#include "model_generator.h"

#include "rbdl/rbdl.h"

using namespace RigidBodyDynamics;
using namespace RigidBodyDynamics::Math;

void generate_planar_tree_recursive (Model *model,
    unsigned int parent_body_id,
    int depth,
    double length) {
  if (depth == 0)
    return;

  // create left child
  Joint joint_rot_z (JointTypeRevolute, Vector3d (0., 0., 1.));
  Body body (length, Vector3d (0., -0.25 * length, 0.), Vector3d (length, length, length));

  Vector3d displacement (-0.5 * length, -0.25 * length, 0.);
  unsigned int child_left = model->AddBody (parent_body_id, Xtrans (displacement), joint_rot_z, body);

  generate_planar_tree_recursive (model,
      child_left,
      depth - 1,
      length * 0.4);

  displacement.set (0.5 * length, -0.25 * length, 0.);
  unsigned int child_right = model->AddBody (parent_body_id, Xtrans (displacement), joint_rot_z, body);

  generate_planar_tree_recursive (model,
      child_right,
      depth - 1,
      length * 0.4);
}

void generate_planar_tree (Model *model, int depth) {
  // we first add a single body that is hanging straight down from 
  // (0, 0, 0). After that we generate the tree recursively such that each
  // call adds two children.
  //
  double length = 1.;

  Joint joint_rot_z (JointTypeRevolute, Vector3d (0., 0., 1.));
  Body body (length, Vector3d (0., -0.25 * length, 0.), Vector3d (length, length, length));

  unsigned int base_child = model->AddBody (0, Xtrans (Vector3d (0., 0., 0.)), joint_rot_z, body);

  generate_planar_tree_recursive (
      model,
      base_child,
      depth,
      length * 0.4);
}