#include "Painter.h"
#include "Font.h"
#include "GraphicsBitmap.h"
#include <SharedGraphics/CharacterBitmap.h>
#include <AK/Assertions.h>
#include <AK/StdLibExtras.h>

#ifdef LIBGUI
#include <LibGUI/GWidget.h>
#include <LibGUI/GWindow.h>
#include <LibGUI/GEventLoop.h>
#include <LibC/stdio.h>
#include <LibC/errno.h>
#include <LibC/string.h>
#endif

Painter::Painter(GraphicsBitmap& bitmap)
{
    m_font = &Font::default_font();
    m_target = &bitmap;
    m_clip_rect = { { 0, 0 }, bitmap.size() };
}

#ifdef LIBGUI
Painter::Painter(GWidget& widget)
    : m_font(&widget.font())
{
    m_window = widget.window();
    m_target = m_window->backing();
    ASSERT(m_target);
    m_translation.move_by(widget.window_relative_rect().location());
    // NOTE: m_clip_rect is in Window coordinates since we are painting into its backing store.
    m_clip_rect = widget.window_relative_rect();
    m_clip_rect.intersect(m_target->rect());
}
#endif

Painter::~Painter()
{
    m_target = nullptr;
}

void Painter::fill_rect_with_draw_op(const Rect& a_rect, Color color)
{
    auto rect = a_rect;
    rect.move_by(m_translation);
    rect.intersect(m_clip_rect);

    if (rect.is_empty())
        return;

    RGBA32* dst = m_target->scanline(rect.top()) + rect.left();
    const unsigned dst_skip = m_target->width();

    for (int i = rect.height() - 1; i >= 0; --i) {
        for (int j = 0; j < rect.width(); ++j)
            set_pixel_with_draw_op(dst[j], color);
        dst += dst_skip;
    }
}

void Painter::fill_rect(const Rect& a_rect, Color color)
{
    if (m_draw_op != DrawOp::Copy) {
        fill_rect_with_draw_op(a_rect, color);
        return;
    }

    auto rect = a_rect;
    rect.move_by(m_translation);
    rect.intersect(m_clip_rect);

    if (rect.is_empty())
        return;

    RGBA32* dst = m_target->scanline(rect.top()) + rect.left();
    const unsigned dst_skip = m_target->width();

    for (int i = rect.height() - 1; i >= 0; --i) {
        fast_dword_fill(dst, color.value(), rect.width());
        dst += dst_skip;
    }
}

void Painter::fill_rect_with_gradient(const Rect& a_rect, Color gradient_start, Color gradient_end)
{
#ifdef NO_FPU
    return fill_rect(a_rect, gradient_start);
#endif
    auto rect = a_rect;
    rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;

    int x_offset = clipped_rect.x() - rect.x();

    RGBA32* dst = m_target->scanline(clipped_rect.top()) + clipped_rect.left();
    const unsigned dst_skip = m_target->width();

    float increment = (1.0/((rect.width())/255.0));

    int r2 = gradient_start.red();
    int g2 = gradient_start.green();
    int b2 = gradient_start.blue();
    int r1 = gradient_end.red();
    int g1 = gradient_end.green();
    int b1 = gradient_end.blue();

    for (int i = clipped_rect.height() - 1; i >= 0; --i) {
        float c = x_offset * increment;
        for (int j = 0; j < clipped_rect.width(); ++j) {
            dst[j] = Color(
                r1 / 255.0 * c + r2 / 255.0 * (255 - c),
                g1 / 255.0 * c + g2 / 255.0 * (255 - c),
                b1 / 255.0 * c + b2 / 255.0 * (255 - c)
            ).value();
            c += increment;
        }
        dst += dst_skip;
    }
}

void Painter::draw_rect(const Rect& a_rect, Color color, bool rough)
{
    Rect rect = a_rect;
    rect.move_by(m_translation);

    auto clipped_rect = Rect::intersection(rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;

    int min_y = clipped_rect.top();
    int max_y = clipped_rect.bottom();

    if (rect.top() >= clipped_rect.top() && rect.top() <= clipped_rect.bottom()) {
        int start_x = rough ? max(rect.x() + 1, clipped_rect.x()) : clipped_rect.x();
        int width = rough ? min(rect.width() - 2, clipped_rect.width()) : clipped_rect.width();
        fast_dword_fill(m_target->scanline(rect.top()) + start_x, color.value(), width);
        ++min_y;
    }
    if (rect.bottom() >= clipped_rect.top() && rect.bottom() <= clipped_rect.bottom()) {
        int start_x = rough ? max(rect.x() + 1, clipped_rect.x()) : clipped_rect.x();
        int width = rough ? min(rect.width() - 2, clipped_rect.width()) : clipped_rect.width();
        fast_dword_fill(m_target->scanline(rect.bottom()) + start_x, color.value(), width);
        --max_y;
    }

    bool draw_left_side = rect.left() >= clipped_rect.left();
    bool draw_right_side = rect.right() == clipped_rect.right();

