#pragma once

#if !defined(MIJIN_UTIL_STRING_HPP_INCLUDED)
#define MIJIN_UTIL_STRING_HPP_INCLUDED 1

#include <algorithm>
#include <array>
#include <charconv>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <iterator>
#include <limits>
#include <locale>
#include <sstream>
#include <string>
#include <string_view>
#include <vector>

#include "./iterators.hpp"
#include "../internal/common.hpp"
#include "../util/traits.hpp"

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public traits
//

template<typename T>
inline constexpr bool is_string_v = is_template_instance_v<std::basic_string, std::remove_cvref_t<T>>;

template<typename T>
concept std_string_type = is_string_v<T>;

template<typename T>
inline constexpr bool is_string_view_v = is_template_instance_v<std::basic_string_view, std::remove_cvref_t<T>>;

template<typename T>
concept std_string_view_type = is_string_view_v<T>;

template<typename T>
inline constexpr bool is_char_v = is_any_type_v<std::remove_cvref_t<T>, char, wchar_t, char8_t, char16_t, char32_t>;

template<typename T>
concept char_type = is_char_v<T>;

template<typename T>
inline constexpr bool is_cstring_v = std::is_pointer_v<T> && is_char_v<std::remove_pointer_t<T>>;

template<typename T>
concept cstring_type = is_cstring_v<T>;

template<typename T>
struct str_char_type
{
    using type = void;
};

template<char_type T>
struct str_char_type<T*>
{
    using type = std::remove_cvref_t<T>;
};

template<std_string_view_type T>
struct str_char_type<T>
{
    using type = typename std::remove_cvref_t<T>::value_type;
};

template<std_string_type T>
struct str_char_type<T>
{
    using type = typename std::remove_cvref_t<T>::value_type;
};

template<typename T>
using str_char_type_t = str_char_type<T>::type;

//
// public types
//

struct SplitOptions
{
    std::size_t limitParts = std::numeric_limits<std::size_t>::max();
    bool ignoreEmpty = true;
};

//
// public functions
//

template <typename TRange, typename TValue = typename TRange::value_type>
[[nodiscard]] std::string join(const TRange& elements, const char* const delimiter)
{
    std::ostringstream oss;
    auto first = std::begin(elements);
    auto last = std::end(elements);

    if (first != last)
    {
        std::copy(first, std::prev(last), std::ostream_iterator<TValue>(oss, delimiter));
        first = std::prev(last);
    }
    if (first != last)
    {
        oss << *first;
    }

    return oss.str();
}

namespace detail
{
template<typename TChar, typename TTraits, typename TOutIterator>
void splitImpl(std::basic_string_view<TChar, TTraits> stringView,
               std::basic_string_view<TChar, TTraits> separator,
               const SplitOptions& options,
               TOutIterator outIterator,
               std::size_t& numEmitted)
{
    using sv_t = std::basic_string_view<TChar, TTraits>;

    MIJIN_ASSERT(options.limitParts > 0, "Cannot split to zero parts.");
    MIJIN_ASSERT(!separator.empty(), "Separator cannot be empty.");

    if (separator.empty())
    {
        return;
    }

    auto emit = [&](std::string_view result)
    {
        *outIterator = result;
        ++outIterator;
        ++numEmitted;
    };

    if (options.limitParts <= 1)
    {
        emit(stringView);
        return;
    }
    auto start = stringView.begin();
    auto pos = start;
    const auto end = stringView.end();

    auto seperatorFound = [&]()
    {
        return pos <= (end - separator.size()) && sv_t(pos, pos + separator.size()) == separator;
    };

