import { Injectable } from '@angular/core';
import { NgbDateParserFormatter, NgbDateStruct } from '@ng-bootstrap/ng-bootstrap';

@Injectable()
export class NgbDateUKParserFormatter extends NgbDateParserFormatter {
    parse(value: string): NgbDateStruct {
        if (value) {
            const dateParts = value.trim().split('/');
            if (dateParts.length === 1 && isNumber(dateParts[0])) {
                return {year: toInteger(dateParts[0]), month: null, day: null};
            } else if (dateParts.length === 2 && isNumber(dateParts[0]) && isNumber(dateParts[1])) {
                return {year: toInteger(dateParts[1]), month: toInteger(dateParts[0]), day: null};
            } else if (dateParts.length === 3 && isNumber(dateParts[0]) && isNumber(dateParts[1]) && isNumber(dateParts[2])) {
                return {year: toInteger(dateParts[2]), month: toInteger(dateParts[1]), day: toInteger(dateParts[0])};
            }
        }
        return null;
    }

    format(date: NgbDateStruct): string {
        let stringDate = '';
        if (date) {
            stringDate += isNumber(date.day) ? padNumber(date.day) + '/' : '';
            stringDate += isNumber(date.month) ? padNumber(date.month) + '/' : '';
            stringDate += date.year;
        }
        return stringDate;
    }
}

function padNumber(value: number) {
    if (isNumber(value)) {
        return `0${value}`.slice(-2);
    } else {
        return '';
    }
}

function isNumber(value: any): boolean {
    return !isNaN(toInteger(value));
}

function toInteger(value: any): number {
    return parseInt(`${value}`, 10);
}