/*
 * Test GL_ARB_vertex_buffer_object
 * Also test GL_ARB_vertex_array_object if supported
 *
 * Brian Paul
 * 16 Sep 2003
 */


#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <glad/glad.h>
#include "glut_wrap.h"

#define NUM_OBJECTS 10

struct object
{
   GLuint ArrayObjectID; /** GL_ARB_vertex_array_object */
   GLuint VertexBufferID;
   GLuint ColorBufferID;
   GLuint ElementsBufferID;
   GLuint NumVerts;
   GLuint VertexOffset;
   GLuint ColorOffset;
   GLuint VertexStride;
   GLuint ColorStride;
   GLuint NumElements;
   GLuint MaxElement;
};

static struct object Objects[NUM_OBJECTS];
static GLuint NumObjects;

static GLuint Win;

static GLfloat Xrot = 0, Yrot = 0, Zrot = 0;
static GLboolean Anim = GL_TRUE;
static GLboolean Have_ARB_vertex_array_object = GL_FALSE;


static void CheckError(int line)
{
   GLenum err = glGetError();
   if (err) {
      printf("GL Error 0x%x at line %d\n", (int) err, line);
   }
}


static void DrawObject( const struct object *obj )
{
   if (Have_ARB_vertex_array_object && obj->ArrayObjectID) {
      glBindVertexArray(obj->ArrayObjectID);

      if (obj->NumElements > 0) {
         /* indexed arrays */
         glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, obj->ElementsBufferID);
         glDrawRangeElements(GL_LINE_LOOP, 0, obj->MaxElement,
                             obj->NumElements, GL_UNSIGNED_INT, NULL);
      }
      else {
         /* non-indexed arrays */
         glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
         glDrawArrays(GL_LINE_LOOP, 0, obj->NumVerts);
      }

      glBindVertexArray(0);
   }
   else {
      /* no vertex array objects, must set vertex/color pointers per draw */

      glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
      glVertexPointer(3, GL_FLOAT, obj->VertexStride, (const void *) (size_t) obj->VertexOffset);
      glEnableClientState(GL_VERTEX_ARRAY);

      /* test push/pop attrib */
      /* XXX this leads to a segfault with NVIDIA's 53.36 driver */
#if 0
      if (1)
      {
         glPushClientAttrib(GL_CLIENT_VERTEX_ARRAY_BIT);
         /*glVertexPointer(3, GL_FLOAT, 0, (const void *) (size_t) (obj->VertexOffset + 10000));*/
         glBindBufferARB(GL_ARRAY_BUFFER_ARB, 999999);
         glPopClientAttrib();
      }
#endif
      glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->ColorBufferID);
      glColorPointer(3, GL_FLOAT, obj->ColorStride, (const void *) (size_t) obj->ColorOffset);
      glEnableClientState(GL_COLOR_ARRAY);

      if (obj->NumElements > 0) {
         /* indexed arrays */
         glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, obj->ElementsBufferID);
         glDrawElements(GL_LINE_LOOP, obj->NumElements, GL_UNSIGNED_INT, NULL);
      }
      else {
         /* non-indexed arrays */
         glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
         glDrawArrays(GL_LINE_LOOP, 0, obj->NumVerts);
      }
   }
}


static void Idle( void )
{
   Zrot = 0.05 * glutGet(GLUT_ELAPSED_TIME);
   glutPostRedisplay();
}


static void Display( void )
{
   int i;

   glClear( GL_COLOR_BUFFER_BIT );

   for (i = 0; i < NumObjects; i++) {
      float x = 7.0 * ((float) i / (NumObjects-1) - 0.5);
      glPushMatrix();
      glTranslatef(x, 0, 0);
      glRotatef(Xrot, 1, 0, 0);
      glRotatef(Yrot, 0, 1, 0);
      glRotatef(Zrot, 0, 0, 1);

