gplib/include/gp/enveloppe/cbor.hpp

#pragma once

#include <gp/bitops.hpp>
#include <gp/optional.hpp>
#include <gp/pair.hpp>
#include <gp/variant.hpp>
#include <gp/vector.hpp>


namespace gp {
	enum class cbor_type : uint8_t {
		uint = 0,
		nint = 1,
		bstr = 2,
		tstr = 3,
		list = 4,
		hmap = 5,
		tags = 6,
		oths = 7
	};

	enum class cbor_oths : uint8_t {
		value_false = 20,
		value_true = 21,
		value_null = 22,
		value_undefined = 23,
		byte = 24,
		word = 25,
		dword = 26,
		qword = 27,
		terminator = 31
	};

	enum class cbor_tags {
		datetime = 0,
		unix_time = 1,
		ubignum = 2,
		nbignum = 3,
		decimal = 4,
		bigfloat = 5,
		cose_encrypt0 = 16,
		cose_mac0 = 17,
		cose_sign1 = 18,
		expected_base64url = 21,
		expected_base64 = 22,
		expected_base16 = 23,
		encoded_cbor = 24,
		url = 32,
		base64url = 33,
		base64 = 34,
		regexp = 35,
		mime = 36,
		cose_encrypt = 96,
		cose_mac = 97,
		cose_sign = 98,
		signature = 55799
	};

	struct cbor_number final {
		bool sign;
		uint64_t value;

		bool is_negative() {
			return sign;
		}

		cbor_number(int64_t v) 
		: sign{v < 0}
		, value{uint64_t((sign ? -1 : 1) * v)}
		{}
	};

	struct ieee754_hf final {
		uint16_t sign : 1;
		uint16_t exponent : 5;
		uint16_t mantissa : 10;
	};

	using cbor_floating_point = gp::fixed_variant<
		ieee754_hf,
		float,
		double
	>; 

	struct undefined_t final {};

	template<typename T>
	using cbor_composite = gp::fixed_variant<
		undefined_t,
		cbor_number,
		gp::buffer<std::byte>,
		bool,
		gp::vector<T>,
		gp::vector<gp::pair<T, T>>,
		gp::nullopt_t,
		cbor_floating_point
	>;

	class cbor_value {

		cbor_composite<cbor_value> contents;
		gp::reference_wrapper<allocator> alloc;
	public:

		cbor_value(allocator& alloc_v)
		: contents(cbor_composite<cbor_value>(undefined_t{}))
		, alloc(alloc_v)
		{}

		cbor_value(cbor_number number, allocator& alloc_v)
		: contents(number)
		, alloc(alloc_v)
		{}

		cbor_value(const cbor_value& oth)
		: contents(oth.contents)
		, alloc(oth.alloc)
		{}

		cbor_value(cbor_value&& oth)
		: contents(gp::move(oth.contents))
		, alloc(gp::move(oth.alloc))
		{}

		cbor_value& operator=(cbor_value& value) {
			contents = value.contents;
			alloc = value.alloc;
			return *this;
		}

		cbor_value& operator=(cbor_value&& value) {
			gp::swap(contents, value.contents);
			gp::swap(alloc, value.alloc);
			return *this;
		}

		cbor_value& operator=(cbor_composite<cbor_value>& value) {
			contents = value;
			return *this;
		}

		template<typename T>
		cbor_value& operator=(T& value) {
			contents = value;
			return *this;
		}

		template<typename T>
		cbor_value& operator=(T&& value) {
			contents = gp::move(value);
			return *this;
		}

		auto new_array() {
			return gp::vector<cbor_value>{alloc};
		}

		auto new_object() {
			return gp::vector<gp::pair<cbor_value, cbor_value>>{alloc};
		}

		static auto encode_float(buffer<std::byte> dest, cbor_floating_point& value) {
			switch(value.type()) {
				case cbor_floating_point::alt<ieee754_hf>():{
					if(dest.size() < 3) return dest.begin();
					dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::word);
					(dest.slice_start(3).slice_end(2).cast<gp::endian_wrapper<ieee754_hf, gp::endian::big>>())[0] = value.value<ieee754_hf>();
					return dest.begin()+3;
				}
				case cbor_floating_point::alt<float>():{
					if(dest.size() < 5) return dest.begin();
					dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::dword);
					(dest.slice_start(5).slice_end(4).cast<gp::endian_wrapper<float, gp::endian::big>>())[0] = value.value<float>();
					return dest.begin()+5;
				}
				case cbor_floating_point::alt<double>():{
					if(dest.size() < 9) return dest.begin();
					dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::qword);
					(dest.slice_start(9).slice_end(8).cast<gp::endian_wrapper<double, gp::endian::big>>())[0] = value.value<double>();
					return dest.begin()+9;
				}
				default: return dest.begin();
			}
		}

