#include "GeneralUtils.h"

// C++
#include <cstdint>
#include <cassert>
#include <algorithm>
#include <filesystem>
#include <map>

template <typename T>
static inline size_t MinSize(const size_t size, const std::basic_string_view<T> string) {
	if (size == SIZE_MAX || size > string.size()) {
		return string.size();
	} else {
		return size;
	}
}

inline bool IsLeadSurrogate(const char16_t c) {
	return (0xD800 <= c) && (c <= 0xDBFF);
}

inline bool IsTrailSurrogate(const char16_t c) {
	return (0xDC00 <= c) && (c <= 0xDFFF);
}

inline void PushUTF8CodePoint(std::string& ret, const char32_t cp) {
	if (cp <= 0x007F) {
		ret.push_back(static_cast<uint8_t>(cp));
	} else if (cp <= 0x07FF) {
		ret.push_back(0xC0 | (cp >> 6));
		ret.push_back(0x80 | (cp & 0x3F));
	} else if (cp <= 0xFFFF) {
		ret.push_back(0xE0 | (cp >> 12));
		ret.push_back(0x80 | ((cp >> 6) & 0x3F));
		ret.push_back(0x80 | (cp & 0x3F));
	} else if (cp <= 0x10FFFF) {
		ret.push_back(0xF0 | (cp >> 18));
		ret.push_back(0x80 | ((cp >> 12) & 0x3F));
		ret.push_back(0x80 | ((cp >> 6) & 0x3F));
		ret.push_back(0x80 | (cp & 0x3F));
	} else {
		assert(false);
	}
}

constexpr const char16_t REPLACEMENT_CHARACTER = 0xFFFD;

bool static _IsSuffixChar(const uint8_t c) {
	return (c & 0xC0) == 0x80;
}

bool GeneralUtils::details::_NextUTF8Char(std::string_view& slice, uint32_t& out) {
	const size_t rem = slice.length();
	if (slice.empty()) return false;
	const uint8_t* bytes = reinterpret_cast<const uint8_t*>(&slice.front());
	if (rem > 0) {
		const uint8_t first = bytes[0];
		if (first < 0x80) { // 1 byte character
			out = static_cast<uint32_t>(first & 0x7F);
			slice.remove_prefix(1);
			return true;
		} else if (first < 0xC0) {
			// middle byte, not valid at start, fall through
		} else if (first < 0xE0) { // two byte character
			if (rem > 1) {
				const uint8_t second = bytes[1];
				if (_IsSuffixChar(second)) {
					out = (static_cast<uint32_t>(first & 0x1F) << 6)
						+ static_cast<uint32_t>(second & 0x3F);
					slice.remove_prefix(2);
					return true;
				}
			}
		} else if (first < 0xF0) { // three byte character
			if (rem > 2) {
				const uint8_t second = bytes[1];
				const uint8_t third = bytes[2];
				if (_IsSuffixChar(second) && _IsSuffixChar(third)) {
					out = (static_cast<uint32_t>(first & 0x0F) << 12)
						+ (static_cast<uint32_t>(second & 0x3F) << 6)
						+ static_cast<uint32_t>(third & 0x3F);
					slice.remove_prefix(3);
					return true;
				}
			}
		} else if (first < 0xF8) { // four byte character
			if (rem > 3) {
				const uint8_t second = bytes[1];
				const uint8_t third = bytes[2];
				const uint8_t fourth = bytes[3];
				if (_IsSuffixChar(second) && _IsSuffixChar(third) && _IsSuffixChar(fourth)) {
					out = (static_cast<uint32_t>(first & 0x07) << 18)
						+ (static_cast<uint32_t>(second & 0x3F) << 12)
						+ (static_cast<uint32_t>(third & 0x3F) << 6)
						+ static_cast<uint32_t>(fourth & 0x3F);
					slice.remove_prefix(4);
					return true;
				}
			}
		}
		out = static_cast<uint32_t>(REPLACEMENT_CHARACTER);
		slice.remove_prefix(1);
		return true;
	}
	return false;
}

