/**
 *  \file dihedrals.cpp   \brief Helpers to extract dihedral information.
 *
 *  Copyright 2007-2013 IMP Inventors. All rights reserved.
 *
 */

#include <IMP/atom/dihedrals.h>

IMPATOM_BEGIN_NAMESPACE

namespace {
  class DihedralAtom {
  public:
    enum WhichResidue { THIS, PREV, NEXT };
  private:
    WhichResidue residue_;
    AtomType type_;
  public:
    DihedralAtom(WhichResidue residue, AtomType type)
         : residue_(residue), type_(type) {}

    Atom get_atom(Residue rd) const {
      if (residue_ == PREV) {
        Hierarchy h = get_previous_residue(rd);
        if (h) {
          Residue r = h.get_as_residue();
          if (r) {
            return IMP::atom::get_atom(r, type_);
          }
        }
      } else if (residue_ == NEXT) {
        Hierarchy h = get_next_residue(rd);
        if (h) {
          Residue r = h.get_as_residue();
          if (r) {
            return IMP::atom::get_atom(r, type_);
          }
        }
      } else {
        return IMP::atom::get_atom(rd, type_);
      }
      return Atom();
    }
  };

  Atoms get_dihedral_atoms(Residue rd, const DihedralAtom *dihedral)
  {
    Atoms atoms;
    for (int i = 0; i < 4; ++i) {
      Atom a = dihedral[i].get_atom(rd);
      if (!a) {
        return Atoms();
      } else {
        atoms.push_back(a);
      }
    }
    return atoms;
  }
}

Atoms get_phi_dihedral_atoms(Residue rd)
{
  static DihedralAtom dihedral[4] = {
    DihedralAtom(DihedralAtom::PREV, AT_C),
    DihedralAtom(DihedralAtom::THIS, AT_N),
    DihedralAtom(DihedralAtom::THIS, AT_CA),
    DihedralAtom(DihedralAtom::THIS, AT_C)
  };
  return get_dihedral_atoms(rd, dihedral);
}

Atoms get_psi_dihedral_atoms(Residue rd)
{
  static DihedralAtom dihedral[4] = {
    DihedralAtom(DihedralAtom::THIS, AT_N),
    DihedralAtom(DihedralAtom::THIS, AT_CA),
    DihedralAtom(DihedralAtom::THIS, AT_C),
    DihedralAtom(DihedralAtom::NEXT, AT_N)
  };
  return get_dihedral_atoms(rd, dihedral);
}

IMPATOM_END_NAMESPACE