/*

 * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/Assertions.h>

#include <AK/StringView.h>

#include <AK/Types.h>

#include <LibLocale/Forward.h>

namespace Locale {

enum class PluralForm {

    Cardinal,

    Ordinal,

};

enum class PluralCategory : u8 {

    Other,

    Zero,

    One,

    Two,

    Few,

    Many,

    // https://unicode.org/reports/tr35/tr35-numbers.html#Explicit_0_1_rules

    ExactlyZero,

    ExactlyOne,

};

// https://unicode.org/reports/tr35/tr35-numbers.html#Plural_Operand_Meanings

struct PluralOperands {

    static constexpr StringView symbol_to_variable_name(char symbol)

    {

        if (symbol == 'n')

            return "number"sv;

        if (symbol == 'i')

            return "integer_digits"sv;

        if (symbol == 'f')

            return "fraction_digits"sv;

        if (symbol == 'v')

            return "number_of_fraction_digits"sv;

        if (symbol == 't')

            return "fraction_digits_without_trailing"sv;

        if (symbol == 'w')

            return "number_of_fraction_digits_without_trailing"sv;

        VERIFY_NOT_REACHED();

    }

    static constexpr bool symbol_requires_floating_point_modulus(char symbol)

    {

        // From TR-35: "The modulus (% or mod) is a remainder operation as defined in Java; for

        // example, where n = 4.3 the result of n mod 3 is 1.3."

        //

        // So, this returns whether the symbol represents a decimal value, and thus requires fmod.

        return symbol == 'n';

    }

    double number { 0 };

    u64 integer_digits { 0 };

    u64 fraction_digits { 0 };

    u64 number_of_fraction_digits { 0 };

    u64 fraction_digits_without_trailing { 0 };

    u64 number_of_fraction_digits_without_trailing { 0 };

};

PluralForm plural_form_from_string(StringView plural_form);

StringView plural_form_to_string(PluralForm plural_form);

// NOTE: This must be defined inline to be callable from the code generators.

constexpr PluralCategory plural_category_from_string(StringView category)

{

    if (category == "other"sv)

        return PluralCategory::Other;

    if (category == "zero"sv)

        return PluralCategory::Zero;

    if (category == "one"sv)

        return PluralCategory::One;

    if (category == "two"sv)

        return PluralCategory::Two;

    if (category == "few"sv)

        return PluralCategory::Few;

    if (category == "many"sv)

        return PluralCategory::Many;

    if (category == "0"sv)

        return PluralCategory::ExactlyZero;

    if (category == "1"sv)

        return PluralCategory::ExactlyOne;

    VERIFY_NOT_REACHED();

}

// NOTE: This must be defined inline to be callable from the code generators.

constexpr StringView plural_category_to_string(PluralCategory category)

{

    switch (category) {

    case PluralCategory::Other:

        return "other"sv;

    case PluralCategory::Zero:

        return "zero"sv;

    case PluralCategory::One:

        return "one"sv;

    case PluralCategory::Two:

        return "two"sv;

    case PluralCategory::Few:

        return "few"sv;

    case PluralCategory::Many:

        return "many"sv;

    case PluralCategory::ExactlyZero:

        return "0"sv;

    case PluralCategory::ExactlyOne:

        return "1"sv;

    }

    VERIFY_NOT_REACHED();

}

PluralCategory determine_plural_category(StringView locale, PluralForm form, PluralOperands operands);

ReadonlySpan<PluralCategory> available_plural_categories(StringView locale, PluralForm form);

PluralCategory determine_plural_range(StringView locale, PluralCategory start, PluralCategory end);

}