/// See <https://www.ietf.org/rfc/rfc2781.html#section-2.1>
bool PushUTF16CodePoint(std::u16string& output, const uint32_t U, const size_t size) {
	if (output.length() >= size) return false;
	if (U < 0x10000) {
		// If U < 0x10000, encode U as a 16-bit unsigned integer and terminate.
		output.push_back(static_cast<uint16_t>(U));
		return true;
	} else if (U > 0x10FFFF) {
		output.push_back(REPLACEMENT_CHARACTER);
		return true;
	} else if (output.length() + 1 < size) {
		// Let U' = U - 0x10000. Because U is less than or equal to 0x10FFFF,
		// U' must be less than or equal to 0xFFFFF. That is, U' can be
		// represented in 20 bits.
		const uint32_t Ut = U - 0x10000;

		// Initialize two 16-bit unsigned integers, W1 and W2, to 0xD800 and
		// 0xDC00, respectively. These integers each have 10 bits free to
		// encode the character value, for a total of 20 bits.
		uint16_t W1 = 0xD800;
		uint16_t W2 = 0xDC00;

		// Assign the 10 high-order bits of the 20-bit U' to the 10 low-order
		// bits of W1 and the 10 low-order bits of U' to the 10 low-order
		// bits of W2.
		W1 += static_cast<uint16_t>((Ut & 0x3FC00) >> 10);
		W2 += static_cast<uint16_t>((Ut & 0x3FF) >> 0);

		// Terminate.
		output.push_back(W1); // high surrogate
		output.push_back(W2); // low surrogate
		return true;
	} else return false;
}

std::u16string GeneralUtils::UTF8ToUTF16(const std::string_view string, const size_t size) {
	const size_t newSize = MinSize(size, string);
	std::u16string output;
	output.reserve(newSize);
	std::string_view iterator = string;

	uint32_t c;
	while (details::_NextUTF8Char(iterator, c) && PushUTF16CodePoint(output, c, size)) {}
	return output;
}

//! Converts an std::string (ASCII) to UCS-2 / UTF-16
std::u16string GeneralUtils::ASCIIToUTF16(const std::string_view string, const size_t size) {
	const size_t newSize = MinSize(size, string);
	std::u16string ret;
	ret.reserve(newSize);

	for (size_t i = 0; i < newSize; ++i) {
		const char c = string[i];
		// Note: both 7-bit ascii characters and REPLACEMENT_CHARACTER fit in one char16_t
		ret.push_back((c > 0 && c <= 127) ? static_cast<char16_t>(c) : REPLACEMENT_CHARACTER);
	}

	return ret;
}

//! Converts a (potentially-ill-formed) UTF-16 string to UTF-8
//! See: <http://simonsapin.github.io/wtf-8/#decoding-ill-formed-utf-16>
std::string GeneralUtils::UTF16ToWTF8(const std::u16string_view string, const size_t size) {
	const size_t newSize = MinSize(size, string);
	std::string ret;
	ret.reserve(newSize);

	for (size_t i = 0; i < newSize; ++i) {
		const char16_t u = string[i];
		if (IsLeadSurrogate(u) && (i + 1) < newSize) {
			const char16_t next = string[i + 1];
			if (IsTrailSurrogate(next)) {
				i += 1;
				const char32_t cp = 0x10000
					+ ((static_cast<char32_t>(u) - 0xD800) << 10)
					+ (static_cast<char32_t>(next) - 0xDC00);
				PushUTF8CodePoint(ret, cp);
			} else {
				PushUTF8CodePoint(ret, u);
			}
		} else {
			PushUTF8CodePoint(ret, u);
		}
	}

	return ret;
}

bool GeneralUtils::CaseInsensitiveStringCompare(const std::string_view a, const std::string_view b) {
	return std::equal(a.begin(), a.end(), b.begin(), b.end(), [](char a, char b) { return tolower(a) == tolower(b); });
}

// MARK: Bits

//! Sets a specific bit in a signed 64-bit integer
int64_t GeneralUtils::SetBit(int64_t value, const uint32_t index) {
	return value |= 1ULL << index;
}