    if (draw_left_side && draw_right_side) {
        // Specialized loop when drawing both sides.
        for (int y = min_y; y <= max_y; ++y) {
            auto* bits = m_target->scanline(y);
            bits[rect.left()] = color.value();
            bits[rect.right()] = color.value();
        }
    } else {
        for (int y = min_y; y <= max_y; ++y) {
            auto* bits = m_target->scanline(y);
            if (draw_left_side)
                bits[rect.left()] = color.value();
            if (draw_right_side)
                bits[rect.right()] = color.value();
        }
    }
}

void Painter::draw_bitmap(const Point& p, const CharacterBitmap& bitmap, Color color)
{
    Rect rect { p, bitmap.size() };
    rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;
    const int first_row = clipped_rect.top() - rect.top();
    const int last_row = clipped_rect.bottom() - rect.top();
    const int first_column = clipped_rect.left() - rect.left();
    const int last_column = clipped_rect.right() - rect.left();
    RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
    const size_t dst_skip = m_target->width();
    const char* bitmap_row = &bitmap.bits()[first_row * bitmap.width() + first_column];
    const size_t bitmap_skip = bitmap.width();

    for (int row = first_row; row <= last_row; ++row) {
        for (int j = 0; j <= (last_column - first_column); ++j) {
            char fc = bitmap_row[j];
            if (fc == '#')
                dst[j] = color.value();
        }
        bitmap_row += bitmap_skip;
        dst += dst_skip;
    }
}

void Painter::draw_bitmap(const Point& p, const GlyphBitmap& bitmap, Color color)
{
    Rect dst_rect { p, bitmap.size() };
    dst_rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;
    const int first_row = clipped_rect.top() - dst_rect.top();
    const int last_row = clipped_rect.bottom() - dst_rect.top();
    const int first_column = clipped_rect.left() - dst_rect.left();
    const int last_column = clipped_rect.right() - dst_rect.left();
    RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
    const size_t dst_skip = m_target->width();

    for (int row = first_row; row <= last_row; ++row) {
        for (int j = 0; j <= (last_column - first_column); ++j) {
            if (bitmap.bit_at(j + first_column, row))
                dst[j] = color.value();
        }
        dst += dst_skip;
    }
}

void Painter::blit_with_opacity(const Point& position, const GraphicsBitmap& source, const Rect& src_rect, float opacity)
{
    ASSERT(!m_target->has_alpha_channel());

    if (!opacity)
        return;
    if (opacity >= 1.0f)
        return blit(position, source, src_rect);

    byte alpha = 255 * opacity;

    Rect safe_src_rect = Rect::intersection(src_rect, source.rect());
    Rect dst_rect(position, safe_src_rect.size());
    dst_rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;
    const int first_row = clipped_rect.top() - dst_rect.top();
    const int last_row = clipped_rect.bottom() - dst_rect.top();
    const int first_column = clipped_rect.left() - dst_rect.left();
    const int last_column = clipped_rect.right() - dst_rect.left();
    RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
    const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
    const size_t dst_skip = m_target->width();
    const unsigned src_skip = source.width();

    for (int row = first_row; row <= last_row; ++row) {
        for (int x = 0; x <= (last_column - first_column); ++x) {
            Color src_color_with_alpha = Color::from_rgb(src[x]);
            src_color_with_alpha.set_alpha(alpha);
            Color dst_color = Color::from_rgb(dst[x]);
            dst[x] = dst_color.blend(src_color_with_alpha).value();
        }
        dst += dst_skip;
        src += src_skip;
    }
}

void Painter::blit_with_alpha(const Point& position, const GraphicsBitmap& source, const Rect& src_rect)
{
    ASSERT(source.has_alpha_channel());
    Rect safe_src_rect = Rect::intersection(src_rect, source.rect());
    Rect dst_rect(position, safe_src_rect.size());
    dst_rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;
    const int first_row = clipped_rect.top() - dst_rect.top();
    const int last_row = clipped_rect.bottom() - dst_rect.top();
    const int first_column = clipped_rect.left() - dst_rect.left();
    const int last_column = clipped_rect.right() - dst_rect.left();
    RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
    const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
    const size_t dst_skip = m_target->width();
    const unsigned src_skip = source.width();

    for (int row = first_row; row <= last_row; ++row) {
        for (int x = 0; x <= (last_column - first_column); ++x) {
            byte alpha = Color::from_rgba(src[x]).alpha();
            if (alpha == 0xff)
                dst[x] = src[x];
            else if (!alpha)
                continue;
            else
                dst[x] = Color::from_rgba(dst[x]).blend(Color::from_rgba(src[x])).value();
        }
        dst += dst_skip;
        src += src_skip;
    }
}

void Painter::blit(const Point& position, const GraphicsBitmap& source, const Rect& src_rect)
{
    if (source.has_alpha_channel())
        return blit_with_alpha(position, source, src_rect);
    auto safe_src_rect = Rect::intersection(src_rect, source.rect());
    ASSERT(source.rect().contains(safe_src_rect));
    Rect dst_rect(position, safe_src_rect.size());
    dst_rect.move_by(m_translation);
    auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
    if (clipped_rect.is_empty())
        return;
    const int first_row = clipped_rect.top() - dst_rect.top();
    const int last_row = clipped_rect.bottom() - dst_rect.top();
    const int first_column = clipped_rect.left() - dst_rect.left();
    RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
    const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
    const size_t dst_skip = m_target->width();
    const unsigned src_skip = source.width();

    for (int row = first_row; row <= last_row; ++row) {
        fast_dword_copy(dst, src, clipped_rect.width());
        dst += dst_skip;
        src += src_skip;
    }
}