      DrawObject(Objects + i);

      glPopMatrix();
   }

   CheckError(__LINE__);
   glutSwapBuffers();
}


static void Reshape( int width, int height )
{
   float ar = (float) width / (float) height;
   glViewport( 0, 0, width, height );
   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glFrustum( -ar, ar, -1.0, 1.0, 5.0, 25.0 );
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}


static void FreeBuffers(void)
{
   int i;
   for (i = 0; i < NUM_OBJECTS; i++) {
      glDeleteBuffersARB(1, &Objects[i].VertexBufferID);
      glDeleteBuffersARB(1, &Objects[i].ColorBufferID);
      glDeleteBuffersARB(1, &Objects[i].ElementsBufferID);
   }
}


static void Key( unsigned char key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 27:
         FreeBuffers();
         glutDestroyWindow(Win);
         exit(0);
         break;
   }
   glutPostRedisplay();
}


static void SpecialKey( int key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         Xrot -= step;
         break;
      case GLUT_KEY_DOWN:
         Xrot += step;
         break;
      case GLUT_KEY_LEFT:
         Yrot -= step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot += step;
         break;
   }
   glutPostRedisplay();
}


/**
 * If GL_ARB_vertex_array_object is supported, create an array object
 * and set all the per-array state.
 */
static void
CreateVertexArrayObject(struct object *obj)
{
   glGenVertexArrays(1, &obj->ArrayObjectID);
   glBindVertexArray(obj->ArrayObjectID);

   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
   glVertexPointer(3, GL_FLOAT, obj->VertexStride, (const void *) (size_t) obj->VertexOffset);
   glEnableClientState(GL_VERTEX_ARRAY);

   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->ColorBufferID);
   glColorPointer(3, GL_FLOAT, obj->ColorStride, (const void *) (size_t) obj->ColorOffset);
   glEnableClientState(GL_COLOR_ARRAY);

   glBindVertexArray(0);
}


/*
 * Non-interleaved position/color data.
 */
static void MakeObject1(struct object *obj)
{
   GLfloat *v, *c;
   void *p;
   int i;
   GLubyte buffer[500];

   for (i = 0; i < 500; i++)
      buffer[i] = i & 0xff;

   obj->VertexBufferID = 0;
   glGenBuffersARB(1, &obj->VertexBufferID);
   obj->ColorBufferID = obj->VertexBufferID;
   assert(obj->VertexBufferID != 0);
   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
   glBufferDataARB(GL_ARRAY_BUFFER_ARB, 500, buffer, GL_STATIC_DRAW_ARB);

   for (i = 0; i < 500; i++)
      buffer[i] = 0;

   glGetBufferSubDataARB(GL_ARRAY_BUFFER_ARB, 0, 500, buffer);

   for (i = 0; i < 500; i++)
      assert(buffer[i] == (i & 0xff));

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_MAPPED_ARB, &i);
   assert(!i);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_USAGE_ARB, &i);

   v = (GLfloat *) glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);

   /* do some sanity tests */
   glGetBufferPointervARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_MAP_POINTER_ARB, &p);
   assert(p == v);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_SIZE_ARB, &i);
   assert(i == 500);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_USAGE_ARB, &i);
   assert(i == GL_STATIC_DRAW_ARB);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_ACCESS_ARB, &i);
   assert(i == GL_WRITE_ONLY_ARB);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_MAPPED_ARB, &i);
   assert(i);

