/*
 * Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include "GeneratorUtil.h"
#include <AK/AllOf.h>
#include <AK/CharacterTypes.h>
#include <AK/Format.h>
#include <AK/GenericLexer.h>
#include <AK/HashFunctions.h>
#include <AK/HashMap.h>
#include <AK/JsonObject.h>
#include <AK/JsonParser.h>
#include <AK/JsonValue.h>
#include <AK/LexicalPath.h>
#include <AK/SourceGenerator.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/Traits.h>
#include <AK/Utf8View.h>
#include <LibCore/ArgsParser.h>
#include <LibCore/DirIterator.h>
#include <LibCore/File.h>
#include <LibUnicode/DateTimeFormat.h>

using StringIndexType = u16;
constexpr auto s_string_index_type = "u16"sv;

using CalendarPatternIndexType = u16;
constexpr auto s_calendar_pattern_index_type = "u16"sv;

struct CalendarPattern : public Unicode::CalendarPattern {
    bool contains_only_date_fields() const
    {
        return !day_period.has_value() && !hour.has_value() && !minute.has_value() && !second.has_value() && !fractional_second_digits.has_value() && !time_zone_name.has_value();
    }

    bool contains_only_time_fields() const
    {
        return !weekday.has_value() && !era.has_value() && !year.has_value() && !month.has_value() && !day.has_value();
    }

    unsigned hash() const
    {
        auto hash = pair_int_hash(pattern_index, pattern12_index);

        auto hash_field = [&](auto const& field) {
            if (field.has_value())
                hash = pair_int_hash(hash, static_cast<u8>(*field));
            else
                hash = pair_int_hash(hash, -1);
        };

        hash_field(era);
        hash_field(year);
        hash_field(month);
        hash_field(weekday);
        hash_field(day);
        hash_field(day_period);
        hash_field(hour);
        hash_field(minute);
        hash_field(second);
        hash_field(fractional_second_digits);
        hash_field(time_zone_name);

        return hash;
    }

    bool operator==(CalendarPattern const& other) const
    {
        return (pattern_index == other.pattern_index)
            && (pattern12_index == other.pattern12_index)
            && (era == other.era)
            && (year == other.year)
            && (month == other.month)
            && (weekday == other.weekday)
            && (day == other.day)
            && (day_period == other.day_period)
            && (hour == other.hour)
            && (minute == other.minute)
            && (second == other.second)
            && (fractional_second_digits == other.fractional_second_digits)
            && (time_zone_name == other.time_zone_name);
    }

    StringIndexType pattern_index { 0 };
    StringIndexType pattern12_index { 0 };
};

template<>
struct AK::Formatter<CalendarPattern> : Formatter<FormatString> {
    ErrorOr<void> format(FormatBuilder& builder, CalendarPattern const& pattern)
    {
        auto field_to_i8 = [](auto const& field) -> i8 {
            if (!field.has_value())
                return -1;
            return static_cast<i8>(*field);
        };

        return Formatter<FormatString>::format(builder,
            "{{ {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {} }}",
            pattern.pattern_index,
            pattern.pattern12_index,
            field_to_i8(pattern.era),
            field_to_i8(pattern.year),
            field_to_i8(pattern.month),
            field_to_i8(pattern.weekday),
            field_to_i8(pattern.day),
            field_to_i8(pattern.day_period),
            field_to_i8(pattern.hour),
            field_to_i8(pattern.minute),
            field_to_i8(pattern.second),
            field_to_i8(pattern.fractional_second_digits),
            field_to_i8(pattern.time_zone_name));
    }
};

template<>
struct AK::Traits<CalendarPattern> : public GenericTraits<CalendarPattern> {
    static unsigned hash(CalendarPattern const& c) { return c.hash(); }
};

struct CalendarFormat {
    CalendarPatternIndexType full_format { 0 };
    CalendarPatternIndexType long_format { 0 };
    CalendarPatternIndexType medium_format { 0 };
    CalendarPatternIndexType short_format { 0 };
};

struct Calendar {
    StringIndexType calendar { 0 };
    CalendarFormat date_formats {};
    CalendarFormat time_formats {};
    CalendarFormat date_time_formats {};
    Vector<CalendarPatternIndexType> available_formats {};
};

struct Locale {
    HashMap<String, Calendar> calendars;
};

struct UnicodeLocaleData {
    UniqueStringStorage<StringIndexType> unique_strings;
    UniqueStorage<CalendarPattern, CalendarPatternIndexType> unique_patterns;
    HashMap<String, Locale> locales;

    HashMap<String, Vector<Unicode::HourCycle>> hour_cycles;
    Vector<String> hour_cycle_regions;

