import {Component, Input, OnChanges} from '@angular/core';
import {EventEmitter} from '@angular/core';

@Component({
    selector: 'ngx-pagination',
    templateUrl: 'ngx-pagination.component.html'
})
export class NgxPaginationComponent implements OnChanges {

    @Input() public type = 'buttons';
    @Input() public page = 1;
    @Input() public pageCount = 1;
    public pages: Array<any> = [];
    public updating = false;

    @Input() public changePageEmitter: EventEmitter<any>;

    ngOnChanges(changes: any) {
        this.pages = this.updatePagination();
    }

    public onPrev() {
        this.goToPage(this.page - 1);
    }

    public onNext() {
        this.goToPage(this.page + 1);
    }

    public goToPage(page: number) {
        this.updating = true;
        this.changePageEmitter.emit(page);
    }

    public updatePagination() {
        this.updating = false;
        const pagesArray: Array<any> = [];
        const currentPage = this.page;
        const pagesCount = this.pageCount;

        if (this.type === 'buttons') {

            const paginationSpan = 2;
            let startPos = 2;
            let endPos = startPos + paginationSpan - 1;
            const middlePos = Math.ceil(paginationSpan / 2);

            // Adjust start and end positions to maintain range and keep current page as active.
            if (currentPage >= startPos + 1) {
                startPos = currentPage - middlePos + 1;
                endPos = startPos + paginationSpan - 1;
                if (endPos + 1 > pagesCount) {
                    startPos = pagesCount - paginationSpan;
                    endPos = pagesCount - 1;
                }
            }

            /*
             * Extra adjustments in case pagination range is larger than results.
             */
            if (startPos < 2) {
                startPos = 2;
            }
            if (endPos >= pagesCount) {
                endPos = pagesCount - 1;
            }
            if (endPos < startPos) {
                endPos = startPos - 1;
            }

            // Only show pagination when there is more than one page.
            if (pagesCount > 1) {

                /*
                 * Create pagination range.
                 */
                pagesArray.push({
                    value: 1,
                    isPage: true,
                    active: +currentPage === 1,
                    disabled: false
                });

                if (startPos > 2) {
                    pagesArray.push({value: '...', isPage: false, active: false, disabled: true});
                }
                for (let i = startPos; i <= endPos; i++) {
                    pagesArray.push({
                        value: i,
                        isPage: true,
                        active: i === +currentPage,
                        disabled: false
                    });
                }
                if (endPos + 1 !== +pagesCount) {
                    pagesArray.push({value: '...', isPage: false, active: false, disabled: true});
                }
                pagesArray.push({
                    value: pagesCount,
                    isPage: true,
                    active: +pagesCount === +currentPage,
                    disabled: false
                });
            }
        } else {
            for (let i = 1; i <= this.pageCount; i++) {
                pagesArray.push(i);
            }
        }

        return pagesArray;
    }
}