#ifndef HALIDE_INTERVAL_H
#define HALIDE_INTERVAL_H

/** \file
 * Defines the Interval class
 */

#include "Expr.h"

namespace Halide {
namespace Internal {

/** A class to represent ranges of Exprs. Can be unbounded above or below. */
struct Interval {

    /** Exprs to represent positive and negative infinity */
    HALIDE_EXPORT static Expr pos_inf, neg_inf;

    /** The lower and upper bound of the interval. They are included
     * in the interval. */
    Expr min, max;

    /** A default-constructed Interval is everything */
    Interval() : min(neg_inf), max(pos_inf) {}

    /** Construct an interval from a lower and upper bound. */
    Interval(Expr min, Expr max) : min(min), max(max) {
        internal_assert(min.defined() && max.defined());
    }

    /** The interval representing everything. */
    static Interval everything() {return Interval(neg_inf, pos_inf);}

    /** The interval representing nothing. */
    static Interval nothing() {return Interval(pos_inf, neg_inf);}

    /** Construct an interval representing a single point */
    static Interval single_point(Expr e) {return Interval(e, e);}

    /** Is the interval the empty set */
    bool is_empty() const {return min.same_as(pos_inf) || max.same_as(neg_inf);}

    /** Is the interval the entire range */
    bool is_everything() const {return min.same_as(neg_inf) && max.same_as(pos_inf);}

    /** Is the interval just a single value (min == max) */
    bool is_single_point() const {return min.same_as(max);}

    /** Is the interval a particular single value */
    bool is_single_point(Expr e) const {return min.same_as(e) && max.same_as(e);}

    /** Does the interval have a finite least upper bound */
    bool has_upper_bound() const {return !max.same_as(pos_inf) && !is_empty();}

    /** Does the interval have a finite greatest lower bound */
    bool has_lower_bound() const {return !min.same_as(neg_inf) && !is_empty();}

    /** Does the interval have a finite upper and lower bound */
    bool is_bounded() const {return has_upper_bound() && has_lower_bound();}

    /** Is the interval the same as another interval */
    bool same_as(const Interval &other) {return min.same_as(other.min) && max.same_as(other.max);}

    /** Expand the interval to include another Interval */
    void include(const Interval &i);

    /** Expand the interval to include an Expr */
    void include(Expr e);

    /** Construct the smallest interval containing two intervals. */
    static Interval make_union(const Interval &a, const Interval &b);

    /** Construct the largest interval contained within two intervals. */
    static Interval make_intersection(const Interval &a, const Interval &b);

    /** An eagerly-simplifying max of two Exprs that respects infinities. */
    static Expr make_max(Expr a, Expr b);

    /** An eagerly-simplifying min of two Exprs that respects infinities. */
    static Expr make_min(Expr a, Expr b);

    bool operator==(const Interval &other) const {
        return (min.same_as(other.min)) && (max.same_as(other.max));
    }
};

void interval_test();

}  // namespace Internal
}  // namespace Halide

#endif