#ifndef BASE_64_HPP
#define BASE_64_HPP

#include <algorithm>
#include <string>

namespace base64 {

	inline std::string get_base64_chars() {
		static std::string base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
			"abcdefghijklmnopqrstuvwxyz"
			"0123456789+/";
		return base64_chars;
	}
	
	inline std::string to_base64(const char* data, size_t size) {
		int counter = 0;
		uint32_t bit_stream = 0;
		const std::string base64_chars = get_base64_chars();
		std::string encoded;
		encoded.reserve(static_cast<unsigned long>(ceil(4.0 / 3.0 * size)));
		int offset = 0;
		for (unsigned int idx = 0; idx < size; idx++) {
			unsigned char c = data[idx];
			auto num_val = static_cast<unsigned int>(c);
			offset = 16 - counter % 3 * 8;
			bit_stream += num_val << offset;
			if (offset == 16) {
				encoded += base64_chars.at(bit_stream >> 18 & 0x3f);
			}
			if (offset == 8) {
				encoded += base64_chars.at(bit_stream >> 12 & 0x3f);
			}
			if (offset == 0 && counter != 3) {
				encoded += base64_chars.at(bit_stream >> 6 & 0x3f);
				encoded += base64_chars.at(bit_stream & 0x3f);
				bit_stream = 0;
			}
			counter++;
		}
		if (offset == 16) {
			encoded += base64_chars.at(bit_stream >> 12 & 0x3f);
			encoded += "==";
		}
		if (offset == 8) {
			encoded += base64_chars.at(bit_stream >> 6 & 0x3f);
			encoded += '=';
		}
		return encoded;
	}

	inline std::string to_base64(std::string const& data) {
		return to_base64(data.c_str(), data.length());
	}

	inline std::string from_base64(std::string const& data) {
		int counter = 0;
		uint32_t bit_stream = 0;
		std::string decoded;
		int offset = 0;
		const std::string base64_chars = get_base64_chars();
		for (unsigned char c : data) {
			auto num_val = base64_chars.find(c);
			if (num_val != std::string::npos) {
				offset = 18 - counter % 4 * 6;
				bit_stream += static_cast<uint32_t>(num_val << offset);
				if (offset == 12) {
					decoded += static_cast<char>(bit_stream >> 16 & 0xff);
				}
				if (offset == 6) {
					decoded += static_cast<char>(bit_stream >> 8 & 0xff);
				}
				if (offset == 0 && counter != 4) {
					decoded += static_cast<char>(bit_stream & 0xff);
					bit_stream = 0;
				}
			}
			else if (c != '=') {
				return std::string();
			}
			counter++;
		}
		return decoded;
	}
}

#endif // BASE_64_HPP