/*
 * Copyright (c) 2022, Luke Wilde <lukew@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Debug.h>
#include <LibGL/GLContext.h>
#include <LibWeb/HTML/HTMLCanvasElement.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/WebGL/WebGLRenderingContextBase.h>

namespace Web::WebGL {

WebGLRenderingContextBase::WebGLRenderingContextBase(HTML::Window& window, HTML::HTMLCanvasElement& canvas_element, NonnullOwnPtr<GL::GLContext> context, WebGLContextAttributes context_creation_parameters, WebGLContextAttributes actual_context_parameters)
    : PlatformObject(window.realm())
    , m_canvas_element(canvas_element)
    , m_context(move(context))
    , m_context_creation_parameters(move(context_creation_parameters))
    , m_actual_context_parameters(move(actual_context_parameters))
{
}

WebGLRenderingContextBase::~WebGLRenderingContextBase() = default;

void WebGLRenderingContextBase::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_canvas_element.ptr());
}

#define RETURN_WITH_WEBGL_ERROR_IF(condition, error)                         \
    if (condition) {                                                         \
        dbgln_if(WEBGL_CONTEXT_DEBUG, "{}(): error {:#x}", __func__, error); \
        set_error(error);                                                    \
        return;                                                              \
    }

void WebGLRenderingContextBase::present()
{
    if (!m_should_present)
        return;

    m_should_present = false;

    // "Before the drawing buffer is presented for compositing the implementation shall ensure that all rendering operations have been flushed to the drawing buffer."
    // FIXME: Is this the operation it means?
    m_context->gl_flush();

    m_context->present();

    // "By default, after compositing the contents of the drawing buffer shall be cleared to their default values, as shown in the table above.
    // This default behavior can be changed by setting the preserveDrawingBuffer attribute of the WebGLContextAttributes object.
    // If this flag is true, the contents of the drawing buffer shall be preserved until the author either clears or overwrites them."
    if (!m_context_creation_parameters.preserve_drawing_buffer) {
        auto current_clear_color = m_context->current_clear_color();
        auto current_clear_depth = m_context->current_clear_depth();
        auto current_clear_stencil = m_context->current_clear_stencil();

        // The implicit clear value for the color buffer is (0, 0, 0, 0)
        m_context->gl_clear_color(0, 0, 0, 0);

        // The implicit clear value for the depth buffer is 1.0.
        m_context->gl_clear_depth(1.0);

        // The implicit clear value for the stencil buffer is 0.
        m_context->gl_clear_stencil(0);

        m_context->gl_clear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

        // Restore the clear values.
        m_context->gl_clear_color(current_clear_color[0], current_clear_color[1], current_clear_color[2], current_clear_color[3]);
        m_context->gl_clear_depth(current_clear_depth);
        m_context->gl_clear_stencil(current_clear_stencil);
    }
}

HTML::HTMLCanvasElement& WebGLRenderingContextBase::canvas_element()
{
    return *m_canvas_element;
}

HTML::HTMLCanvasElement const& WebGLRenderingContextBase::canvas_element() const
{
    return *m_canvas_element;
}

JS::NonnullGCPtr<HTML::HTMLCanvasElement> WebGLRenderingContextBase::canvas_for_binding() const
{
    return *m_canvas_element;
}

void WebGLRenderingContextBase::needs_to_present()
{
    m_should_present = true;

    if (!canvas_element().layout_node())
        return;
    canvas_element().layout_node()->set_needs_display();
}

void WebGLRenderingContextBase::set_error(GLenum error)
{
    auto context_error = m_context->gl_get_error();
    if (context_error != GL_NO_ERROR)
        m_error = context_error;
    else
        m_error = error;
}

bool WebGLRenderingContextBase::is_context_lost() const
{
    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::is_context_lost()");
    return m_context_lost;
}

Optional<Vector<String>> WebGLRenderingContextBase::get_supported_extensions() const
{
    if (m_context_lost)
        return Optional<Vector<String>> {};

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::get_supported_extensions()");

    // FIXME: We don't currently support any extensions.
    return Vector<String> {};
}

JS::Object* WebGLRenderingContextBase::get_extension(String const& name) const
{
    if (m_context_lost)
        return nullptr;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::get_extension(name='{}')", name);

    // FIXME: We don't currently support any extensions.
    return nullptr;
}

void WebGLRenderingContextBase::active_texture(GLenum texture)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::active_texture(texture=0x{:08x})", texture);
    m_context->gl_active_texture(texture);
}

void WebGLRenderingContextBase::clear(GLbitfield mask)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::clear(mask=0x{:08x})", mask);
    m_context->gl_clear(mask);

