Conversion.h

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/** @noop License Comment
 *  @file
 *  @copyright
 *  This Source Code is subject to the terms of the Mozilla Public License, v2.0.
 *  If a copy of the MPL was not distributed with this file You can obtain one at
 *  https://mozilla.org/MPL/2.0/
 *  
 *  @author David Mórász
 *  @date 2025
 */
 
 
#pragma once
 
#include <ranges>
 
#include "CoreMinimal.h"
 
#include "Mcro/Concepts.h"
#include "Mcro/Range/Iterators.h"
#include "Mcro/Text/TupleAsString.h"
#include "Mcro/Templates.h"
#include "Mcro/Text.h"
 
#include "Mcro/LibraryIncludes/Start.h"
#include "range/v3/all.hpp"
#include "Mcro/LibraryIncludes/End.h"
 
namespace Mcro::Range
{
    using namespace Mcro::Templates;
    using namespace Mcro::Concepts;
 
    struct FRangeStringFormatOptions
    {
        FString Start     { TEXT_"[" };
        FString End       { TEXT_"]" };
        FString Separator { TEXT_", " };
    };
    
    namespace Detail
    {
        template <CRangeMember Range>
        struct TRangeWithStringFormat
        {
            TRangeWithStringFormat(Range const& range, FRangeStringFormatOptions const& options)
                : Storage(range)
                , Options(options)
            {}
            
            auto begin() const { return Storage.begin(); }
            auto end() const { return Storage.end(); }
            
            FRangeStringFormatOptions Options;
        private:
            Range const& Storage;
        };
    }
 
    /** @brief Specify a separator sequence for a range when converting it to a string */
    FORCEINLINE auto Separator(FString const& separator)
    {
        return ranges::make_pipeable([separator] <CRangeMember Input> (Input&& range)
        {
            if constexpr (CIsTemplate<Input, Detail::TRangeWithStringFormat>)
            {
                range.Options.Separator = separator;
                return range;
            }
            else return Detail::TRangeWithStringFormat(range, {.Separator = separator});
        });
    }
 
    /** @brief Specify a start and an end sequence enclosing this range when converting it to a string */
    FORCEINLINE auto Enclosure(FString const& start, FString const& end)
    {
        return ranges::make_pipeable([=] <CRangeMember Input> (Input&& range)
        {
            if constexpr (CIsTemplate<Input, Detail::TRangeWithStringFormat>)
            {
                range.Options.Start = start;
                range.Options.End = end;
                return range;
            }
            else return Detail::TRangeWithStringFormat(range, {.Start = start, .End = end});
        });
    };
 
    /** @brief Don't use a separator when this range is rendered to a string */
    FORCEINLINE auto NoSeparator()
    {
        return ranges::make_pipeable([] <CRangeMember Input> (Input&& range)
        {
            if constexpr (CIsTemplate<Input, Detail::TRangeWithStringFormat>)
            {
                range.Options.Separator = {};
                return range;
            }
            else return Detail::TRangeWithStringFormat(range, {.Separator = {}});
        });
    }
 
    /** @brief Don't enclose this range in anything when it's rendered to a string */
    FORCEINLINE auto NoEnclosure()
    {
        return ranges::make_pipeable([] <CRangeMember Input> (Input&& range)
        {
            if constexpr (CIsTemplate<Input, Detail::TRangeWithStringFormat>)
            {
                range.Options.Start = {};
                range.Options.End = {};
                return range;
            }
            else return Detail::TRangeWithStringFormat(range, {.Start = {}, .End = {}});
        });
    }
 
    /**
     *  @brief
     *  Don't insert anything else than the contents of the input range when that is rendered as a string just append
     *  each item one after the other.
     */
    FORCEINLINE auto NoDecorators()
    {
        return ranges::make_pipeable([] <CRangeMember Input> (Input&& range)
        {
            if constexpr (CIsTemplate<Input, Detail::TRangeWithStringFormat>)
            {
                range.Options = {{}, {}, {}};
                return range;
            }
            else return Detail::TRangeWithStringFormat(range, {{}, {}, {}});
        });
    }
 
    namespace Detail
    {
        template <typename CharType>
        void CopyCharactersToBuffer(CharType const& value, int32 chunks, int32& position, TArray<CharType>& buffer)
        {
            if (buffer.Num() == position) buffer.AddZeroed(chunks);
            buffer[position] = value;
            ++position;
        }
 
