/**
 * \file
 * \brief  Simple closed interval class
 *//*
 * Copyright 2007 Michael Sloan <mgsloan@gmail.com>
 *
 * Original Rect/Range code by:
 *   Lauris Kaplinski <lauris@kaplinski.com>
 *   Nathan Hurst <njh@mail.csse.monash.edu.au>
 *   bulia byak <buliabyak@users.sf.net>
 *   MenTaLguY <mental@rydia.net>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it either under the terms of the GNU Lesser General Public
 * License version 2.1 as published by the Free Software Foundation
 * (the "LGPL") or, at your option, under the terms of the Mozilla
 * Public License Version 1.1 (the "MPL"). If you do not alter this
 * notice, a recipient may use your version of this file under either
 * the MPL or the LGPL.
 *
 * You should have received a copy of the LGPL along with this library
 * in the file COPYING-LGPL-2.1; if not, output to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 * You should have received a copy of the MPL along with this library
 * in the file COPYING-MPL-1.1
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
 * the specific language governing rights and limitations.
 *
 */
#ifndef LIB2GEOM_SEEN_INTERVAL_H
#define LIB2GEOM_SEEN_INTERVAL_H

#include <assert.h>
#include <boost/none.hpp>
#include <boost/optional.hpp>
#include <boost/operators.hpp>
#include <2geom/coord.h>
#include <2geom/isnan.h>

namespace Geom {

class OptInterval;

/** 
 * @brief Range of numbers that is never empty.
 *
 * Intervals are closed ranges \f$[a, b]\f$, which means they include their endpoints.
 * To use them as open ranges, you can use the interiorContains() methods.
 *
 * @ingroup Primitives
 */
class Interval
    : boost::equality_comparable< Interval
    , boost::additive< Interval
    , boost::multipliable< Interval
    , boost::arithmetic< Interval, Coord
    , boost::orable< Interval
      > > > > >
{
private:
    /// @invariant _b[0] <= _b[1]
    Coord _b[2];

public:
    /// @name Create intervals.
    /// @{
    /** @brief Create an interval that contains only zero. */
    explicit Interval() { _b[0] = 0;  _b[1] = 0; }
    /** @brief Create an interval that contains a single point. */
    explicit Interval(Coord u) { _b[0] = _b[1] = u; }
    /** @brief Create an interval that contains all points between @c u and @c v. */
    Interval(Coord u, Coord v) {
        if (u <= v) {
            _b[0] = u; _b[1] = v;
        } else {
            _b[0] = v; _b[1] = u;
        }
    }

    /** @brief Create an interval containing a range of values.
     * The resulting interval will contain all values from the given range.
     * The return type of iterators must be convertible to Coord. The given range
     * must not be empty. For potentially empty ranges, see OptInterval.
     * @param start Beginning of the range
     * @param end   End of the range
     * @return Interval that contains all values from [start, end). */
    template <typename InputIterator>
    static Interval from_range(InputIterator start, InputIterator end) {
        assert(start != end);
        Interval result(*start++);
        for (; start != end; ++start) result.expandTo(*start);
        return result;
    }
    /** @brief Create an interval from a C-style array of values it should contain. */
    static Interval from_array(Coord const *c, unsigned n) {
        Interval result = from_range(c, c+n);
        return result;
    }
    /// @}

    /// @name Inspect endpoints.
    /// @{
    Coord operator[](unsigned i) const { return _b[i]; }
    Coord& operator[](unsigned i) { return _b[i]; }

    Coord min() const { return _b[0]; }
    Coord max() const { return _b[1]; }
    Coord extent() const { return _b[1] - _b[0]; }
    Coord middle() const { return (_b[1] + _b[0]) * 0.5; }
    bool isSingular() const { return _b[0] == _b[1]; }
    bool isFinite() const {
        return IS_FINITE(_b[0]) && IS_FINITE(_b[1]);
    }
    /// @}

