libcruft-util/cruft/util/extent.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2010-2020, Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "coord/fwd.hpp"
#include "coord/base.hpp"
#include "vector.hpp"
#include "point.hpp"
#include "random.hpp"

#include <cstddef>

namespace cruft {
    /**
     * A pure n-dimensional size, without positioning
     */
    template <size_t S, typename T>
    struct extent : public ::cruft::coord::base<S,T,::cruft::extent<S,T>>
    {
        using ::cruft::coord::base<S,T,::cruft::extent<S,T>>::base;

        extent () = default;
        explicit extent (::cruft::vector<S,T>);

        constexpr T
        area (void) const
        {
            return std::accumulate (std::begin (this->data),
                                    std::end   (this->data),
                                    T {1},
                                    std::multiplies<T> ());
        }

        constexpr T
        diameter (void) const
        {
            return static_cast<T> (
                std::sqrt (
                    std::accumulate (std::begin (this->data),
                                     std::end   (this->data),
                                     T {0},
                                     [] (auto a, auto b) { return a + b * b; })
                )
            );
        }

        template <typename U = float>
        constexpr
        U aspect (void) const
        {
            return static_cast<U> (this->w) / this->h;
        }

        /// tests whether a point would lie within:
        ///     region { origin, *this }, inclusive of borders.
        ///
        /// included for parity with cruft::region.
        constexpr bool
        inclusive (cruft::point<S,T> p) const
        {
            return all (p >= T{0} && p <= *this);
        }


        /// tests whether a point would like within:
        ///     region { origin, *this }, exclusive of the bottom-right border
        /// included for parity with cruft::region
        constexpr bool
        exclusive (point<S,T> p) const
        {
            return all (p >= T{0} && p < *this);
        }

        ::cruft::extent<S,T> expanded (::cruft::vector<S,T>) const;
        ::cruft::extent<S,T> expanded (T) const;
        ::cruft::extent<S,T> contracted (::cruft::vector<S,T>) const;
        ::cruft::extent<S,T> contracted (T) const;

        bool empty (void) const;

        static constexpr
        ::cruft::extent<S,T> max (void)
        {
            return extent<S,T> {
                std::numeric_limits<T>::max ()
            };
        }


        static constexpr
        ::cruft::extent<S,T> min (void)
        {
            return extent<S,T> { 0 };
        }


        ///////////////////////////////////////////////////////////////////////
        class iterator {
        public:
            using iterator_category = std::forward_iterator_tag;
            using value_type = point<S,T>;
            using difference_type = size_t;
            using pointer = value_type*;
            using reference = value_type&;


            iterator (point<S,T> _cursor, extent<S,T> _target):
                m_cursor (_cursor),
                m_target (_target)
            { ; }


                  point<S,T>& operator* ()       & { return m_cursor; }
            const point<S,T>& operator* () const & { return m_cursor; }

            iterator& operator++ (void)&
            {
                ++m_cursor[0];

                for (size_t i = 0; i < S - 1; ++i) {
                    if (m_cursor[i] < m_target[i])
                        break;

                    m_cursor[i] = 0;
                    m_cursor[i+1]++;
                }

                return *this;
            }


            bool operator!= (const iterator &rhs) const { return m_cursor != rhs.m_cursor; }
            bool operator== (const iterator &rhs) const { return m_cursor == rhs.m_cursor; }

        private:
            point<S,T>  m_cursor;
            extent<S,T> m_target;
        };


        auto step (void) const
        {
            point<S,T> last {0};
            last[S-1] = this->data[S-1];

            return cruft::view {
                iterator {point<S,T> {0}, *this},
                iterator {last, *this}
            };
        }
    };


    ///////////////////////////////////////////////////////////////////////////
    // convenience typedefs
    template <typename T> using extent2 = extent<2,T>;
    template <typename T> using extent3 = extent<3,T>;

    template <size_t S> using extentu = extent<S,unsigned>;
    template <size_t S> using extenti = extent<S,int>;
    template <size_t S> using extentf = extent<S,float>;
    template <size_t S> using extentd = extent<S,double>;


    typedef extent2<int> extent2i;
    typedef extent2<unsigned> extent2u;
    typedef extent2<float> extent2f;
    typedef extent2<double> extent2d;


    typedef extent3<unsigned> extent3u;
    typedef extent3<float> extent3f;


    ///////////////////////////////////////////////////////////////////////////
    template <size_t S, typename T>
    cruft::point<S,T>
    sample (cruft::extent<S,T> shape)
    {
        return sample (shape, cruft::random::generator ());
    }


    /// Return a uniform random point that lies within the extent.
    ///
    /// The interval conventions are the same as for the std library; close for
    /// integers, half-open for reals.
    template <size_t S, typename T, typename GeneratorT>
    cruft::point<S,T>
    sample (cruft::extent<S,T> shape, GeneratorT &&gen)
    {
        cruft::point<S,T> p;
        for (size_t i = 0; i < S; ++i)
            p[i] = cruft::random::uniform (T{0}, shape[i], gen);
        return p;
    }


    //-------------------------------------------------------------------------
    template <typename T>
    extent2<T>
    rotate90 (extent2<T> val, int steps);
}