/*
 * Copyright (c) 2022, Tim Flynn <trflynn89@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include "ClockSettingsWidget.h"
#include <Applications/ClockSettings/ClockSettingsWidgetGML.h>
#include <LibGUI/ComboBox.h>
#include <LibGUI/Event.h>
#include <LibGUI/ImageWidget.h>
#include <LibGUI/ItemListModel.h>
#include <LibGUI/Label.h>
#include <LibGUI/Layout.h>
#include <LibGUI/Margins.h>
#include <LibGUI/Painter.h>
#include <LibGfx/Palette.h>
#include <LibTimeZone/TimeZone.h>
#include <math.h>
#include <spawn.h>
#include <unistd.h>

using StringViewListModel = GUI::ItemListModel<StringView, Span<StringView const>>;

static constexpr auto PI_OVER_180 = M_PIf32 / 180.0f;
static constexpr auto PI_OVER_4 = M_PIf32 / 4.0f;
static constexpr auto TAU = M_PIf32 * 2.0f;

// The map as stored on disk is a valid Mercadian projected map. But it has quite a bit of dead space that
// we can remove. This makes the map non-Mercadian, so we need to adjust our math based on what we removed.
static constexpr auto TIME_ZONE_MAP_NORTHERN_TRIM = 78;
static constexpr auto TIME_ZONE_MAP_SOUTHERN_TRIM = 50;

ClockSettingsWidget::ClockSettingsWidget()
{
    load_from_gml(clock_settings_widget_gml);

    static auto time_zones = TimeZone::all_time_zones();
    m_time_zone = TimeZone::system_time_zone();

    m_time_zone_combo_box = *find_descendant_of_type_named<GUI::ComboBox>("time_zone_input");
    m_time_zone_combo_box->set_only_allow_values_from_model(true);
    m_time_zone_combo_box->set_model(*StringViewListModel::create(time_zones));
    m_time_zone_combo_box->set_text(m_time_zone);

    auto time_zone_map_bitmap = Gfx::Bitmap::try_load_from_file("/res/graphics/map.png"sv).release_value_but_fixme_should_propagate_errors();
    auto time_zone_rect = time_zone_map_bitmap->rect().shrunken(TIME_ZONE_MAP_NORTHERN_TRIM, 0, TIME_ZONE_MAP_SOUTHERN_TRIM, 0);
    time_zone_map_bitmap = time_zone_map_bitmap->cropped(time_zone_rect).release_value_but_fixme_should_propagate_errors();

    m_time_zone_map = *find_descendant_of_type_named<GUI::ImageWidget>("time_zone_map");
    m_time_zone_map->set_bitmap(time_zone_map_bitmap);

    auto time_zone_marker = Gfx::Bitmap::try_load_from_file("/res/icons/32x32/ladyball.png").release_value_but_fixme_should_propagate_errors();
    m_time_zone_marker = time_zone_marker->scaled(0.75f, 0.75f).release_value_but_fixme_should_propagate_errors();

    set_time_zone_location();
}

void ClockSettingsWidget::second_paint_event(GUI::PaintEvent& event)
{
    GUI::Widget::second_paint_event(event);

    if (!m_time_zone_location.has_value())
        return;

    GUI::Painter painter(*this);
    painter.add_clip_rect(event.rect());
    painter.add_clip_rect(m_time_zone_map->relative_rect());

    auto x = m_time_zone_map->x() + m_time_zone_map->parent_widget()->layout()->margins().left();
    auto y = m_time_zone_map->y() + m_time_zone_map->parent_widget()->layout()->margins().top();

    auto point = m_time_zone_location->to_type<int>().translated(x, y);
    point.translate_by(-m_time_zone_marker->width() / 2, -m_time_zone_marker->height() / 2);
    painter.blit(point, *m_time_zone_marker, rect());
}

void ClockSettingsWidget::reset_default_values()
{
    m_time_zone = "UTC"sv;
    m_time_zone_combo_box->set_text(m_time_zone);
    m_time_zone_location.clear();

    set_time_zone();
    update();
}

void ClockSettingsWidget::apply_settings()
{
    m_time_zone = m_time_zone_combo_box->text();

    set_time_zone_location();
    set_time_zone();
    update();
}

void ClockSettingsWidget::set_time_zone_location()
{
    m_time_zone_location = compute_time_zone_location();
}

// https://en.wikipedia.org/wiki/Mercator_projection#Derivation
Optional<Gfx::FloatPoint> ClockSettingsWidget::compute_time_zone_location() const
{
    auto location = TimeZone::get_time_zone_location(m_time_zone);
    if (!location.has_value())
        return {};

    auto latitude = location->latitude.decimal_coordinate();
    auto longitude = location->longitude.decimal_coordinate();

    auto rect = m_time_zone_map->bitmap()->rect().to_type<float>();

    latitude = logf(tanf(PI_OVER_4 + (latitude * PI_OVER_180 / 2.0f)));

    auto mercadian_x = (longitude + 180.0f) * (rect.width() / 360.0f);
    auto mercadian_y = (rect.height() / 2.0f) - (rect.width() * latitude / TAU);

    mercadian_y -= TIME_ZONE_MAP_NORTHERN_TRIM / 2;
    mercadian_y += TIME_ZONE_MAP_SOUTHERN_TRIM / 2;

    return Gfx::FloatPoint { mercadian_x, mercadian_y };
}

void ClockSettingsWidget::set_time_zone() const
{
    pid_t child_pid = 0;
    char const* argv[] = { "/bin/timezone", m_time_zone.characters(), nullptr };

    if ((errno = posix_spawn(&child_pid, "/bin/timezone", nullptr, nullptr, const_cast<char**>(argv), environ))) {
        perror("posix_spawn");
        exit(1);
    }
}