/**
 * \brief Solve an instance of the "Variable Placement with Separation
 * Constraints" problem.
 *
 * Authors:
 *   Tim Dwyer <tgdwyer@gmail.com>
 *
 * Copyright (C) 2005 Authors
 *
 * Released under GNU LGPL.  Read the file 'COPYING' for more information.
 */

#include <cassert>
#include "constraint.h"
#include "block.h"
#include "blocks.h"
#include "solve_VPSC.h"
#include <math.h>
#include <sstream>
#ifdef RECTANGLE_OVERLAP_LOGGING
#include <fstream>
#endif
#include <map>

using namespace std;

namespace vpsc {

static const double ZERO_UPPERBOUND=-0.0000001;

IncSolver::IncSolver(const unsigned n, Variable* const vs[], const unsigned m, Constraint *cs[])
  : Solver(n,vs,m,cs), splitCnt(0) {
  inactive.assign(cs,cs+m);

  for(ConstraintList::iterator i=inactive.begin(); i!=inactive.end(); ++i) {
    (*i)->active=false;
  }
}
Solver::Solver(const unsigned n, Variable* const vs[], const unsigned m, Constraint *cs[]) : m(m), cs(cs), n(n), vs(vs) {
  bs=new Blocks(n, vs);
#ifdef RECTANGLE_OVERLAP_LOGGING
  printBlocks();
  //assert(!constraintGraphIsCyclic(n,vs));
#endif
}
Solver::~Solver() {
  delete bs;
}

// useful in debugging
void Solver::printBlocks() {
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);

  for(set<Block*>::iterator i=bs->begin(); i!=bs->end(); ++i) {
    Block *b=*i;
    f<<"  "<<*b<<endl;
  }

  for(unsigned i=0; i<m; i++) {
    f<<"  "<<*cs[i]<<endl;
  }

#endif
}
/**
* Produces a feasible - though not necessarily optimal - solution by
* examining blocks in the partial order defined by the directed acyclic
* localGraph of constraints. For each block (when processing left to right) we
* maintain the invariant that all constraints to the left of the block
* (incoming constraints) are satisfied. This is done by repeatedly merging
* blocks into bigger blocks across violated constraints (most violated
* first) fixing the position of variables inside blocks relative to one
* another so that constraints internal to the block are satisfied.
*/
void Solver::satisfy() {
  list<Variable*> *vs=bs->totalOrder();

  for(list<Variable*>::iterator i=vs->begin(); i!=vs->end(); ++i) {
    Variable *v=*i;

    if(!v->block->deleted) {
      bs->mergeLeft(v->block);
    }
  }

  bs->cleanup();

  for(unsigned i=0; i<m; i++) {
    if(cs[i]->slack() < ZERO_UPPERBOUND) {
#ifdef RECTANGLE_OVERLAP_LOGGING
      ofstream f(LOGFILE,ios::app);
      f<<"Error: Unsatisfied constraint: "<<*cs[i]<<endl;
#endif
      //assert(cs[i]->slack()>-0.0000001);
      throw "Unsatisfied constraint";
    }
  }

  delete vs;
}

void Solver::refine() {
  bool solved=false;
  // Solve shouldn't loop indefinately
  // ... but just to make sure we limit the number of iterations
  unsigned maxtries=100;

  while(!solved&&maxtries>0) {
    solved=true;
    maxtries--;

    for(set<Block*>::const_iterator i=bs->begin(); i!=bs->end(); ++i) {
      Block *b=*i;
      b->setUpInConstraints();
      b->setUpOutConstraints();
    }

    for(set<Block*>::const_iterator i=bs->begin(); i!=bs->end(); ++i) {
      Block *b=*i;
      Constraint *c=b->findMinLM();

      if(c!=NULL && c->lm<0) {
#ifdef RECTANGLE_OVERLAP_LOGGING
        ofstream f(LOGFILE,ios::app);
        f<<"Split on constraint: "<<*c<<endl;
#endif
        // Split on c
        Block *l=NULL, *r=NULL;
        bs->split(b,l,r,c);
        bs->cleanup();
        // split alters the block set so we have to restart
        solved=false;
        break;
      }
    }
  }

  for(unsigned i=0; i<m; i++) {
    if(cs[i]->slack() < ZERO_UPPERBOUND) {
      assert(cs[i]->slack()>ZERO_UPPERBOUND);
      throw "Unsatisfied constraint";
    }
  }
}
/**
 * Calculate the optimal solution. After using satisfy() to produce a
 * feasible solution, refine() examines each block to see if further
 * refinement is possible by splitting the block. This is done repeatedly
 * until no further improvement is possible.
 */
void Solver::solve() {
  satisfy();
  refine();
}