[[gnu::flatten]] void Painter::draw_glyph(const Point& point, char ch, Color color)
{
    draw_bitmap(point, font().glyph_bitmap(ch), color);
}

void Painter::draw_text(const Rect& rect, const String& text, TextAlignment alignment, Color color)
{
    Point point;
    
    if (alignment == TextAlignment::TopLeft) {
        point = rect.location();
    } else if (alignment == TextAlignment::CenterLeft) {
        point = { rect.x(), rect.center().y() - (font().glyph_height() / 2) };
    } else if (alignment == TextAlignment::CenterRight) {
        int text_width = text.length() * font().glyph_width();
        point = { rect.right() - text_width, rect.center().y() - (font().glyph_height() / 2) };
    } else if (alignment == TextAlignment::Center) {
        int text_width = text.length() * font().glyph_width();
        point = rect.center();
        point.move_by(-(text_width / 2), -(font().glyph_height() / 2));
    } else {
        ASSERT_NOT_REACHED();
    }

    for (unsigned i = 0; i < text.length(); ++i, point.move_by(font().glyph_width(), 0)) {
        byte ch = text[i];
        if (ch == ' ')
            continue;
        draw_glyph(point, ch, color);
    }
}

void Painter::set_pixel(const Point& p, Color color)
{
    auto point = p;
    point.move_by(m_translation);
    if (!m_clip_rect.contains(point))
        return;
    m_target->scanline(point.y())[point.x()] = color.value();
}

[[gnu::always_inline]] void Painter::set_pixel_with_draw_op(dword& pixel, const Color& color)
{
    if (m_draw_op == DrawOp::Copy)
        pixel = color.value();
    else if (m_draw_op == DrawOp::Xor)
        pixel ^= color.value();
}

void Painter::draw_line(const Point& p1, const Point& p2, Color color)
{
    auto point1 = p1;
    point1.move_by(m_translation);

    auto point2 = p2;
    point2.move_by(m_translation);

    // Special case: vertical line.
    if (point1.x() == point2.x()) {
        const int x = point1.x();
        if (x < m_clip_rect.left() || x > m_clip_rect.right())
            return;
        if (point1.y() > point2.y())
            swap(point1, point2);
        if (point1.y() > m_clip_rect.bottom())
            return;
        if (point2.y() < m_clip_rect.top())
            return;
        int min_y = max(point1.y(), m_clip_rect.top());
        int max_y = min(point2.y(), m_clip_rect.bottom());
        for (int y = min_y; y <= max_y; ++y)
            set_pixel_with_draw_op(m_target->scanline(y)[x], color);
        return;
    }

    if (point1.x() > point2.x())
        swap(point1, point2);

    // Special case: horizontal line.
    if (point1.y() == point2.y()) {
        const int y = point1.y();
        if (y < m_clip_rect.top() || y > m_clip_rect.bottom())
            return;
        if (point1.x() > point2.x())
            swap(point1, point2);
        if (point1.x() > m_clip_rect.right())
            return;
        if (point2.x() < m_clip_rect.left())
            return;
        int min_x = max(point1.x(), m_clip_rect.left());
        int max_x = min(point2.x(), m_clip_rect.right());
        auto* pixels = m_target->scanline(point1.y());
        if (m_draw_op == DrawOp::Copy) {
            fast_dword_fill(pixels + min_x, color.value(), max_x - min_x + 1);
        } else {
            for (int x = min_x; x <= max_x; ++x)
                set_pixel_with_draw_op(pixels[x], color);
        }
        return;
    }

    // FIXME: Implement clipping below.
    ASSERT_NOT_REACHED();

#if 0
    const double dx = point2.x() - point1.x();
    const double dy = point2.y() - point1.y();
    const double delta_error = fabs(dy / dx);
    double error = 0;
    const double y_step = dy == 0 ? 0 : (dy > 0 ? 1 : -1);

    int y = point1.y();
    for (int x = point1.x(); x <= point2.x(); ++x) {
        m_target->scanline(y)[x] = color.value();
        error += delta_error;
        if (error >= 0.5) {
            y = (double)y + y_step;
            error -= 1.0;
        }
    }
#endif
}

void Painter::draw_focus_rect(const Rect& rect)
{
    Rect focus_rect = rect;
    focus_rect.move_by(1, 1);
    focus_rect.set_width(focus_rect.width() - 2);
    focus_rect.set_height(focus_rect.height() - 2);
    draw_rect(focus_rect, Color(96, 96, 192));
}

void Painter::set_clip_rect(const Rect& rect)
{
    m_clip_rect = Rect::intersection(rect, m_target->rect());
}

void Painter::clear_clip_rect()
{
    m_clip_rect = m_target->rect();
}