    Vector<String> calendars;
    Vector<Alias> calendar_aliases {
        // FIXME: Aliases should come from BCP47. See: https://unicode-org.atlassian.net/browse/CLDR-15158
        { "gregorian"sv, "gregory"sv },
    };
};

static ErrorOr<void> parse_hour_cycles(String core_path, UnicodeLocaleData& locale_data)
{
    // https://unicode.org/reports/tr35/tr35-dates.html#Time_Data
    LexicalPath time_data_path(move(core_path));
    time_data_path = time_data_path.append("supplemental"sv);
    time_data_path = time_data_path.append("timeData.json"sv);

    auto time_data_file = TRY(Core::File::open(time_data_path.string(), Core::OpenMode::ReadOnly));
    auto time_data = TRY(JsonValue::from_string(time_data_file->read_all()));
    auto const& supplemental_object = time_data.as_object().get("supplemental"sv);
    auto const& time_data_object = supplemental_object.as_object().get("timeData"sv);

    auto parse_hour_cycle = [](StringView hour_cycle) -> Optional<Unicode::HourCycle> {
        if (hour_cycle == "h"sv)
            return Unicode::HourCycle::H12;
        if (hour_cycle == "H"sv)
            return Unicode::HourCycle::H23;
        if (hour_cycle == "K"sv)
            return Unicode::HourCycle::H11;
        if (hour_cycle == "k"sv)
            return Unicode::HourCycle::H24;
        return {};
    };

    time_data_object.as_object().for_each_member([&](auto const& key, JsonValue const& value) {
        auto allowed_hour_cycles_string = value.as_object().get("_allowed"sv).as_string();
        auto allowed_hour_cycles = allowed_hour_cycles_string.split_view(' ');

        Vector<Unicode::HourCycle> hour_cycles;

        for (auto allowed_hour_cycle : allowed_hour_cycles) {
            if (auto hour_cycle = parse_hour_cycle(allowed_hour_cycle); hour_cycle.has_value())
                hour_cycles.append(*hour_cycle);
        }

        locale_data.hour_cycles.set(key, move(hour_cycles));

        if (!locale_data.hour_cycle_regions.contains_slow(key))
            locale_data.hour_cycle_regions.append(key);
    });

    return {};
};

static constexpr auto is_char(char ch)
{
    return [ch](auto c) { return c == ch; };
}

// For patterns that are 12-hour aware, we need to generate two patterns: one with the day period
// (e.g. {ampm}) in the pattern, and one without the day period. We need to take care to remove
// extra spaces around the day period. Some example expected removals:
//
// "{hour}:{minute} {ampm}" becomes "{hour}:{minute}" (remove the space before {ampm})
// "{ampm} {hour}" becomes "{hour}" (remove the space after {ampm})
// "{hour}:{minute} {ampm} {timeZoneName}" becomes "{hour}:{minute} {timeZoneName}" (remove one of the spaces around {ampm})
static String remove_period_from_pattern(String pattern)
{
    for (auto remove : AK::Array { "({ampm})"sv, "{ampm}"sv, "({dayPeriod})"sv, "{dayPeriod}"sv }) {
        auto index = pattern.find(remove);
        if (!index.has_value())
            continue;

        constexpr u32 space = ' ';
        constexpr u32 open = '{';
        constexpr u32 close = '}';

        Utf8View utf8_pattern { pattern };
        Optional<u32> before_removal;
        Optional<u32> after_removal;

        for (auto it = utf8_pattern.begin(); utf8_pattern.byte_offset_of(it) < *index; ++it)
            before_removal = *it;
        if (auto it = utf8_pattern.iterator_at_byte_offset(*index + remove.length()); it != utf8_pattern.end())
            after_removal = *it;

        if ((before_removal == space) && (after_removal != open)) {
            pattern = String::formatted("{}{}",
                pattern.substring_view(0, *index - 1),
                pattern.substring_view(*index + remove.length()));
        } else if ((after_removal == space) && (before_removal != close)) {
            pattern = String::formatted("{}{}",
                pattern.substring_view(0, *index),
                pattern.substring_view(*index + remove.length() + 1));
        } else {
            pattern = String::formatted("{}{}",
                pattern.substring_view(0, *index),
                pattern.substring_view(*index + remove.length()));
        }
    }

    return pattern;
}

static Optional<CalendarPatternIndexType> parse_date_time_pattern(String pattern, UnicodeLocaleData& locale_data)
{
    // https://unicode.org/reports/tr35/tr35-dates.html#Date_Field_Symbol_Table
    using Unicode::CalendarPatternStyle;

    CalendarPattern format {};

