#include "say.h"

#include <stdexcept>
#include <unordered_map>


namespace say {

using namespace std;

namespace {

const unordered_map<number_t, string> number_map = {
        {0,  "zero"},
        {1,  "one"},
        {2,  "two"},
        {3,  "three"},
        {4,  "four"},
        {5,  "five"},
        {6,  "six"},
        {7,  "seven"},
        {8,  "eight"},
        {9,  "nine"},
        {10, "ten"},
        {11, "eleven"},
        {12, "twelve"},
        {13, "thirteen"},
        {20, "twenty"},
        {30, "thirty"},
        {40, "forty"},
        {50, "fifty"},
        {80, "eighty"}
    };

struct order_t
{
    number_t divisor;
    number_t max;
    string   separator;
    string   suffix;
};

const order_t orders[] = {
    {10,         100,           "-", "ty"},
    {100,        1000,          " ", " hundred"},
    {1000,       1000000,       " ", " thousand"},
    {1000000,    1000000000,    " ", " million"},
    {1000000000, 1000000000000, " ", " billion"}
};

}


string in_english(number_t number)
{
    if (number_map.count(number))
        return number_map.at(number);

    if (number > 13 && number < 20)
        return number_map.at(number - 10) + "teen";

    for (auto o : orders) {

        if (number >= o.divisor && number < o.max) {

            if (number % o.divisor == 0)
                return in_english(number / o.divisor) + o.suffix;

            number_t reminder = number % o.divisor;
            number_t div_part = number - reminder;

            return in_english(div_part) + o.separator + in_english(reminder);
        }
    }

    throw domain_error("can't say the number");
}


}