   /* Make rectangle */
   v[0] = -1;  v[1] = -1;  v[2] = 0;
   v[3] =  1;  v[4] = -1;  v[5] = 0;
   v[6] =  1;  v[7] =  1;  v[8] = 0;
   v[9] = -1;  v[10] = 1;  v[11] = 0;
   c = v + 12;
   c[0] = 1;  c[1] = 0;  c[2] = 0;
   c[3] = 1;  c[4] = 0;  c[5] = 0;
   c[6] = 1;  c[7] = 0;  c[8] = 1;
   c[9] = 1;  c[10] = 0;  c[11] = 1;
   obj->NumVerts = 4;
   obj->VertexOffset = 0;
   obj->ColorOffset = 3 * sizeof(GLfloat) * obj->NumVerts;
   obj->VertexStride = 0;
   obj->ColorStride = 0;
   obj->NumElements = 0;
   obj->MaxElement = 0;

   glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);

   glGetBufferPointervARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_MAP_POINTER_ARB, &p);
   assert(!p);

   glGetBufferParameterivARB(GL_ARRAY_BUFFER_ARB, GL_BUFFER_MAPPED_ARB, &i);
   assert(!i);

   if (Have_ARB_vertex_array_object) {
      CreateVertexArrayObject(obj);
   }
}


/*
 * Interleaved position/color data.
 */
static void MakeObject2(struct object *obj)
{
   GLfloat *v;
   int start = 40; /* bytes, to test non-zero array offsets */

   glGenBuffersARB(1, &obj->VertexBufferID);
   obj->ColorBufferID = obj->VertexBufferID;

   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
   glBufferDataARB(GL_ARRAY_BUFFER_ARB, 1000, NULL, GL_STATIC_DRAW_ARB);
   v = (GLfloat *) glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);

   v += start / sizeof(GLfloat);

   /* Make triangle: interleaved colors, then positions */
   /*   R            G          B           X           Y            Z  */
   v[0] = 0;   v[1] = 1;   v[2] = 0;   v[3] = -1;  v[4] = -1;   v[5] = 0;
   v[6] = 0;   v[7] = 1;   v[8] = 0;   v[9] = 1;   v[10] = -1;  v[11] = 0;
   v[12] = 1;  v[13] = 1;  v[14] = 0;  v[15] = 0;  v[16] =  1;  v[17] = 0;

   obj->NumVerts = 3;
   obj->VertexOffset = start + 3 * sizeof(GLfloat);
   obj->ColorOffset = start;
   obj->VertexStride = 6 * sizeof(GLfloat);
   obj->ColorStride = 6 * sizeof(GLfloat);

   obj->NumElements = 0;
   obj->MaxElement = 0;

   glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);

   if (Have_ARB_vertex_array_object) {
      CreateVertexArrayObject(obj);
   }
}


/*
 * Use an index buffer and glDrawElements().
 */
static void MakeObject3(struct object *obj)
{
   GLfloat vertexData[1000];
   GLfloat *v, *c;
   GLuint *i;
   int bytes;

   /* Make rectangle */
   v = vertexData;
   v[0] = -1;  v[1] = -0.5;  v[2] = 0;
   v[3] =  1;  v[4] = -0.5;  v[5] = 0;
   v[6] =  1;  v[7] =  0.5;  v[8] = 0;
   v[9] = -1;  v[10] = 0.5;  v[11] = 0;
   c = vertexData + 12;
   c[0] = 0;  c[1] = 0;  c[2] = 1;
   c[3] = 0;  c[4] = 0;  c[5] = 1;
   c[6] = 0;  c[7] = 1;  c[8] = 1;
   c[9] = 0;  c[10] = 1;  c[11] = 1;
   obj->NumVerts = 4;
   obj->VertexOffset = 0;
   obj->ColorOffset = 3 * sizeof(GLfloat) * obj->NumVerts;
   obj->VertexStride = 0;
   obj->ColorStride = 0;

   bytes = obj->NumVerts * (3 + 3) * sizeof(GLfloat);

   /* Don't use glMap/UnmapBuffer for this object */
   glGenBuffersARB(1, &obj->VertexBufferID);
   obj->ColorBufferID = obj->VertexBufferID;

   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
   glBufferDataARB(GL_ARRAY_BUFFER_ARB, bytes, vertexData, GL_STATIC_DRAW_ARB);

