// Copyright 2017 Google Inc.
//
// 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 apid

type EventSelector string

type Event interface{}

type EventHandler interface {
	Handle(event Event)
}

type EventHandlerFunc func(event Event)

type EventsService interface {
	// Publish an event to the selector.
	// It will send a copy of the delivered event to the returned channel, after all listeners have responded to the event.
	// Call "Emit()" for non-blocking, "<-Emit()" for blocking.
	Emit(selector EventSelector, event Event) chan Event

	// publish an event to the selector, call the passed handler when all listeners have responded to the event
	EmitWithCallback(selector EventSelector, event Event, handler EventHandlerFunc)

	// when an event matching selector occurs, run the provided handler
	Listen(selector EventSelector, handler EventHandler)

	// when an event matching selector occurs, run the provided handler function
	ListenFunc(selector EventSelector, handler EventHandlerFunc)

	// when an event matching selector occurs, run the provided handler function and stop listening
	ListenOnceFunc(selector EventSelector, handler EventHandlerFunc)

	// remove a listener
	StopListening(selector EventSelector, handler EventHandler)

	// shut it down
	Close()
}

const EventDeliveredSelector EventSelector = "event delivered"

type EventDeliveryEvent struct {
	Description string
	Selector    EventSelector
	Event       Event
	Count       int
}

// use reflect.DeepEqual to compare this type
type PluginsInitializedEvent struct {
	Description string
	// using slice member will make the type "PluginsInitializedEvent" uncomparable
	Plugins     []PluginData
	ApidVersion string
}

type PluginData struct {
	Name      string
	Version   string
	ExtraData map[string]interface{}
}