//! Clears a specific bit in a signed 64-bit integer
int64_t GeneralUtils::ClearBit(int64_t value, const uint32_t index) {
	return value &= ~(1ULL << index);
}

//! Checks a specific bit in a signed 64-bit integer
bool GeneralUtils::CheckBit(int64_t value, const uint32_t index) {
	return value & (1ULL << index);
}

bool GeneralUtils::ReplaceInString(std::string& str, const std::string_view from, const std::string_view to) {
	const size_t start_pos = str.find(from);
	if (start_pos == std::string::npos)
		return false;
	str.replace(start_pos, from.length(), to);
	return true;
}

std::vector<std::wstring> GeneralUtils::SplitString(const std::wstring_view str, const wchar_t delimiter) {
	std::vector<std::wstring> vector = std::vector<std::wstring>();
	std::wstring current;

	for (const wchar_t c : str) {
		if (c == delimiter) {
			vector.push_back(current);
			current = L"";
		} else {
			current += c;
		}
	}

	vector.push_back(std::move(current));
	return vector;
}

std::vector<std::u16string> GeneralUtils::SplitString(const std::u16string_view str, const char16_t delimiter) {
	std::vector<std::u16string> vector = std::vector<std::u16string>();
	std::u16string current;

	for (const char16_t c : str) {
		if (c == delimiter) {
			vector.push_back(current);
			current = u"";
		} else {
			current += c;
		}
	}

	vector.push_back(std::move(current));
	return vector;
}

std::vector<std::string> GeneralUtils::SplitString(const std::string_view str, const char delimiter) {
	std::vector<std::string> vector = std::vector<std::string>();
	std::string current = "";

	for (const char c : str) {
		if (c == delimiter) {
			vector.push_back(current);
			current = "";
		} else {
			current += c;
		}
	}

	vector.push_back(std::move(current));
	return vector;
}

std::u16string GeneralUtils::ReadWString(RakNet::BitStream& inStream) {
	uint32_t length;
	inStream.Read<uint32_t>(length);

	std::u16string string;
	for (uint32_t i = 0; i < length; ++i) {
		uint16_t c;
		inStream.Read(c);
		string.push_back(c);
	}

	return string;
}

std::vector<std::string> GeneralUtils::GetSqlFileNamesFromFolder(const std::string_view folder) {
	// Because we dont know how large the initial number before the first _ is we need to make it a map like so.
	std::map<uint32_t, std::string> filenames{};
	for (const auto& t : std::filesystem::directory_iterator(folder)) {
		if (t.is_directory() || t.is_symlink()) continue;
		auto filename = t.path().filename().string();
		const auto index = std::stoi(GeneralUtils::SplitString(filename, '_').at(0));
		filenames.emplace(index, std::move(filename));
	}

	// Now sort the map by the oldest migration.
	std::vector<std::string> sortedFiles{};
	auto fileIterator = filenames.cbegin();
	auto oldest = filenames.cbegin();
	while (!filenames.empty()) {
		if (fileIterator == filenames.cend()) {
			sortedFiles.push_back(oldest->second);
			filenames.erase(oldest);
			fileIterator = filenames.cbegin();
			oldest = filenames.cbegin();
			continue;
		}
		if (oldest->first > fileIterator->first) oldest = fileIterator;
		++fileIterator;
	}

	return sortedFiles;
}

#if !(__GNUC__ >= 11 || _MSC_VER >= 1924)

// MacOS floating-point parse function specializations
namespace GeneralUtils::details {
	template <>
	[[nodiscard]] float _parse<float>(const std::string_view str, size_t& parseNum) {
		return std::stof(std::string{ str }, &parseNum);
	}

	template <>
	[[nodiscard]] double _parse<double>(const std::string_view str, size_t& parseNum) {
		return std::stod(std::string{ str }, &parseNum);
	}

	template <>
	[[nodiscard]] long double _parse<long double>(const std::string_view str, size_t& parseNum) {
		return std::stold(std::string{ str }, &parseNum);
	}
}

#endif