/*
 * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
/* Conversion to use vertex buffer objects by Michael J. Clark */

/* 
 * Port to Mendel Linux Wayland by Peter Nordström 1 June 2020 
 * 
 * Window handling and egl initialization done externally in
 * simple-egl.c
 */

#include <assert.h>
#include <GLES/gl.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

extern void HandleFrame(void);

#ifndef M_PI
#define M_PI 3.14159265
#endif

static GLfloat viewDist = 40.0;

typedef struct {
  GLfloat pos[3];
  GLfloat norm[3];
} vertex_t;

typedef struct {
  vertex_t *vertices;
  GLushort *indices;
  GLfloat color[4];
  int nvertices, nindices;
  GLuint ibo;
} gear_t;

static gear_t *red_gear;
static gear_t *green_gear;
static gear_t *blue_gear;

/**

  Draw a gear wheel.  You'll probably want to call this function when
  building a display list since we do a lot of trig here.

  Input:  inner_radius - radius of hole at center
          outer_radius - radius at center of teeth
          width - width of gear
          teeth - number of teeth
          tooth_depth - depth of tooth

 **/

static gear_t*
gear(GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
     GLint teeth, GLfloat tooth_depth, GLfloat color[])
{
  GLint i, j;
  GLfloat r0, r1, r2;
  GLfloat ta, da;
  GLfloat u1, v1, u2, v2, len;
  GLfloat cos_ta, cos_ta_1da, cos_ta_2da, cos_ta_3da, cos_ta_4da;
  GLfloat sin_ta, sin_ta_1da, sin_ta_2da, sin_ta_3da, sin_ta_4da;
  GLushort ix0, ix1, ix2, ix3, ix4, ix5;
  vertex_t *vt, *nm;
  GLushort *ix;

  gear_t *gear = calloc(1, sizeof(gear_t));
  gear->nvertices = teeth * 40;
  gear->nindices = teeth * 66 * 3;
  gear->vertices = calloc(gear->nvertices, sizeof(vertex_t));
  gear->indices = calloc(gear->nindices, sizeof(GLushort));
  memcpy(&gear->color[0], &color[0], sizeof(GLfloat) * 4);


  r0 = inner_radius;
  r1 = outer_radius - tooth_depth / 2.0;
  r2 = outer_radius + tooth_depth / 2.0;
  da = 2.0 * M_PI / teeth / 4.0;

  vt = gear->vertices;
  nm = gear->vertices;
  ix = gear->indices;

#define VERTEX(x,y,z) ((vt->pos[0] = x),(vt->pos[1] = y),(vt->pos[2] = z), \
                       (vt++ - gear->vertices))
#define NORMAL(x,y,z) ((nm->norm[0] = x),(nm->norm[1] = y),(nm->norm[2] = z), \
                       (nm++ - gear->vertices))
#define INDEX(a,b,c) ((*ix++ = a),(*ix++ = b),(*ix++ = c))

  for (i = 0; i < teeth; i++) {
    ta = i * 2.0 * M_PI / (teeth);

    cos_ta = cos(ta);
    cos_ta_1da = cos(ta + da);
    cos_ta_2da = cos(ta + 2 * da);
    cos_ta_3da = cos(ta + 3 * da);
    cos_ta_4da = cos(ta + 4 * da);
    sin_ta = sin(ta);
    sin_ta_1da = sin(ta + da);
    sin_ta_2da = sin(ta + 2 * da);
    sin_ta_3da = sin(ta + 3 * da);
    sin_ta_4da = sin(ta + 4 * da);

    u1 = r2 * cos_ta_1da - r1 * cos_ta;
    v1 = r2 * sin_ta_1da - r1 * sin_ta;
    len = sqrt(u1 * u1 + v1 * v1);
    u1 /= len;
    v1 /= len;
    u2 = r1 * cos_ta_3da - r2 * cos_ta_2da;
    v2 = r1 * sin_ta_3da - r2 * sin_ta_2da;

