// Support functions used by Jax.Mesh

Jax.Mesh.prototype.eachTriangle = function(callback) {
  var mesh = this;
  var vertcount, a;
  
  var indices = mesh.getIndexBuffer(), vertices = mesh.vertices;
  if (vertices.length == 0) return;
  
  if (indices) {
    if (indices.length == 0) return;
    indices = indices.getTypedArray();
    vertcount = indices.length;
  } else
    vertcount = vertices.length;
    
  function call(i1, i2, i3) {
    var v1, v2, v3, i = false;
    
    if (indices) {
      i = true;
      v1 = vertices[indices[i1]];
      v2 = vertices[indices[i2]];
      v3 = vertices[indices[i3]];
    } else {
      i = false;
      v1 = vertices[i1];
      v2 = vertices[i2];
      v3 = vertices[i3];
    }
      
    if (!v1 || !v2 || !v3) return;
    callback(v1.array, v2.array, v3.array);
  }
  
  switch(mesh.draw_mode) {
    case GL_TRIANGLE_STRIP:
      for (a = 2; a < vertcount; a += 2) {
        call(a-2, a-1, a);
        call(a, a-1, a+1);
      }
      break;
    case GL_TRIANGLES:
      for (a = 0; a < vertcount; a += 3)
        call(a, a+1, a+2);
      break;
    case GL_TRIANGLE_FAN:
      for (a = 2; a < vertcount; a++)
        call(0, a-1, a);
      break;
    default:
      return;
  }
};

Jax.Mesh.prototype.buildTriangles = function() {
  var mesh = this;
  mesh.triangles.clear();
  
  mesh.eachTriangle(function(v1, v2, v3) {
    var tri = new Jax.Geometry.Triangle();
    tri.assign(v1, v2, v3);
    mesh.triangles.push(tri);
  });
};

Jax.Mesh.prototype.calculateBounds = function(vertices) {
  var self = this;
  if (vertices.length == 0) {
    self.bounds.left = self.bounds.right = 0;
    self.bounds.top = self.bounds.bottom = 0;
    self.bounds.front = self.bounds.back = 0;
    self.bounds.width = self.bounds.height = self.bounds.depth = 0;
  } else {
    self.bounds.left = self.bounds.right = null;
    self.bounds.top = self.bounds.bottom = null;
    self.bounds.front = self.bounds.back = null;
    self.bounds.width = self.bounds.height = self.bounds.depth = null;
  }

  var i, v;
  
  for (i = 0; i < vertices.length; i++)
  {
    // x, i % 3 == 0
    v = vertices[i];
    if (self.bounds.left  == null || v < self.bounds.left)   self.bounds.left   = v;
    if (self.bounds.right == null || v > self.bounds.right)  self.bounds.right  = v;
    
    // y, i % 3 == 1
    v = vertices[++i];
    if (self.bounds.bottom== null || v < self.bounds.bottom) self.bounds.bottom = v;
    if (self.bounds.top   == null || v > self.bounds.top)    self.bounds.top    = v;
    
    // z, i % 3 == 2
    v = vertices[++i];
    if (self.bounds.front == null || v > self.bounds.front)  self.bounds.front  = v;
    if (self.bounds.back  == null || v < self.bounds.back)   self.bounds.back   = v;
  }
  
  self.bounds.width = self.bounds.right - self.bounds.left;
  self.bounds.height= self.bounds.top   - self.bounds.bottom;
  self.bounds.depth = self.bounds.front - self.bounds.back;
};