// Copyright 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/output/program_binding.h"

#include "base/debug/trace_event.h"
#include "cc/output/geometry_binding.h"
#include "gpu/command_buffer/client/gles2_interface.h"
#include "third_party/khronos/GLES2/gl2.h"

using gpu::gles2::GLES2Interface;

namespace cc {

ProgramBindingBase::ProgramBindingBase()
    : program_(0),
      vertex_shader_id_(0),
      fragment_shader_id_(0),
      initialized_(false) {}

ProgramBindingBase::~ProgramBindingBase() {
  // If you hit these asserts, you initialized but forgot to call Cleanup().
  DCHECK(!program_);
  DCHECK(!vertex_shader_id_);
  DCHECK(!fragment_shader_id_);
  DCHECK(!initialized_);
}

bool ProgramBindingBase::Init(GLES2Interface* context,
                              const std::string& vertex_shader,
                              const std::string& fragment_shader) {
  TRACE_EVENT0("cc", "ProgramBindingBase::init");
  vertex_shader_id_ = LoadShader(context, GL_VERTEX_SHADER, vertex_shader);
  if (!vertex_shader_id_)
    return false;

  fragment_shader_id_ =
      LoadShader(context, GL_FRAGMENT_SHADER, fragment_shader);
  if (!fragment_shader_id_) {
    context->DeleteShader(vertex_shader_id_);
    vertex_shader_id_ = 0;
    return false;
  }

  program_ =
      CreateShaderProgram(context, vertex_shader_id_, fragment_shader_id_);
  return !!program_;
}

bool ProgramBindingBase::Link(GLES2Interface* context) {
  context->LinkProgram(program_);
  CleanupShaders(context);
  if (!program_)
    return false;
#ifndef NDEBUG
  int linked = 0;
  context->GetProgramiv(program_, GL_LINK_STATUS, &linked);
  if (!linked)
    return false;
#endif
  return true;
}

void ProgramBindingBase::Cleanup(GLES2Interface* context) {
  initialized_ = false;
  if (!program_)
    return;

  DCHECK(context);
  context->DeleteProgram(program_);
  program_ = 0;

  CleanupShaders(context);
}

unsigned ProgramBindingBase::LoadShader(GLES2Interface* context,
                                        unsigned type,
                                        const std::string& shader_source) {
  unsigned shader = context->CreateShader(type);
  if (!shader)
    return 0u;

  const char* shader_source_str[] = { shader_source.data() };
  int shader_length[] = { static_cast<int>(shader_source.length()) };
  context->ShaderSource(
      shader, 1,
      shader_source_str,
      shader_length);
  context->CompileShader(shader);
#ifndef NDEBUG
  int compiled = 0;
  context->GetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
  if (!compiled)
    return 0u;
#endif
  return shader;
}

unsigned ProgramBindingBase::CreateShaderProgram(GLES2Interface* context,
                                                 unsigned vertex_shader,
                                                 unsigned fragment_shader) {
  unsigned program_object = context->CreateProgram();
  if (!program_object)
    return 0;

  context->AttachShader(program_object, vertex_shader);
  context->AttachShader(program_object, fragment_shader);

  // Bind the common attrib locations.
  context->BindAttribLocation(
      program_object, GeometryBinding::PositionAttribLocation(), "a_position");
  context->BindAttribLocation(
      program_object, GeometryBinding::TexCoordAttribLocation(), "a_texCoord");
  context->BindAttribLocation(program_object,
                              GeometryBinding::TriangleIndexAttribLocation(),
                              "a_index");

  return program_object;
}

void ProgramBindingBase::CleanupShaders(GLES2Interface* context) {
  if (vertex_shader_id_) {
    context->DeleteShader(vertex_shader_id_);
    vertex_shader_id_ = 0;
  }
  if (fragment_shader_id_) {
    context->DeleteShader(fragment_shader_id_);
    fragment_shader_id_ = 0;
  }
}

}  // namespace cc