#include "glfunc.h"

#include <QOpenGLFunctions>
#include <QOpenGLVertexArrayObject>
#include <QOpenGLBuffer>

const GLfloat blit_vertices[] = {
  -1.0f, -1.0f, 0.0f,
  1.0f, -1.0f, 0.0f,
  1.0f, 1.0f, 0.0f,

  -1.0f, -1.0f, 0.0f,
  -1.0f, 1.0f, 0.0f,
  1.0f, 1.0f, 0.0f
};

const GLfloat blit_texcoords[] = {
  0.0, 0.0,
  1.0, 0.0,
  1.0, 1.0,

  0.0, 0.0,
  0.0, 1.0,
  1.0, 1.0
};

const GLfloat flipped_blit_texcoords[] = {
  0.0, 1.0,
  1.0, 1.0,
  1.0, 0.0,

  0.0, 1.0,
  0.0, 0.0,
  1.0, 0.0
};

/**
 * @brief Set up texture mipmaps
 * @param f
 */
void PrepareToDraw(QOpenGLFunctions* f) {
  f->glGenerateMipmap(GL_TEXTURE_2D);
  f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
  f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
  f->glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
}

void olive::gl::Blit(QOpenGLShaderProgram* pipeline, bool flipped, QMatrix4x4 matrix) {

  QOpenGLFunctions* func = QOpenGLContext::currentContext()->functions();
  PrepareToDraw(func);

  QOpenGLVertexArrayObject m_vao;
  m_vao.create();
  m_vao.bind();

  QOpenGLBuffer m_vbo;
  m_vbo.create();
  m_vbo.bind();
  m_vbo.allocate(blit_vertices, 18 * sizeof(GLfloat));
  m_vbo.release();

  QOpenGLBuffer m_vbo2;
  m_vbo2.create();
  m_vbo2.bind();
  m_vbo2.allocate(flipped ? flipped_blit_texcoords : blit_texcoords, 12 * sizeof(GLfloat));
  m_vbo2.release();

  pipeline->bind();

  pipeline->setUniformValue("mvp_matrix", matrix);
  pipeline->setUniformValue("texture", 0);

  GLuint vertex_location = pipeline->attributeLocation("a_position");
  m_vbo.bind();
  func->glEnableVertexAttribArray(vertex_location);
  func->glVertexAttribPointer(vertex_location, 3, GL_FLOAT, GL_FALSE, 0, 0);
  m_vbo.release();

  GLuint tex_location = pipeline->attributeLocation("a_texcoord");
  m_vbo2.bind();
  func->glEnableVertexAttribArray(tex_location);
  func->glVertexAttribPointer(tex_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
  m_vbo2.release();

  func->glDrawArrays(GL_TRIANGLES, 0, 6);

  pipeline->release();
}