numToWord.d

import std.stdio;
import std.string;
import std.conv;

//Splits the number where the comma would be
//123,456 -> [123, 456]
//1,234 -> [1, 234]
string[] splitNum(long toSplit)
{
    string[] ret;
    while(toSplit)
    {
        ret ~= to!string(toSplit % 1000);
        toSplit /= 1000;
    }

    return ret.reverse;
}

string wordify(long num)
{
    writeln(num);

    string[] digits = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
    if(num >= 0 && num <= 9)
    {
        return digits[num];
    }

    string[] mods = ["", "thousand", "million", "billion", "trillion"];
    string[] teens = ["ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"];
    string[] tens = ["twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"];

    string[] stringedNum = splitNum(num);
    string ret;
    int count = cast(int) stringedNum.length - 1;

    foreach(int i, string word; stringedNum)
    {
        //wordifies first digit of three digit number
        //123 -> one hundred and
        if(word.length == 3)
        {
            ret ~= digits[word[0] - '0'] ~ " hundred and ";
            word = word[1..$];
        }

        //for two digit numbers
        if(word.length == 2)
        {
            int index = word[1] - '0';
            //for num >= 10 && num <= 19
            if(word[0] != '0' && word[0] == '1')
            {
                ret ~= teens[index] ~ " ";
            }
            //for num >= 20 && <= 99
            else if(word[0] != '0' && word[0] != '1')
            {
                ret ~= tens[word[0] - '0' - 2];
                if(word[1] - '0')
                {
                    ret ~= "-" ~ digits[index];
                }
                ret ~= " ";
            }
            //for num is a three digit number, and the middle digit is a zero
            else
            {
                ret ~= digits[index] ~ " ";
            }
        }
        //single digit numbers
        else
        {
            ret ~= digits[word[0] - '0'] ~ " ";
        }

        if(i + 1 == stringedNum.length) { break; }

        ret ~= mods[count--] ~ ", ";
    }

    return ret;
}

void main(string[] args)
{
    writeln(wordify(1));
    writeln(wordify(123));
    writeln(wordify(1765));
    writeln(wordify(9843421));
    writeln(wordify(594956191569));
    writeln(wordify(9844513561589));
    writeln(wordify(10960506329090));
}