:
// "projects/PROJECT_ID/locations/REGION/reservations/RESERVATION_ID".
func (ac *AdminClient) Reservation(ctx context.Context, reservation string) (*ReservationConfig, error) {
	if _, err := wire.ParseReservationPath(reservation); err != nil {
		return nil, err
	}
	respb, err := ac.admin.GetReservation(ctx, &pb.GetReservationRequest{Name: reservation})
	if err != nil {
		return nil, err
	}
	return protoToReservationConfig(respb), nil
}

// Reservations retrieves the list of reservation configs for a given project
// and region. A valid parent path has the format:
// "projects/PROJECT_ID/locations/REGION".
func (ac *AdminClient) Reservations(ctx context.Context, parent string) *ReservationIterator {
	if _, err := wire.ParseLocationPath(parent); err != nil {
		return &ReservationIterator{err: err}
	}
	return &ReservationIterator{
		it: ac.admin.ListReservations(ctx, &pb.ListReservationsRequest{Parent: parent}),
	}
}

// ReservationTopics retrieves the list of topic paths for a reservation.
// A valid reservation path has the format:
// "projects/PROJECT_ID/locations/REGION/reservations/RESERVATION_ID".
func (ac *AdminClient) ReservationTopics(ctx context.Context, reservation string) *TopicPathIterator {
	if _, err := wire.ParseReservationPath(reservation); err != nil {
		return &TopicPathIterator{err: err}
	}
	return &TopicPathIterator{
		it: ac.admin.ListReservationTopics(ctx, &pb.ListReservationTopicsRequest{Name: reservation}),
	}
}

// Close releases any resources held by the client when it is no longer
// required. If the client is available for the lifetime of the program, then
// Close need not be called at exit.
func (ac *AdminClient) Close() error {
	return ac.admin.Close()
}

// TopicIterator is an iterator that returns a list of topic configs.
type TopicIterator struct {
	it  *vkit.TopicIterator
	err error
}

// Next returns the next topic config. The second return value will be
// iterator.Done if there are no more topic configs.
func (t *TopicIterator) Next() (*TopicConfig, error) {
	if t.err != nil {
		return nil, t.err
	}
	topicpb, err := t.it.Next()
	if err != nil {
		return nil, err
	}
	return protoToTopicConfig(topicpb)
}

// SubscriptionIterator is an iterator that returns a list of subscription
// configs.
type SubscriptionIterator struct {
	it  *vkit.SubscriptionIterator
	err error
}

// Next returns the next subscription config. The second return value will be
// iterator.Done if there are no more subscription configs.
func (s *SubscriptionIterator) Next() (*SubscriptionConfig, error) {
	if s.err != nil {
		return nil, s.err
	}
	subspb, err := s.it.Next()
	if err != nil {
		return nil, err
	}
	return protoToSubscriptionConfig(subspb), nil
}

// TopicPathIterator is an iterator that returns a list of topic paths.
type TopicPathIterator struct {
	it  *vkit.StringIterator
	err error
}

// Next returns the next topic path, which has format:
// "projects/PROJECT_ID/locations/LOCATION/topics/TOPIC_ID". The second return
// value will be iterator.Done if there are no more topic paths.
func (sp *TopicPathIterator) Next() (string, error) {
	if sp.err != nil {
		return "", sp.err
	}
	topicPath, err := sp.it.Next()
	if err != nil {
		return "", err
	}
	return topicPath, nil
}

// SubscriptionPathIterator is an iterator that returns a list of subscription
// paths.
type SubscriptionPathIterator struct {
	it  *vkit.StringIterator
	err error
}

// Next returns the next subscription path, which has format:
// "projects/PROJECT_ID/locations/LOCATION/subscriptions/SUBSCRIPTION_ID". The
// second return value will be iterator.Done if there are no more subscription
// paths.
func (sp *SubscriptionPathIterator) Next() (string, error) {
	if sp.err != nil {
		return "", sp.err
	}
	subsPath, err := sp.it.Next()
	if err != nil {
		return "", err
	}
	return subsPath, nil
}

// ReservationIterator is an iterator that returns a list of reservation
// configs.
type ReservationIterator struct {
	it  *vkit.ReservationIterator
	err error
}

// Next returns the next reservation config. The second return value will be
// iterator.Done if there are no more reservation configs.
func (r *ReservationIterator) Next() (*ReservationConfig, error) {
	if r.err != nil {
		return nil, r.err
	}
	respb, err := r.it.Next()
	if err != nil {
		return nil, err
	}
	return protoToReservationConfig(respb), nil
}