#include <iostream>
#include <string>
#include <codecvt>
#include <stdexcept>
#include <sstream>
#include <iomanip>
#include <vector>

std::vector<std::string> extractUTF16HexValues(const std::string& input) {
    std::vector<std::string> utf16HexValues;
    std::stringstream ss(input);
    std::string token;

    // Iterate over tokens separated by "\\u"
    while (std::getline(ss, token, '\\')) {
        if (token.empty())
            continue;

        // Check if the token starts with "u" and has exactly 4 characters following it
        if (token[0] == 'u' && token.length() == 5) {
            // Extract the hexadecimal part
            std::string hexValue = token.substr(1, 4);
            utf16HexValues.push_back(hexValue);
        }
    }

    return utf16HexValues;
}

std::string convertUTF16HexToUTF8Hex(const std::vector<std::string>& utf16HexValues) {
    try {
        std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> converter;
        std::stringstream utf8HexStream;
        std::u16string utf16String;

        // Combine all UTF-16 hexadecimal values into a single u16string
        for (const std::string& utf16Hex : utf16HexValues) {
            uint16_t utf16Value = std::stoi(utf16Hex, nullptr, 16);
            utf16String.push_back(utf16Value);
        }

        // Convert the UTF-16 u16string to UTF-8
        std::string utf8Encoded = converter.to_bytes(utf16String);

        // Convert each byte to hexadecimal representation and append to the result
        for (unsigned char c : utf8Encoded) {
            utf8HexStream << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(c);
        }

        return utf8HexStream.str();
    } catch (const std::invalid_argument& e) {
        std::cerr << "Error: " << e.what() << std::endl;
        return "";
    } catch (const std::out_of_range& e) {
        std::cerr << "Error: Invalid UTF-16 hexadecimal value." << std::endl;
        return "";
    }
}

std::string convertUTF8HexToUTF8Bytes(const std::string& utf8Hex) {
    std::stringstream utf8ByteStream;

    // Iterate over pairs of characters representing hexadecimal values
    for (size_t i = 0; i < utf8Hex.length(); i += 2) {
        // Get the next two characters
        std::string byteHex = utf8Hex.substr(i, 2);

        // Convert hexadecimal string to integer
        int byteValue;
        std::stringstream(byteHex) >> std::hex >> byteValue;

        // Append the byte as a character to the string
        utf8ByteStream << static_cast<char>(byteValue);
    }

    return utf8ByteStream.str();
}

int main() {
    std::string input = "\\uD83E\\uDDA0";
    std::vector<std::string> utf16HexValues = extractUTF16HexValues(input);
    
    //std::vector<std::string> utf16HexValues = {"D83E", "DDA0"};
    std::string utf8Hex = convertUTF16HexToUTF8Hex(utf16HexValues);
    if (!utf8Hex.empty()) {
        std::cout << "UTF-8 Hex: " << utf8Hex << std::endl; // Output: F09FA6A0

        std::string utf8Bytes = convertUTF8HexToUTF8Bytes(utf8Hex);
        std::cout << "UTF-8 Bytes: " << utf8Bytes << std::endl; // Output: ?
    }
    return 0;
}