BLT/include/blt/iterator/enumerate.h

#pragma once
/*
 *  Copyright (C) 2024  Brett Terpstra
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#ifndef BLT_ITERATOR_ENUMERATE_H
#define BLT_ITERATOR_ENUMERATE_H

#include <blt/iterator/common.h>
#include <tuple>

namespace blt
{
    
    namespace iterator
    {
        /**
         * struct which is returned by the enumerator.
         * @tparam T type to store.
         */
        template<typename T>
        struct enumerate_item
        {
            blt::size_t index;
            T value;
        };
        
        template<typename Iter>
        class enumerate_wrapper : public passthrough_wrapper<Iter, enumerate_wrapper<Iter>>
        {
            public:
                enumerate_wrapper(blt::size_t index, Iter iter): passthrough_wrapper<Iter, enumerate_wrapper<Iter>>(std::move(iter)), index(index)
                {}
                
                using iterator_category = typename std::iterator_traits<Iter>::iterator_category;
                using value_type = enumerate_item<meta::deref_return_t<Iter>>;
                using difference_type = blt::ptrdiff_t;
                using pointer = value_type;
                using reference = value_type;
                
                enumerate_item<meta::deref_return_t<Iter>> operator*() const
                {
                    return {index, *this->iter};
                }
                
                enumerate_wrapper& operator++()
                {
                    ++index;
                    ++this->iter;
                    return *this;
                }
                
                enumerate_wrapper& operator--()
                {
                    --index;
                    --this->iter;
                    return *this;
                }
                
                friend enumerate_wrapper operator+(const enumerate_wrapper& a, blt::ptrdiff_t n)
                {
                    static_assert(meta::is_random_access_iterator_v<Iter>, "Iterator must allow random access");
                    auto copy = a;
                    copy.index += n;
                    copy.iter = copy.iter + n;
                    return copy;
                }
                
                friend enumerate_wrapper operator-(const enumerate_wrapper& a, blt::ptrdiff_t n)
                {
                    static_assert(meta::is_random_access_iterator_v<Iter>, "Iterator must allow random access");
                    auto copy = a;
                    copy.index -= n;
                    copy.iter = copy.iter - n;
                    return copy;
                }
            
            private:
                blt::size_t index;
        };
    }
    
    template<typename Iter>
    class enumerate_iterator_container : public iterator::iterator_container<iterator::enumerate_wrapper<Iter>>
    {
        public:
            using iterator::iterator_container<iterator::enumerate_wrapper<Iter>>::iterator_container;
            
            enumerate_iterator_container(Iter begin, Iter end, blt::size_t size):
                    iterator::iterator_container<iterator::enumerate_wrapper<Iter>>(
                            iterator::enumerate_wrapper<Iter>{0, std::move(begin)}, iterator::enumerate_wrapper<Iter>{size, std::move(end)})
            {}
    };
    
    template<typename Iter>
    enumerate_iterator_container(Iter, Iter, blt::size_t) -> enumerate_iterator_container<Iter>;
    
    namespace iterator::impl
    {
        template<typename Derived>
        class enumerate_t
        {
            public:
                auto enumerate()
                {
                    auto* d = static_cast<Derived*>(this);
                    return enumerate_iterator_container{d->begin(), d->end(), static_cast<blt::size_t>(std::distance(d->begin(), d->end()))};
                }
        };
    }
    
    template<typename T>
    static inline auto enumerate(T& container)
    {
        return enumerate_iterator_container{container.begin(), container.end(), container.size()};
    }
    
    template<typename T>
    static inline auto enumerate(const T& container)
    {
        return enumerate_iterator_container{container.begin(), container.end(), container.size()};
    }
    
    template<typename T, blt::size_t size>
    static inline auto enumerate(const T(& container)[size])
    {
        return enumerate_iterator_container{&container[0], &container[size], size};
    }
    
    template<typename T, blt::size_t size>
    static inline auto enumerate(T(& container)[size])
    {
        return enumerate_iterator_container{&container[0], &container[size], size};
    }
    
}

#endif //BLT_ITERATOR_ENUMERATE_H