SkipWhile.h

#pragma once
 
#include <cstdlib>
#include <optional>
 
#include "../Common.h"
#include "../util/TraitImpl.h"
 
namespace CXXIter {
 
    // ################################################################################################
    // SKIP WHILE
    // ################################################################################################
    namespace op {
        template<typename TChainInput, typename TSkipPredicate>
        class [[nodiscard(CXXITER_CHAINER_NODISCARD_WARNING)]] SkipWhile : public IterApi<SkipWhile<TChainInput, TSkipPredicate>> {
            friend struct trait::Iterator<SkipWhile<TChainInput, TSkipPredicate>>;
        private:
            TChainInput input;
            TSkipPredicate skipPredicate;
            bool skipEnded = false;
        public:
            constexpr SkipWhile(TChainInput&& input, TSkipPredicate skipPredicate) : input(std::move(input)), skipPredicate(skipPredicate) {}
        };
    }
    // ------------------------------------------------------------------------------------------------
    template<typename TChainInput, typename TSkipPredicate>
    struct trait::Iterator<op::SkipWhile<TChainInput, TSkipPredicate>> {
        using ChainInputIterator = trait::Iterator<TChainInput>;
        using InputItem = typename TChainInput::Item;
        // CXXIter Interface
        using Self = op::SkipWhile<TChainInput, TSkipPredicate>;
        using Item = InputItem;
 
        static constexpr inline IterValue<Item> next(Self& self) {
            while(true) {
                auto item = ChainInputIterator::next(self.input);
                if(!item.has_value()) [[unlikely]] { return {}; }
                if(self.skipEnded) { return item; }
                if(!self.skipPredicate(item.value())) {
                    self.skipEnded = true;
                    return item;
                }
            }
        }
        static constexpr inline SizeHint sizeHint(const Self& self) {
            SizeHint input = ChainInputIterator::sizeHint(self.input);
            return SizeHint(0, input.upperBound);
        }
        static constexpr inline size_t advanceBy(Self& self, size_t n) { return util::advanceByPull(self, n); }
    };
 
}