        template <CStringOrView String>
        void CopyStringToBufferUnsafe(String const& value, int32& position, TArray<TCHAR>& buffer)
        {
            FMemory::Memcpy(buffer.GetData() + position, GetData(value), value.Len() * sizeof(TCHAR));
            position += value.Len();
        }
 
        template <CStringOrView String>
        void CopyStringItemToBuffer(String const& value, FString const& separator, int32 chunks, int32& position, TArray<TCHAR>& buffer)
        {
            int nextLength = value.Len() + separator.Len();
                
            if (buffer.Num() <= position + nextLength) buffer.AddZeroed(chunks);
            if (!separator.IsEmpty())
                CopyStringToBufferUnsafe(separator, position, buffer);
            CopyStringToBufferUnsafe(value, position, buffer);
        }
    }
 
    /**
     *  @brief  Render an input range as a string.
     *
     *  For ranges of any char type, the output is an uninterrupted string of them. Other char types than TCHAR will
     *  be converted to the encoding of the current TCHAR.
     *
     *  For ranges of strings and string-views individual items will be directly copy-appended to the output separated
     *  by `, ` (unless another separator sequence is set via `Separator`)
     *
     *  For anything else, `Mcro::Text::AsString` is used. In fact this function serves as the basis for `AsString` for
     *  any range type. Like for strings, any other type is separated by `, ` (unless another separator sequence is set
     *  via `Separator`). For convenience a piped version is also provided of this function.
     */
    template <CRangeMember Range>
    FString RenderAsString(Range&& range)
    {
        using ElementType = TRangeElementType<Range>;
        
        if (IteratorEquals(range.begin(), range.end()))
            return {};
 
        constexpr int chunks = 16384;
        int32 position = 0;
        FRangeStringFormatOptions rangeFormatOptions;
        
        if constexpr (CIsTemplate<Range, Detail::TRangeWithStringFormat>)
            rangeFormatOptions = range.Options;
 
        if constexpr (CChar<ElementType>)
        {
            TArray<ElementType> buffer;
            for (ElementType const& character : range)
                Detail::CopyCharactersToBuffer(character, chunks, position, buffer);
            
            if constexpr (CCurrentChar<ElementType>)
                return Mcro::Text::Detail::MakeStringFromPtrSize(buffer.GetData(), position);
            else
            {
                TStdStringView<ElementType> stringView(buffer.GetData(), position);
                return UnrealConvert(stringView);
            }
        }
        else if constexpr (CStringOrView<ElementType>)
        {
            TArray<TCHAR> buffer;
            for (auto it = range.begin(); !IteratorEquals(it, range.end()); ++it)
            {
                ElementType const& value = *it;
                bool isFirst = IteratorEquals(it, range.begin());
                Detail::CopyStringItemToBuffer(
                    value,
                    isFirst ? FString() : rangeFormatOptions.Separator,
                    chunks,
                    position, buffer
                );
            }
            FString output = Mcro::Text::Detail::MakeStringFromPtrSize(buffer.GetData(), position);
            return rangeFormatOptions.Start + output + rangeFormatOptions.End;
        }
        else
        {
            TArray<TCHAR> buffer;
            for (auto it = range.begin(); !IteratorEquals(it, range.end()); ++it)
            {
                ElementType const& value = *it;
                FString valueString = AsString(value);
 
                bool isFirst = IteratorEquals(it, range.begin());
                Detail::CopyStringItemToBuffer(
                    valueString,
                    isFirst ? FString() : rangeFormatOptions.Separator,
                    chunks,
                    position, buffer
                );
            }
            FString output = Mcro::Text::Detail::MakeStringFromPtrSize(buffer.GetData(), position);
            return rangeFormatOptions.Start + output + rangeFormatOptions.End;
        }
    }
 
    FORCEINLINE auto RenderAsString()
    {
        return ranges::make_pipeable([]<CRangeMember Input>(Input&& range)
        {
            return RenderAsString(FWD(range));
        });
    }
    