    /* front face */
    ix0 = VERTEX(r0 * cos_ta,          r0 * sin_ta,          width * 0.5);
    ix1 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          width * 0.5);
    ix2 = VERTEX(r0 * cos_ta_2da,      r0 * sin_ta_2da,      width * 0.5);
    ix3 = VERTEX(r1 * cos_ta_2da,      r1 * sin_ta_2da,      width * 0.5);
    ix4 = VERTEX(r0 * cos_ta_4da,      r0 * sin_ta_4da,      width * 0.5);
    ix5 = VERTEX(r1 * cos_ta_4da,      r1 * sin_ta_4da,      width * 0.5);
    for (j = 0; j < 6; j++) {
      NORMAL(0.0,                  0.0,                  1.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
    INDEX(ix2, ix3, ix4);
    INDEX(ix3, ix5, ix4);

    /* front sides of teeth */
    ix0 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          width * 0.5);
    ix1 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      width * 0.5);
    ix2 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      width * 0.5);
    ix3 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(0.0,                  0.0,                  1.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);

    /* back face */
    ix0 = VERTEX(r0 * cos_ta,          r0 * sin_ta,          -width * 0.5);
    ix1 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          -width * 0.5);
    ix2 = VERTEX(r0 * cos_ta_2da,      r0 * sin_ta_2da,      -width * 0.5);
    ix3 = VERTEX(r1 * cos_ta_2da,      r1 * sin_ta_2da,      -width * 0.5);
    ix4 = VERTEX(r0 * cos_ta_4da,      r0 * sin_ta_4da,      -width * 0.5);
    ix5 = VERTEX(r1 * cos_ta_4da,      r1 * sin_ta_4da,      -width * 0.5);
    for (j = 0; j < 6; j++) {
      NORMAL(0.0,                  0.0,                  -1.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
    INDEX(ix2, ix3, ix4);
    INDEX(ix3, ix5, ix4);

    /* back sides of teeth */
    ix0 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      -width * 0.5);
    ix1 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      -width * 0.5);
    ix2 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          -width * 0.5);
    ix3 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      -width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(0.0,                  0.0,                  -1.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);

    /* draw outward faces of teeth */
    ix0 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          width * 0.5);
    ix1 = VERTEX(r1 * cos_ta,          r1 * sin_ta,          -width * 0.5);
    ix2 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      width * 0.5);
    ix3 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      -width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(v1,                   -u1,                  0.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
    ix0 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      width * 0.5);
    ix1 = VERTEX(r2 * cos_ta_1da,      r2 * sin_ta_1da,      -width * 0.5);
    ix2 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      width * 0.5);
    ix3 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      -width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(cos_ta,               sin_ta,               0.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
    ix0 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      width * 0.5);
    ix1 = VERTEX(r2 * cos_ta_2da,      r2 * sin_ta_2da,      -width * 0.5);
    ix2 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      width * 0.5);
    ix3 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      -width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(v2,                   -u2,                  0.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
    ix0 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      width * 0.5);
    ix1 = VERTEX(r1 * cos_ta_3da,      r1 * sin_ta_3da,      -width * 0.5);
    ix2 = VERTEX(r1 * cos_ta_4da,      r1 * sin_ta_4da,      width * 0.5);
    ix3 = VERTEX(r1 * cos_ta_4da,      r1 * sin_ta_4da,      -width * 0.5);
    for (j = 0; j < 4; j++) {
      NORMAL(cos_ta,               sin_ta,               0.0);
    }
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);