    // FIXME: This should only be done if this is targeting the front buffer.
    needs_to_present();
}

void WebGLRenderingContextBase::clear_color(GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::clear_color(red={}, green={}, blue={}, alpha={})", red, green, blue, alpha);
    m_context->gl_clear_color(red, green, blue, alpha);
}

void WebGLRenderingContextBase::clear_depth(GLclampf depth)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::clear_depth(depth={})", depth);
    m_context->gl_clear_depth(depth);
}

void WebGLRenderingContextBase::clear_stencil(GLint s)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::clear_stencil(s=0x{:08x})", s);
    m_context->gl_clear_stencil(s);
}

void WebGLRenderingContextBase::color_mask(GLboolean red, GLboolean green, GLboolean blue, GLboolean alpha)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::color_mask(red={}, green={}, blue={}, alpha={})", red, green, blue, alpha);
    m_context->gl_color_mask(red, green, blue, alpha);
}

void WebGLRenderingContextBase::cull_face(GLenum mode)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::cull_face(mode=0x{:08x})", mode);
    m_context->gl_cull_face(mode);
}

void WebGLRenderingContextBase::depth_func(GLenum func)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::depth_func(func=0x{:08x})", func);
    m_context->gl_depth_func(func);
}

void WebGLRenderingContextBase::depth_mask(GLboolean mask)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::depth_mask(mask={})", mask);
    m_context->gl_depth_mask(mask);
}

void WebGLRenderingContextBase::depth_range(GLclampf z_near, GLclampf z_far)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::depth_range(z_near={}, z_far={})", z_near, z_far);

    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#VIEWPORT_DEPTH_RANGE
    // "The WebGL API does not support depth ranges with where the near plane is mapped to a value greater than that of the far plane. A call to depthRange will generate an INVALID_OPERATION error if zNear is greater than zFar."
    RETURN_WITH_WEBGL_ERROR_IF(z_near > z_far, GL_INVALID_OPERATION);
    m_context->gl_depth_range(z_near, z_far);
}

void WebGLRenderingContextBase::finish()
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::finish()");
    m_context->gl_finish();
}

void WebGLRenderingContextBase::flush()
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::flush()");
    m_context->gl_flush();
}

void WebGLRenderingContextBase::front_face(GLenum mode)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::front_face(mode=0x{:08x})", mode);
    m_context->gl_front_face(mode);
}

GLenum WebGLRenderingContextBase::get_error()
{
    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::get_error()");

    // "If the context's webgl context lost flag is set, returns CONTEXT_LOST_WEBGL the first time this method is called. Afterward, returns NO_ERROR until the context has been restored."
    // FIXME: The plan here is to make the context lost handler unconditionally set m_error to CONTEXT_LOST_WEBGL, which we currently do not have.
    //        The idea for the unconditional set is that any potentially error generating functions will not execute when the context is lost.
    if (m_error != GL_NO_ERROR || m_context_lost) {
        auto last_error = m_error;
        m_error = GL_NO_ERROR;
        return last_error;
    }

    return m_context->gl_get_error();
}

void WebGLRenderingContextBase::line_width(GLfloat width)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::line_width(width={})", width);

    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#NAN_LINE_WIDTH
    // "In the WebGL API, if the width parameter passed to lineWidth is set to NaN, an INVALID_VALUE error is generated and the line width is not changed."
    RETURN_WITH_WEBGL_ERROR_IF(isnan(width), GL_INVALID_VALUE);
    m_context->gl_line_width(width);
}

void WebGLRenderingContextBase::polygon_offset(GLfloat factor, GLfloat units)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::polygon_offset(factor={}, units={})", factor, units);
    m_context->gl_polygon_offset(factor, units);
}

void WebGLRenderingContextBase::scissor(GLint x, GLint y, GLsizei width, GLsizei height)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::scissor(x={}, y={}, width={}, height={})", x, y, width, height);
    m_context->gl_scissor(x, y, width, height);
}

void WebGLRenderingContextBase::stencil_op(GLenum fail, GLenum zfail, GLenum zpass)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::stencil_op(fail=0x{:08x}, zfail=0x{:08x}, zpass=0x{:08x})", fail, zfail, zpass);
    m_context->gl_stencil_op_separate(GL_FRONT_AND_BACK, fail, zfail, zpass);
}

void WebGLRenderingContextBase::stencil_op_separate(GLenum face, GLenum fail, GLenum zfail, GLenum zpass)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::stencil_op_separate(face=0x{:08x}, fail=0x{:08x}, zfail=0x{:08x}, zpass=0x{:08x})", face, fail, zfail, zpass);
    m_context->gl_stencil_op_separate(face, fail, zfail, zpass);
}

void WebGLRenderingContextBase::viewport(GLint x, GLint y, GLsizei width, GLsizei height)
{
    if (m_context_lost)
        return;

    dbgln_if(WEBGL_CONTEXT_DEBUG, "WebGLRenderingContextBase::viewport(x={}, y={}, width={}, height={})", x, y, width, height);
    m_context->gl_viewport(x, y, width, height);
}

}