    /**
     *  @brief  Render a range as the given container.
     *
     *  This functor will iterate over the entire input range and copy its values to the newly created container
     *  one-by-one with its `Add` function. If you want a more optimised way to do that use `OutputTo` where you can
     *  supply your own container as an l-value.
     *
     *  usage:
     *  @code
     *  using namespace ranges;
     *  auto result = views::ints(0)
     *      | views::stride(2)
     *      | views::take(5)
     *      | RenderAs<TArray>();
     *      
     *  // -> TArray<int32> {0, 2, 4, 6, 8}
     *  @endcode
     *  
     *  @tparam Target
     *  An Unreal container template which has a public function member `Add`, the element-type of which will be deduced
     *  from the input left side range.
     */
    template <template <typename> typename Target>
    class RenderAs
    {
        template <CRangeMember From, typename Value = TRangeElementType<From>>
        requires CUnrealRange<Target<Value>>
        Target<Value> Convert(From&& range) const
        {
            Target<Value> result;
            for (Value const& value : range)
                result.Add(value);
            return result;
        }
        
    public:
        RenderAs() {};
 
        template <CRangeMember From>
        friend auto operator | (From&& range, RenderAs&& functor)
        {
            return functor.Convert(FWD(range));
        }
        
        template <CRangeMember From>
        auto Render(From&& range) const
        {
            return Convert(FWD(range));
        }
    };
 
    /**
     *  @brief  Render a range to an already existing container.
     *
     *  This functor will iterate over the entire input range and copy its values to the given container one-by-one.
     *  Target container must expose iterators which allows modifying its content. If the input range has more items
     *  than the target container current size, then start using its `Add` function. 
     *
     *  usage:
     *  @code
     *  using namespace ranges;
     *  TArray<int32> Storage;
     *  Storage.SetNumUninitialized(5);
     *  
     *  auto result = views::ints(0, 10)
     *      | views::stride(2)
     *      | OutputTo(Storage);
     *      
     *  // -> TArray<int32> {0, 2, 4, 6, 8}
     *  @endcode
     *  
     *  @tparam Target
     *  An Unreal container which has a public function member `Add`, the element-type of which will be deduced from
     *  the target output container.
     */
    template <CUnrealRange Target>
    class OutputTo
    {
        using ElementType = TRangeElementType<Target>;
        Target& Storage;
 
        template <CRangeMember From, CConvertibleToDecayed<ElementType> Value = TRangeElementType<From>>
        void Convert(From&& range)
        {
            auto it = Storage.begin();
            auto endIt = Storage.end(); 
            for (Value const& value : range)
            {
                if (IteratorEquals(it, endIt))
                    Storage.Add(value);
                else
                {
                    *it = value;
                    ++it;
                }
            }
        }
 
    public:
        OutputTo(Target& target) : Storage(target) {}
 
        template <CRangeMember From>
        friend Target& operator | (From&& range, OutputTo&& functor)
        {
            functor.Convert(FWD(range));
            return functor.Storage;
        }
    };
 
    /**
     *  @brief
     *  Render a range of tuples or range of ranges with at least 2 elements as a TMap.
     *
     *  This functor will iterate over the entire input range and copy its values to the newly created container
     *  one-by-one with its `Add` function.
     *
     *  When working with range-of-ranges then ranges which doesn't have at least two elements will be silently ignored.
     *
     *  usage (from tuples):
     *  @code
     *  using namespace ranges;
     *  TArray<int32> MyKeyArray {1, 2, 3, 4, 5};
     *  TArray<FString> MyValueArray {TEXT_"foo", TEXT_"bar"};
     *  
     *  auto result = views::zip(MyKeyArray, views::cycle(MyValueArray))
     *      | RenderAsMap();
     *      
     *  // -> TMap<int32, FString> {{1, "foo"}, {2, "bar"}, {3, "foo"}, {4, "bar"}, {5, "foo"}}
     *  @endcode
     *  
     *  usage (from inner-ranges):
     *  @code
     *  using namespace ranges;
     *  auto result = views::ints(0, 9)
     *      | views::chunk(2)
     *      | RenderAsMap();
     *      
     *  // -> TMap<int32, int32> {{0, 1}, {2, 3}, {4, 5}, {6, 7}}
     *  // notice how 8 is discarded from the end, as that range didn't have 2 items 
     *  @endcode
     */
    class RenderAsMap
    {
        template <
            CRangeMember From,
            CTuple Value = TRangeElementType<From>,
            typename MapType = TMap<TTypeAtDecayed<0, Value>, TTypeAtDecayed<1, Value>>
        >
        requires (GetSize<Value>() >= 2)
        static void Convert(From&& range, MapType& result)
        {
            for (Value const& value : range)
                result.Add(GetItem<0>(value), GetItem<1>(value));
        }
        