    GenericLexer lexer { pattern };
    StringBuilder builder;
    bool hour12 { false };

    while (!lexer.is_eof()) {
        // Literal strings enclosed by quotes are to be appended to the pattern as-is without further
        // processing (this just avoids conflicts with the patterns below).
        if (lexer.next_is(is_quote)) {
            builder.append(lexer.consume_quoted_string());
            continue;
        }

        auto starting_char = lexer.peek();
        auto segment = lexer.consume_while([&](char ch) { return ch == starting_char; });

        // Era
        if (all_of(segment, is_char('G'))) {
            builder.append("{era}");

            if (segment.length() <= 3)
                format.era = CalendarPatternStyle::Short;
            else if (segment.length() == 4)
                format.era = CalendarPatternStyle::Long;
            else
                format.era = CalendarPatternStyle::Narrow;
        }

        // Year
        else if (all_of(segment, is_any_of("yYuUr"sv))) {
            builder.append("{year}");

            if (segment.length() == 2)
                format.year = CalendarPatternStyle::TwoDigit;
            else
                format.year = CalendarPatternStyle::Numeric;
        }

        // Quarter
        else if (all_of(segment, is_any_of("qQ"sv))) {
            // Intl.DateTimeFormat does not support quarter formatting, so drop these patterns.
            return {};
        }

        // Month
        else if (all_of(segment, is_any_of("ML"sv))) {
            builder.append("{month}");

            if (segment.length() == 1)
                format.month = CalendarPatternStyle::Numeric;
            else if (segment.length() == 2)
                format.month = CalendarPatternStyle::TwoDigit;
            else if (segment.length() == 3)
                format.month = CalendarPatternStyle::Short;
            else if (segment.length() == 4)
                format.month = CalendarPatternStyle::Long;
            else if (segment.length() == 5)
                format.month = CalendarPatternStyle::Narrow;
        } else if (all_of(segment, is_char('l'))) {
            // Using 'l' for month formatting is deprecated by TR-35, ensure it is not used.
            return {};
        }

        // Week
        else if (all_of(segment, is_any_of("wW"sv))) {
            // Intl.DateTimeFormat does not support week formatting, so drop these patterns.
            return {};
        }

        // Day
        else if (all_of(segment, is_char('d'))) {
            builder.append("{day}");

            if (segment.length() == 1)
                format.day = CalendarPatternStyle::Numeric;
            else
                format.day = CalendarPatternStyle::TwoDigit;
        } else if (all_of(segment, is_any_of("DFG"sv))) {
            builder.append("{day}");
            format.day = CalendarPatternStyle::Numeric;
        }

        // Weekday
        else if (all_of(segment, is_char('E'))) {
            builder.append("{weekday}");

            if (segment.length() == 4)
                format.weekday = CalendarPatternStyle::Long;
            else if (segment.length() == 5)
                format.weekday = CalendarPatternStyle::Narrow;
            else
                format.weekday = CalendarPatternStyle::Short;
        } else if (all_of(segment, is_any_of("ec"sv))) {
            builder.append("{weekday}");

            // TR-35 defines "e", "c", and "cc" as as numeric, and "ee" as 2-digit, but those
            // pattern styles are not supported by Intl.DateTimeFormat.
            if (segment.length() <= 2)
                return {};

            if (segment.length() == 4)
                format.weekday = CalendarPatternStyle::Long;
            else if (segment.length() == 5)
                format.weekday = CalendarPatternStyle::Narrow;
            else
                format.weekday = CalendarPatternStyle::Short;
        }

        // Period
        else if (all_of(segment, is_any_of("ab"sv))) {
            builder.append("{ampm}");
            hour12 = true;

            if (segment.length() == 4)
                format.day_period = CalendarPatternStyle::Long;
            else if (segment.length() == 5)
                format.day_period = CalendarPatternStyle::Narrow;
            else
                format.day_period = CalendarPatternStyle::Short;
        } else if (all_of(segment, is_char('B'))) {
            builder.append("{dayPeriod}");
            hour12 = true;

            if (segment.length() == 4)
                format.day_period = CalendarPatternStyle::Long;
            else if (segment.length() == 5)
                format.day_period = CalendarPatternStyle::Narrow;
            else
                format.day_period = CalendarPatternStyle::Short;
        }

        // Hour
        else if (all_of(segment, is_any_of("hHKk"sv))) {
            builder.append("{hour}");

            if ((segment[0] == 'h') || (segment[0] == 'K'))
                hour12 = true;

            if (segment.length() == 1)
                format.hour = CalendarPatternStyle::Numeric;
            else
                format.hour = CalendarPatternStyle::TwoDigit;
        } else if (all_of(segment, is_any_of("jJC"sv))) {
            // TR-35 indicates these should not be used.
            return {};
        }

