/**
 * FormValidation (https://formvalidation.io)
 * The best validation library for JavaScript
 * (c) 2013 - 2020 Nguyen Huu Phuoc <me@phuoc.ng>
 */

import isValidDate from '../../utils/isValidDate';

/**
 * Validate Czech Republic VAT number
 *
 * @returns {ValidateResult}
 */
export default function czVat(value: string) {
    let v = value;
    if (/^CZ[0-9]{8,10}$/.test(v)) {
        v = v.substr(2);
    }
    if (!/^[0-9]{8,10}$/.test(v)) {
        return {
            meta: {},
            valid: false,
        };
    }

    let sum = 0;
    let i = 0;
    if (v.length === 8) {
        // Do not allow to start with '9'
        if (`${v.charAt(0)}` === '9') {
            return {
                meta: {},
                valid: false,
            };
        }

        sum = 0;
        for (i = 0; i < 7; i++) {
            sum += parseInt(v.charAt(i), 10) * (8 - i);
        }
        sum = 11 - sum % 11;
        if (sum === 10) {
            sum = 0;
        }
        if (sum === 11) {
            sum = 1;
        }

        return {
            meta: {},
            valid: `${sum}` === v.substr(7, 1),
        };
    } else if (v.length === 9 && (`${v.charAt(0)}` === '6')) {
        sum = 0;
        // Skip the first (which is 6)
        for (i = 0; i < 7; i++) {
            sum += parseInt(v.charAt(i + 1), 10) * (8 - i);
        }
        sum = 11 - sum % 11;
        if (sum === 10) {
            sum = 0;
        }
        if (sum === 11) {
            sum = 1;
        }
        sum = [8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 10][sum - 1];
        return {
            meta: {},
            valid: `${sum}` === v.substr(8, 1),
        };
    } else if (v.length === 9 || v.length === 10) {
        // Validate Czech birth number (Rodné číslo), which is also national identifier
        let year = 1900 + parseInt(v.substr(0, 2), 10);
        const month = parseInt(v.substr(2, 2), 10) % 50 % 20;
        const day = parseInt(v.substr(4, 2), 10);
        if (v.length === 9) {
            if (year >= 1980) {
                year -= 100;
            }
            if (year > 1953) {
                return {
                    meta: {},
                    valid: false,
                };
            }
        } else if (year < 1954) {
            year += 100;
        }

        if (!isValidDate(year, month, day)) {
            return {
                meta: {},
                valid: false,
            };
        }

        // Check that the birth date is not in the future
        if (v.length === 10) {
            let check = parseInt(v.substr(0, 9), 10) % 11;
            if (year < 1985) {
                check = check % 10;
            }
            return {
                meta: {},
                valid: `${check}` === v.substr(9, 1),
            };
        }

        return {
            meta: {},
            valid: true,
        };
    }

    return {
        meta: {},
        valid: false,
    };
}