    /// @name Test coordinates and other intervals for inclusion.
    /// @{
    /** @brief Check whether the interval includes this number. */
    bool contains(Coord val) const { return _b[0] <= val && val <= _b[1]; }
    /** @brief Check whether the interior of the interval includes this number.
     * Interior means all numbers in the interval except its ends. */
    bool interiorContains(Coord val) const { return _b[0] < val && val < _b[1]; }
    /** @brief Check whether the interval includes the given interval. */
    bool contains(Interval const &val) const { return _b[0] <= val._b[0] && val._b[1] <= _b[1]; }
    /** @brief Check whether the interior of the interval includes the given interval.
     * Interior means all numbers in the interval except its ends. */
    bool interiorContains(Interval const &val) const { return _b[0] < val._b[0] && val._b[1] < _b[1]; }
    /** @brief Check whether the intervals have any common elements. */
    bool intersects(Interval const &val) const {
        return contains(val._b[0]) || contains(val._b[1]) || val.contains(*this);
    }
    /** @brief Check whether the interiors of the intervals have any common elements. */
    bool interiorIntersects(Interval const &val) const {
        return interiorContains(val._b[0]) || interiorContains(val._b[1]) || val.interiorContains(*this);
    }
    /// @}

    /// @name Modify the interval.
    /// @{
    //TODO: NaN handleage for the next two?
    /** @brief Set the lower boundary of the interval.
     * When the given number is larger than the interval's largest element,
     * it will be reduced to the single number @c val. */
    void setMin(Coord val) {
        if(val > _b[1]) {
            _b[0] = _b[1] = val;
        } else {
            _b[0] = val;
        }
    }
    /** @brief Set the upper boundary of the interval.
     * When the given number is smaller than the interval's smallest element,
     * it will be reduced to the single number @c val. */
    void setMax(Coord val) {
        if(val < _b[0]) {
            _b[1] = _b[0] = val;
        } else {
            _b[1] = val;
        }
    }
    /** @brief Extend the interval to include the given number. */
    void expandTo(Coord val) {
       if(val < _b[0]) _b[0] = val;
       if(val > _b[1]) _b[1] = val;  //no else, as we want to handle NaN
    }
    /** @brief Expand or shrink the interval in both directions by the given amount.
     * After this method, the interval's length (extent) will be increased by
     * <code>amount * 2</code>. Negative values can be given; they will shrink the interval.
     * Shrinking by a value larger than half the interval's length will create a degenerate
     * interval containing only the midpoint of the original. */
    void expandBy(double amount) {
        _b[0] -= amount;
        _b[1] += amount;
        if (_b[0] > _b[1]) {
            Coord halfway = (_b[0]+_b[1])/2;
            _b[0] = _b[1] = halfway;
        }
    }
    /** @brief Union the interval with another one.
     * The resulting interval will contain all points of both intervals.
     * It might also contain some points which didn't belong to either - this happens
     * when the intervals did not have any common elements. */
    void unionWith(const Interval & a) {
        if(a._b[0] < _b[0]) _b[0] = a._b[0];
        if(a._b[1] > _b[1]) _b[1] = a._b[1];
    }
    /// @}

    /// @name Operators
    /// @{
    inline operator OptInterval();
    bool operator==(Interval const &other) const { return _b[0] == other._b[0] && _b[1] == other._b[1]; }
    
    //IMPL: OffsetableConcept
    //TODO: rename output_type to something else in the concept
    typedef Coord output_type;
    /** @brief Offset the interval by a specified amount */
    Interval &operator+=(Coord amnt) {
        _b[0] += amnt; _b[1] += amnt;
        return *this;
    }
    /** @brief Offset the interval by the negation of the specified amount */
    Interval &operator-=(Coord amnt) {
        _b[0] -= amnt; _b[1] -= amnt;
        return *this;
    }
    
    // IMPL: ScalableConcept
    /** @brief Return an interval mirrored about 0 */
    Interval operator-() const { return Interval(-_b[1], -_b[0]); }
    /** @brief Scale an interval */
    Interval &operator*=(Coord s) {
        _b[0] *= s;
        _b[1] *= s;
        if(s < 0) std::swap(_b[0], _b[1]);
        return *this;
    }
    /** @brief Scale an interval by the inverse of the specified value */
    Interval &operator/=(Coord s) {
        _b[0] /= s;
        _b[1] /= s;
        if(s < 0) std::swap(_b[0], _b[1]);
        return *this;
    }
    // IMPL: AddableConcept
    /** @brief Add two intervals.
     * Sum is defined as the set of points that can be obtained by adding any two values
     * from both operands: \f$S = \{x \in A, y \in B: x + y\}\f$ */
    Interval &operator+=(Interval const &o) {
        _b[0] += o._b[0];
        _b[1] += o._b[1];
        return *this;
    }
    /** @brief Subtract two intervals.
     * Difference is defined as the set of points that can be obtained by subtracting
     * any value from the second operand from any value from the first operand:
     * \f$S = \{x \in A, y \in B: x - y\}\f$ */
    Interval &operator-=(Interval const &o) {
        // equal to *this += -o
        _b[0] -= o._b[1];
        _b[1] -= o._b[0];
        return *this;
    }
    /** @brief Multiply two intervals.
     * Product is defined as the set of points that can be obtained by multiplying
     * any value from the second operand by any value from the first operand:
     * \f$S = \{x \in A, y \in B: x * y\}\f$ */
    Interval &operator*=(Interval const &o) {
        // TODO implement properly
        Coord mn = min(), mx = max();
        expandTo(mn * o.min());
        expandTo(mn * o.max());
        expandTo(mx * o.min());
        expandTo(mx * o.max());
        return *this;
    }
    /** @brief Union two intervals.
     * Note that intersection is only defined for OptIntervals, because the result
     * of an intersection can be empty, while an Interval cannot. */
    Interval &operator|=(Interval const &o) {
        unionWith(o);
        return *this;
    }
    /// @}
};