        // Minute
        else if (all_of(segment, is_char('m'))) {
            builder.append("{minute}");

            if (segment.length() == 1)
                format.minute = CalendarPatternStyle::Numeric;
            else
                format.minute = CalendarPatternStyle::TwoDigit;
        }

        // Second
        else if (all_of(segment, is_char('s'))) {
            builder.append("{second}");

            if (segment.length() == 1)
                format.second = CalendarPatternStyle::Numeric;
            else
                format.second = CalendarPatternStyle::TwoDigit;
        } else if (all_of(segment, is_char('S'))) {
            builder.append("{fractionalSecondDigits}");

            VERIFY(segment.length() <= 3);
            format.fractional_second_digits = static_cast<u8>(segment.length());
        } else if (all_of(segment, is_char('A'))) {
            // Intl.DateTimeFormat does not support millisecond formatting, so drop these patterns.
            return {};
        }

        // Zone
        else if (all_of(segment, is_any_of("zZOvVXx"))) {
            builder.append("{timeZoneName}");

            if (segment.length() < 4)
                format.time_zone_name = CalendarPatternStyle::Short;
            else
                format.time_zone_name = CalendarPatternStyle::Long;
        }

        // Non-patterns
        else {
            builder.append(segment);
        }
    }

    pattern = builder.build();

    if (hour12) {
        auto pattern_without_period = remove_period_from_pattern(pattern);

        format.pattern_index = locale_data.unique_strings.ensure(move(pattern_without_period));
        format.pattern12_index = locale_data.unique_strings.ensure(move(pattern));
    } else {
        format.pattern_index = locale_data.unique_strings.ensure(move(pattern));
    }

    return locale_data.unique_patterns.ensure(move(format));
}

static void generate_missing_patterns(Calendar& calendar, Vector<CalendarPattern> date_formats, Vector<CalendarPattern> time_formats, UnicodeLocaleData& locale_data)
{
    // https://unicode.org/reports/tr35/tr35-dates.html#Missing_Skeleton_Fields
    auto replace_pattern = [&](auto format, auto time_format, auto date_format) {
        auto pattern = locale_data.unique_strings.get(format);
        auto time_pattern = locale_data.unique_strings.get(time_format);
        auto date_pattern = locale_data.unique_strings.get(date_format);

        auto new_pattern = pattern.replace("{0}", time_pattern).replace("{1}", date_pattern);
        return locale_data.unique_strings.ensure(move(new_pattern));
    };

    auto append_if_unique = [&](auto format) {
        auto format_index = locale_data.unique_patterns.ensure(move(format));

        if (!calendar.available_formats.contains_slow(format_index))
            calendar.available_formats.append(format_index);
    };

    for (auto const& format : date_formats)
        append_if_unique(format);
    for (auto const& format : time_formats)
        append_if_unique(format);

    for (auto const& date_format : date_formats) {
        CalendarPatternIndexType date_time_format_index = 0;

        if (date_format.month == Unicode::CalendarPatternStyle::Long) {
            if (date_format.weekday.has_value())
                date_time_format_index = calendar.date_time_formats.full_format;
            else
                date_time_format_index = calendar.date_time_formats.long_format;
        } else if (date_format.month == Unicode::CalendarPatternStyle::Short) {
            date_time_format_index = calendar.date_time_formats.medium_format;
        } else {
            date_time_format_index = calendar.date_time_formats.short_format;
        }

        for (auto const& time_format : time_formats) {
            auto format = locale_data.unique_patterns.get(date_time_format_index);

            if (time_format.pattern12_index != 0)
                format.pattern12_index = replace_pattern(format.pattern_index, time_format.pattern12_index, date_format.pattern_index);
            format.pattern_index = replace_pattern(format.pattern_index, time_format.pattern_index, date_format.pattern_index);

            format.for_each_calendar_field_zipped_with(date_format, [](auto& field, auto const& date_field) {
                if (date_field.has_value())
                    field = date_field;
            });
            format.for_each_calendar_field_zipped_with(time_format, [](auto& field, auto const& time_field) {
                if (time_field.has_value())
                    field = time_field;
            });

            append_if_unique(move(format));
        }
    }
}

static ErrorOr<void> parse_calendars(String locale_calendars_path, UnicodeLocaleData& locale_data, Locale& locale)
{
    LexicalPath calendars_path(move(locale_calendars_path));
    if (!calendars_path.basename().starts_with("ca-"sv))
        return {};