		static auto encode_length(buffer<std::byte> dest, cbor_type major, uint64_t value) {
			auto num = value;
			if(value <= 23) {
				if(dest.size() < 1) return dest.begin();
				dest[0] = std::byte(((uint8_t)major << 5u) + value);
				return dest.begin()+1;
			} else if(value <= 255) {
				if(dest.size() < 2) return dest.begin();
				dest[0] = std::byte(((uint8_t)major << 5u) + (uint8_t)cbor_oths::byte);
				dest[1] = std::byte(value);
				return dest.begin() + 2;
			} else if(value <= 65535) {
				if(dest.size() < 3) return dest.begin();
				dest[0] = std::byte(((uint8_t)major << 5u) + (uint8_t)cbor_oths::word);
				(dest.slice_start(3).slice_end(2).cast<gp::endian_wrapper<uint16_t, gp::endian::big>>())[0] = num;
				return dest.begin()+3;
			} else if(value <= 4294967295) {
				if(dest.size() < 5) return dest.begin();
				dest[0] = std::byte(((uint8_t)major << 5u) + (uint8_t)cbor_oths::dword);
				(dest.slice_start(5).slice_end(4).cast<gp::endian_wrapper<uint32_t, gp::endian::big>>())[0] = num;
				return dest.begin()+5;
			} else {
				if(dest.size() < 9) return dest.begin();
				dest[0] = std::byte(((uint8_t)major << 5u) + (uint8_t)cbor_oths::qword);
				(dest.slice_start(9).slice_end(8).cast<gp::endian_wrapper<uint64_t, gp::endian::big>>())[0] = num;
				return dest.begin()+9;
			}
		}

		auto encode(buffer<std::byte> dest) {
			switch(contents.type()) {
				case cbor_composite<cbor_value>::alt<undefined_t>(): {
					if(dest.size() < 1) return dest.begin();
					dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::value_undefined);
					return dest.begin()+1;
				}
				case cbor_composite<cbor_value>::alt<cbor_number>(): {
					auto& ref = contents.value<cbor_number>();
					return encode_length(
						dest, 
						ref.is_negative() ? cbor_type::nint : cbor_type::uint,
						ref.value
					);
				}
				case cbor_composite<cbor_value>::alt<gp::buffer<std::byte>>(): {
					auto& ref = contents.value<gp::buffer<std::byte>>();
					auto it = encode_length(
						dest,
						cbor_type::bstr,
						ref.size()
					);
					if(it == dest.begin()) return it;

					for(auto a : ref) {
						*(it++) = a;
					}
					return it;
				}
				case cbor_composite<cbor_value>::alt<bool>(): {
					if(dest.size() < 1) return dest.begin();
					if(contents.value<bool>()) 
						dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::value_true);
					else 
						dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::value_false);
					return dest.begin()+1;
				}
				case cbor_composite<cbor_value>::alt<gp::vector<cbor_value>>(): {
					auto& ary = contents.value<gp::vector<cbor_value>>();
					auto it_begin = encode_length(dest, cbor_type::list, ary.size());
					if(it_begin == dest.begin()) return dest.begin();
					for(auto& elem : ary) {
						auto slice = dest.slice_end(dest.size() - (it_begin - dest.begin()));
						auto it = elem.encode(slice);
						if(it == it_begin) 
							return dest.begin();
						it_begin = it;
					}
					return it_begin;
				}
				case cbor_composite<cbor_value>::alt<gp::vector<gp::pair<cbor_value, cbor_value>>>(): {
					auto& ary = contents.value<gp::vector<gp::pair<cbor_value,cbor_value>>>();
					auto it_begin = encode_length(dest, cbor_type::hmap, ary.size());
					if(it_begin == dest.begin()) return dest.begin();
					
					for(auto& elem : ary) {
						auto slice = dest.slice_end(dest.size() - (it_begin - dest.begin()));
						auto it = elem.first.encode(slice);
						if(it == it_begin) return dest.begin();
						it_begin = it;

						slice = dest.slice_end(dest.size() - (it_begin - dest.begin()));
						it = elem.second.encode(slice);
						if(it == it_begin) return dest.begin();
						it_begin = it;
					}
					return it_begin;
				}
				case cbor_composite<cbor_value>::alt<gp::nullopt_t>(): {
					if(dest.size() < 1) return dest.begin();
					dest[0] = std::byte(((uint8_t)cbor_type::oths << 5u) + (uint8_t)cbor_oths::value_null);
					return dest.begin()+1;
				}
				case cbor_composite<cbor_value>::alt<cbor_floating_point>(): {
					return encode_float(dest, contents.value<cbor_floating_point>());
				}
				default: return dest.begin();
			}
		}
	};
}