/**
 *  \file charmm_helpers.h
 *  \brief Helpers for the CHARMM forcefield support.
 *
 *  Copyright 2007-2010 IMP Inventors. All rights reserved.
 *
 */

#ifndef IMPATOM_INTERNAL_CHARMM_HELPERS_H
#define IMPATOM_INTERNAL_CHARMM_HELPERS_H

#include "../atom_config.h"

#include <IMP/base_types.h>

IMPATOM_BEGIN_INTERNAL_NAMESPACE

class CHARMMBondNames
{
  std::string a_, b_;
public:
  CHARMMBondNames(std::string a, std::string b) : a_(a), b_(b) {
    // store atom type names sorted so AB == BA
    if (a_ > b_) {
      std::swap(a_, b_);
    }
  }
  inline bool operator==(const CHARMMBondNames &other) const {
    return a_ == other.a_ && b_ == other.b_;
  }
  inline bool operator<(const CHARMMBondNames &other) const {
    return a_ + b_ < other.a_ + other.b_;
  }
};

class CHARMMAngleNames
{
  std::string a_, b_, c_;
public:
  CHARMMAngleNames(std::string a, std::string b, std::string c)
           : a_(a), b_(b), c_(c) {
    // store atom type names sorted so ABC == CBA (but not other permutations)
    if (a_ > c_) {
      std::swap(a_, c_);
    }
  }
  inline bool operator==(const CHARMMAngleNames &other) const {
    return a_ == other.a_ && b_ == other.b_ && c_ == other.c_;
  }
  inline bool operator<(const CHARMMAngleNames &other) const {
    return a_ + b_ + c_ < other.a_ + other.b_ + other.c_;
  }
};

class CHARMMDihedralNames
{
  std::string a_, b_, c_, d_;

  static inline int match(std::string ref, std::string cmp,
                          bool allow_wildcards) {
    if (ref == cmp) {
      return 0;
    } else if (ref == "X" && allow_wildcards) {
      return 1;
    } else {
      return MISMATCH;
    }
  }

public:
  const static int MISMATCH = 100;
  CHARMMDihedralNames(std::string a, std::string b, std::string c,
                      std::string d) : a_(a), b_(b), c_(c), d_(d) {}

  inline int match(const CHARMMDihedralNames &other,
                   bool allow_wildcards) const {
    int n_match = match(a_, other.a_, allow_wildcards)
                  + match(b_, other.b_, allow_wildcards)
                  + match(c_, other.c_, allow_wildcards)
                  + match(d_, other.d_, allow_wildcards);
    int n_match_rev = match(a_, other.d_, allow_wildcards)
                      + match(b_, other.c_, allow_wildcards)
                      + match(c_, other.b_, allow_wildcards)
                      + match(d_, other.a_, allow_wildcards);
    return std::min(n_match, n_match_rev);
  }
};

IMPATOM_END_INTERNAL_NAMESPACE

#endif  /* IMPATOM_INTERNAL_CHARMM_HELPERS_H */