import {Injectable} from '@angular/core';
import {InvalidNationalCodeError} from './InvalidNationalCode.error';

/**
 * For validating Iranian National code (number), you can use this service in your components or every other places using DI or not.
 */
@Injectable({
    providedIn: 'root'
})
export class NationalCodeService {
    /**
     * This method adds zero character at the beginning of the input until the length of the result reach to 10.
     *
     * This method removes spaces from right and left sides of the input.
     *
     * ATTENTION: This method doesn't any validation about correctness of the input if it has correct length (between 8 and 10).
     *
     * @param nationalCode a number with at most 10 digits or a string with at most 10 character.
     * @return a string with length equal to 10.
     * @throws InvalidNationalCodeError when length of the input value is greater than 10.
     */
    normalize(nationalCode: number | string): string {
        if (!nationalCode) {
            throw new InvalidNationalCodeError();
        }
        let normalizedNationalCode= nationalCode.toString();
        normalizedNationalCode = normalizedNationalCode.trim();
        const nationalCodeLength = normalizedNationalCode.length;
        if (nationalCodeLength > 10 || nationalCodeLength < 8) {
            throw new InvalidNationalCodeError(normalizedNationalCode);
        }
        return '0'.repeat(10 - nationalCodeLength) + normalizedNationalCode;
    }

    /**
     * This method first normalizes the input using `normalize` method and implicitly checks input length, So you DO NOT NEED to
     * normalize input before, but this will not make any bad effect.
     *
     * [Then checking validation of the input using algorithm described in this link]{@link http://www.aliarash.com/article/codemeli/codemeli.htm}
     *
     * @param nationalCode
     */
    isValid(nationalCode: number | string): boolean {
        if (!nationalCode) {
            return false;
        }
        let NormalizedNationalCode = nationalCode.toString();
        if (this._isRepetitive(NormalizedNationalCode)) {
            return false;
        }
        try {
            NormalizedNationalCode = this.normalize(NormalizedNationalCode); // Normalizing the input and checking input length validation implicitly.
        } catch (e) {
            return false; // Input length is not in the valid range.
        }
        let multiplicationResult = 0;
        for (let i = 0; i < 9; i++) {
            multiplicationResult += parseInt(NormalizedNationalCode.charAt(i), 10) * (10 - i);
        }
        const reminder = multiplicationResult % 11;
        const controlNum = parseInt(NormalizedNationalCode.charAt(9), 10);
        let desiredControlNum = reminder;
        if (reminder > 1) {
            desiredControlNum = 11 - reminder;
        }
        return desiredControlNum === controlNum;
    }

    /**
     *
     * [We are using for loop instead of match or split because it has better performance according to this link]{@link https://stackoverflow.com/a/46312614/5400597}
     *
     * @return true if all characters of the `input` are equal and input length is greater than 1. Otherwise returns false.
     * @param input
     */
    private _isRepetitive(input: string): boolean {
        if (input.length < 2) {
            return false;
        }
        const firstChar = input.charAt(0);
        for (let i = 1; i < input.length; i++) {
            if (input.charAt(i) !== firstChar) {
                return false;
            }
        }
        return true;
    }
}