    while (pos != end)
    {
        if (seperatorFound())
        {
            if (!options.ignoreEmpty || pos != start)
            {
                emit(std::string_view(start, pos));
            }
            start = pos = (pos + separator.size());
            if (numEmitted == options.limitParts - 1)
            {
                if (options.ignoreEmpty)
                {
                    while (seperatorFound())
                    {
                        pos += separator.size();
                    }
                }
                emit(std::string_view(pos, end));
                return;
            }
            if (!options.ignoreEmpty && pos == end)
            {
                // skipped a separator at the very end, add an empty entry
                emit("");
                return;
            }
        }
        else
        {
            ++pos;
        }
    }

    if (start != end)
    {
        emit(std::string_view(start, end));
    }
}

template<typename TChar, typename TTraits>
std::vector<std::basic_string_view<TChar, TTraits>> splitImpl(std::basic_string_view<TChar, TTraits> stringView,
                                                              std::basic_string_view<TChar, TTraits> separator,
                                                              const SplitOptions& options)
{
    std::vector<std::basic_string_view<TChar, TTraits>> result;
    std::size_t numEmitted = 0;
    splitImpl(stringView, separator, options, std::back_inserter(result), numEmitted);
    return result;
}


template<std::size_t count, typename TChar, typename TTraits>
std::array<std::basic_string_view<TChar, TTraits>, count> splitFixedImpl(std::basic_string_view<TChar, TTraits> stringView,
                                                                         std::basic_string_view<TChar, TTraits> separator,
                                                                         SplitOptions options,
                                                                         std::size_t* outNumResults)
{
    options.limitParts = count;

    std::array<std::basic_string_view<TChar, TTraits>, count> result;
    std::size_t numEmitted = 0;
    splitImpl(stringView, separator, options, result.begin(), numEmitted);
    if (outNumResults != nullptr)
    {
        *outNumResults = numEmitted;
    }
    return result;
}

template<typename TChar, typename TTraitsA, typename TTraitsB>
bool equalsIgnoreCaseImpl(std::basic_string_view<TChar, TTraitsA> stringA, std::basic_string_view<TChar, TTraitsB> stringB) MIJIN_NOEXCEPT
{
    if (stringA.size() != stringB.size())
    {
        return false;
    }

    for (const auto [charA, charB] : zip(stringA, stringB))
    {
        if (std::tolower(charA) != std::tolower(charB))
        {
            return false;
        }
    }

    return true;
}

template<typename TChar, typename TTraits>
std::basic_string_view<TChar, TTraits> trimPrefixImpl(std::basic_string_view<TChar, TTraits> stringView,
                                                      std::basic_string_view<TChar, TTraits> charsToTrim)
{
    stringView.remove_prefix(std::min(stringView.find_first_not_of(charsToTrim), stringView.size()));
    return stringView;
}

template<typename TChar, typename TTraits>
std::basic_string_view<TChar, TTraits> trimSuffixImpl(std::basic_string_view<TChar, TTraits> stringView,
                                                      std::basic_string_view<TChar, TTraits> charsToTrim)
{
    stringView.remove_suffix(stringView.size() - std::min(stringView.find_last_not_of(charsToTrim) + 1, stringView.size()));
    return stringView;
}

template<typename TChar, typename TTraits>
std::basic_string_view<TChar, TTraits> trimImpl(std::basic_string_view<TChar, TTraits> stringView,
                                                std::basic_string_view<TChar, TTraits> charsToTrim)
{
    return trimPrefixImpl(trimSuffixImpl(stringView, charsToTrim), charsToTrim);
}

template<typename TChar>
static const std::array DEFAULT_TRIM_CHARS_DATA = {TChar(' '), TChar('\t'), TChar('\r'), TChar('\n')};

template<typename TChar>
static const std::basic_string_view<TChar, std::char_traits<TChar>> DEFAULT_TRIM_CHARS
    = {DEFAULT_TRIM_CHARS_DATA<TChar>.begin(), DEFAULT_TRIM_CHARS_DATA<TChar>.end()};
}

template<typename TLeft, typename TRight>
[[nodiscard]] auto split(TLeft&& stringView, TRight&& separator, const SplitOptions& options = {})
{
    return detail::splitImpl(std::basic_string_view(std::forward<TLeft>(stringView)),
                             std::basic_string_view(std::forward<TRight>(separator)), options);
}