    auto calendars_file = TRY(Core::File::open(calendars_path.string(), Core::OpenMode::ReadOnly));
    auto calendars = TRY(JsonValue::from_string(calendars_file->read_all()));

    auto const& main_object = calendars.as_object().get("main"sv);
    auto const& locale_object = main_object.as_object().get(calendars_path.parent().basename());
    auto const& dates_object = locale_object.as_object().get("dates"sv);
    auto const& calendars_object = dates_object.as_object().get("calendars"sv);

    auto ensure_calendar = [&](auto const& calendar) -> Calendar& {
        return locale.calendars.ensure(calendar, [&]() {
            auto calendar_index = locale_data.unique_strings.ensure(calendar);
            return Calendar { .calendar = calendar_index };
        });
    };

    auto parse_patterns = [&](auto& formats, auto const& patterns_object, Vector<CalendarPattern>* patterns) {
        auto parse_pattern = [&](auto name) {
            auto format = patterns_object.get(name);
            auto format_index = parse_date_time_pattern(format.as_string(), locale_data).value();

            if (patterns)
                patterns->append(locale_data.unique_patterns.get(format_index));

            return format_index;
        };

        formats.full_format = parse_pattern("full"sv);
        formats.long_format = parse_pattern("long"sv);
        formats.medium_format = parse_pattern("medium"sv);
        formats.short_format = parse_pattern("short"sv);
    };

    calendars_object.as_object().for_each_member([&](auto const& calendar_name, JsonValue const& value) {
        // The generic calendar is not a supported Unicode calendar key, so skip it:
        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale/calendar#unicode_calendar_keys
        if (calendar_name == "generic"sv)
            return;

        auto& calendar = ensure_calendar(calendar_name);

        if (!locale_data.calendars.contains_slow(calendar_name))
            locale_data.calendars.append(calendar_name);

        Vector<CalendarPattern> date_formats;
        Vector<CalendarPattern> time_formats;

        auto const& date_formats_object = value.as_object().get("dateFormats"sv);
        parse_patterns(calendar.date_formats, date_formats_object.as_object(), &date_formats);

        auto const& time_formats_object = value.as_object().get("timeFormats"sv);
        parse_patterns(calendar.time_formats, time_formats_object.as_object(), &time_formats);

        auto const& date_time_formats_object = value.as_object().get("dateTimeFormats"sv);
        parse_patterns(calendar.date_time_formats, date_time_formats_object.as_object(), nullptr);

        auto const& available_formats = date_time_formats_object.as_object().get("availableFormats"sv);
        available_formats.as_object().for_each_member([&](auto const&, JsonValue const& pattern) {
            auto pattern_index = parse_date_time_pattern(pattern.as_string(), locale_data);
            if (!pattern_index.has_value())
                return;

            auto const& format = locale_data.unique_patterns.get(*pattern_index);
            if (format.contains_only_date_fields())
                date_formats.append(format);
            else if (format.contains_only_time_fields())
                time_formats.append(format);

            if (!calendar.available_formats.contains_slow(*pattern_index))
                calendar.available_formats.append(*pattern_index);
        });

        generate_missing_patterns(calendar, move(date_formats), move(time_formats), locale_data);
    });

    return {};
}

static ErrorOr<void> parse_all_locales(String core_path, String dates_path, UnicodeLocaleData& locale_data)
{
    TRY(parse_hour_cycles(move(core_path), locale_data));
    auto dates_iterator = TRY(path_to_dir_iterator(move(dates_path)));

    auto remove_variants_from_path = [&](String path) -> ErrorOr<String> {
        auto parsed_locale = TRY(CanonicalLanguageID<StringIndexType>::parse(locale_data.unique_strings, LexicalPath::basename(path)));

        StringBuilder builder;
        builder.append(locale_data.unique_strings.get(parsed_locale.language));
        if (auto script = locale_data.unique_strings.get(parsed_locale.script); !script.is_empty())
            builder.appendff("-{}", script);
        if (auto region = locale_data.unique_strings.get(parsed_locale.region); !region.is_empty())
            builder.appendff("-{}", region);

        return builder.build();
    };

    while (dates_iterator.has_next()) {
        auto dates_path = TRY(next_path_from_dir_iterator(dates_iterator));
        auto calendars_iterator = TRY(path_to_dir_iterator(dates_path, {}));

        auto language = TRY(remove_variants_from_path(dates_path));
        auto& locale = locale_data.locales.ensure(language);

        while (calendars_iterator.has_next()) {
            auto calendars_path = TRY(next_path_from_dir_iterator(calendars_iterator));
            TRY(parse_calendars(move(calendars_path), locale_data, locale));
        }
    }