void IncSolver::solve() {
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);
  f<<"solve_inc()..."<<endl;
#endif
  double lastcost,cost = bs->cost();

  do {
    lastcost=cost;
    satisfy();
    splitBlocks();
    cost = bs->cost();
#ifdef RECTANGLE_OVERLAP_LOGGING
    f<<"  cost="<<cost<<endl;
#endif
  }
  while(fabs(lastcost-cost)>0.0001);
}
/**
 * incremental version of satisfy that allows refinement after blocks are
 * moved.
 *
 *  - move blocks to new positions
 *  - repeatedly merge across most violated constraint until no more
 *    violated constraints exist
 *
 * Note: there is a special case to handle when the most violated constraint
 * is between two variables in the same block.  Then, we must split the block
 * over an active constraint between the two variables.  We choose the
 * constraint with the most negative lagrangian multiplier.
 */
void IncSolver::satisfy() {
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);
  f<<"satisfy_inc()..."<<endl;
#endif
  splitBlocks();
  long splitCtr = 0;
  Constraint* v = NULL;

  while((v=mostViolated(inactive))&&(v->equality || v->slack() < ZERO_UPPERBOUND)) {
    assert(!v->active);
    Block *lb = v->left->block, *rb = v->right->block;

    if(lb != rb) {
      lb->merge(rb,v);
    }
    else {
      if(lb->isActiveDirectedPathBetween(v->right,v->left)) {
        // cycle found, relax the violated, cyclic constraint
        v->gap = v->slack();
        continue;
      }

      if(splitCtr++>10000) {
        throw "Cycle Error!";
      }

      // constraint is within block, need to split first
      inactive.push_back(lb->splitBetween(v->left,v->right,lb,rb));
      lb->merge(rb,v);
      bs->insert(lb);
    }
  }

#ifdef RECTANGLE_OVERLAP_LOGGING
  f<<"  finished merges."<<endl;
#endif
  bs->cleanup();

  for(unsigned i=0; i<m; i++) {
    v=cs[i];

    if(v->slack() < ZERO_UPPERBOUND) {
      ostringstream s;
      s<<"Unsatisfied constraint: "<<*v;
#ifdef RECTANGLE_OVERLAP_LOGGING
      ofstream f(LOGFILE,ios::app);
      f<<s.str()<<endl;
#endif
      throw s.str().c_str();
    }
  }

#ifdef RECTANGLE_OVERLAP_LOGGING
  f<<"  finished cleanup."<<endl;
  printBlocks();
#endif
}
void IncSolver::moveBlocks() {
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);
  f<<"moveBlocks()..."<<endl;
#endif

  for(set<Block*>::const_iterator i(bs->begin()); i!=bs->end(); ++i) {
    Block *b = *i;
    b->wposn = b->desiredWeightedPosition();
    b->posn = b->wposn / b->weight;
  }

#ifdef RECTANGLE_OVERLAP_LOGGING
  f<<"  moved blocks."<<endl;
#endif
}
void IncSolver::splitBlocks() {
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);
#endif
  moveBlocks();
  splitCnt=0;

  // Split each block if necessary on min LM
  for(set<Block*>::const_iterator i(bs->begin()); i!=bs->end(); ++i) {
    Block* b = *i;
    Constraint* v=b->findMinLM();

    if(v!=NULL && v->lm < ZERO_UPPERBOUND) {
      assert(!v->equality);
#ifdef RECTANGLE_OVERLAP_LOGGING
      f<<"    found split point: "<<*v<<" lm="<<v->lm<<endl;
#endif
      splitCnt++;
      Block *b = v->left->block, *l=NULL, *r=NULL;
      assert(v->left->block == v->right->block);
      double pos = b->posn;
      b->split(l,r,v);
      l->posn=r->posn=pos;
      l->wposn = l->posn * l->weight;
      r->wposn = r->posn * r->weight;
      bs->insert(l);
      bs->insert(r);
      b->deleted=true;
      inactive.push_back(v);
#ifdef RECTANGLE_OVERLAP_LOGGING
      f<<"  new blocks: "<<*l<<" and "<<*r<<endl;
#endif
    }
  }

#ifdef RECTANGLE_OVERLAP_LOGGING
  f<<"  finished splits."<<endl;
#endif
  bs->cleanup();
}

