/*
Copyright 2020 The Knative Authors

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

    http://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
limitations under the License.
*/

package v1

import (
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"knative.dev/pkg/apis"
	duckv1 "knative.dev/pkg/apis/duck/v1"
	"knative.dev/pkg/kmeta"

	eventingduckv1 "knative.dev/eventing/pkg/apis/duck/v1"
)

// +genclient
// +genreconciler
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// +k8s:defaulter-gen=true

// Subscription routes events received on a Channel to a DNS name and
// corresponds to the subscriptions.channels.knative.dev CRD.
type Subscription struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata"`
	Spec              SubscriptionSpec   `json:"spec"`
	Status            SubscriptionStatus `json:"status,omitempty"`
}

var (
	// Check that Subscription can be validated, can be defaulted, and has immutable fields.
	_ apis.Validatable = (*Subscription)(nil)
	_ apis.Defaultable = (*Subscription)(nil)

	// Check that Subscription can return its spec untyped.
	_ apis.HasSpec = (*Subscription)(nil)

	_ runtime.Object = (*Subscription)(nil)

	// Check that we can create OwnerReferences to a Subscription.
	_ kmeta.OwnerRefable = (*Subscription)(nil)

	// Check that the type conforms to the duck Knative Resource shape.
	_ duckv1.KRShaped = (*Subscription)(nil)
)

// SubscriptionSpec specifies the Channel for incoming events, a Subscriber target
// for processing those events and where to put the result of the processing. Only
// From (where the events are coming from) is always required. You can optionally
// only Process the events (results in no output events) by leaving out the Result.
// You can also perform an identity transformation on the incoming events by leaving
// out the Subscriber and only specifying Result.
//
// The following are all valid specifications:
// channel --[subscriber]--> reply
// Sink, no outgoing events:
// channel -- subscriber
// no-op function (identity transformation):
// channel --> reply
type SubscriptionSpec struct {
	// Reference to a channel that will be used to create the subscription
	// You can specify only the following fields of the ObjectReference:
	//   - Kind
	//   - APIVersion
	//   - Name
	//  The resource pointed by this ObjectReference must meet the
	// contract to the ChannelableSpec duck type. If the resource does not
	// meet this contract it will be reflected in the Subscription's status.
	//
	// This field is immutable. We have no good answer on what happens to
	// the events that are currently in the channel being consumed from
	// and what the semantics there should be. For now, you can always
	// delete the Subscription and recreate it to point to a different
	// channel, giving the user more control over what semantics should
	// be used (drain the channel first, possibly have events dropped,
	// etc.)
	Channel corev1.ObjectReference `json:"channel"`

	// Subscriber is reference to (optional) function for processing events.
	// Events from the Channel will be delivered here and replies are
	// sent to a Destination as specified by the Reply.
	// +optional
	Subscriber *duckv1.Destination `json:"subscriber,omitempty"`

	// Reply specifies (optionally) how to handle events returned from
	// the Subscriber target.
	// +optional
	Reply *duckv1.Destination `json:"reply,omitempty"`

	// Delivery configuration
	// +optional
	Delivery *eventingduckv1.DeliverySpec `json:"delivery,omitempty"`
}

// SubscriptionStatus (computed) for a subscription
type SubscriptionStatus struct {
	// inherits duck/v1 Status, which currently provides:
	// * ObservedGeneration - the 'Generation' of the Service that was last processed by the controller.
	// * Conditions - the latest available observations of a resource's current state.
	duckv1.Status `json:",inline"`

	// PhysicalSubscription is the fully resolved values that this Subscription represents.
	PhysicalSubscription SubscriptionStatusPhysicalSubscription `json:"physicalSubscription,omitempty"`
}

// SubscriptionStatusPhysicalSubscription represents the fully resolved values for this
// Subscription.
type SubscriptionStatusPhysicalSubscription struct {
	// SubscriberURI is the fully resolved URI for spec.subscriber.
	// +optional
	SubscriberURI *apis.URL `json:"subscriberUri,omitempty"`

	// ReplyURI is the fully resolved URI for the spec.reply.
	// +optional
	ReplyURI *apis.URL `json:"replyUri,omitempty"`

	// ReplyURI is the fully resolved URI for the spec.delivery.deadLetterSink.
	// +optional
	DeadLetterSinkURI *apis.URL `json:"deadLetterSinkUri,omitempty"`
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// SubscriptionList returned in list operations
type SubscriptionList struct {
	metav1.TypeMeta `json:",inline"`
	metav1.ListMeta `json:"metadata"`
	Items           []Subscription `json:"items"`
}

// GetGroupVersionKind returns GroupVersionKind for Subscriptions
func (*Subscription) GetGroupVersionKind() schema.GroupVersionKind {
	return SchemeGroupVersion.WithKind("Subscription")
}

// GetUntypedSpec returns the spec of the Subscription.
func (s *Subscription) GetUntypedSpec() interface{} {
	return s.Spec
}

// GetStatus retrieves the status of the Subscription. Implements the KRShaped interface.
func (s *Subscription) GetStatus() *duckv1.Status {
	return &s.Status.Status
}
