#include <LibGUI/GScrollBar.h>
#include <LibGUI/GStyle.h>
#include <SharedGraphics/GraphicsBitmap.h>
#include <SharedGraphics/Painter.h>

GScrollBar::GScrollBar(GWidget* parent)
    : GWidget(parent)
{
}

GScrollBar::~GScrollBar()
{
}

void GScrollBar::set_range(int min, int max)
{
    ASSERT(min <= max);
    if (m_min == min && m_max == max)
        return;

    m_min = min;
    m_max = max;

    int old_value = m_value;
    if (m_value < m_min)
        m_value = m_min;
    if (m_value > m_max)
        m_value = m_max;
    if (on_change && m_value != old_value)
        on_change(m_value);

    update();
}

void GScrollBar::set_value(int value)
{
    if (value < m_min)
        value = m_min;
    if (value > m_max)
        value = m_max;
    if (value == m_value)
        return;
    m_value = value;
    if (on_change)
        on_change(value);
    update();
}

Rect GScrollBar::up_button_rect() const
{
    return { 0, 0, button_size(), button_size() };
}

Rect GScrollBar::down_button_rect() const
{
    return { 0, height() - button_size(), button_size(), button_size() };
}

Rect GScrollBar::upper_gutter_rect() const
{
    return { 0, button_size(), button_size(), scrubber_rect().top() - button_size() };
}

Rect GScrollBar::lower_gutter_rect() const
{
    auto scrubber_rect = this->scrubber_rect();
    return { 0, scrubber_rect.bottom(), button_size(), height() - button_size() - scrubber_rect.bottom() };
}

int GScrollBar::scrubbable_range_in_pixels() const
{
    return height() - button_size() * 3;
}

bool GScrollBar::has_scrubber() const
{
    return m_max != m_min;
}

Rect GScrollBar::scrubber_rect() const
{
    int range_size = m_max - m_min;
    if (range_size == 0)
        return { 0, button_size(), button_size(), height() - button_size() * 2 };
    float available_y = scrubbable_range_in_pixels();
    float y_step = available_y / range_size;
    float y = button_size() + (y_step * m_value);
    return { 0, (int)y, button_size(), button_size() };
}

static const char* s_up_arrow_bitmap_data = {
    "          "
    "          "
    "    ##    "
    "   ####   "
    "  ######  "
    " ######## "
    "    ##    "
    "    ##    "
    "    ##    "
    "          "
};

static const char* s_down_arrow_bitmap_data = {
    "          "
    "    ##    "
    "    ##    "
    "    ##    "
    " ######## "
    "  ######  "
    "   ####   "
    "    ##    "
    "          "
    "          "
};

static CharacterBitmap* s_up_arrow_bitmap;
static CharacterBitmap* s_down_arrow_bitmap;

void GScrollBar::paint_event(GPaintEvent&)
{
    if (!s_up_arrow_bitmap)
        s_up_arrow_bitmap = CharacterBitmap::create_from_ascii(s_up_arrow_bitmap_data, 10, 10).leak_ref();
    if (!s_down_arrow_bitmap)
        s_down_arrow_bitmap = CharacterBitmap::create_from_ascii(s_down_arrow_bitmap_data, 10, 10).leak_ref();

    Painter painter(*this);

    painter.fill_rect(rect(), Color(164, 164, 164));

    GStyle::the().paint_button(painter, up_button_rect(), false);
    painter.draw_bitmap(up_button_rect().location().translated(3, 3), *s_up_arrow_bitmap, has_scrubber() ? Color::Black : Color::MidGray);

    GStyle::the().paint_button(painter, down_button_rect(), false);
    painter.draw_bitmap(down_button_rect().location().translated(3, 3), *s_down_arrow_bitmap, has_scrubber() ? Color::Black : Color::MidGray);

    if (has_scrubber())
        GStyle::the().paint_button(painter, scrubber_rect(), m_scrubbing);
}

void GScrollBar::mousedown_event(GMouseEvent& event)
{
    if (event.button() != GMouseButton::Left)
        return;
    if (up_button_rect().contains(event.position())) {
        set_value(value() - m_step);
        return;
    }
    if (down_button_rect().contains(event.position())) {
        set_value(value() + m_step);
        return;
    }
    if (upper_gutter_rect().contains(event.position())) {
        set_value(value() - m_big_step);
        return;
    }
    if (lower_gutter_rect().contains(event.position())) {
        set_value(value() + m_big_step);
        return;
    }
    if (has_scrubber() && scrubber_rect().contains(event.position())) {
        m_scrubbing = true;
        m_scrub_start_value = value();
        m_scrub_origin = event.position();
        set_global_cursor_tracking(true);
        update();
        return;
    }
}

void GScrollBar::mouseup_event(GMouseEvent& event)
{
    if (event.button() != GMouseButton::Left)
        return;
    if (!m_scrubbing)
        return;
    m_scrubbing = false;
    set_global_cursor_tracking(false);
    update();
}

void GScrollBar::mousemove_event(GMouseEvent& event)
{
    if (!m_scrubbing)
        return;
    float delta = event.y() - m_scrub_origin.y();
    float scrubbable_range = scrubbable_range_in_pixels();
    float value_steps_per_scrubbed_pixel = (m_max - m_min) / scrubbable_range;
    float new_value = m_scrub_start_value + (value_steps_per_scrubbed_pixel * delta);
    set_value(new_value);
}