import {
    Directive,
    ElementRef,
    HostListener,
    Input,
    OnInit,
} from '@angular/core';

@Directive({
    selector: '[positiveNumbers]',
})
export class PositiveNumbersDirective implements OnInit {
    @Input()
    public minAttribute: number = 0;

    private _regex: RegExp = new RegExp(/^[0-9]+(\.[0-9]*){0,1}$/g);

    private _specialKeys = [
        'Backspace', 'Tab', 'End', 'Home',
        'ArrowLeft', 'ArrowRight', 'ArrowUp', 'ArrowDown',
    ];

    constructor(
        private _elementRef: ElementRef,
    ) {}

    public ngOnInit() {
        this._elementRef.nativeElement.setAttribute('min', this.minAttribute);
    }

    @HostListener('keydown', ['$event'])
    public keydown(event: KeyboardEvent) {
        if (this._specialKeys.some((key) => key === event.key)) {
            return;
        }
        const current = (
            this._elementRef.nativeElement as HTMLInputElement).value;
        const next = current.concat(event.key);
        if (next && !next.match(this._regex)) {
            event.preventDefault();
        }
    }
}