/******************************************************************************
 * Top contributors (to current version):
 *   Dejan Jovanovic, Clark Barrett, Morgan Deters
 *
 * This file is part of the cvc5 project.
 *
 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
 * in the top-level source directory and their institutional affiliations.
 * All rights reserved.  See the file COPYING in the top-level source
 * directory for licensing information.
 * ****************************************************************************
 *
 * A substitution mapping for theory simplification.
 */

#include "theory/substitutions.h"
#include "expr/node_algorithm.h"
#include "theory/rewriter.h"

using namespace std;

namespace cvc5 {
namespace theory {

SubstitutionMap::SubstitutionMap(context::Context* context)
    : d_context(),
      d_substitutions(context ? context : &d_context),
      d_substitutionCache(),
      d_cacheInvalidated(false),
      d_cacheInvalidator(context ? context : &d_context, d_cacheInvalidated)
{
}

struct substitution_stack_element {
  TNode d_node;
  bool d_children_added;
  substitution_stack_element(TNode node) : d_node(node), d_children_added(false)
  {
  }
};/* struct substitution_stack_element */

Node SubstitutionMap::internalSubstitute(TNode t, NodeCache& cache) {

  Debug("substitution::internal") << "SubstitutionMap::internalSubstitute(" << t << ")" << endl;

  if (d_substitutions.empty()) {
    return t;
  }

  // Do a topological sort of the subexpressions and substitute them
  vector<substitution_stack_element> toVisit;
  toVisit.push_back((TNode) t);

  while (!toVisit.empty())
  {
    // The current node we are processing
    substitution_stack_element& stackHead = toVisit.back();
    TNode current = stackHead.d_node;

    Debug("substitution::internal") << "SubstitutionMap::internalSubstitute(" << t << "): processing " << current << endl;

    // If node already in the cache we're done, pop from the stack
    NodeCache::iterator find = cache.find(current);
    if (find != cache.end()) {
      toVisit.pop_back();
      continue;
    }

    NodeMap::iterator find2 = d_substitutions.find(current);
    if (find2 != d_substitutions.end()) {
      Node rhs = (*find2).second;
      Assert(rhs != current);
      internalSubstitute(rhs, cache);
      d_substitutions[current] = cache[rhs];
      cache[current] = cache[rhs];
      toVisit.pop_back();
      continue;
    }

    // Not yet substituted, so process
    if (stackHead.d_children_added)
    {
      // Children have been processed, so substitute
      NodeBuilder builder(current.getKind());
      if (current.getMetaKind() == kind::metakind::PARAMETERIZED) {
        builder << Node(cache[current.getOperator()]);
      }
      for (unsigned i = 0; i < current.getNumChildren(); ++ i) {
        Assert(cache.find(current[i]) != cache.end());
        builder << Node(cache[current[i]]);
      }
      // Mark the substitution and continue
      Node result = builder;
      if (result != current) {
        find = cache.find(result);
        if (find != cache.end()) {
          result = find->second;
        }
        else {
          find2 = d_substitutions.find(result);
          if (find2 != d_substitutions.end()) {
            Node rhs = (*find2).second;
            Assert(rhs != result);
            internalSubstitute(rhs, cache);
            d_substitutions[result] = cache[rhs];
            cache[result] = cache[rhs];
            result = cache[rhs];
          }
        }
      }
      Debug("substitution::internal") << "SubstitutionMap::internalSubstitute(" << t << "): setting " << current << " -> " << result << endl;
      cache[current] = result;
      toVisit.pop_back();
    }
    else
    {
      // Mark that we have added the children if any
      if (current.getNumChildren() > 0 || current.getMetaKind() == kind::metakind::PARAMETERIZED) {
        stackHead.d_children_added = true;
        // We need to add the operator, if any
        if(current.getMetaKind() == kind::metakind::PARAMETERIZED) {
          TNode opNode = current.getOperator();
          NodeCache::iterator opFind = cache.find(opNode);
          if (opFind == cache.end()) {
            toVisit.push_back(opNode);
          }
        }
        // We need to add the children
        for(TNode::iterator child_it = current.begin(); child_it != current.end(); ++ child_it) {
          TNode childNode = *child_it;
          NodeCache::iterator childFind = cache.find(childNode);
          if (childFind == cache.end()) {
            toVisit.push_back(childNode);
          }
        }
      } else {
        // No children, so we're done
        Debug("substitution::internal") << "SubstitutionMap::internalSubstitute(" << t << "): setting " << current << " -> " << current << endl;
        cache[current] = current;
        toVisit.pop_back();
      }
    }
  }

  // Return the substituted version
  return cache[t];
}/* SubstitutionMap::internalSubstitute() */


void SubstitutionMap::addSubstitution(TNode x, TNode t, bool invalidateCache)
{
  Debug("substitution") << "SubstitutionMap::addSubstitution(" << x << ", " << t << ")" << endl;
  Assert(d_substitutions.find(x) == d_substitutions.end());

  // this causes a later assert-fail (the rhs != current one, above) anyway
  // putting it here is easier to diagnose
  Assert(x != t) << "cannot substitute a term for itself";

  d_substitutions[x] = t;

  // Also invalidate the cache if necessary
  if (invalidateCache) {
    d_cacheInvalidated = true;
  }
  else {
    d_substitutionCache[x] = d_substitutions[x];
  }
}


void SubstitutionMap::addSubstitutions(SubstitutionMap& subMap, bool invalidateCache)
{
  SubstitutionMap::NodeMap::const_iterator it = subMap.begin();
  SubstitutionMap::NodeMap::const_iterator it_end = subMap.end();
  for (; it != it_end; ++ it) {
    Assert(d_substitutions.find((*it).first) == d_substitutions.end());
    d_substitutions[(*it).first] = (*it).second;
    if (!invalidateCache) {
      d_substitutionCache[(*it).first] = d_substitutions[(*it).first];
    }
  }
  if (invalidateCache) {
    d_cacheInvalidated = true;
  }
}

Node SubstitutionMap::apply(TNode t, bool doRewrite) {

  Debug("substitution") << "SubstitutionMap::apply(" << t << ")" << endl;

  // Setup the cache
  if (d_cacheInvalidated) {
    d_substitutionCache.clear();
    d_cacheInvalidated = false;
    Debug("substitution") << "-- reset the cache" << endl;
  }

  // Perform the substitution
  Node result = internalSubstitute(t, d_substitutionCache);
  Debug("substitution") << "SubstitutionMap::apply(" << t << ") => " << result << endl;

  if (doRewrite)
  {
    result = Rewriter::rewrite(result);
  }

  return result;
}

void SubstitutionMap::print(ostream& out) const {
  NodeMap::const_iterator it = d_substitutions.begin();
  NodeMap::const_iterator it_end = d_substitutions.end();
  for (; it != it_end; ++ it) {
    out << (*it).first << " -> " << (*it).second << endl;
  }
}

void SubstitutionMap::debugPrint() const { print(CVC5Message.getStream()); }

}  // namespace theory

std::ostream& operator<<(std::ostream& out, const theory::SubstitutionMap::iterator& i) {
  return out << "[CDMap-iterator]";
}

}  // namespace cvc5