// (C) Copyright 2015 Moodle Pty Ltd.
//
// 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.

import { BehaviorSubject, Subject } from 'rxjs';
import { CoreEvents } from '../singletons/events';
import { CoreDelegate, CoreDelegateDisplayHandler, CoreDelegateToDisplay } from './delegate';

/**
 * Superclass to help creating sorted delegates.
 */
export class CoreSortedDelegate<
    DisplayType extends CoreDelegateToDisplay,
    HandlerType extends CoreDelegateDisplayHandler<DisplayType>>
    extends CoreDelegate<HandlerType> {

    protected loaded = false;
    protected sortedHandlersRxJs: Subject<DisplayType[]> = new BehaviorSubject<DisplayType[]>([]);
    protected sortedHandlers: DisplayType[] = [];

    /**
     * Constructor of the Delegate.
     *
     * @param delegateName Delegate name used for logging purposes.
     * @param listenSiteEvents Whether to update the handler when a site event occurs (login, site updated, ...).
     */
    constructor(delegateName: string) {
        super(delegateName, true);

        CoreEvents.on(CoreEvents.LOGOUT, this.clearSortedHandlers.bind(this));
    }

    /**
     * Check if handlers are loaded.
     *
     * @return True if handlers are loaded, false otherwise.
     */
    areHandlersLoaded(): boolean {
        return this.loaded;
    }

    /**
     * Clear current site handlers. Reserved for core use.
     */
    protected clearSortedHandlers(): void {
        this.loaded = false;
        this.sortedHandlersRxJs.next([]);
        this.sortedHandlers = [];
    }

    /**
     * Get the handlers for the current site.
     *
     * @return An observable that will receive the handlers.
     */
    getHandlers(): DisplayType[] {
        return this.sortedHandlers;
    }

    /**
     * Get the handlers for the current site.
     *
     * @return An observable that will receive the handlers.
     */
    getHandlersObservable(): Subject<DisplayType[]> {
        return this.sortedHandlersRxJs;
    }

    /**
     * Update handlers Data.
     */
    updateData(): void {
        const displayData: DisplayType[] = [];

        for (const name in this.enabledHandlers) {
            const handler = this.enabledHandlers[name];
            const data = <DisplayType> handler.getDisplayData();

            data.priority = handler.priority;
            data.name = handler.name;

            displayData.push(data);
        }

        // Sort them by priority.
        displayData.sort((a, b) => (b.priority || 0) - (a.priority || 0));

        this.loaded = true;
        this.sortedHandlersRxJs.next(displayData);
        this.sortedHandlers = displayData;
    }

}