template<std::size_t count, typename TLeft, typename TRight>
[[nodiscard]] auto splitFixed(TLeft&& stringView, TRight&& separator, SplitOptions options = {}, std::size_t* outNumResults = nullptr)
{
    return detail::splitFixedImpl<count>(std::basic_string_view(std::forward<TLeft>(stringView)),
                                         std::basic_string_view(std::forward<TRight>(separator)), options, outNumResults);
}

template<typename TString, typename TChars>
[[nodiscard]]
auto trimPrefix(TString&& string, TChars&& chars)
{
    return detail::trimPrefixImpl(std::string_view(std::forward<TString>(string)), std::string_view(std::forward<TChars>(chars)));
}

template<typename TString>
[[nodiscard]]
auto trimPrefix(TString&& string)
{
    return trimPrefix(string, detail::DEFAULT_TRIM_CHARS<str_char_type_t<TString>>);
}

template<typename TString, typename TChars>
[[nodiscard]]
auto trimSuffix(TString&& string, TChars&& chars)
{
    return detail::trimSuffixImpl(std::string_view(std::forward<TString>(string)), std::string_view(std::forward<TChars>(chars)));
}

template<typename TString>
[[nodiscard]]
auto trimSuffix(TString&& string)
{
    return trimSuffix(string, detail::DEFAULT_TRIM_CHARS<str_char_type_t<TString>>);
}

template<typename TString, typename TChars>
[[nodiscard]]
auto trim(TString&& string, TChars&& chars)
{
    return detail::trimImpl(std::string_view(std::forward<TString>(string)), std::string_view(std::forward<TChars>(chars)));
}

template<typename TString>
[[nodiscard]]
auto trim(TString&& string)
{
    return trim(string, detail::DEFAULT_TRIM_CHARS<str_char_type_t<TString>>);
}

template<typename TLeft, typename TRight>
[[nodiscard]] bool equalsIgnoreCase(TLeft&& left, TRight&& right) MIJIN_NOEXCEPT
{
    return detail::equalsIgnoreCaseImpl(std::string_view(left), std::string_view(right));
}

template<typename TChar, typename TTraits, typename TAllocator>
constexpr void makeLower(std::basic_string<TChar, TTraits, TAllocator>& string)
{
    std::transform(string.begin(), string.end(), string.begin(), [locale = std::locale()](TChar chr)
    {
        return std::tolower<TChar>(chr, locale);
    });
}

template<typename TChar, typename TTraits, typename TAllocator>
constexpr void makeUpper(std::basic_string<TChar, TTraits, TAllocator>& string)
{
    std::transform(string.begin(), string.end(), string.begin(), [locale = std::locale()](TChar chr)
    {
        return std::toupper<TChar>(chr, locale);
    });
}

template<typename... TArgs>
[[nodiscard]]
constexpr auto toLower(TArgs&&... args)
{
    std::basic_string string(std::forward<TArgs>(args)...);
    makeLower(string);
    return string;
}

template<typename... TArgs>
[[nodiscard]]
constexpr auto toUpper(TArgs&&... args)
{
    std::basic_string string(std::forward<TArgs>(args)...);
    makeUpper(string);
    return string;
}


template<std::integral TNumber>
[[nodiscard]]
constexpr bool toNumber(std::string_view stringView, TNumber& outNumber, int base = 10) MIJIN_NOEXCEPT
{
    const char* start = &*stringView.begin();
    const char* end = start + stringView.size();
    const std::from_chars_result res = std::from_chars(start, end, outNumber, base);
    return res.ec == std::errc{} && res.ptr == end;
}

