IBANs.java

package net.andreinc.mockneat.unit.financial;

/**
 * Copyright 2017, Andrei N. Ciobanu

 Permission is hereby granted, free of charge, to any user obtaining a copy of this software and associated
 documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit
 persons to whom the Software is furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 OTHERWISE, ARISING FROM, FREE_TEXT OF OR PARAM CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS PARAM THE SOFTWARE.
 */

import net.andreinc.mockneat.MockNeat;
import net.andreinc.mockneat.abstraction.MockUnitBase;
import net.andreinc.mockneat.abstraction.MockUnitString;
import net.andreinc.mockneat.types.Pair;
import net.andreinc.mockneat.types.enums.CharsType;
import net.andreinc.mockneat.types.enums.IBANType;

import java.math.BigInteger;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;

import static java.lang.Character.toLowerCase;
import static java.math.BigInteger.valueOf;
import static java.util.stream.IntStream.range;
import static net.andreinc.mockneat.alphabets.Alphabets.DIGITS;
import static net.andreinc.mockneat.alphabets.Alphabets.LETTERS_UPPERCASE;
import static net.andreinc.mockneat.utils.ValidationUtils.notEmpty;
import static net.andreinc.mockneat.utils.ValidationUtils.notNull;

public class IBANs extends MockUnitBase implements MockUnitString {

    private static final Map<Character, String> VALUE_MAP = new HashMap<>();

    static {
        // Initialize a map:
        // (A, a) -> 10
        // (B, b) -> 11
        // ...
        // (Z, z) -> 35
        range(0, LETTERS_UPPERCASE.size()).forEach( i -> {
            Character upper = LETTERS_UPPERCASE.get(i);
            Character lower=  toLowerCase(upper);
            String value = (i + 10) + "";
            VALUE_MAP.put(lower, value);
            VALUE_MAP.put(upper, value);
        });

        range(0, DIGITS.size()).forEach( i -> {
            VALUE_MAP.put(DIGITS.get(i), DIGITS.get(i)+"");
        });
    }

    public IBANs(MockNeat mockNeat) {
        super(mockNeat);
    }

    @Override
    public Supplier<String> supplier() {
        return () -> {
            IBANType type = mockNeat.from(IBANType.class).val();
            return generate(type);
        };
    }

    public MockUnitString type(IBANType ibanType) {
        notNull(ibanType, "ibanType");
        return () -> () -> generate(ibanType);
    }

    public MockUnitString types(IBANType... ibanTypes) {
        notEmpty(ibanTypes, "ibanTypes");
        return () -> () -> {
            IBANType type = mockNeat.from(ibanTypes).val();
            return generate(type);
        };
    }

    private String generate(IBANType ibanType) {

        List<Pair<Integer, CharsType>> bbanGroup = ibanType.getBban();
        String prefix = ibanType.getPrefix();

        // Will contain the final IBAN code as returned by the method
        final StringBuilder iban = new StringBuilder(ibanType.getLength());
        // Will contain the bban section (the numbers that come after <CountryCode><CheckDigits>
        final StringBuilder bban = new StringBuilder(ibanType.getLength() - 4);
        // Will be used to calculate the check digits
        final StringBuilder numeric = new StringBuilder(ibanType.getLength() * 2);

        // Apending the country prefix
        iban.append(prefix);

        // Generate BBAN and the NUMERIC IBAN needed to generate the check digits
        bbanGroup.forEach(pair -> {
            int groupLength = pair.getFirst();
            CharsType type = pair.getSecond();
            Character currentChar;
            while(groupLength-->0) {
                currentChar = mockNeat.chars().type(type).val();
                bban.append(currentChar);
                numeric.append(VALUE_MAP.get(currentChar));
            }
        });

        // Add prefix at the end of the numeric representation
        numeric.append(VALUE_MAP.get(prefix.charAt(0)));
        numeric.append(VALUE_MAP.get(prefix.charAt(1)));

        // Check digits are added as 0s.
        numeric.append("00");

        return iban.append(checkDigits(numeric.toString()))
                    .append(bban)
                    .toString();
    }

    public String checkDigits(String numericIBAN) {
        BigInteger bigInteger = new BigInteger(numericIBAN);
        Integer remainder = bigInteger.mod(valueOf(97)).intValue();

        Integer checkDigits = 98 - remainder;

        return (checkDigits<10) ?
                // if the remainder is only 1 digit,
                // we add a new 0
                "0" + checkDigits : ""  + checkDigits ;
    }
}