/**
 * Relational pipes
 * Copyright © 2021 František Kučera (Frantovo.cz, GlobalCode.info)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
#pragma once

#include <memory>
#include <vector>
#include <sstream>
#include <iomanip>
#include <cmath>

namespace relpipe {
namespace in {
namespace asn1 {
namespace lib {

class ASN1ContentHandler {
public:

	enum class CollectionType : uint64_t {
		Constructed, // TODO: special event?
		Sequence = 16,
		Set = 17
	};

	enum class StringType : uint64_t {
		OctetString,
		UTF8String,
		NumericString,
		PrintableString,
		T61String,
		VideotexString,
		IA5String,
		GraphicString,
		VisibleString,
		GeneralString,
		UniversalString,
		CharacterString,
		BMPString,
	};

	class Integer {
	private:
		// TODO: use std::string (of octets, not ASCII) instead of std::vector?
		// TODO: use this class as BigInteger across Relational pipes?
		std::vector<uint8_t> data;
	public:

		/**
		 * @param data integer octets as in BER encoding
		 */
		Integer(std::vector<uint8_t> data) : data(data) {
		}

		virtual ~Integer() {
		}

		size_t size() const {
			return data.size();
		}

		const uint8_t& operator[](std::size_t index) const {
			return data[index];
		}

		const std::string toHex() const {
			std::stringstream hex;
			hex << std::hex << std::setfill('0');
			for (uint8_t b : data) hex << std::setw(2) << (int) b;
			return hex.str();
		}

		const std::string toString() const {
			try {
				return std::to_string(toInt64());
			} catch (...) {
				// integer has more than 64 bits → only HEX form value will be available
				// TODO: support longer values than 64 bits
				// TODO: do not ignore zero-length error?
				return "";
			}
		}

		const int64_t toInt64() const {
			int64_t value = 0;

			if (data.size() > sizeof (value)) throw std::invalid_argument("Integer is too long");
			else if (data.size() == 0) throw std::invalid_argument("Integer has zero length");

			value = data[0];
			bool negative = data[0] & 0x80;

			for (size_t i = 1, limit = data.size(); i < limit; i++) value = (value << 8) | data[i];

			if (negative) value -= std::pow(256, data.size());

			return value;
		}

	};

	class ObjectIdentifier {
	private:
		// TODO: use std::string (of octets, not ASCII) instead of std::vector?
		// TODO: use this class across Relational pipes as one of basic types?
		std::vector<uint8_t> data;

	public:

		/**
		 * @param data integer octets as in BER encoding
		 */
		ObjectIdentifier(std::vector<uint8_t> data) : data(data) {
			// TODO: cache size and element values?
		}

		virtual ~ObjectIdentifier() {
		}

		/**
		 * @return number of elements, not octets
		 */
		size_t size() const {
			return 0; // FIXME: correct OID size
		}

		/**
		 * @param index 0 = root element
		 * @return value of the element at given position
		 */
		const uint8_t& operator[](std::size_t index) const {
			return data[index]; // FIXME: correct OID value
		}

		const std::string toString() const {
			if (data.size() == 0) return "";

			std::stringstream result;

			result << (data[0] / 40) << "." << (data[0] % 40); // first two elements are encoded in the first octet

			for (size_t i = 1, limit = data.size(), octet = 0, element = 0; i < limit; i++) {
				octet = data[i];
				element = element << 7 | (octet & 0xFF >> 1);
				// TODO: throw exception if the element value overflows? (should not happen) or format even longer values
				if ((octet & 1 << 7) == 0) {
					result << "." << element;
					element = 0;
				}
			}

			return result.str();
		}

	};

	virtual ~ASN1ContentHandler() = default;

	// TODO: more metadata, support OID decoding and ASN.1 modules (schema), probably through a plug-in

	virtual void writeStreamStart() = 0;
	virtual void writeStreamEnd() = 0;

	virtual void writeCollectionStart(CollectionType type) = 0;
	virtual void writeCollectionEnd() = 0;
	virtual void writeBoolean(bool value) = 0;
	virtual void writeNull() = 0;
	virtual void writeInteger(Integer value) = 0;
	virtual void writeString(StringType type, std::string value) = 0;
	virtual void writeOID(ObjectIdentifier value) = 0;
	// Object descriptor
	// virtual void writeReal(float value) = 0;
	// Enumerated
	// Embedded PVD
	// Relative OID
	// TIME
	// UTC time
	// Generalized time
	// Date
	// Time of day
	// Date-time
	// Duration
	// OID-IRI
	// Relative OID-IRI

};

class ASN1ContentHandlerProxy : public ASN1ContentHandler {
private:
	std::vector<std::shared_ptr<ASN1ContentHandler>> handlers;
public:

	void addHandler(std::shared_ptr<ASN1ContentHandler> handler) {
		handlers.push_back(handler);
	}

#define handler for (auto ___h : handlers) ___h

	void writeStreamStart() override {
		handler->writeStreamStart();
	}

	void writeStreamEnd() override {
		handler->writeStreamEnd();
	}

	void writeCollectionStart(CollectionType type) override {
		handler->writeCollectionStart(type);
	}

	void writeCollectionEnd() override {
		handler->writeCollectionEnd();
	}

	void writeBoolean(bool value) override {
		handler->writeBoolean(value);
	}

	void writeNull() override {
		handler->writeNull();
	}

	void writeInteger(Integer value) override {
		handler->writeInteger(value);
	}

	void writeString(StringType type, std::string value) override {
		handler->writeString(type, value);
	}

	void writeOID(ObjectIdentifier value) override {
		handler->writeOID(value);
	}


#undef handler

};


}
}
}
}