poi/src/main/java/org/apache/poi/ss/formula/functions/Roman.java

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package org.apache.poi.ss.formula.functions;

import org.apache.poi.ss.formula.eval.ErrorEval;
import org.apache.poi.ss.formula.eval.EvaluationException;
import org.apache.poi.ss.formula.eval.OperandResolver;
import org.apache.poi.ss.formula.eval.StringEval;
import org.apache.poi.ss.formula.eval.ValueEval;

/**
 * Implementation for Excel Roman() function.
 * <p>
 * <b>Syntax</b>:<br> <b>Roman  </b>(<b>number</b>,<b>form</b>)<br>
 * <p>
 * Converts an arabic numeral to roman, as text.
 * <p>
 * Number  Required. The Arabic numeral you want converted.<p>
 * Form    Optional. A number specifying the type of roman numeral you want.
 *         The roman numeral style ranges from Classic to Simplified, becoming more concise as the value of form increases.
 * <p>
 * Return_type     a roman numeral, as text
 */
public class Roman extends Fixed2ArgFunction {

    //M (1000), CM (900), D (500), CD (400), C (100), XC (90), L (50), XL (40), X (10), IX (9), V (5), IV (4) and I (1).
    private static final int[] VALUES = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};

    private static final String[] ROMAN = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

    private static final String[][] REPLACEMENTS = {
        { // form > 0
            "XLV",  "VL",   //  45
            "XCV",  "VC",   //  95
            "CDL",  "LD",   // 450
            "CML",  "LM",   // 950
            "CMVC", "LMVL"  // 995
        },{ // Form == 1 only
            "CDXC", "LDXL", // 490
            "CDVC", "LDVL", // 495
            "CMXC", "LMXL", // 990
            "XCIX", "VCIV", //  99
            "XLIX", "VLIV"  //  49
        },{ // form > 1
            "XLIX", "IL",   //  49
            "XCIX", "IC",   //  99
            "CDXC", "XD",   // 490
            "CDVC", "XDV",  // 495
            "CDIC", "XDIX", // 499
            "LMVL", "XMV",  // 995
            "CMIC", "XMIX", // 999
            "CMXC", "XM"    // 990
        },{ // form > 2
            "XDV",  "VD",   // 495
            "XDIX", "VDIV", // 499
            "XMV",  "VM",   // 995
            "XMIX", "VMIV"  // 999
        },{ // form == 4
            "VDIV", "ID",   // 499
            "VMIV", "IM"    // 999
        }
    };



    @Override
    public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval numberVE, ValueEval formVE) {
        final int number;
        try {
            ValueEval ve = OperandResolver.getSingleValue(numberVE, srcRowIndex, srcColumnIndex);
            number = OperandResolver.coerceValueToInt(ve);
        } catch (EvaluationException e) {
            return ErrorEval.VALUE_INVALID;
        }
        if (number < 0) {
            return ErrorEval.VALUE_INVALID;
        }
        if (number > 3999) {
            return ErrorEval.VALUE_INVALID;
        }
        if (number == 0) {
            return new StringEval("");
        }

        final int form;
        try {
            ValueEval ve = OperandResolver.getSingleValue(formVE, srcRowIndex, srcColumnIndex);
            form = OperandResolver.coerceValueToInt(ve);
        } catch (EvaluationException e) {
            return ErrorEval.NUM_ERROR;
        }

        if (form > 4 || form < 0) {
            return ErrorEval.VALUE_INVALID;
        }

        String result = this.integerToRoman(number);

        if (form == 0) {
            return new StringEval(result);
        }

        return new StringEval(makeConcise(result, form));
    }

    /**
     * Classic conversion.
     *
     * @param number the number
     */
    private String integerToRoman(int number) {
        StringBuilder result = new StringBuilder();
        for (int i = 0; i < 13; i++) {
            while (number >= VALUES[i]) {
                number -= VALUES[i];
                result.append(ROMAN[i]);
            }
        }
        return result.toString();
    }

    /**
     * Use conversion rule to factor some parts and make them more concise
     *
     * @param input the input string
     * @param form the level of conciseness [0..4] with 4 being most concise and simplified
     */
    public String makeConcise(final String input, final int form) {
        String result = input;
        for (int i=0; i<=form && i<=4 && form > 0; i++) {
            if (i==1 && form>1) {
                // Replacement[1] is only meant for form == 1
                continue;
            }
            String[] repl = REPLACEMENTS[i];
            for (int j = 0; j < (repl.length - 1); j += 2) {
                result = result.replace(repl[j],repl[j+1]);
            }
        }
        return result;
    }
}