template<typename TChar, typename TTraits, std::integral TNumber>
[[nodiscard]]
constexpr bool toNumber(std::basic_string_view<TChar, TTraits> stringView, TNumber& outNumber, int base = 10) MIJIN_NOEXCEPT requires (!std::is_same_v<TChar, char>)
{
    std::string asString;
    asString.resize(stringView.size());
    // should only contain number symbols, so just cast down to char
    std::transform(stringView.begin(), stringView.end(), asString.begin(), [](TChar chr) { return static_cast<char>(chr); });
    return toNumber(asString, outNumber, base);
}

template<std::floating_point TNumber>
[[nodiscard]]
constexpr bool toNumber(std::string_view stringView, TNumber& outNumber, std::chars_format fmt = std::chars_format::general) MIJIN_NOEXCEPT
{
    const char* start = &*stringView.begin();
    const char* end = start + stringView.size();
    const std::from_chars_result res = std::from_chars(start, end, outNumber, fmt);
    return res.ec == std::errc{} && res.ptr == end;
}

template<typename TChar, typename TTraits, std::floating_point TNumber>
[[nodiscard]]
constexpr bool toNumber(std::basic_string_view<TChar, TTraits> stringView, TNumber& outNumber, std::chars_format fmt = std::chars_format::general) MIJIN_NOEXCEPT requires (!std::is_same_v<TChar, char>)
{
    std::string asString;
    asString.resize(stringView.size());
    // should only contain number symbols, so just cast down to char
    std::transform(stringView.begin(), stringView.end(), asString.begin(), [](TChar chr) { return static_cast<char>(chr); });
    return toNumber(asString, outNumber, fmt);
}

template<typename TChar>
[[nodiscard]]
constexpr bool isDecimalChar(TChar chr) noexcept
{
    return (chr >= TChar('0') && chr <= TChar('9'));
}

template<typename TChar>
[[nodiscard]]
constexpr bool isHexadecimalChar(TChar chr) noexcept
{
    return isDecimalChar(chr)
        || (chr >= TChar('A') && chr <= TChar('F'))
        || (chr >= TChar('a') && chr <= TChar('f'));
}

template<typename TChar>
bool compareIgnoreCase(TChar left, TChar right) MIJIN_NOEXCEPT
{
    return std::tolower(left) == std::tolower(right);
}

[[nodiscard]]
inline auto findIgnoreCase(std::string_view haystack, std::string_view needle)
{
    return std::ranges::search(haystack, needle, &compareIgnoreCase<char>);
}

[[nodiscard]]
inline bool startsWithIgnoreCase(std::string_view string, std::string_view part)
{
    if (part.size() > string.size())
    {
        return false;
    }
    return std::ranges::equal(string.substr(0, part.size()), part, &compareIgnoreCase<char>);
}

[[nodiscard]]
inline bool endsWithIgnoreCase(std::string_view string, std::string_view part)
{
    if (part.size() > string.size())
    {
        return false;
    }
    return std::ranges::equal(string.substr(string.size() - part.size()), part, &compareIgnoreCase<char>);
}

namespace pipe
{
struct Join
{
    const char* delimiter;

    explicit Join(const char* delimiter_) MIJIN_NOEXCEPT: delimiter(delimiter_) {}
};

template<typename TIterable>
auto operator|(TIterable&& iterable, const Join& joiner)
{
    return join(std::forward<TIterable>(iterable), joiner.delimiter);
}
} // namespace pipe

struct [[nodiscard]] ConvertCharTypeResult
{
    unsigned numRead = 0;
    unsigned numWritten = 0;

    constexpr operator bool() const MIJIN_NOEXCEPT
    {
        return numRead != 0 || numWritten != 0;
    }
    constexpr bool operator !() const MIJIN_NOEXCEPT
    {
        return !static_cast<bool>(*this);
    }
};

template<typename TFrom, typename TTo>
ConvertCharTypeResult convertCharType(const TFrom* chrFrom, std::size_t numFrom, TTo* outTo, std::size_t numTo, std::mbstate_t& mbstate) MIJIN_NOEXCEPT
{
    if constexpr (std::is_same_v<TFrom, char>)
    {
        if constexpr (std::is_same_v<TTo, wchar_t>)
        {
            const std::size_t result = std::mbrtowc(outTo, chrFrom, numFrom, &mbstate);
            if (result == static_cast<std::size_t>(-1))
            {
                return {};
            }
            return {
                .numRead = static_cast<unsigned>(result),
                .numWritten = 1
            };
        }
        if constexpr (std::is_same_v<TTo, char8_t>)
        {

