#pragma once

#include <gp/algorithms/repeat.hpp>
#include <gp/math/boolean/bitops.hpp>
#include <gp/functional/optional.hpp>
#include <gp/utils/pair.hpp>
#include <gp/functional/variant.hpp>
#include <gp/containers/vector.hpp>

#include <concepts>

// TODO: Rewrite in a more ORM-like way
// TODO: Implement some bignum for support

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)}
		{}

		cbor_number(bool s, uint64_t v) 
		: sign{s}
		, value{v}
		{}
	};

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

		// TODO: support for denormalized values and NaNs
		operator float() {
			auto a = (uint32_t)((sign<<16) | ((exponent+0x1C000)<<13) | (mantissa<<13));
			return *(float*)&a;
		}

		operator double() {
			return (float)*this;
		}
	};





















	inline vector<char>& push_integer_with_header_as_cbor(vector<char>& src, uint8_t header, uint64_t value) {
		auto norm_v = (value<0) ? -value : value;
		if(norm_v <= 23) {
			src.push_back(header+norm_v);
		} else if(norm_v < (1ll<<8ll)) {
			src.push_back(header+24);
			src.push_back(norm_v);
		} else if(norm_v < (1ll<<16ll)) {
			endian_wrapper<uint16_t, endian::big> wrapper = norm_v;
			src.push_back(header+25);
			for(auto byte : wrapper.bytes) {
				src.push_back(byte);
			}
		} else if(norm_v < (1ll<<32ll)) {
			endian_wrapper<uint32_t, endian::big> wrapper = norm_v;
			src.push_back(header+26);
			for(auto byte : wrapper.bytes) {
				src.push_back(byte);
			}
		} else {
			endian_wrapper<uint64_t, endian::big> wrapper = norm_v;
			src.push_back(header+27);
			for(auto byte : wrapper.bytes) {
				src.push_back(byte);
			}
		}
		return src;
	}

	/**
	 * @brief Pushes an integer as CBOR on the vector
	 * 
	 * @param src the vector on which the push happens
	 * @param value the value to push, can be signed
	 * @return vector<char>& the same reference that was received for the source
	 */
	template<std::signed_integral T>
	inline vector<char>& push_as_cbor(vector<char>& src, T value) {
		uint8_t sign = (value<0) ? 0b00100000 : 0;
		auto norm_v = (value<0) ? -value : value;
		return push_integer_with_header_as_cbor(src, sign, norm_v);
	}

	/**
	 * @brief Pushes an unsigned integer as CBOR on the vector
	 * 
	 * @param src the vector on which the push happens
	 * @param value the value to push, cannot be signed
	 * @return vector<char>& the same reference that was received for the source
	 */
	template<std::unsigned_integral T>
	inline vector<char>& push_as_cbor(vector<char>& src, T value) {
		return push_integer_with_header_as_cbor(src, 0, value);
	}

	inline vector<char>& push_as_cbor(vector<char>& src, std::nullptr_t) {
		src.push_back(0b11110110);
		return src;
	}

	struct cbor_undefined{};

	inline vector<char>& push_as_cbor(vector<char>& src, cbor_undefined) {
		src.push_back(0b11110111);
		return src;
	}

	inline vector<char>& push_as_cbor(vector<char>& src, bool value) {
		src.push_back(0b11110100+(value ? 1 : 0));
		return src;
	}

	inline vector<char>& push_as_cbor(vector<char>& src, gp::buffer<char> value) {
		push_integer_with_header_as_cbor(src, (uint8_t)0b01000000, value.size());
		for(auto byte : value) {
			src.push_back(byte);
		}
		return src;
	}

	struct cbor_array_initiator {
		size_t size;
	};
	
	struct cbor_associative_array_initiator {
		size_t size;
	};

	inline vector<char>& push_as_cbor(vector<char>& src, cbor_array_initiator value) {
		return push_integer_with_header_as_cbor(src, (uint8_t)0b10000000, value.size);
	}