/** @brief Union two intervals
 * @relates Interval */
inline Interval unify(Interval const &a, Interval const &b) {
    return a | b;
}

/**
 * @brief A range of numbers that can be empty.
 * @ingroup Primitives
 */
class OptInterval
    : public boost::optional<Interval>
    , boost::orable< OptInterval
    , boost::andable< OptInterval
      > >
{
public:
    /// @name Create optionally empty intervals.
    /// @{
    /** @brief Create an empty interval. */
    OptInterval() : boost::optional<Interval>() {};
    /** @brief Wrap an existing interval. */
    OptInterval(Interval const &a) : boost::optional<Interval>(a) {};
    /** @brief Create an interval containing a single point. */
    OptInterval(Coord u) : boost::optional<Interval>(Interval(u)) {};
    /** @brief Create an interval containing a range of numbers. */
    OptInterval(Coord u, Coord v) : boost::optional<Interval>(Interval(u,v)) {};

    /** @brief Create a possibly empty interval containing a range of values.
     * The resulting interval will contain all values from the given range.
     * The return type of iterators must be convertible to double. The given range
     * may be empty.
     * @param start Beginning of the range
     * @param end   End of the range
     * @return Interval that contains all values from [start, end), or nothing if the range
     *         is empty. */
    template <typename InputIterator>
    static OptInterval from_range(InputIterator start, InputIterator end) {
        if (start == end) {
            OptInterval ret;
            return ret;
        }
        OptInterval ret(Interval::from_range(start, end));
        return ret;
    }
    /// @}

    /** @brief Check whether this OptInterval is empty. */
    bool isEmpty() { return !*this; };

    /** @brief Union with another interval, gracefully handling empty ones. */
    inline void unionWith(OptInterval const &a) {
        if (a) {
            if (*this) { // check that we are not empty
                (*this)->unionWith(*a);
            } else {
                *this = a;
            }
        }
    }
    inline void intersectWith(OptInterval const &o) {
        if (o && *this) {
            Coord u, v;
            u = std::max((*this)->min(), o->min());
            v = std::min((*this)->max(), o->max());
            if (u <= v) {
                *this = Interval(u, v);
                return;
            }
        }
        (*static_cast<boost::optional<Interval>*>(this)) = boost::none;
    }
    OptInterval &operator|=(OptInterval const &o) {
        unionWith(o);
        return *this;
    }
    OptInterval &operator&=(OptInterval const &o) {
        intersectWith(o);
        return *this;
    }
};

/** @brief Intersect two intervals and return a possibly empty range of numbers
 * @relates OptInterval */
inline OptInterval intersect(Interval const &a, Interval const &b) {
    return OptInterval(a) & OptInterval(b);
}
/** @brief Intersect two intervals and return a possibly empty range of numbers
 * @relates OptInterval */
inline OptInterval operator&(Interval const &a, Interval const &b) {
    return OptInterval(a) & OptInterval(b);
}

inline Interval::operator OptInterval() {
    return OptInterval(*this);
}

#ifdef _GLIBCXX_IOSTREAM
inline std::ostream &operator<< (std::ostream &os, 
                                 const Geom::Interval &I) {
    os << "Interval("<<I[0] << ", "<<I[1] << ")";
    return os;
}
#endif

}
#endif //SEEN_INTERVAL_H

/*
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*/
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