import {
    Directive,
    OnInit,
    OnDestroy,
    Input,
    Output,
    EventEmitter
} from '@angular/core';
import { Subscription } from 'rxjs/Subscription';

import { Redhawk }                from '../models/index';

import { RedhawkService } from './redhawk.service';
import { redhawkServiceProvider } from './redhawk-service-provider';

/**
 * The REDHAWK Directive is the entry point, top-level directive for dependency
 * injection when accessing the REST services for a REDHAWK Domain.
 * 
 * @example
 * <div arRedhawk [(arModel)]="my_model">
 */
@Directive({
    selector: '[arRedhawk]',
    exportAs: 'arRedhawk',
    providers: [
        redhawkServiceProvider()
    ]
})
export class RedhawkDirective implements OnInit, OnDestroy {
    /** The name to apply to the REDHAWK Service */
    @Input() serviceName: string;

    /** Setter for "Banana in a Box Syntax"  */
    @Input('arModel') model: Redhawk;
    /** Emitter for "Banana in a Box Syntax" */
    @Output('arModelChange') modelChange: EventEmitter<Redhawk>;

    /** Internal subscription for the model */
    private subscription: Subscription;

    /**
     * Constructor
     * @param service The service either imported from up the hierarchy or instantiated
     *                by this directive.
     */
    constructor(public service: RedhawkService) {
        this.modelChange = new EventEmitter<Redhawk>();
        this.subscription = this.service.model$.subscribe(it => {
            this.model = it;
            this.modelChange.emit(this.model);
        });
    }

    /**
     * Implementation of the OnChanges interface updates the service's uniqueID
     * @param changes The changes made to this component
     */
    ngOnInit() {
        this.service.uniqueId = this.serviceName || 'Default';
    }

    /**
     * Implementation of the OnDestroy interface unsubscribes from the model observable.
     */
    ngOnDestroy() {
        this.subscription.unsubscribe();
    }
}