/**
 * \brief A block is a group of variables that must be moved together to improve
 * the goal function without violating already active constraints.
 * The variables in a block are spanned by a tree of active constraints.
 *
 * Authors:
 *   Tim Dwyer <tgdwyer@gmail.com>
 *
 * Copyright (C) 2005 Authors
 *
 * Released under GNU LGPL.  Read the file 'COPYING' for more information.
 */
#include <cassert>
#include "pairingheap/PairingHeap.h"
#include "constraint.h"
#include "block.h"
#include "blocks.h"
#ifdef RECTANGLE_OVERLAP_LOGGING
#include <fstream>
using std::ios;
using std::ofstream;
using std::endl;
#endif
using std::vector;

namespace vpsc {
void Block::addVariable(Variable* const v) {
	v->block=this;
	vars->push_back(v);
	weight+=v->weight;
	wposn += v->weight * (v->desiredPosition - v->offset);
	posn=wposn/weight;
}
Block::Block(Variable* const v) {
	timeStamp=0;
	posn=weight=wposn=0;
	in=NULL;
	out=NULL;
	deleted=false;
	vars=new vector<Variable*>;
	if(v!=NULL) {
		v->offset=0;
		addVariable(v);
	}
}

double Block::desiredWeightedPosition() {
	double wp = 0;
	for (Vit v=vars->begin();v!=vars->end();++v) {
		wp += ((*v)->desiredPosition - (*v)->offset) * (*v)->weight;
	}
	return wp;
}
Block::~Block(void)
{
	delete vars;
	delete in;
	delete out;
}
void Block::setUpInConstraints() {
	setUpConstraintHeap(in,true);
}
void Block::setUpOutConstraints() {
	setUpConstraintHeap(out,false);
}
void Block::setUpConstraintHeap(PairingHeap<Constraint*>* &h,bool in) {
	delete h;
	h = new PairingHeap<Constraint*>(&compareConstraints);
	for (Vit i=vars->begin();i!=vars->end();++i) {
		Variable *v=*i;
		vector<Constraint*> *cs=in?&(v->in):&(v->out);
		for (Cit j=cs->begin();j!=cs->end();++j) {
			Constraint *c=*j;
			c->timeStamp=blockTimeCtr;
			if ((c->left->block != this && in) || (c->right->block != this && !in)) {
				h->insert(c);
			}
		}
	}
}	
void Block::merge(Block* b, Constraint* c) {
#ifdef RECTANGLE_OVERLAP_LOGGING
	ofstream f(LOGFILE,ios::app);
	f<<"  merging on: "<<*c<<",c->left->offset="<<c->left->offset<<",c->right->offset="<<c->right->offset<<endl;
#endif
	double dist = c->right->offset - c->left->offset - c->gap;
	Block *l=c->left->block;
	Block *r=c->right->block;
	if (vars->size() < b->vars->size()) {
		r->merge(l,c,dist);
	} else {
	       	l->merge(r,c,-dist);
	}
#ifdef RECTANGLE_OVERLAP_LOGGING
	f<<"  merged block="<<(b->deleted?*this:*b)<<endl;
#endif
}
/**
 * Merges b into this block across c.  Can be either a
 * right merge or a left merge
 * @param b block to merge into this
 * @param c constraint being merged
 * @param distance separation required to satisfy c
 */
void Block::merge(Block *b, Constraint *c, double dist) {
#ifdef RECTANGLE_OVERLAP_LOGGING
	ofstream f(LOGFILE,ios::app);
	f<<"    merging: "<<*b<<"dist="<<dist<<endl;
#endif
	c->active=true;
	wposn+=b->wposn-dist*b->weight;
	weight+=b->weight;
	posn=wposn/weight;
	for(Vit i=b->vars->begin();i!=b->vars->end();++i) {
		Variable *v=*i;
		v->block=this;
		v->offset+=dist;
		vars->push_back(v);
	}
	b->deleted=true;
}