   /* Setup a buffer of indices to test the ELEMENTS path */
   glGenBuffersARB(1, &obj->ElementsBufferID);
   glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, obj->ElementsBufferID);
   glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 100, NULL, GL_STATIC_DRAW_ARB);
   i = (GLuint *) glMapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, GL_READ_WRITE_ARB);
   i[0] = 0;
   i[1] = 1;
   i[2] = 2;
   i[3] = 3;
   glUnmapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB);
   obj->NumElements = 4;
   obj->MaxElement = 3;

   if (Have_ARB_vertex_array_object) {
      CreateVertexArrayObject(obj);
   }
}


/*
 * Vertex and color data in different buffers.
 */
static void MakeObject4(struct object *obj)
{
   static const GLfloat vertexData[] = {
      0,   -1,  0,
      0.5,  0,  0,
      0,    1,  0,
      -0.5, 0,  0
   };
   static const GLfloat colorData[] = {
      1,    1,   1,
      1,    1,   0,
      .5,  .5,   0,
      1,    1,   0
   };

   obj->VertexOffset = 0;
   obj->VertexStride = 0;
   obj->ColorOffset = 0;
   obj->ColorStride = 0;
   obj->NumVerts = 4;

   glGenBuffersARB(1, &obj->VertexBufferID);
   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->VertexBufferID);
   glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(vertexData), vertexData,
                   GL_STATIC_DRAW_ARB);

   glGenBuffersARB(1, &obj->ColorBufferID);
   glBindBufferARB(GL_ARRAY_BUFFER_ARB, obj->ColorBufferID);
   glBufferDataARB(GL_ARRAY_BUFFER_ARB, sizeof(colorData), colorData,
                   GL_STATIC_DRAW_ARB);

   /* Setup a buffer of indices to test the ELEMENTS path */
   obj->ElementsBufferID = 0;
   obj->NumElements = 0;
   obj->MaxElement = 0;

   if (Have_ARB_vertex_array_object) {
      CreateVertexArrayObject(obj);
   }
}



static void Init( void )
{
   if (!glutExtensionSupported("GL_ARB_vertex_buffer_object")) {
      printf("GL_ARB_vertex_buffer_object not found!\n");
      exit(0);
   }
   printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER));

   Have_ARB_vertex_array_object =
      glutExtensionSupported("GL_ARB_vertex_array_object");

   printf("Using GL_ARB_vertex_array_object: %s\n",
          (Have_ARB_vertex_array_object ? "yes" : "no"));


   /* Test buffer object deletion */
   if (1) {
      static GLubyte data[1000];
      GLuint id = 999;
      glBindBufferARB(GL_ARRAY_BUFFER_ARB, id);
      glBufferDataARB(GL_ARRAY_BUFFER_ARB, 1000, data, GL_STATIC_DRAW_ARB);
      glVertexPointer(3, GL_FLOAT, 0, (void *) 0);
      glDeleteBuffersARB(1, &id);
      assert(!glIsBufferARB(id));
      glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
      glVertexPointer(3, GL_FLOAT, 0, (void *) 0);
      assert(!glIsBufferARB(id));
   }

   memset(Objects, 0, sizeof(Objects));
   MakeObject1(Objects + 0);
   MakeObject2(Objects + 1);
   MakeObject3(Objects + 2);
   MakeObject4(Objects + 3);
   NumObjects = 4;
}


int main( int argc, char *argv[] )
{
   glutInit( &argc, argv );
   glutInitWindowPosition( 0, 0 );
   glutInitWindowSize( 600, 300 );
   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
   Win = glutCreateWindow(argv[0]);
   gladLoadGL();
   glutReshapeFunc( Reshape );
   glutKeyboardFunc( Key );
   glutSpecialFunc( SpecialKey );
   glutDisplayFunc( Display );
   if (Anim)
      glutIdleFunc(Idle);
   Init();
   glutMainLoop();
   return 0;
}