        template <
            CRangeMember From,
            CRangeMember InnerRange = TRangeElementType<From>,
            typename Value = TRangeElementType<InnerRange>,
            typename MapType = TMap<Value, Value>
        >
        static void Convert(From&& range, MapType& result)
        {
            for (InnerRange const& innerRange : range)
            {
                // TODO: support TMultiMap
                auto it = innerRange.begin();
                if (IteratorEquals(it, innerRange.end())) continue;
                Value const& key = *it;
                ++it;
                if (IteratorEquals(it, innerRange.end())) continue;
                Value const& value = *it;
                result.Add(key, value);
            }
        }
        
        template <
            CRangeMember From,
            CTuple Value = TRangeElementType<From>,
            typename MapType = TMap<TTypeAtDecayed<0, Value>, TTypeAtDecayed<1, Value>>
        >
        requires (GetSize<Value>() >= 2)
        MapType Convert(From&& range) const
        {
            MapType result;
            Convert(FWD(range), result);
            return result;
        }
        
        template <
            CRangeMember From,
            CRangeMember InnerRange = TRangeElementType<From>,
            typename Value = TRangeElementType<InnerRange>,
            typename MapType = TMap<Value, Value>
        >
        MapType Convert(From&& range) const
        {
            MapType result;
            Convert(FWD(range), result);
            return result;
        }
 
    public:
        template <CIsTemplate<TMap> Target>
        friend class OutputToMap;
        
        RenderAsMap() {};
 
        template <CRangeMember From>
        friend auto operator | (From&& range, RenderAsMap&& functor)
        {
            return functor.Convert(FWD(range));
        }
        
        template <CRangeMember From>
        auto Render(From&& range) const
        {
            return Convert(FWD(range));
        }
    };
 
    /**
     *  @brief
     *  Output a range of tuples or range of ranges with at least 2 elements to an already existing TMap.
     *
     *  This functor will iterate over the entire input range and copy its values to the existing TMap one-by-one with
     *  its `Add` function.
     *
     *  When working with range-of-ranges then ranges which doesn't have at least two elements will be silently ignored.
     *
     *  usage (from tuples):
     *  @code
     *  using namespace ranges;
     *  TArray<int32> MyKeyArray {1, 2, 3, 4, 5};
     *  TArray<FString> MyValueArray {TEXT_"foo", TEXT_"bar"};
     *  
     *  auto result = views::zip(MyKeyArray, views::cycle(MyValueArray))
     *      | RenderAsMap();
     *      
     *  // -> TMap<int32, FString> {{1, "foo"}, {2, "bar"}, {3, "foo"}, {4, "bar"}, {5, "foo"}}
     *  @endcode
     *  
     *  usage (from inner-ranges):
     *  @code
     *  using namespace ranges;
     *  auto result = views::ints(0, 9)
     *      | views::chunk(2)
     *      | RenderAsMap();
     *      
     *  // -> TMap<int32, int32> {{0, 1}, {2, 3}, {4, 5}, {6, 7}}
     *  // notice how 8 is discarded from the end, as that range didn't have 2 items 
     *  @endcode
     *  
     *  @tparam Target  A TMap. Its key-value types will be deduced from the target output map.
     */
    template <CIsTemplate<TMap> Target>
    class OutputToMap
    {
        using KeyType = typename Target::KeyType;
        using ValueType = typename Target::ValueType;
        Target& Storage;
 
    public:
        OutputToMap(Target& target) : Storage(target) {};
 
        template <
            CRangeMember From,
            CTupleConvertsToArgs<KeyType, ValueType> = TRangeElementType<From>
        >
        friend Target& operator | (From&& range, OutputToMap&& functor)
        {
            RenderAsMap::Convert(FWD(range), functor.Storage);
            return functor.Storage;
        }
    };
}
 
namespace Mcro::Text
{
    using namespace Mcro::Range;
    
    template <CRangeMember Operand>
    requires (
        !CDirectStringFormatArgument<Operand>
        && !CHasToString<Operand>
    )
    struct TAsFormatArgument<Operand>
    {
        template <CConvertibleToDecayed<Operand> Arg>
        FString operator () (Arg&& left) const { return RenderAsString(left); }
    };
}