    return {};
}

static String format_identifier(StringView owner, String identifier)
{
    identifier = identifier.replace("-"sv, "_"sv, true);

    if (all_of(identifier, is_ascii_digit))
        return String::formatted("{}_{}", owner[0], identifier);
    if (is_ascii_lower_alpha(identifier[0]))
        return String::formatted("{:c}{}", to_ascii_uppercase(identifier[0]), identifier.substring_view(1));
    return identifier;
}

static void generate_unicode_locale_header(Core::File& file, UnicodeLocaleData& locale_data)
{
    StringBuilder builder;
    SourceGenerator generator { builder };

    generator.append(R"~~~(
#pragma once

#include <AK/Optional.h>
#include <AK/StringView.h>
#include <LibUnicode/Forward.h>

namespace Unicode {
)~~~");

    generate_enum(generator, format_identifier, "Calendar"sv, {}, locale_data.calendars, locale_data.calendar_aliases);
    generate_enum(generator, format_identifier, "HourCycleRegion"sv, {}, locale_data.hour_cycle_regions);

    generator.append(R"~~~(
namespace Detail {

Optional<Calendar> calendar_from_string(StringView calendar);

Optional<HourCycleRegion> hour_cycle_region_from_string(StringView hour_cycle_region);
Vector<Unicode::HourCycle> get_regional_hour_cycles(StringView region);

Optional<Unicode::CalendarFormat> get_calendar_date_format(StringView locale, StringView calendar);
Optional<Unicode::CalendarFormat> get_calendar_time_format(StringView locale, StringView calendar);
Optional<Unicode::CalendarFormat> get_calendar_date_time_format(StringView locale, StringView calendar);
Vector<Unicode::CalendarPattern> get_calendar_available_formats(StringView locale, StringView calendar);

}

}
)~~~");

    VERIFY(file.write(generator.as_string_view()));
}

static void generate_unicode_locale_implementation(Core::File& file, UnicodeLocaleData& locale_data)
{
    StringBuilder builder;
    SourceGenerator generator { builder };
    generator.set("string_index_type"sv, s_string_index_type);
    generator.set("calendar_pattern_index_type"sv, s_calendar_pattern_index_type);

    generator.append(R"~~~(
#include <AK/Array.h>
#include <AK/BinarySearch.h>
#include <LibUnicode/DateTimeFormat.h>
#include <LibUnicode/Locale.h>
#include <LibUnicode/UnicodeDateTimeFormat.h>

namespace Unicode::Detail {
)~~~");

    locale_data.unique_strings.generate(generator);

    generator.append(R"~~~(
struct CalendarPattern {
    Unicode::CalendarPattern to_unicode_calendar_pattern() const {
        Unicode::CalendarPattern calendar_pattern {};

        calendar_pattern.pattern = s_string_list[pattern];
        if (pattern12 != 0)
            calendar_pattern.pattern12 = s_string_list[pattern12];

        if (era != -1)
            calendar_pattern.era = static_cast<Unicode::CalendarPatternStyle>(era);
        if (year != -1)
            calendar_pattern.year = static_cast<Unicode::CalendarPatternStyle>(year);
        if (month != -1)
            calendar_pattern.month = static_cast<Unicode::CalendarPatternStyle>(month);
        if (weekday != -1)
            calendar_pattern.weekday = static_cast<Unicode::CalendarPatternStyle>(weekday);
        if (day != -1)
            calendar_pattern.day = static_cast<Unicode::CalendarPatternStyle>(day);
        if (day_period != -1)
            calendar_pattern.day_period = static_cast<Unicode::CalendarPatternStyle>(day_period);
        if (hour != -1)
            calendar_pattern.hour = static_cast<Unicode::CalendarPatternStyle>(hour);
        if (minute != -1)
            calendar_pattern.minute = static_cast<Unicode::CalendarPatternStyle>(minute);
        if (second != -1)
            calendar_pattern.second = static_cast<Unicode::CalendarPatternStyle>(second);
        if (fractional_second_digits != -1)
            calendar_pattern.fractional_second_digits = static_cast<u8>(fractional_second_digits);
        if (time_zone_name != -1)
            calendar_pattern.time_zone_name = static_cast<Unicode::CalendarPatternStyle>(time_zone_name);

        return calendar_pattern;
    }

    @string_index_type@ pattern { 0 };
    @string_index_type@ pattern12 { 0 };

    i8 era { -1 };
    i8 year { -1 };
    i8 month { -1 };
    i8 weekday { -1 };
    i8 day { -1 };
    i8 day_period { -1 };
    i8 hour { -1 };
    i8 minute { -1 };
    i8 second { -1 };
    i8 fractional_second_digits { -1 };
    i8 time_zone_name { -1 };
};
)~~~");

