/* -*- C++ -*-

 * src/lemon/lp_base.h - Part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Combinatorial Optimization Research Group, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef LEMON_LP_BASE_H

#define LEMON_LP_BASE_H

#include<vector>

#include<lemon/error.h>

#include"lin_expr.h"

///\file

///\brief The interface of the LP solver interface.

namespace lemon {

  ///Internal data structure to convert floating id's to fix one's

  ///\todo This might by implemented to be usable in other places.

  class _FixId 

  {

    std::vector<int> index;

    std::vector<int> cross;

    int first_free;

  public:

    _FixId() : first_free(-1) {};

    ///Convert a floating id to a fix one

    ///\param n is a floating id

    ///\return the corresponding fix id

    int fixId(int n) {return cross[n];}

    ///Convert a fix id to a floating one

    ///\param n is a fix id

    ///\return the corresponding floating id

    int floatingId(int n) { return index[n];}

    ///Add a new floating id.

    ///\param n is a floating id

    ///\return the fix id of the new value

    ///\todo Multiple additions should also be handled.

    int insert(int n)

    {

      if(n>=int(cross.size())) {

	cross.resize(n+1);

	if(first_free==-1) {

	  cross[n]=index.size();

	  index.push_back(n);

	}

	else {

	  cross[n]=first_free;

	  int next=index[first_free];

	  index[first_free]=n;

	  first_free=next;

	}

      }

      else throw LogicError(); //floatingId-s must form a continuous range;

    }

    ///Remove a fix id.

    ///\param n is a fix id

    ///

    void erase(int n) 

    {

      int fl=index[n];

      index[n]=first_free;

      first_free=n;

      for(int i=fl+1;i<int(cross.size());++i) {

	cross[i-1]=cross[i];

	index[cross[i]]--;

      }

      cross.pop_back();

    }

    ///An upper bound on the largest fix id.

    ///\todo Do we need this?

    ///

    std::size_t maxFixId() { return cross.size()-1; }

  };

  ///Common base class for LP solvers

  class LpSolverBase {

  public:

    /// \e

    typedef double Value;

    /// \e 

    static const Value INF;

    ///\e

    class Col { protected: int id; friend class LpSolverBase; };

    ///\e

    class Row { protected: int id; friend class LpSolverBase; };

    typedef SparseLinExpr<Col, Value> Expr;

  protected:

    _FixId rows;

    _FixId cols;

    //MATRIX MANIPULATING FUNCTIONS

    /// \e

    virtual int _addCol() = 0;

    /// \e

    virtual int _addRow() = 0;

    /// \e

    /// \warning Arrays are indexed from 1 (datum at index 0 is ignored)

    ///

    virtual void _setRowCoeffs(int i, 

			       int length,

                               int  const * indices, 

                               Value  const * values ) = 0;

    /// \e

    /// \warning Arrays are indexed from 1 (datum at index 0 is ignored)

    ///

    virtual void _setColCoeffs(int i, 

			       int length,

                               int  const * indices, 

                               Value  const * values ) = 0;

    /// \e

    /// The lower bound of a variable (column) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or -INF.

    virtual void _setColLowerBound(int i, Value value) = 0;

    /// \e

    /// The upper bound of a variable (column) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or INF.

    virtual void _setColUpperBound(int i, Value value) = 0;

    /// \e

    /// The lower bound of a linear expression (row) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or -INF.

    virtual void _setRowLowerBound(int i, Value value) = 0;

    /// \e

    /// The upper bound of a linear expression (row) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or INF.

    virtual void _setRowUpperBound(int i, Value value) = 0;

    /// \e

    virtual void _setObjCoeff(int i, Value obj_coef) = 0;

    ///\e

    ///\bug unimplemented!!!!

    void clearObj() {}

  public:

    ///\e

    virtual ~LpSolverBase() {}

    ///Add a new empty column (i.e a new variable) to the LP

    Col addCol() { Col c; c.id=cols.insert(_addCol()); return c;}

    ///Add a new empty row (i.e a new constaint) to the LP

    Row addRow() { Row r; r.id=rows.insert(_addRow()); return r;}

    ///Add a new row (i.e a new constaint) to the LP

    ///\param l lower bound (-INF means no bound)

    ///\param e a linear expression (see \ref Expr)

    ///\param u upper bound (INF means no bound)

    ///\bug This is a temportary function. The interface will change to

    ///a better one.

    Row addRow(Value l,Expr e, Value u) {

      Row r=addRow();

      std::vector<int> indices;

      std::vector<Value> values;

      indices.push_back(0);

      values.push_back(0);

      for(Expr::iterator i=e.begin(); i!=e.end(); ++i) {

	indices.push_back(cols.floatingId((*i).first.id));

	values.push_back((*i).second);

      }

      _setRowCoeffs(rows.floatingId(r.id),indices.size()-1,

		    &indices[0],&values[0]);

      _setRowLowerBound(rows.floatingId(r.id),l);

      _setRowUpperBound(rows.floatingId(r.id),l);

      return r;

    }

    /// Set the lower bound of a column (i.e a variable)

    /// The upper bound of a variable (column) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or -INF.

    virtual void setColLowerBound(Col c, Value value) {

      _setColLowerBound(cols.floatingId(c.id),value);

    }

    /// Set the upper bound of a column (i.e a variable)

    /// The upper bound of a variable (column) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or INF.

    virtual void setColUpperBound(Col c, Value value) {

      _setColUpperBound(cols.floatingId(c.id),value);

    };

    /// Set the lower bound of a row (i.e a constraint)

    /// The lower bound of a linear expression (row) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or -INF.

    virtual void setRowLowerBound(Row r, Value value) {

      _setRowLowerBound(rows.floatingId(r.id),value);

    };

    /// Set the upper bound of a row (i.e a constraint)

    /// The upper bound of a linear expression (row) have to be given by an 

    /// extended number of type Value, i.e. a finite number of type 

    /// Value or INF.

    virtual void setRowUpperBound(Row r, Value value) {

      _setRowUpperBound(rows.floatingId(r.id),value);

    };

    ///Set an element of the objective function

    void setObjCoeff(Col c, Value v) {_setObjCoeff(cols.floatingId(c.id),v); };

    ///Set the objective function

    ///\param e is a linear expression of type \ref Expr.

    ///\todo What to do with the constant component?

    void setObj(Expr e) {

      clearObj();

      for (Expr::iterator i=e.begin(); i!=e.end(); ++i)

	setObjCoeff((*i).first,(*i).second);

    }

  };  

} //namespace lemon

#endif //LEMON_LP_BASE_H