void Block::mergeIn(Block *b) {
#ifdef RECTANGLE_OVERLAP_LOGGING
	ofstream f(LOGFILE,ios::app);
	f<<"  merging constraint heaps... "<<endl;
#endif
	// We check the top of the heaps to remove possible internal constraints
	findMinInConstraint();
	b->findMinInConstraint();
	in->merge(b->in);
#ifdef RECTANGLE_OVERLAP_LOGGING
	f<<"  merged heap: "<<*in<<endl;
#endif
}
void Block::mergeOut(Block *b) {	
	findMinOutConstraint();
	b->findMinOutConstraint();
	out->merge(b->out);
}
Constraint *Block::findMinInConstraint() {
	Constraint *v = NULL;
	vector<Constraint*> outOfDate;
	while (!in->isEmpty()) {
		v = in->findMin();
		Block *lb=v->left->block;
		Block *rb=v->right->block;
		// rb may not be this if called between merge and mergeIn
#ifdef RECTANGLE_OVERLAP_LOGGING
		ofstream f(LOGFILE,ios::app);
		f<<"  checking constraint ... "<<*v;
		f<<"    timestamps: left="<<lb->timeStamp<<" right="<<rb->timeStamp<<" constraint="<<v->timeStamp<<endl;
#endif
		if(lb == rb) {
			// constraint has been merged into the same block
#ifdef RECTANGLE_OVERLAP_LOGGING
			if(v->slack()<0) {
				f<<"  violated internal constraint found! "<<*v<<endl;
				f<<"     lb="<<*lb<<endl;
				f<<"     rb="<<*rb<<endl;
			}
#endif
			in->deleteMin();
#ifdef RECTANGLE_OVERLAP_LOGGING
			f<<" ... skipping internal constraint"<<endl;
#endif
		} else if(v->timeStamp < lb->timeStamp) {
			// block at other end of constraint has been moved since this
			in->deleteMin();
			outOfDate.push_back(v);
#ifdef RECTANGLE_OVERLAP_LOGGING
			f<<"    reinserting out of date (reinsert later)"<<endl;
#endif
		} else {
			break;
		}
	}
	for(Cit i=outOfDate.begin();i!=outOfDate.end();++i) {
		v=*i;
		v->timeStamp=blockTimeCtr;
		in->insert(v);
	}
	if(in->isEmpty()) {
		v=NULL;
	} else {
		v=in->findMin();
	}
	return v;
}
Constraint *Block::findMinOutConstraint() {
	if(out->isEmpty()) return NULL;
	Constraint *v = out->findMin();
	while (v->left->block == v->right->block) {
		out->deleteMin();
		if(out->isEmpty()) return NULL;
		v = out->findMin();
	}
	return v;
}
void Block::deleteMinInConstraint() {
	in->deleteMin();
#ifdef RECTANGLE_OVERLAP_LOGGING
	ofstream f(LOGFILE,ios::app);
	f<<"deleteMinInConstraint... "<<endl;
	f<<"  result: "<<*in<<endl;
#endif
}
void Block::deleteMinOutConstraint() {
	out->deleteMin();
}
inline bool Block::canFollowLeft(Constraint *c, const Variable* const last) {
	return c->left->block==this && c->active && last!=c->left;
}
inline bool Block::canFollowRight(Constraint *c, const Variable* const last) {
	return c->right->block==this && c->active && last!=c->right;
}

// computes the derivative of v and the lagrange multipliers
// of v's out constraints (as the recursive sum of those below.
// Does not backtrack over u.
// also records the constraint with minimum lagrange multiplier
// in min_lm
double Block::compute_dfdv(Variable* const v, Variable* const u,
	       	Constraint *&min_lm) {
	double dfdv=v->weight*(v->position() - v->desiredPosition);
	for(Cit it=v->out.begin();it!=v->out.end();++it) {
		Constraint *c=*it;
		if(canFollowRight(c,u)) {
			dfdv+=c->lm=compute_dfdv(c->right,v,min_lm);
			if(!c->equality&&(min_lm==NULL||c->lm<min_lm->lm)) min_lm=c;
		}
	}
	for(Cit it=v->in.begin();it!=v->in.end();++it) {
		Constraint *c=*it;
		if(canFollowLeft(c,u)) {
			dfdv-=c->lm=-compute_dfdv(c->left,v,min_lm);
			if(!c->equality&&(min_lm==NULL||c->lm<min_lm->lm)) min_lm=c;
		}
	}
	return dfdv;
}


// computes dfdv for each variable and uses the sum of dfdv on either side of
// the constraint c to compute the lagrangian multiplier lm_c.
// The top level v and r are variables between which we want to find the
// constraint with the smallest lm.  
// When we find r we pass NULL to subsequent recursive calls, 
// thus r=NULL indicates constraints are not on the shortest path.
// Similarly, m is initially NULL and is only assigned a value if the next
// variable to be visited is r or if a possible min constraint is returned from
// a nested call (rather than NULL).
// Then, the search for the m with minimum lm occurs as we return from
// the recursion (checking only constraints traversed left-to-right 
// in order to avoid creating any new violations).
// We also do not consider equality constraints as potential split points
Block::Pair Block::compute_dfdv_between(
		Variable* r, Variable* const v, Variable* const u, 
		const Direction dir = NONE, bool changedDirection = false) {
	double dfdv=v->weight*(v->position() - v->desiredPosition);
	Constraint *m=NULL;
	for(Cit it(v->in.begin());it!=v->in.end();++it) {
		Constraint *c=*it;
		if(canFollowLeft(c,u)) {
			if(dir==RIGHT) { 
				changedDirection = true; 
			}
			if(c->left==r) {
			       	r=NULL;
			        if(!c->equality) m=c; 
			}
			Pair p=compute_dfdv_between(r,c->left,v,
					LEFT,changedDirection);
			dfdv -= c->lm = -p.first;
			if(r && p.second) 
				m = p.second;
		}
	}
	for(Cit it(v->out.begin());it!=v->out.end();++it) {
		Constraint *c=*it;
		if(canFollowRight(c,u)) {
			if(dir==LEFT) { 
				changedDirection = true; 
			}
			if(c->right==r) {
			       	r=NULL; 
			        if(!c->equality) m=c; 
			}
			Pair p=compute_dfdv_between(r,c->right,v,
					RIGHT,changedDirection);
			dfdv += c->lm = p.first;
			if(r && p.second) 
				m = changedDirection && !c->equality && c->lm < p.second->lm 
					? c 
					: p.second;
		}
	}
	return Pair(dfdv,m);
}