	inline vector<char>& push_as_cbor(vector<char>& src, cbor_associative_array_initiator value) {
		return push_integer_with_header_as_cbor(src, (uint8_t)0b10100000, value.size);
	}

	template<typename First, typename Second>
	inline vector<char>& push_as_cbor(vector<char>& src, gp::pair<First, Second> value) {
		push_as_cbor(src,value.first);
		return push_as_cbor(src,value.second);
	}

	template<typename First, typename Second>
	inline vector<char>& push_as_cbor(vector<char>& src, gp::pair<First, Second>& value) {
		push_as_cbor(src,value.first);
		return push_as_cbor(src,value.second);
	}

	struct cbor_tag_initiator {
		union {
			size_t as_integer;
			cbor_tags tag;
		};
	};

	inline vector<char>& push_as_cbor(vector<char>& src, cbor_tag_initiator value) {
		return push_integer_with_header_as_cbor(src, (uint8_t)0b11000000, value.as_integer);
	}

	using parsing_state = gp::buffer<char>;
	
	template<typename T>
	gp::pair<gp::optional<T>, parsing_state> read_cbor(parsing_state state, gp::allocator&);

	inline gp::pair<gp::optional<uint64_t>, parsing_state> pull_arbitrary_integer_from_cbor(parsing_state state) {
		auto local = (uint8_t)0b00011111 & (uint8_t)*state.begin();
		if(local <= 23) {
			return {*state.begin(), {state.begin()+1, state.end()}};
		} else {
			switch((cbor_oths)local) {
				case cbor_oths::byte: {
					if(state.size() < 2)  return {nullopt, state};
					return {*(state.begin()+1), {state.begin()+2, state.end()}};
				}
				case cbor_oths::word: {
					if(state.size() < 3)  return {nullopt, state};
					return {
						uint16_t(*(state.slice_start(3).slice_end(2).cast<gp::endian_wrapper<uint16_t, endian::big>>().begin())), 
						{state.begin()+3, state.end()}
					};
				}
				case cbor_oths::dword: {
					if(state.size() < 5) return {nullopt, state};
					return {
						uint32_t(*(state.slice_start(5).slice_end(4).cast<gp::endian_wrapper<uint32_t, endian::big>>().begin())), 
						{state.begin()+5, state.end()}
					};
				}
				case cbor_oths::qword: {
					if(state.size() < 9) return {nullopt, state};
					return {
						uint64_t(*(state.slice_start(9).slice_end(8).cast<gp::endian_wrapper<uint64_t, endian::big>>().begin())), 
						{state.begin()+9, state.end()}
					};
				}
				default: {
					return {nullopt, state};
				}
			}
		}
	}
	
	template<std::integral T>
	inline gp::pair<gp::optional<int64_t>, parsing_state> read_cbor(parsing_state state, gp::allocator&) {
		// TODO: Handling of over and underflow
		if(state.size()) return {nullopt, state};
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::uint:
			{
				auto[value, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(value.has_value()) return {value.value(), new_state};
				break;
			}
			case cbor_type::nint:
			{
				auto[value, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(value.has_value()) return {-value.value(), new_state};
				break;
			}
			default:
				break;
		}
		return {nullopt, state};
	}


	template<>
	inline gp::pair<gp::optional<cbor_tag_initiator>, parsing_state> read_cbor<cbor_tag_initiator>(parsing_state state, gp::allocator&) {
		if(state.size()) return {nullopt, state};
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::tags:
			{
				auto[value, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(value.has_value()) return {cbor_tag_initiator{.as_integer = value.value()}, new_state};
				break;
			}
			default: break;
		}
		return {nullopt, state};
	}

	template<>
	inline gp::pair<gp::optional<gp::vector<char>>, parsing_state> read_cbor<gp::vector<char>>(parsing_state state, gp::allocator& alloc) {
		if(state.size()) return {nullopt, state};
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::bstr:
			{
				const auto[size, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(!size.has_value()) break;
				if(new_state.size()<size.value()) break;
				gp::vector<char> return_value{alloc};
				if(!return_value.reserve(size.value())) break;
				auto end_it = new_state.begin() + size.value();
				for(auto it = new_state.begin(); it != end_it; it++) {
					return_value.push_back(*it);
				}
				return {optional<gp::vector<char>>(gp::move(return_value)), parsing_state(new_state.begin() + size.value(), new_state.end())};
				break;
			}
			default: break;
		}
		return {nullopt, state};
	}

