// 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 (
	"fmt"
	"time"

	"cloud.google.com/go/internal/optional"
	"github.com/golang/protobuf/ptypes"

	pb "google.golang.org/genproto/googleapis/cloud/pubsublite/v1"
	fmpb "google.golang.org/genproto/protobuf/field_mask"
)

// TopicConfig describes the properties of a Google Pub/Sub Lite topic.
// See https://cloud.google.com/pubsub/lite/docs/topics for more information
// about how topics are configured.
type TopicConfig struct {
	// The full path of a topic.
	Name TopicPath

	// The number of partitions in the topic. Must be at least 1. Cannot be
	// changed after creation.
	PartitionCount int64

	// Publish throughput capacity per partition in MiB/s.
	// Must be >= 4 and <= 16.
	PublishCapacityMiBPerSec int32

	// Subscribe throughput capacity per partition in MiB/s.
	// Must be >= 4 and <= 32.
	SubscribeCapacityMiBPerSec int32

	// The provisioned storage, in bytes, per partition. If the number of bytes
	// stored in any of the topic's partitions grows beyond this value, older
	// messages will be dropped to make room for newer ones, regardless of the
	// value of `RetentionDuration`.
	PerPartitionBytes int64

	// How long a published message is retained. If unset, messages will be
	// retained as long as the bytes retained for each partition is below
	// `PerPartitionBytes`.
	RetentionDuration optional.Duration
}

func (tc *TopicConfig) toProto() *pb.Topic {
	topicpb := &pb.Topic{
		Name: tc.Name.String(),
		PartitionConfig: &pb.Topic_PartitionConfig{
			Count: tc.PartitionCount,
			Dimension: &pb.Topic_PartitionConfig_Capacity_{
				Capacity: &pb.Topic_PartitionConfig_Capacity{
					PublishMibPerSec:   tc.PublishCapacityMiBPerSec,
					SubscribeMibPerSec: tc.SubscribeCapacityMiBPerSec,
				},
			},
		},
		RetentionConfig: &pb.Topic_RetentionConfig{
			PerPartitionBytes: tc.PerPartitionBytes,
		},
	}
	if tc.RetentionDuration != nil {
		duration := optional.ToDuration(tc.RetentionDuration)
		if duration >= 0 {
			topicpb.RetentionConfig.Period = ptypes.DurationProto(duration)
		}
	}
	return topicpb
}

func protoToTopicConfig(t *pb.Topic) (*TopicConfig, error) {
	name, err := ParseTopicPath(t.GetName())
	if err != nil {
		return nil, fmt.Errorf("pubsublite: invalid topic name %q in topic config", t.GetName())
	}

	partitionCfg := t.GetPartitionConfig()
	retentionCfg := t.GetRetentionConfig()
	topic := &TopicConfig{
		Name:                       name,
		PartitionCount:             partitionCfg.GetCount(),
		PublishCapacityMiBPerSec:   partitionCfg.GetCapacity().GetPublishMibPerSec(),
		SubscribeCapacityMiBPerSec: partitionCfg.GetCapacity().GetSubscribeMibPerSec(),
		PerPartitionBytes:          retentionCfg.GetPerPartitionBytes(),
	}
	// An unset retention period proto denotes "infinite retention".
	if retentionCfg.Period != nil {
		period, err := ptypes.Duration(retentionCfg.Period)
		if err != nil {
			return nil, fmt.Errorf("pubsublite: invalid retention period in topic config: %v", err)
		}
		topic.RetentionDuration = period
	}
	return topic, nil
}

// InfiniteRetention is sentinel used when updating topic configs to clear a
// retention duration (i.e. retain messages as long as there is available
// storage).
const InfiniteRetention = time.Duration(-1)

// TopicConfigToUpdate specifies the properties to update for a topic.
type TopicConfigToUpdate struct {
	// The full path of the topic to update. Required.
	Name TopicPath

	// If non-zero, will update the publish throughput capacity per partition.
	PublishCapacityMiBPerSec int32

	// If non-zero, will update the subscribe throughput capacity per partition.
	SubscribeCapacityMiBPerSec int32

	// If non-zero, will update the provisioned storage per partition.
	PerPartitionBytes int64

