/**
 * Looking Glass
 * Copyright (C) 2017-2021 The Looking Glass Authors
 * https://looking-glass.io
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "damage.h"
#include "common/debug.h"
#include "common/KVMFR.h"
#include "common/locking.h"

#include "app.h"
#include "shader.h"

#include <stdlib.h>
#include <string.h>

// these headers are auto generated by cmake
#include "damage.vert.h"
#include "damage.frag.h"

struct EGL_Damage
{
  EGL_Shader * shader;

  GLfloat transform[6];
  GLuint  buffers[2];
  GLuint  vao;
  int     count;

  bool          show;
  KeybindHandle toggleHandle;

  int   width     , height;
  float translateX, translateY;
  float scaleX    , scaleY;
  bool  rotate;

  // uniforms
  GLint uTransform;
};

void egl_damage_show_toggle(int key, void * opaque)
{
  EGL_Damage * damage = opaque;
  damage->show ^= true;
}

bool egl_damage_init(EGL_Damage ** damage)
{
  *damage = (EGL_Damage *)malloc(sizeof(EGL_Damage));
  if (!*damage)
  {
    DEBUG_ERROR("Failed to malloc EGL_Alert");
    return false;
  }

  memset(*damage, 0, sizeof(EGL_Damage));

  if (!egl_shader_init(&(*damage)->shader))
  {
    DEBUG_ERROR("Failed to initialize the damage shader");
    return false;
  }

  if (!egl_shader_compile((*damage)->shader,
        b_shader_damage_vert, b_shader_damage_vert_size,
        b_shader_damage_frag, b_shader_damage_frag_size))
  {
    DEBUG_ERROR("Failed to compile the damage shader");
    return false;
  }

  glGenVertexArrays(1, &(*damage)->vao);
  glBindVertexArray((*damage)->vao);

  glGenBuffers(2, (*damage)->buffers);
  glBindBuffer(GL_ARRAY_BUFFER, (*damage)->buffers[0]);
  glBufferData(GL_ARRAY_BUFFER, KVMFR_MAX_DAMAGE_RECTS * 8 * sizeof(GLfloat), NULL, GL_STREAM_DRAW);
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, NULL);
  glBindBuffer(GL_ARRAY_BUFFER, 0);

  GLushort indices[KVMFR_MAX_DAMAGE_RECTS * 6];
  for (int i = 0; i < KVMFR_MAX_DAMAGE_RECTS; ++i)
  {
    indices[6 * i + 0] = 4 * i + 0;
    indices[6 * i + 1] = 4 * i + 1;
    indices[6 * i + 2] = 4 * i + 2;
    indices[6 * i + 3] = 4 * i + 0;
    indices[6 * i + 4] = 4 * i + 2;
    indices[6 * i + 5] = 4 * i + 3;
  }

  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, (*damage)->buffers[1]);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof indices, indices, GL_STATIC_DRAW);

  glBindVertexArray(0);

  (*damage)->count = -1;
  (*damage)->uTransform = egl_shader_get_uniform_location((*damage)->shader, "transform");
  (*damage)->toggleHandle = app_registerKeybind(KEY_A, egl_damage_show_toggle, *damage, "Toggle damage display");

  return true;
}

void egl_damage_free(EGL_Damage ** damage)
{
  if (!*damage)
    return;

  app_releaseKeybind(&(*damage)->toggleHandle);
  glDeleteVertexArrays(1, &(*damage)->vao);
  glDeleteBuffers(2, (*damage)->buffers);
  egl_shader_free(&(*damage)->shader);

  free(*damage);
  *damage = NULL;
}

static void update_matrix(EGL_Damage * damage)
{
  int width  = damage->rotate ? damage->height : damage->width;
  int height = damage->rotate ? damage->width  : damage->height;
  damage->transform[0] = 2.0f * damage->scaleX / width;
  damage->transform[1] = 0.0f;
  damage->transform[2] = 0.0f;
  damage->transform[3] = -2.0f * damage->scaleY / height;
  damage->transform[4] = damage->translateX - damage->scaleX;
  damage->transform[5] = damage->translateY + damage->scaleY;
}

void egl_damage_setup(EGL_Damage * damage, int width, int height)
{
  damage->width  = width;
  damage->height = height;
  update_matrix(damage);
}

void egl_damage_resize(EGL_Damage * damage, float translateX, float translateY,
    float scaleX, float scaleY)
{
  damage->translateX = translateX;
  damage->translateY = translateY;
  damage->scaleX     = scaleX;
  damage->scaleY     = scaleY;
  update_matrix(damage);
}

inline static void rectToVertices(GLfloat * vertex, const FrameDamageRect * rect)
{
  vertex[0] = rect->x;
  vertex[1] = rect->y;
  vertex[2] = rect->x + rect->width;
  vertex[3] = rect->y;
  vertex[4] = rect->x + rect->width;
  vertex[5] = rect->y + rect->height;
  vertex[6] = rect->x;
  vertex[7] = rect->y + rect->height;
}

bool egl_damage_render(EGL_Damage * damage, bool rotate, const struct DesktopDamage * data)
{
  if (!damage->show || (!data && damage->count == -1))
    return false;

  if (rotate != damage->rotate)
  {
    damage->rotate = rotate;
    update_matrix(damage);
  }

  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

  egl_shader_use(damage->shader);
  glUniformMatrix3x2fv(damage->uTransform, 1, GL_FALSE, damage->transform);

  if (data)
  {
    damage->count = data->count;
    GLfloat vertices[KVMFR_MAX_DAMAGE_RECTS * 8];
    if (damage->count == 0)
    {
      FrameDamageRect full = {
        .x = 0, .y = 0, .width = damage->width, .height = damage->height,
      };
      damage->count = 1;
      rectToVertices(vertices, &full);
    }
    else
    {
      for (int i = 0; i < damage->count; ++i)
        rectToVertices(vertices + i * 8, data->rects + i);
    }

    glBindBuffer(GL_ARRAY_BUFFER, damage->buffers[0]);
    glBufferSubData(GL_ARRAY_BUFFER, 0, damage->count * 8 * sizeof(GLfloat),
        vertices);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
  }

  glBindVertexArray(damage->vao);
  glDrawElements(GL_TRIANGLES, 6 * damage->count, GL_UNSIGNED_SHORT, NULL);
  glBindVertexArray(0);

  glDisable(GL_BLEND);
  return true;
}