#ifndef _INSIDE_H_
#define _INSIDE_H_

#include <vector>
#include <algorithm>
#include "hg.h"

// semiring for Inside/Outside
struct Boolean {
  bool x;
  Boolean() : x() {  }
  Boolean(bool i) : x(i) {  }
  operator bool() const { return x; }
  // normally you'd use the logical (short circuit) || &&  operators, but bool really is guaranteed to be 0 or 1 numerically.
  void operator+=(Boolean o) { x|=o.x; }
  friend inline Boolean operator +(Boolean a,Boolean b) {
    return Boolean(a.x|b.x);
  }
  void operator*=(Boolean o) { x&=o.x; }
  friend inline Boolean operator *(Boolean a,Boolean b) {
    return Boolean(a.x&b.x);
  }
};

// run the inside algorithm and return the inside score
// if result is non-NULL, result will contain the inside
// score for each node
// NOTE: WeightType()  must construct the semiring's additive identity
//       WeightType(1) must construct the semiring's multiplicative identity
template<typename WeightType, typename WeightFunction>
WeightType Inside(const Hypergraph& hg,
                  std::vector<WeightType>* result = NULL,
                  const WeightFunction& weight = WeightFunction()) {
  const int num_nodes = hg.nodes_.size();
  std::vector<WeightType> dummy;
  std::vector<WeightType>& inside_score = result ? *result : dummy;
  inside_score.resize(num_nodes);
  std::fill(inside_score.begin(), inside_score.end(), WeightType());
  for (int i = 0; i < num_nodes; ++i) {
    const Hypergraph::Node& cur_node = hg.nodes_[i];
    WeightType* const cur_node_inside_score = &inside_score[i];
    const int num_in_edges = cur_node.in_edges_.size();
    if (num_in_edges == 0) {
      *cur_node_inside_score = WeightType(1);
      continue;
    }
    for (int j = 0; j < num_in_edges; ++j) {
      const Hypergraph::Edge& edge = hg.edges_[cur_node.in_edges_[j]];
      WeightType score = weight(edge);
      for (int k = 0; k < edge.tail_nodes_.size(); ++k) {
        const int tail_node_index = edge.tail_nodes_[k];
        score *= inside_score[tail_node_index];
      }
      *cur_node_inside_score += score;
    }
  }
  return inside_score.back();
}

template<typename WeightType, typename WeightFunction>
void Outside(const Hypergraph& hg,
             std::vector<WeightType>& inside_score,
             std::vector<WeightType>* result,
             const WeightFunction& weight = WeightFunction()) {
  assert(result);
  const int num_nodes = hg.nodes_.size();
  assert(inside_score.size() == num_nodes);
  std::vector<WeightType>& outside_score = *result;
  outside_score.resize(num_nodes);
  std::fill(outside_score.begin(), outside_score.end(), WeightType());
  outside_score.back() = WeightType(1);
  for (int i = num_nodes - 1; i >= 0; --i) {
    const Hypergraph::Node& cur_node = hg.nodes_[i];
    const WeightType& head_node_outside_score = outside_score[i];
    const int num_in_edges = cur_node.in_edges_.size();
    for (int j = 0; j < num_in_edges; ++j) {
      const Hypergraph::Edge& edge = hg.edges_[cur_node.in_edges_[j]];
      WeightType head_and_edge_weight = weight(edge);
      head_and_edge_weight *= head_node_outside_score;
      const int num_tail_nodes = edge.tail_nodes_.size();
      for (int k = 0; k < num_tail_nodes; ++k) {
        const int update_tail_node_index = edge.tail_nodes_[k];
        WeightType* const tail_outside_score = &outside_score[update_tail_node_index];
        WeightType inside_contribution = WeightType(1);
        for (int l = 0; l < num_tail_nodes; ++l) {
          const int other_tail_node_index = edge.tail_nodes_[l];
          if (update_tail_node_index != other_tail_node_index)
            inside_contribution *= inside_score[other_tail_node_index];
        }
        inside_contribution *= head_and_edge_weight;
        *tail_outside_score += inside_contribution;
      }
    }
  }
}

// this is the Inside-Outside optimization described in Li and Eisner (EMNLP 2009)
// for computing the inside algorithm over expensive semirings
// (such as expectations over features).  See Figure 4.
// NOTE: XType * KType must be valid (and yield XType)
// NOTE: This may do things slightly differently than you are used to, please
// read the description in Li and Eisner (2009) carefully!
template<typename KType, typename KWeightFunction, typename XType, typename XWeightFunction>
KType InsideOutside(const Hypergraph& hg,
                    XType* result_x,
                    const KWeightFunction& kwf = KWeightFunction(),
                    const XWeightFunction& xwf = XWeightFunction()) {
  const int num_nodes = hg.nodes_.size();
  std::vector<KType> inside, outside;
  const KType k = Inside<KType,KWeightFunction>(hg, &inside, kwf);
  Outside<KType,KWeightFunction>(hg, inside, &outside, kwf);
  XType& x = *result_x;
  x = XType();      // default constructor is semiring 0
  for (int i = 0; i < num_nodes; ++i) {
    const Hypergraph::Node& cur_node = hg.nodes_[i];
    const int num_in_edges = cur_node.in_edges_.size();
    for (int j = 0; j < num_in_edges; ++j) {
      const Hypergraph::Edge& edge = hg.edges_[cur_node.in_edges_[j]];
      KType kbar_e = outside[i];
      const int num_tail_nodes = edge.tail_nodes_.size();
      for (int k = 0; k < num_tail_nodes; ++k)
        kbar_e *= inside[edge.tail_nodes_[k]];
      x += xwf(edge) * kbar_e;
    }
  }
  return k;
}

#endif