livetrax/libs/canvas/kiwi/constraint.h

/*-----------------------------------------------------------------------------
  | Copyright (c) 2013-2017, Nucleic Development Team.
  |
  | Distributed under the terms of the Modified BSD License.
  |
  | The full license is in the file LICENSE, distributed with this software.
  |----------------------------------------------------------------------------*/
#pragma once
#include <ostream>
#include <map>
#include <vector>
#include "expression.h"
#include "shareddata.h"
#include "strength.h"
#include "term.h"
#include "variable.h"

namespace kiwi
{

enum RelationalOperator
{
	OP_LE,
	OP_GE,
	OP_EQ
};

static std::ostream& operator<< (std::ostream& o, RelationalOperator op)
{
	switch (op) {
	case OP_LE:
		o << "<=";
		break;
	case OP_GE:
		o << ">=";
		break;
	case OP_EQ:
		o << "==";
		break;
	}
	return o;
}

class Constraint
{

  public:
	Constraint() : m_data(0) {}

	Constraint(const Expression &expr,
	           RelationalOperator op,
	           double strength = strength::required) : m_data(new ConstraintData(expr, op, strength)) {}

	Constraint(const Constraint &other, double strength) : m_data(new ConstraintData(other, strength)) {}

	~Constraint() {}

	const Expression &expression() const
	{
		return m_data->m_expression;
	}

	RelationalOperator op() const
	{
		return m_data->m_op;
	}

	double strength() const
	{
		return m_data->m_strength;
	}

	bool operator!() const
	{
		return !m_data;
	}

	bool involves (Variable const & v) const {
		if (expression().involves (v)) {
			return true;
		}
		return false;
	}

  private:
	static Expression reduce(const Expression &expr)
	{
		std::map<Variable, double> vars;
		typedef std::vector<Term>::const_iterator iter_t;
		iter_t end = expr.terms().end();
		for (iter_t it = expr.terms().begin(); it != end; ++it)
			vars[it->variable()] += it->coefficient();
		std::vector<Term> terms(vars.begin(), vars.end());
		return Expression(terms, expr.constant());
	}

	class ConstraintData : public SharedData
	{

	  public:
		ConstraintData(const Expression &expr,
		               RelationalOperator op,
		               double strength) : SharedData(),
		                                  m_expression(reduce(expr)),
		                                  m_strength(strength::clip(strength)),
		                                  m_op(op) {}

		ConstraintData(const Constraint &other, double strength) : SharedData(),
		                                                           m_expression(other.expression()),
		                                                           m_strength(strength::clip(strength)),
		                                                           m_op(other.op()) {}

		~ConstraintData() {}

		Expression m_expression;
		double m_strength;
		RelationalOperator m_op;

	  private:
		ConstraintData(const ConstraintData &other);

		ConstraintData &operator=(const ConstraintData &other);
	};

	SharedDataPtr<ConstraintData> m_data;

	friend bool operator<(const Constraint &lhs, const Constraint &rhs)
	{
		return lhs.m_data < rhs.m_data;
	}

	friend bool operator==(const Constraint &lhs, const Constraint &rhs)
	{
		return lhs.m_data == rhs.m_data;
	}

	friend bool operator!=(const Constraint &lhs, const Constraint &rhs)
	{
		return lhs.m_data != rhs.m_data;
	}
};

static std::ostream& operator<< (std::ostream& o, kiwi::Constraint const & c)
{
	return o << c.expression() << " OP " << c.op();
}

} // namespace kiwi