	// If specified, will update how long a published message is retained. To
	// clear a retention duration (i.e. retain messages as long as there is
	// available storage), set this to `pubsublite.InfiniteRetention`.
	RetentionDuration optional.Duration
}

func (tc *TopicConfigToUpdate) toUpdateRequest() *pb.UpdateTopicRequest {
	updatedTopic := &pb.Topic{
		Name: tc.Name.String(),
		PartitionConfig: &pb.Topic_PartitionConfig{
			Dimension: &pb.Topic_PartitionConfig_Capacity_{
				Capacity: &pb.Topic_PartitionConfig_Capacity{
					PublishMibPerSec:   tc.PublishCapacityMiBPerSec,
					SubscribeMibPerSec: tc.SubscribeCapacityMiBPerSec,
				},
			},
		},
		RetentionConfig: &pb.Topic_RetentionConfig{
			PerPartitionBytes: tc.PerPartitionBytes,
		},
	}

	var fields []string
	if tc.PublishCapacityMiBPerSec > 0 {
		fields = append(fields, "partition_config.capacity.publish_mib_per_sec")
	}
	if tc.SubscribeCapacityMiBPerSec > 0 {
		fields = append(fields, "partition_config.capacity.subscribe_mib_per_sec")
	}
	if tc.PerPartitionBytes > 0 {
		fields = append(fields, "retention_config.per_partition_bytes")
	}
	if tc.RetentionDuration != nil {
		fields = append(fields, "retention_config.period")
		duration := optional.ToDuration(tc.RetentionDuration)
		// An unset retention period proto denotes "infinite retention".
		if duration >= 0 {
			updatedTopic.RetentionConfig.Period = ptypes.DurationProto(duration)
		}
	}

	return &pb.UpdateTopicRequest{
		Topic:      updatedTopic,
		UpdateMask: &fmpb.FieldMask{Paths: fields},
	}
}

// DeliveryRequirement specifies when a subscription should send messages to
// subscribers relative to persistence in storage.
type DeliveryRequirement int32

const (
	// UnspecifiedDeliveryRequirement represents and unset delivery requirement.
	UnspecifiedDeliveryRequirement = DeliveryRequirement(pb.Subscription_DeliveryConfig_DELIVERY_REQUIREMENT_UNSPECIFIED)

	// DeliverImmediately means the server will not not wait for a published
	// message to be successfully written to storage before delivering it to
	// subscribers.
	DeliverImmediately = DeliveryRequirement(pb.Subscription_DeliveryConfig_DELIVER_IMMEDIATELY)

	// DeliverAfterStored means the server will not deliver a published message to
	// subscribers until the message has been successfully written to storage.
	// This will result in higher end-to-end latency, but consistent delivery.
	DeliverAfterStored = DeliveryRequirement(pb.Subscription_DeliveryConfig_DELIVER_AFTER_STORED)
)

// SubscriptionConfig describes the properties of a Google Pub/Sub Lite
// subscription, which is attached to a topic.
// See https://cloud.google.com/pubsub/lite/docs/subscriptions for more
// information about how subscriptions are configured.
type SubscriptionConfig struct {
	// The full path of a subscription.
	Name SubscriptionPath

	// The name of the topic this subscription is attached to. This cannot be
	// changed after creation.
	Topic TopicPath

	// Whether a message should be delivered to subscribers immediately after it
	// has been published or after it has been successfully written to storage.
	DeliveryRequirement DeliveryRequirement
}

func (sc *SubscriptionConfig) toProto() *pb.Subscription {
	return &pb.Subscription{
		Name:  sc.Name.String(),
		Topic: sc.Topic.String(),
		DeliveryConfig: &pb.Subscription_DeliveryConfig{
			DeliveryRequirement: pb.Subscription_DeliveryConfig_DeliveryRequirement(sc.DeliveryRequirement),
		},
	}
}

func protoToSubscriptionConfig(s *pb.Subscription) (*SubscriptionConfig, error) {
	name, err := ParseSubscriptionPath(s.GetName())
	if err != nil {
		return nil, fmt.Errorf("pubsublite: invalid subscription name %q in subscription config", s.GetName())
	}
	topic, err := ParseTopicPath(s.GetTopic())
	if err != nil {
		return nil, fmt.Errorf("pubsublite: invalid topic name %q in subscription config", s.GetTopic())
	}
	return &SubscriptionConfig{
		Name:                name,
		Topic:               topic,
		DeliveryRequirement: DeliveryRequirement(s.GetDeliveryConfig().GetDeliveryRequirement().Number()),
	}, nil
}

// SubscriptionConfigToUpdate specifies the properties to update for a
// subscription.
type SubscriptionConfigToUpdate struct {
	// The full path of the subscription to update. Required.
	Name SubscriptionPath

	// If non-zero, updates the message delivery requirement.
	DeliveryRequirement DeliveryRequirement
}

func (sc *SubscriptionConfigToUpdate) toUpdateRequest() *pb.UpdateSubscriptionRequest {
	updatedSubs := &pb.Subscription{
		Name: sc.Name.String(),
		DeliveryConfig: &pb.Subscription_DeliveryConfig{
			DeliveryRequirement: pb.Subscription_DeliveryConfig_DeliveryRequirement(sc.DeliveryRequirement),
		},
	}

	var fields []string
	if sc.DeliveryRequirement > 0 {
		fields = append(fields, "delivery_config.delivery_requirement")
	}

	return &pb.UpdateSubscriptionRequest{
		Subscription: updatedSubs,
		UpdateMask:   &fmpb.FieldMask{Paths: fields},
	}
}