    locale_data.unique_patterns.generate(generator, "CalendarPattern"sv, "s_calendar_patterns"sv, 10);

    generator.append(R"~~~(
struct CalendarFormat {
    Unicode::CalendarFormat to_unicode_calendar_format() const {
        Unicode::CalendarFormat calendar_format {};

        calendar_format.full_format = s_calendar_patterns[full_format].to_unicode_calendar_pattern();
        calendar_format.long_format = s_calendar_patterns[long_format].to_unicode_calendar_pattern();
        calendar_format.medium_format = s_calendar_patterns[medium_format].to_unicode_calendar_pattern();
        calendar_format.short_format = s_calendar_patterns[short_format].to_unicode_calendar_pattern();

        return calendar_format;
    }

    @calendar_pattern_index_type@ full_format { 0 };
    @calendar_pattern_index_type@ long_format { 0 };
    @calendar_pattern_index_type@ medium_format { 0 };
    @calendar_pattern_index_type@ short_format { 0 };
};

struct CalendarData {
    @string_index_type@ calendar { 0 };
    CalendarFormat date_formats {};
    CalendarFormat time_formats {};
    CalendarFormat date_time_formats {};
    Span<@calendar_pattern_index_type@ const> available_formats {};
};
)~~~");

    auto append_calendar_format = [&](auto const& calendar_format) {
        generator.set("full_format", String::number(calendar_format.full_format));
        generator.set("long_format", String::number(calendar_format.long_format));
        generator.set("medium_format", String::number(calendar_format.medium_format));
        generator.set("short_format", String::number(calendar_format.short_format));
        generator.append("{ @full_format@, @long_format@, @medium_format@, @short_format@ },");
    };

    auto append_calendars = [&](String name, auto const& calendars) {
        auto format_name = [&](StringView calendar_key) {
            return String::formatted("{}_{}_formats", name, calendar_key);
        };

        for (auto const& calendar_key : locale_data.calendars) {
            auto const& calendar = calendars.find(calendar_key)->value;

            generator.set("name", format_name(calendar_key));
            generator.set("size", String::number(calendar.available_formats.size()));

            generator.append(R"~~~(
static constexpr Array<@calendar_pattern_index_type@, @size@> @name@ { {)~~~");

            bool first = true;
            for (auto format : calendar.available_formats) {
                generator.append(first ? " " : ", ");
                generator.append(String::number(format));
                first = false;
            }

            generator.append(" } };");
        }

        generator.set("name", name);
        generator.set("size", String::number(calendars.size()));

        generator.append(R"~~~(
static constexpr Array<CalendarData, @size@> @name@ { {)~~~");

        for (auto const& calendar_key : locale_data.calendars) {
            auto const& calendar = calendars.find(calendar_key)->value;

            generator.set("name", format_name(calendar_key));
            generator.set("calendar"sv, String::number(calendar.calendar));
            generator.append(R"~~~(
    { @calendar@, )~~~");

            append_calendar_format(calendar.date_formats);
            generator.append(" ");
            append_calendar_format(calendar.time_formats);
            generator.append(" ");
            append_calendar_format(calendar.date_time_formats);
            generator.append(" @name@.span() },");
        }

        generator.append(R"~~~(
} };
)~~~");
    };

    auto append_hour_cycles = [&](String name, auto const& hour_cycle_region) {
        auto const& hour_cycles = locale_data.hour_cycles.find(hour_cycle_region)->value;

        generator.set("name", name);
        generator.set("size", String::number(hour_cycles.size()));

        generator.append(R"~~~(
static constexpr Array<u8, @size@> @name@ { { )~~~");

        for (auto hour_cycle : hour_cycles) {
            generator.set("hour_cycle", String::number(static_cast<u8>(hour_cycle)));
            generator.append("@hour_cycle@, ");
        }

        generator.append("} };");
    };

    generate_mapping(generator, locale_data.locales, "CalendarData"sv, "s_calendars"sv, "s_calendars_{}", [&](auto const& name, auto const& value) { append_calendars(name, value.calendars); });
    generate_mapping(generator, locale_data.hour_cycle_regions, "u8"sv, "s_hour_cycles"sv, "s_hour_cycles_{}", [&](auto const& name, auto const& value) { append_hour_cycles(name, value); });

    auto append_from_string = [&](StringView enum_title, StringView enum_snake, auto const& values, Vector<Alias> const& aliases = {}) {
        HashValueMap<String> hashes;
        hashes.ensure_capacity(values.size());