    /* draw inside radius cylinder */
    ix0 = VERTEX(r0 * cos_ta,          r0 * sin_ta,          -width * 0.5);
    ix1 = VERTEX(r0 * cos_ta,          r0 * sin_ta,          width * 0.5);
    ix2 = VERTEX(r0 * cos_ta_4da,      r0 * sin_ta_4da,      -width * 0.5);
    ix3 = VERTEX(r0 * cos_ta_4da,      r0 * sin_ta_4da,      width * 0.5);
    NORMAL(-cos_ta,              -sin_ta,              0.0);
    NORMAL(-cos_ta,              -sin_ta,              0.0);
    NORMAL(-cos_ta_4da,          -sin_ta_4da,          0.0);
    NORMAL(-cos_ta_4da,          -sin_ta_4da,          0.0);
    INDEX(ix0, ix1, ix2);
    INDEX(ix1, ix3, ix2);
  }

  return gear;
}


void draw_gear(gear_t* gear) {
  glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, gear->color);
  glVertexPointer(3, GL_FLOAT, sizeof(vertex_t), gear->vertices[0].pos);
  glNormalPointer(GL_FLOAT, sizeof(vertex_t), gear->vertices[0].norm);
  glDrawElements(GL_TRIANGLES, gear->nindices/3, GL_UNSIGNED_SHORT,
                 gear->indices);
}

static GLfloat view_rotx = 20.0, view_roty = 30.0, view_rotz = 0.0;
static gear_t *gear1, *gear2, *gear3;
static GLfloat angle = 0.0;

static void
draw(void)
{
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glPushMatrix();

  glTranslatef(0.0, 0.0, -viewDist);

  glRotatef(view_rotx, 1.0, 0.0, 0.0);
  glRotatef(view_roty, 0.0, 1.0, 0.0);
  glRotatef(view_rotz, 0.0, 0.0, 1.0);

  glPushMatrix();
  glTranslatef(-3.0, -2.0, 0.0);
  glRotatef(angle, 0.0, 0.0, 1.0);
  draw_gear(gear1);
  glPopMatrix();

  glPushMatrix();
  glTranslatef(3.1, -2.0, 0.0);
  glRotatef(-2.0 * angle - 9.0, 0.0, 0.0, 1.0);
  draw_gear(gear2);
  glPopMatrix();

  glPushMatrix();
  glTranslatef(-3.1, 4.2, 0.0);
  glRotatef(-2.0 * angle - 25.0, 0.0, 0.0, 1.0);
  draw_gear(gear3);
  glPopMatrix();

  glPopMatrix();
}

/* new window size or exposure */
static void
reshape(int width, int height)
{
  GLfloat h = (GLfloat) height / (GLfloat) width;

  glViewport(0, 0, (GLint) width, (GLint) height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glFrustumf(-1.0, 1.0, -h, h, 5.0, 200.0);
  glMatrixMode(GL_MODELVIEW);
}

void initialize() {
  glShadeModel(GL_SMOOTH);
  glEnableClientState(GL_NORMAL_ARRAY);
  glEnableClientState(GL_VERTEX_ARRAY);

  static GLfloat pos[4] = {5.0, 5.0, 10.0, 0.0};
  static GLfloat red[4] = {0.8, 0.1, 0.0, 1.0};
  static GLfloat green[4] = {0.0, 0.8, 0.2, 1.0};
  static GLfloat blue[4] = {0.2, 0.2, 1.0, 1.0};

  glLightfv(GL_LIGHT0, GL_POSITION, pos);
  glEnable(GL_CULL_FACE);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_DEPTH_TEST);

  /* make the gears */
  gear1 = gear(1.0, 4.0, 1.0, 20, 0.7, red);
  gear2 = gear(0.5, 2.0, 2.0, 10, 0.7, green);
  gear3 = gear(1.3, 2.0, 0.5, 10, 0.7, blue);
}

void RunGears() {
  double dt = 0.01666;

  initialize();
  reshape(600, 600);

  while (1) {
    dt = 0.01666;

    /* advance rotation for next frame */
    angle += 70.0 * dt;  /* 70 degrees per second */
    if (angle > 3600.0)
      angle -= 3600.0;

    draw();
    HandleFrame();
  }
}