/*!
 * @license
 * Copyright 2019 Alfresco Software, 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 { Component, EventEmitter, Input, OnInit, Output, ViewChild, ViewEncapsulation, OnDestroy } from '@angular/core';
import { SitesService, LogService } from '@alfresco/adf-core';
import { SitePaging, SiteEntry } from '@alfresco/js-api';
import { MatSelect } from '@angular/material';
import { Subject } from 'rxjs';
import { takeUntil } from 'rxjs/operators';

export enum Relations {
    Members = 'members',
    Containers = 'containers'
}

@Component({
    selector: 'adf-sites-dropdown',
    styleUrls: ['./sites-dropdown.component.scss'],
    templateUrl: './sites-dropdown.component.html',
    encapsulation: ViewEncapsulation.None,
    host: { 'class': 'adf-sites-dropdown' }
})
export class DropdownSitesComponent implements OnInit, OnDestroy {

    /** Hide the "My Files" option. */
    @Input()
    hideMyFiles: boolean = false;

    /** A custom list of sites to be displayed by the dropdown. If no value
     * is given, the sites of the current user are displayed by default. A
     * list of objects only with properties 'title' and 'guid' is enough to
     * be able to display the dropdown.
     */
    @Input()
    siteList: SitePaging = null;

    /** Id of the selected site */
    @Input()
    value: string = null;

    /** Text or a translation key to act as a placeholder. Default value is the
     * key "DROPDOWN.PLACEHOLDER_LABEL".
     */
    @Input()
    placeholder: string = 'DROPDOWN.PLACEHOLDER_LABEL';

    /** Filter for the results of the sites query. Possible values are
     * "members" and "containers". When "members" is used, the site list
     * will be restricted to the sites that the user is a member of.
     */
    @Input()
    relations: string;

    /** Emitted when the user selects a site. When the default option is selected,
     * an empty model is emitted.
     */
    @Output()
    change: EventEmitter<SiteEntry> = new EventEmitter();

    @ViewChild('siteSelect')
    siteSelect: MatSelect;

    private loading = true;
    private skipCount = 0;
    private readonly MAX_ITEMS = 50;
    private readonly ITEM_HEIGHT = 45;
    private readonly ITEM_HEIGHT_TO_WAIT_BEFORE_LOAD_NEXT = (this.ITEM_HEIGHT * (this.MAX_ITEMS / 2));
    private onDestroy$ = new Subject<boolean>();

    selected: SiteEntry = null;
    MY_FILES_VALUE = '-my-';

    constructor(private sitesService: SitesService,
                private logService: LogService) {
    }

    ngOnInit() {
        this.siteSelect.openedChange
            .pipe(takeUntil(this.onDestroy$))
            .subscribe(() => {
                if (this.siteSelect.panelOpen) {
                    this.siteSelect.panel.nativeElement.addEventListener('scroll', (event) => this.loadAllOnScroll(event));
                }
            });

        if (!this.siteList) {
            this.loadSiteList();
        }
    }

    ngOnDestroy() {
        this.onDestroy$.next(true);
        this.onDestroy$.complete();
    }

    loadAllOnScroll(event) {
        if (this.isInfiniteScrollingEnabled() && this.isScrollInNextFetchArea(event)) {
            this.loading = true;
            this.loadSiteList();
        }
    }

    isScrollInNextFetchArea(event) {
        return event.target.scrollTop >= (event.target.scrollHeight - event.target.offsetHeight - this.ITEM_HEIGHT_TO_WAIT_BEFORE_LOAD_NEXT);
    }

    selectedSite(event: any) {
        this.change.emit(event.value);
    }

    private loadSiteList() {
        const extendedOptions: any = {
            skipCount: this.skipCount,
            maxItems: this.MAX_ITEMS
        };

        this.skipCount += this.MAX_ITEMS;

        if (this.relations) {
            extendedOptions.relations = [this.relations];
        }

        this.sitesService.getSites(extendedOptions).subscribe((sitePaging: SitePaging) => {

                if (!this.siteList) {
                    this.siteList = this.relations === Relations.Members ? this.filteredResultsByMember(sitePaging) : sitePaging;

                    if (!this.hideMyFiles) {
                        const siteEntry = new SiteEntry({
                            entry: {
                                id: '-my-',
                                guid: '-my-',
                                title: 'DROPDOWN.MY_FILES_OPTION'
                            }
                        });

                        this.siteList.list.entries.unshift(siteEntry);

                        if (!this.value) {
                            this.value = '-my-';
                        }
                    }

                } else {
                    const siteList: SitePaging = this.relations === Relations.Members ? this.filteredResultsByMember(sitePaging) : sitePaging;

                    this.siteList.list.entries = this.siteList.list.entries.concat(siteList.list.entries);
                    this.siteList.list.pagination = sitePaging.list.pagination;
                }

                this.selected = this.siteList.list.entries.find((site: SiteEntry) => site.entry.id === this.value);

                this.loading = false;
            },
            (error) => {
                this.logService.error(error);
            });
    }

    showLoading(): boolean {
        return this.loading && (this.siteList && this.siteList.list.pagination && this.siteList.list.pagination.hasMoreItems);
    }

    isInfiniteScrollingEnabled(): boolean {
        return !this.loading && (this.siteList && this.siteList.list.pagination && this.siteList.list.pagination.hasMoreItems);
    }

    private filteredResultsByMember(sites: SitePaging): SitePaging {
        const loggedUserName = this.sitesService.getEcmCurrentLoggedUserName();
        sites.list.entries = sites.list.entries.filter((site) => this.isCurrentUserMember(site, loggedUserName));
        return sites;
    }

    private isCurrentUserMember(site, loggedUserName): boolean {
        return site.entry.visibility === 'PUBLIC' ||
            !!site.relations.members.list.entries.find((member) => {
                return member.entry.id.toLowerCase() === loggedUserName.toLowerCase();
            });
    }

}