        for (auto const& value : values)
            hashes.set(value.hash(), format_identifier(enum_title, value));
        for (auto const& alias : aliases)
            hashes.set(alias.alias.hash(), format_identifier(enum_title, alias.alias));

        generate_value_from_string(generator, "{}_from_string"sv, enum_title, enum_snake, move(hashes));
    };

    append_from_string("Calendar"sv, "calendar"sv, locale_data.calendars, locale_data.calendar_aliases);
    append_from_string("HourCycleRegion"sv, "hour_cycle_region"sv, locale_data.hour_cycle_regions);

    generator.append(R"~~~(
Vector<Unicode::HourCycle> get_regional_hour_cycles(StringView region)
{
    auto region_value = hour_cycle_region_from_string(region);
    if (!region_value.has_value())
        return {};

    auto region_index = to_underlying(*region_value);
    auto const& regional_hour_cycles = s_hour_cycles.at(region_index);

    Vector<Unicode::HourCycle> hour_cycles;
    hour_cycles.ensure_capacity(regional_hour_cycles.size());

    for (auto hour_cycle : regional_hour_cycles)
        hour_cycles.unchecked_append(static_cast<Unicode::HourCycle>(hour_cycle));

    return hour_cycles;
}

static CalendarData const* find_calendar_data(StringView locale, StringView calendar)
{
    auto locale_value = locale_from_string(locale);
    if (!locale_value.has_value())
        return nullptr;

    auto calendar_value = calendar_from_string(calendar);
    if (!calendar_value.has_value())
        return nullptr;

    auto locale_index = to_underlying(*locale_value) - 1; // Subtract 1 because 0 == Locale::None.
    auto calendar_index = to_underlying(*calendar_value);

    auto const& calendars = s_calendars.at(locale_index);
    return &calendars[calendar_index];
}

Optional<Unicode::CalendarFormat> get_calendar_date_format(StringView locale, StringView calendar)
{
    if (auto const* data = find_calendar_data(locale, calendar); data != nullptr)
        return data->date_formats.to_unicode_calendar_format();
    return {};
}

Optional<Unicode::CalendarFormat> get_calendar_time_format(StringView locale, StringView calendar)
{
    if (auto const* data = find_calendar_data(locale, calendar); data != nullptr)
        return data->time_formats.to_unicode_calendar_format();
    return {};
}

Optional<Unicode::CalendarFormat> get_calendar_date_time_format(StringView locale, StringView calendar)
{
    if (auto const* data = find_calendar_data(locale, calendar); data != nullptr)
        return data->date_time_formats.to_unicode_calendar_format();
    return {};
}

Vector<Unicode::CalendarPattern> get_calendar_available_formats(StringView locale, StringView calendar)
{
    Vector<Unicode::CalendarPattern> result {};

    if (auto const* data = find_calendar_data(locale, calendar); data != nullptr) {
        result.ensure_capacity(data->available_formats.size());

        for (auto const& format : data->available_formats)
            result.unchecked_append(s_calendar_patterns[format].to_unicode_calendar_pattern());
    }

    return result;
}

}
)~~~");

    VERIFY(file.write(generator.as_string_view()));
}

ErrorOr<int> serenity_main(Main::Arguments arguments)
{
    StringView generated_header_path;
    StringView generated_implementation_path;
    StringView core_path;
    StringView dates_path;

    Core::ArgsParser args_parser;
    args_parser.add_option(generated_header_path, "Path to the Unicode locale header file to generate", "generated-header-path", 'h', "generated-header-path");
    args_parser.add_option(generated_implementation_path, "Path to the Unicode locale implementation file to generate", "generated-implementation-path", 'c', "generated-implementation-path");
    args_parser.add_option(core_path, "Path to cldr-core directory", "core-path", 'r', "core-path");
    args_parser.add_option(dates_path, "Path to cldr-dates directory", "dates-path", 'd', "dates-path");
    args_parser.parse(arguments);

    auto open_file = [&](StringView path) -> ErrorOr<NonnullRefPtr<Core::File>> {
        if (path.is_empty()) {
            args_parser.print_usage(stderr, arguments.argv[0]);
            return Error::from_string_literal("Must provide all command line options"sv);
        }

        return Core::File::open(path, Core::OpenMode::ReadWrite);
    };

    auto generated_header_file = TRY(open_file(generated_header_path));
    auto generated_implementation_file = TRY(open_file(generated_implementation_path));

    UnicodeLocaleData locale_data;
    TRY(parse_all_locales(core_path, dates_path, locale_data));

    generate_unicode_locale_header(generated_header_file, locale_data);
    generate_unicode_locale_implementation(generated_implementation_file, locale_data);

    return 0;
}