/**
 * Scan constraint list for the most violated constraint, or the first equality
 * constraint
 */
Constraint* IncSolver::mostViolated(ConstraintList &l) {
  double minSlack = DBL_MAX;
  Constraint* v=NULL;
#ifdef RECTANGLE_OVERLAP_LOGGING
  ofstream f(LOGFILE,ios::app);
  f<<"Looking for most violated..."<<endl;
#endif
  ConstraintList::iterator end = l.end();
  ConstraintList::iterator deletePoint = end;

  for(ConstraintList::iterator i=l.begin(); i!=end; ++i) {
    Constraint *c=*i;
    double slack = c->slack();

    if(c->equality || slack < minSlack) {
      minSlack=slack;
      v=c;
      deletePoint=i;

      if(c->equality) break;
    }
  }

  // Because the constraint list is not order dependent we just
  // move the last element over the deletePoint and resize
  // downwards.  There is always at least 1 element in the
  // vector because of search.
  if(deletePoint != end && (minSlack<ZERO_UPPERBOUND||v->equality)) {
    *deletePoint = l[l.size()-1];
    l.resize(l.size()-1);
  }

#ifdef RECTANGLE_OVERLAP_LOGGING
  f<<"  most violated is: "<<*v<<endl;
#endif
  return v;
}

struct node {
  set<node*> in;
  set<node*> out;
};
// useful in debugging - cycles would be BAD
bool Solver::constraintGraphIsCyclic(const unsigned n, Variable* const vs[]) {
  map<Variable*, node*> varmap;
  vector<node*> localGraph;

  for(unsigned i=0; i<n; i++) {
    node *u=new node;
    localGraph.push_back(u);
    varmap[vs[i]]=u;
  }

  for(unsigned i=0; i<n; i++) {
    for(vector<Constraint*>::iterator c=vs[i]->in.begin(); c!=vs[i]->in.end(); ++c) {
      Variable *l=(*c)->left;
      varmap[vs[i]]->in.insert(varmap[l]);
    }

    for(vector<Constraint*>::iterator c=vs[i]->out.begin(); c!=vs[i]->out.end(); ++c) {
      Variable *r=(*c)->right;
      varmap[vs[i]]->out.insert(varmap[r]);
    }
  }

  while(!localGraph.empty()) {
    node *u=NULL;
    vector<node*>::iterator i=localGraph.begin();

    for(; i!=localGraph.end(); ++i) {
      u=*i;

      if(u->in.empty()) {
        break;
      }
    }

    if(i==localGraph.end() && !localGraph.empty()) {
      //cycle found!
      return true;
    }
    else {
      localGraph.erase(i);

      for(set<node*>::iterator j=u->out.begin(); j!=u->out.end(); ++j) {
        node *v=*j;
        v->in.erase(u);
      }

      delete u;
    }
  }

  for(unsigned i=0; i<localGraph.size(); ++i) {
    delete localGraph[i];
  }

  return false;
}

#ifndef NDEBUG
// useful in debugging - cycles would be BAD
bool Solver::blockGraphIsCyclic() {
  map<Block*, node*> bmap;
  vector<node*> localGraph;

  for(set<Block*>::const_iterator i=bs->begin(); i!=bs->end(); ++i) {
    Block *b=*i;
    node *u=new node;
    localGraph.push_back(u);
    bmap[b]=u;
  }

  for(set<Block*>::const_iterator i=bs->begin(); i!=bs->end(); ++i) {
    Block *b=*i;
    b->setUpInConstraints();
    Constraint *c=b->findMinInConstraint();

    while(c!=NULL) {
      Block *l=c->left->block;
      bmap[b]->in.insert(bmap[l]);
      b->deleteMinInConstraint();
      c=b->findMinInConstraint();
    }

    b->setUpOutConstraints();
    c=b->findMinOutConstraint();

    while(c!=NULL) {
      Block *r=c->right->block;
      bmap[b]->out.insert(bmap[r]);
      b->deleteMinOutConstraint();
      c=b->findMinOutConstraint();
    }
  }

  while(!localGraph.empty()) {
    node *u=NULL;
    vector<node*>::iterator i=localGraph.begin();

    for(; i!=localGraph.end(); ++i) {
      u=*i;

      if(u->in.empty()) {
        break;
      }
    }

    if(i==localGraph.end() && !localGraph.empty()) {
      //cycle found!
      return true;
    }
    else {
      localGraph.erase(i);

      for(set<node*>::iterator j=u->out.begin(); j!=u->out.end(); ++j) {
        node *v=*j;
        v->in.erase(u);
      }

      delete u;
    }
  }

  for(unsigned i=0; i<localGraph.size(); i++) {
    delete localGraph[i];
  }

  return false;
}
#endif
}