/**
 * 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>

#include "ProxyVector.h"

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

namespace UniversalType {
static const uint64_t EndOfContent = 0x00;
static const uint64_t Boolean = 0x01;
static const uint64_t Integer = 0x02;
static const uint64_t BitString = 0x03;
static const uint64_t OctetString = 0x04;
static const uint64_t Null = 0x05;
static const uint64_t ObjectIdentifier = 0x06;
static const uint64_t ObjectDescriptor = 0x07;
static const uint64_t External = 0x08;
static const uint64_t Real = 0x09;
static const uint64_t Enumerated = 0xA;
static const uint64_t Embedded = 0xB;
static const uint64_t UTF8String = 0xC;
static const uint64_t RelativeObjectIdentifier = 0xD;
static const uint64_t Time = 0xE;
static const uint64_t Reserved = 0xF;
static const uint64_t Sequence = 0x10;
static const uint64_t Set = 0x11;
static const uint64_t NumericString = 0x12;
static const uint64_t PrintableString = 0x13;
static const uint64_t T61String = 0x14;
static const uint64_t VideotexString = 0x15;
static const uint64_t IA5String = 0x16;
static const uint64_t UTCTime = 0x17;
static const uint64_t GeneralizedTime = 0x18;
static const uint64_t GraphicString = 0x19;
static const uint64_t VisibleString = 0x1A;
static const uint64_t GeneralString = 0x1B;
static const uint64_t UniversalString = 0x1C;
static const uint64_t CharacterString = 0x1D;
static const uint64_t BMPString = 0x1E;
static const uint64_t Date = 0x1F;
static const uint64_t TimeOfDay = 0x20;
static const uint64_t DateTime = 0x21;
static const uint64_t Duration = 0x22;
static const uint64_t ObjectIdentifierIRI = 0x23;
static const uint64_t RelativeObjectIdentifierIRI = 0x24;
}

class ASN1ContentHandler {
public:

	enum class TagClass : uint8_t {
		Universal = 0,
		Application = 1,
		ContextSpecific = 2,
		Private = 3
	};

	enum class PC : uint8_t {
		Primitive = 0,
		Constructed = 1
	};

	class Header {
	public:
		TagClass tagClass;
		PC pc;
		uint64_t tag;
	};

	enum class StringType : uint64_t {
		UTF8String = 0xC,
		NumericString = 0x12,
		PrintableString = 0x13,
		T61String = 0x14,
		VideotexString = 0x15,
		IA5String = 0x16,
		GraphicString = 0x19,
		VisibleString = 0x1A,
		GeneralString = 0x1B,
		UniversalString = 0x1C,
		CharacterString = 0x1D,
		BMPString = 0x1E,
	};

	enum class DateTimeType : uint64_t {
		UTCTime,
		GeneralizedTime,
		Time,
		Date,
		TimeOfDay,
		DateTime,
		Duration,
		// TODO: review date/time types
	};


	// TODO: separate implementation of particular types from the interface, separate SPI from API?

	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();
		}

	};

	class DateTime {
	public:

		enum class Precision {
			Year,
			Month,
			Day,
			Hour,
			Minute,
			Second,
			Milisecond,
			Nanosecond
		};

		// TODO: timezone (in minutes or 1/4 hours)

		Precision precision = Precision::Second;
		int32_t year = 1970;
		int8_t month = 1;
		int8_t day = 1;
		int8_t hour = 0;
		int8_t minute = 0;
		int8_t second = 0;
		int32_t nanosecond = 0;
		int8_t timezoneHour = 0;
		int8_t timezoneMinute = 0;

		virtual ~DateTime() {
		}

		const std::string toString() const {
			std::stringstream result;
			result << std::setfill('0');
			result << std::setw(4) << (int) year;
			result << "-" << std::setw(2) << (int) month;
			result << "-" << std::setw(2) << (int) day;
			result << "T" << std::setw(2) << (int) hour;
			result << ":" << std::setw(2) << (int) minute;
			result << ":" << std::setw(2) << (int) second;
			if (precision == Precision::Nanosecond) result << "," << (int) nanosecond;
			result << (timezoneHour < 0 ? "-" : "+");
			result << std::setw(2) << (int) std::abs(timezoneHour);
			result << ":" << std::setw(2) << (int) timezoneMinute;
			return result.str();
		}
	};

	virtual ~ASN1ContentHandler() = default;

	// TODO: more metadata, support OID decoding and ASN.1 modules (schema), probably through a plug-in
	// TODO: support also extension extractor plug-ins? (could decode some opaque structures like octet strings and replace them with nested elements) e.g. subjectAltName in https://datatracker.ietf.org/doc/html/rfc5280#section-4.2.1.6

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

	virtual void writeCollectionStart(const Header& header) = 0;
	virtual void writeCollectionEnd() = 0;
	virtual void writeBoolean(bool value) = 0;
	virtual void writeNull() = 0;
	virtual void writeInteger(Integer value) = 0;
	/**
	 * @param type original type in ASN.1
	 * @param value original text converted to UTF-8
	 */
	virtual void writeTextString(StringType type, std::string value) = 0;
	/**
	 * @param value arbitrary sequence of octets (bytes), usually not a human-readable text
	 */
	virtual void writeOctetString(std::string value) = 0;
	/**
	 * @param value arbitrary sequence of bits (booleans), usually not a human-readable text
	 */
	virtual void writeBitString(std::vector<bool> value) = 0;
	virtual void writeOID(ObjectIdentifier value) = 0;
	virtual void writeDateTime(DateTimeType type, DateTime value) = 0;
	// Object descriptor
	// virtual void writeReal(float value) = 0;
	// Enumerated
	// Embedded PVD
	// Relative OID
	// OID-IRI
	// Relative OID-IRI

};

class ASN1ContentHandlerProxy : public ASN1ContentHandler {
private:
	ProxyVector<ASN1ContentHandler> handlers;
public:

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

	void writeStreamStart() override {
		handlers.forward(&ASN1ContentHandler::writeStreamStart);
	}

	void writeStreamEnd() override {
		handlers.forward(&ASN1ContentHandler::writeStreamEnd);
	}

	void writeCollectionStart(const Header& header) override {
		handlers.forward(&ASN1ContentHandler::writeCollectionStart, header);
	}

	void writeCollectionEnd() override {
		handlers.forward(&ASN1ContentHandler::writeCollectionEnd);
	}

	void writeBoolean(bool value) override {
		handlers.forward(&ASN1ContentHandler::writeBoolean, value);
	}

	void writeNull() override {
		handlers.forward(&ASN1ContentHandler::writeNull);
	}

	void writeInteger(Integer value) override {
		handlers.forward(&ASN1ContentHandler::writeInteger, value);
	}

	void writeTextString(StringType type, std::string value) override {
		handlers.forward(&ASN1ContentHandler::writeTextString, type, value);
	}

	void writeOctetString(std::string value) override {
		handlers.forward(&ASN1ContentHandler::writeOctetString, value);
	}

	void writeBitString(std::vector<bool> value) override {
		handlers.forward(&ASN1ContentHandler::writeBitString, value);
	}

	void writeOID(ObjectIdentifier value) override {
		handlers.forward(&ASN1ContentHandler::writeOID, value);
	}

	void writeDateTime(DateTimeType type, DateTime value) override {
		handlers.forward(&ASN1ContentHandler::writeDateTime, type, value);
	}

};


}
}
}
}