/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "WebGL2Context.h"

#include "gfxPrefs.h"
#include "GLContext.h"
#include "mozilla/dom/WebGL2RenderingContextBinding.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Telemetry.h"
#include "nsPrintfCString.h"
#include "WebGLBuffer.h"
#include "WebGLFormats.h"
#include "WebGLTransformFeedback.h"

namespace mozilla {

WebGL2Context::WebGL2Context() : WebGLContext() {
  MOZ_ASSERT(IsSupported(),
             "not supposed to create a WebGL2Context"
             "context when not supported");
}

WebGL2Context::~WebGL2Context() {}

UniquePtr<webgl::FormatUsageAuthority> WebGL2Context::CreateFormatUsage(
    gl::GLContext* gl) const {
  return webgl::FormatUsageAuthority::CreateForWebGL2(gl);
}

/*static*/ bool WebGL2Context::IsSupported() {
  return gfxPrefs::WebGL2Enabled();
}

/*static*/ WebGL2Context* WebGL2Context::Create() {
  return new WebGL2Context();
}

JSObject* WebGL2Context::WrapObject(JSContext* cx,
                                    JS::Handle<JSObject*> givenProto) {
  return dom::WebGL2RenderingContextBinding::Wrap(cx, this, givenProto);
}

////////////////////////////////////////////////////////////////////////////////
// WebGL 2 initialisation

static const gl::GLFeature kRequiredFeatures[] = {
    gl::GLFeature::blend_minmax,
    gl::GLFeature::clear_buffers,
    gl::GLFeature::copy_buffer,
    gl::GLFeature::depth_texture,
    gl::GLFeature::draw_instanced,
    gl::GLFeature::draw_range_elements,
    gl::GLFeature::element_index_uint,
    gl::GLFeature::frag_color_float,
    gl::GLFeature::frag_depth,
    gl::GLFeature::framebuffer_object,
    gl::GLFeature::get_integer_indexed,
    gl::GLFeature::get_integer64_indexed,
    gl::GLFeature::gpu_shader4,
    gl::GLFeature::instanced_arrays,
    gl::GLFeature::instanced_non_arrays,
    gl::GLFeature::map_buffer_range,  // Used by GetBufferSubData.
    gl::GLFeature::occlusion_query2,
    gl::GLFeature::packed_depth_stencil,
    gl::GLFeature::query_objects,
    gl::GLFeature::renderbuffer_color_float,
    gl::GLFeature::renderbuffer_color_half_float,
    gl::GLFeature::sRGB,
    gl::GLFeature::sampler_objects,
    gl::GLFeature::standard_derivatives,
    gl::GLFeature::texture_3D,
    gl::GLFeature::texture_3D_compressed,
    gl::GLFeature::texture_3D_copy,
    gl::GLFeature::texture_float,
    gl::GLFeature::texture_half_float,
    gl::GLFeature::texture_half_float_linear,
    gl::GLFeature::texture_non_power_of_two,
    gl::GLFeature::texture_storage,
    gl::GLFeature::transform_feedback2,
    gl::GLFeature::uniform_buffer_object,
    gl::GLFeature::uniform_matrix_nonsquare,
    gl::GLFeature::vertex_array_object};

bool WebGLContext::InitWebGL2(FailureReason* const out_failReason) {
  MOZ_ASSERT(IsWebGL2(), "WebGLContext is not a WebGL 2 context!");

  std::vector<gl::GLFeature> missingList;

  const auto fnGatherMissing = [&](gl::GLFeature cur) {
    if (!gl->IsSupported(cur)) {
      missingList.push_back(cur);
    }
  };

  const auto fnGatherMissing2 = [&](gl::GLFeature main, gl::GLFeature alt) {
    if (!gl->IsSupported(main) && !gl->IsSupported(alt)) {
      missingList.push_back(main);
    }
  };

  ////

  for (const auto& cur : kRequiredFeatures) {
    fnGatherMissing(cur);
  }

  // On desktop, we fake occlusion_query_boolean with occlusion_query if
  // necessary. (See WebGL2ContextQueries.cpp)
  fnGatherMissing2(gl::GLFeature::occlusion_query_boolean,
                   gl::GLFeature::occlusion_query);

#ifdef XP_MACOSX
  // On OSX, GL core profile is used. This requires texture swizzle
  // support to emulate legacy texture formats: ALPHA, LUMINANCE,
  // and LUMINANCE_ALPHA.
  fnGatherMissing(gl::GLFeature::texture_swizzle);
#endif

  fnGatherMissing2(gl::GLFeature::prim_restart_fixed,
                   gl::GLFeature::prim_restart);

  ////

  if (!missingList.empty()) {
    nsAutoCString exts;
    for (auto itr = missingList.begin(); itr != missingList.end(); ++itr) {
      exts.AppendLiteral("\n  ");
      exts.Append(gl::GLContext::GetFeatureName(*itr));
    }

    const nsPrintfCString reason(
        "WebGL 2 requires support for the following"
        " features: %s",
        exts.BeginReading());
    *out_failReason = FailureReason("FEATURE_FAILURE_WEBGL2_OCCL", reason);
    return false;
  }

  // we initialise WebGL 2 related stuff.
  gl->GetUIntegerv(LOCAL_GL_MAX_TRANSFORM_FEEDBACK_SEPARATE_ATTRIBS,
                   &mGLMaxTransformFeedbackSeparateAttribs);
  gl->GetUIntegerv(LOCAL_GL_MAX_UNIFORM_BUFFER_BINDINGS,
                   &mGLMaxUniformBufferBindings);

  mIndexedUniformBufferBindings.resize(mGLMaxUniformBufferBindings);

  mDefaultTransformFeedback = new WebGLTransformFeedback(this, 0);
  mBoundTransformFeedback = mDefaultTransformFeedback;

  gl->fGenTransformFeedbacks(1, &mEmptyTFO);

  ////

  if (!gl->IsGLES()) {
    // Desktop OpenGL requires the following to be enabled in order to
    // support sRGB operations on framebuffers.
    gl->fEnable(LOCAL_GL_FRAMEBUFFER_SRGB_EXT);
  }

  if (gl->IsSupported(gl::GLFeature::prim_restart_fixed)) {
    gl->fEnable(LOCAL_GL_PRIMITIVE_RESTART_FIXED_INDEX);
  } else {
    MOZ_ASSERT(gl->IsSupported(gl::GLFeature::prim_restart));
  }

  //////

  return true;
}

}  // namespace mozilla