// resets LMs for all active constraints to 0 by
// traversing active constraint tree starting from v,
// not back tracking over u
void Block::reset_active_lm(Variable* const v, Variable* const u) {
	for(Cit it=v->out.begin();it!=v->out.end();++it) {
		Constraint *c=*it;
		if(canFollowRight(c,u)) {
			c->lm=0;
			reset_active_lm(c->right,v);
		}
	}
	for(Cit it=v->in.begin();it!=v->in.end();++it) {
		Constraint *c=*it;
		if(canFollowLeft(c,u)) {
			c->lm=0;
			reset_active_lm(c->left,v);
		}
	}
}
/**
 * finds the constraint with the minimum lagrange multiplier, that is, the constraint
 * that most wants to split
 */
Constraint *Block::findMinLM() {
	Constraint *min_lm=NULL;
	reset_active_lm(vars->front(),NULL);
	compute_dfdv(vars->front(),NULL,min_lm);
	return min_lm;
}
Constraint *Block::findMinLMBetween(Variable* const lv, Variable* const rv) {
	Constraint *min_lm=NULL;
	reset_active_lm(vars->front(),NULL);
	min_lm=compute_dfdv_between(rv,lv,NULL).second;
	return min_lm;
}

// populates block b by traversing the active constraint tree adding variables as they're 
// visited.  Starts from variable v and does not backtrack over variable u.
void Block::populateSplitBlock(Block *b, Variable* const v, Variable* const u) {
	b->addVariable(v);
	for (Cit c=v->in.begin();c!=v->in.end();++c) {
		if (canFollowLeft(*c,u))
			populateSplitBlock(b, (*c)->left, v);
	}
	for (Cit c=v->out.begin();c!=v->out.end();++c) {
		if (canFollowRight(*c,u)) 
			populateSplitBlock(b, (*c)->right, v);
	}
}
// Search active constraint tree from u to see if there is a directed path to v.
// Returns true if path is found with all constraints in path having their visited flag
// set true.
bool Block::isActiveDirectedPathBetween(Variable* u, Variable *v) {
	if(u==v) return true;
	for (Cit c=u->out.begin();c!=u->out.end();++c) {
		if(canFollowRight(*c,NULL)) {
			if(isActiveDirectedPathBetween((*c)->right,v)) {
				(*c)->visited=true;
				return true;
			}
			(*c)->visited=false;
		}
	}
	return false;
}
/**
 * Block needs to be split because of a violated constraint between vl and vr.
 * We need to search the active constraint tree between l and r and find the constraint
 * with min lagrangrian multiplier and split at that point.
 * Returns the split constraint
 */
Constraint* Block::splitBetween(Variable* const vl, Variable* const vr,
	       	Block* &lb, Block* &rb) {
#ifdef RECTANGLE_OVERLAP_LOGGING
	ofstream f(LOGFILE,ios::app);
	f<<"  need to split between: "<<*vl<<" and "<<*vr<<endl;
#endif
	Constraint *c=findMinLMBetween(vl, vr);
#ifdef RECTANGLE_OVERLAP_LOGGING
	f<<"  going to split on: "<<*c<<endl;
#endif
	split(lb,rb,c);
	deleted = true;
	return c;
}
/**
 * Creates two new blocks, l and r, and splits this block across constraint c,
 * placing the left subtree of constraints (and associated variables) into l
 * and the right into r.
 */
void Block::split(Block* &l, Block* &r, Constraint* c) {
	c->active=false;
	l=new Block();
	populateSplitBlock(l,c->left,c->right);
	r=new Block();
	populateSplitBlock(r,c->right,c->left);
}

/**
 * Computes the cost (squared euclidean distance from desired positions) of the
 * current positions for variables in this block
 */
double Block::cost() {
	double c = 0;
	for (Vit v=vars->begin();v!=vars->end();++v) {
		double diff = (*v)->position() - (*v)->desiredPosition;
		c += (*v)->weight * diff * diff;
	}
	return c;
}
ostream& operator <<(ostream &os, const Block& b)
{
	os<<"Block:";
	for(Block::Vit v=b.vars->begin();v!=b.vars->end();++v) {
		os<<" "<<**v;
	}
	if(b.deleted) {
		os<<" Deleted!";
	}
    return os;
}
}
