import { EventEmitter } from '@angular/core'
import { PaginationInstance } from './pagination-instance';

export class PaginationService {

    public change: EventEmitter<string> = new EventEmitter<string>();
    public total: EventEmitter<number> = new EventEmitter<number>();

    private instances: { [ id: string ]: PaginationInstance } = {};
    private DEFAULT_ID = 'DEFAULT_PAGINATION_ID';

    public defaultId(): string { return this.DEFAULT_ID }

    public register(instance: PaginationInstance) {
        if (!instance.id) {
            instance.id = this.DEFAULT_ID;
        }

        if (!this.instances[ instance.id ]) {
            this.instances[ instance.id ] = instance;
            this.change.emit(instance.id);
            this.total.emit(instance.totalItems);
        } else {
            let changed = this.updateInstance(instance);
            if (changed) {
                this.change.emit(instance.id);
                this.total.emit(instance.totalItems);
            }
        }
    }

    private updateInstance(instance: PaginationInstance): boolean {
        let changed = false;
        for (let prop in this.instances[ instance.id ]) {
            if (instance[ prop ] !== this.instances[ instance.id ][ prop ]) {
                this.instances[ instance.id ][ prop ] = instance[ prop ];
                changed = true;
            }
        }
        return changed;
    }

    public getCurrentPage(id: string): number {
        if (this.instances[ id ]) {
            return this.instances[ id ].currentPage;
        }
    }

    public setCurrentPage(id: string, page: number) {
        if (this.instances[ id ]) {
            let instance = this.instances[ id ];
            let maxPage = Math.ceil(instance.totalItems / instance.itemsPerPage);
            if (page <= maxPage && 1 <= page) {
                this.instances[ id ].currentPage = page;
                this.change.emit(id);
            }
        }
    }

    public setTotalItems(id: string, totalItems: number) {
        if (this.instances[ id ] && 0 <= totalItems) {
            this.instances[ id ].totalItems = totalItems;
            this.change.emit(id);
        }
    }

    public setItemsPerPage(id: string, itemsPerPage: number) {
        if (this.instances[ id ]) {
            this.instances[ id ].itemsPerPage = itemsPerPage;
            this.change.emit(id);
        }
    }

    public getInstance(id: string = this.DEFAULT_ID): PaginationInstance {
        if (this.instances[ id ]) {
            return this.clone(this.instances[ id ]);
        }
        return {} as PaginationInstance;
    }

    private clone(obj: any): any {
        var target = {};
        for (var i in obj) {
            if (obj.hasOwnProperty(i)) {
                target[ i ] = obj[ i ];
            }
        }
        return target;
    }

}