        }
    }
    if constexpr (std::is_same_v<TFrom, wchar_t>)
    {
        if constexpr (std::is_same_v<TTo, char>)
        {
            if (numTo < MB_CUR_MAX)
            {
                char tmpBuf[MB_LEN_MAX];
                const ConvertCharTypeResult result = convertCharType(chrFrom, numFrom, tmpBuf, MB_LEN_MAX, mbstate);
                if (result && result.numWritten <= numTo)
                {
                    std::memcpy(outTo, tmpBuf, result.numWritten);
                }
                return result;
            }
            const std::size_t result = std::wcrtomb(outTo, *chrFrom, &mbstate);
            if (result == static_cast<std::size_t>(-1))
            {
                return {};
            }
            return {
                .numRead = 1,
                .numWritten = static_cast<unsigned>(result)
            };
        }
        if constexpr (std::is_same_v<TTo, char8_t>)
        {

        }
    }
    if constexpr (std::is_same_v<TFrom, char8_t>)
    {

    }
}
template<typename TFrom, typename TTo>
ConvertCharTypeResult convertCharType(const TFrom* chrFrom, std::size_t numFrom, TTo* outTo, std::size_t numTo) MIJIN_NOEXCEPT
{
    std::mbstate_t mbstate;
    return convertCharType(chrFrom, numFrom, outTo, numTo, mbstate);
}

template<typename TIterator>
struct [[nodiscard]] ConvertStringTypeResult
{
    TIterator iterator;
    bool success;
};

template<typename TTo, typename TFrom, typename TFromTraits, std::output_iterator<TTo> TIterator>
ConvertStringTypeResult<TIterator> convertStringType(std::basic_string_view<TFrom, TFromTraits> strFrom, TIterator outIterator)
{
    TTo outBuffer[MB_LEN_MAX];

    std::mbstate_t mbstate = {};
    for (auto it = strFrom.begin(); it != strFrom.end();)
    {
        const std::size_t remaining = std::distance(it, strFrom.end());
        const ConvertCharTypeResult result = convertCharType(&*it, remaining, outBuffer, MB_LEN_MAX, mbstate);
        if (!result)
        {
            return {
                .iterator = outIterator,
                .success = false
            };
        }
        for (unsigned pos = 0; pos < result.numWritten; ++pos)
        {
            *outIterator = outBuffer[pos];
            ++outIterator;
        }
        it = std::next(it, result.numRead);
    }

    return {
        .iterator = outIterator,
        .success = true
    };
}

template<typename TFrom, typename TFromTraits, typename TTo, typename TToTraits, typename TToAllocator>
bool convertStringType(std::basic_string_view<TFrom, TFromTraits> strFrom, std::basic_string<TTo, TToTraits, TToAllocator>& outString)
{
    if constexpr (std::is_same_v<TTo, TFrom>)
    {
        outString += strFrom;
        return true;
    }
    else
    {
        return convertStringType<TTo>(strFrom, std::back_inserter(outString)).success;
    }
}

template<typename TFrom, typename TTo, typename TToTraits, typename TToAllocator>
bool convertStringType(const TFrom* strFrom, std::basic_string<TTo, TToTraits, TToAllocator>& outString)
{
    return convertStringType(std::basic_string_view<TFrom>(strFrom), outString);
}
} // namespace mijin

#endif // !defined(MIJIN_UTIL_STRING_HPP_INCLUDED)