/**
 * Stone of Orthanc
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2020 Osimis S.A., Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program. If not, see
 * <http://www.gnu.org/licenses/>.
 **/


#include "OpenGLTextureProgram.h"
#include "OpenGLShaderVersionDirective.h"

#include <OrthancException.h>

static const unsigned int COMPONENTS = 2;
static const unsigned int COUNT = 6;  // 2 triangles in 2D

static const char* VERTEX_SHADER = 
  ORTHANC_STONE_OPENGL_SHADER_VERSION_DIRECTIVE
  "attribute vec2 a_texcoord;             \n"
  "attribute vec4 a_position;             \n"
  "uniform mat4 u_matrix;                 \n"
  "varying vec2 v_texcoord;               \n"
  "void main()                            \n"
  "{                                      \n"
  "  gl_Position = u_matrix * a_position; \n"
  "  v_texcoord = a_texcoord;             \n"
  "}";


namespace OrthancStone
{
  namespace Internals
  {
    void OpenGLTextureProgram::InitializeExecution(OpenGL::OpenGLTexture& texture,
                                                   const AffineTransform2D& transform,
                                                   unsigned int canvasWidth,
                                                   unsigned int canvasHeight)
    {
      if (!context_.IsContextLost())
      {
        context_.MakeCurrent();
        program_->Use();

        AffineTransform2D scale = AffineTransform2D::CreateScaling
        (texture.GetWidth(), texture.GetHeight());

        AffineTransform2D t = AffineTransform2D::Combine(transform, scale);

        float m[16];
        t.ConvertToOpenGLMatrix(m, canvasWidth, canvasHeight);

        texture.Bind(program_->GetUniformLocation("u_texture"));
        glUniformMatrix4fv(program_->GetUniformLocation("u_matrix"), 1, GL_FALSE, m);

        glBindBuffer(GL_ARRAY_BUFFER, buffers_[0]);
        glEnableVertexAttribArray(positionLocation_);
        glVertexAttribPointer(positionLocation_, COMPONENTS, GL_FLOAT, GL_FALSE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER, buffers_[1]);
        glEnableVertexAttribArray(textureLocation_);
        glVertexAttribPointer(textureLocation_, COMPONENTS, GL_FLOAT, GL_FALSE, 0, 0);
      }
    }

    void OpenGLTextureProgram::FinalizeExecution()
    {
      if (!context_.IsContextLost())
      {
        glDisableVertexAttribArray(positionLocation_);
        glDisableVertexAttribArray(textureLocation_);
      }
    }

    OpenGLTextureProgram::OpenGLTextureProgram(OpenGL::IOpenGLContext& context,
                                               const char* fragmentShader) :
      context_(context)
    {
      static const float POSITIONS[COMPONENTS * COUNT] = {
        0, 0,
        0, 1,
        1, 0,
        1, 0,
        0, 1,
        1, 1
      };

      if (!context_.IsContextLost())
      {
        context_.MakeCurrent();

        program_.reset(new OpenGL::OpenGLProgram(context_));
        program_->CompileShaders(VERTEX_SHADER, fragmentShader);

        positionLocation_ = program_->GetAttributeLocation("a_position");
        textureLocation_ = program_->GetAttributeLocation("a_texcoord");

        glGenBuffers(2, buffers_);

        glBindBuffer(GL_ARRAY_BUFFER, buffers_[0]);
        glBufferData(GL_ARRAY_BUFFER, sizeof(float) * COMPONENTS * COUNT, POSITIONS, GL_STATIC_DRAW);

        glBindBuffer(GL_ARRAY_BUFFER, buffers_[1]);
        glBufferData(GL_ARRAY_BUFFER, sizeof(float) * COMPONENTS * COUNT, POSITIONS, GL_STATIC_DRAW);
      }
    }

    OpenGLTextureProgram::~OpenGLTextureProgram()
    {
      if (!context_.IsContextLost())
      {
        ORTHANC_OPENGL_TRACE_CURRENT_CONTEXT("OpenGLTextureProgram::~OpenGLTextureProgram() | About to call glDeleteBuffers");
        context_.MakeCurrent();
        glDeleteBuffers(2, buffers_);
      }
    }


    void OpenGLTextureProgram::Execution::DrawTriangles()
    {
      if (!that_.context_.IsContextLost())
      {
        glDrawArrays(GL_TRIANGLES, 0, COUNT);
      }
    }
  }
}