	template<>
	inline gp::pair<gp::optional<std::nullptr_t>, parsing_state> read_cbor<std::nullptr_t>(parsing_state state, gp::allocator& alloc) {
		if(state.size()) return {nullopt, state};
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::oths:
			{
				const auto[value, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(!value.has_value()) break;
				if(new_state.size()<value.value()) break;
				gp::vector<char> return_value{alloc};
				if(value.value() == 22)
				{
					return {optional(nullptr), parsing_state(new_state.begin()+1, new_state.end())};
				}
				break;
			}
			default: break;
		}
		return {nullopt, state};
	}

	template<>
	inline gp::pair<gp::optional<cbor_undefined>, parsing_state> read_cbor<cbor_undefined>(parsing_state state, gp::allocator& alloc) {
		if(state.size()) return {nullopt, state};
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::oths:
			{
				const auto[value, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(!value.has_value()) break;
				if(new_state.size()<value.value()) break;
				gp::vector<char> return_value{alloc};
				if(value.value() == 23)
				{
					return {optional(cbor_undefined{}), parsing_state(new_state.begin()+1, new_state.end())};
				}
				break;
			}
			default: break;
		}
		return {nullopt, state};
	}

	/**
	 * @brief 
	 * 
	 * @param state 
	 * @param callback a callback that returns a new parsing state for every element read. It should follow the heredescribed signature: parsing_state(parsing_state, gp::allocator&)
	 * @param count_callback a callback that is used to check if the process should proceed given a count of elements in the list. It should follow the heredescribed signature: bool(uint64_t)
	 * @param alloc 
	 */
	template<typename applier_cb, typename counter_cb>
	inline parsing_state read_cbor_array(parsing_state state, gp::allocator& alloc, applier_cb callback, counter_cb count_callback = [](uint64_t) -> bool {return true;}) {
		if(state.size()) return state;
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::list:
			{
				const auto[size, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(!size.has_value()) return state;
				if(new_state.size()<size.value()) return state;
				if(!count_callback(size.value()))return state;
				parsing_state forward = new_state;
				for(auto idx = 0ull; idx != size.value(); idx++) {
					if(forward.size() == 0) return state;
					forward = callback(forward, alloc);
				}
				return forward;
			}
			default: return state;
		}
	}

	/**
	 * @brief 
	 * 
	 * @param state 
	 * @param callback a callback that returns a new parsing state for every element read. It should follow the heredescribed signature: parsing_state(parsing_state, gp::allocator&), it MUST read exactly 2 cbor value from the stream.
	 * @param count_callback a callback that is used to check if the process should proceed given a count of elements in the list. It should follow the heredescribed signature: bool(uint64_t)
	 * @param alloc 
	 */
	template<typename applier_cb, typename counter_cb>
	inline parsing_state read_cbor_kv_list(parsing_state state, gp::allocator& alloc, applier_cb callback, counter_cb count_callback = [](uint64_t) -> bool {return true;}) {
		if(!state.size()) return state;
		auto type = cbor_type(((uint8_t)0b11100000 & (uint8_t)*state.begin()) >> 5);

		switch(type) {
			case cbor_type::hmap:
			{
				const auto[size, new_state] = pull_arbitrary_integer_from_cbor(state);
				if(!size.has_value()) return state;
				if(!count_callback(size.value()))return state;
				parsing_state forward = new_state;
				for(auto idx = 0ull; idx != size.value(); idx++) {
					if(forward.size() < 2ull) return state;
					forward = callback(forward, alloc);
					forward = callback(forward, alloc);
				}
				return forward;
			}
			default: return state;
		}
	}
}