/**

 * Relational pipes

 * Copyright © 2022 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 <string>

#include <vector>

#include <codecvt>

#include <regex>

#include <locale>

#include <stdexcept>

#include <iomanip>

#include <curl/curl.h>

#include <uuid/uuid.h>

#include <relpipe/common/type/typedefs.h>

#include <relpipe/reader/TypeId.h>

#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>

#include <relpipe/reader/handlers/AttributeMetadata.h>

#include <relpipe/writer/Factory.h>

#include <relpipe/writer/TypeId.h>

#include <relpipe/cli/RelpipeCLIException.h>

#include "Configuration.h"

#include "HTTPClient.h"

namespace relpipe {

namespace tr {

namespace http {

class HTTPHandler : public relpipe::reader::handlers::RelationalReaderStringHandler {

private:

	class HeaderDefinition {

	public:

		std::wregex request = std::wregex(L".*");

		std::wregex url = std::wregex(L".*");

		relpipe::common::type::StringX name;

		relpipe::common::type::StringX value;

		bool matches(const relpipe::common::type::StringX& request, const relpipe::common::type::StringX& url) const {

			bool result = false;

			result |= std::regex_match(request, this->request);

			result |= std::regex_match(url, this->url);

			return result;

		}

	};

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.

	shared_ptr<relpipe::writer::RelationalWriter> relationalWriter;

	Configuration configuration;

	relpipe::common::type::StringX currentRelationName;

	std::vector<relpipe::reader::handlers::AttributeMetadata> currentReaderMetadata;

	std::vector<relpipe::writer::AttributeMetadata> currentWriterMetadata;

	HeaderDefinition requestHeader;

	relpipe::common::type::StringX requestId;

	HTTPClient::Request request;

	std::vector<HeaderDefinition> requestHeaders;

	std::vector<relpipe::common::type::StringX> responseHeaders;

	size_t currentAttributeIndex = 0;

	size_t currentRecordNumber = 1;

	void writeHeaders() {

		if (responseHeaders.size()) {

			relationalWriter->startRelation(L"header",{

				{L"request", relpipe::writer::TypeId::STRING},

				{L"url", relpipe::writer::TypeId::STRING},

				{L"name", relpipe::writer::TypeId::STRING},

				{L"value", relpipe::writer::TypeId::STRING},

			}, true);

			for (auto s : responseHeaders) relationalWriter->writeAttribute(s);

			responseHeaders.clear();

		}

	}

	HTTPClient::Method parseMethod(const relpipe::common::type::StringX& value) {

		if (value.size() == 0) return HTTPClient::Method::GET;

		else if (value == L"GET") return HTTPClient::Method::GET;

		else if (value == L"HEAD") return HTTPClient::Method::HEAD;

		else if (value == L"POST") return HTTPClient::Method::POST;

		else if (value == L"PUT") return HTTPClient::Method::PUT;

		else if (value == L"DELETE") return HTTPClient::Method::DELETE;

		else if (value == L"PATCH") return HTTPClient::Method::PATCH;

		else throw std::invalid_argument("Unsupported HTTP method: " + convertor.to_bytes(value));

	}

	relpipe::common::type::StringX getHeaderAttributePrefix() {

		// might be configurable - parametrized

		return L"header.";

	}

	bool isHeaderAttribute(const relpipe::common::type::StringX& attributeName) {

		return attributeName.rfind(getHeaderAttributePrefix(), 0) == 0;

	}

	relpipe::common::type::StringX fetchHeaderName(const relpipe::common::type::StringX& attributeName) {

		return attributeName.substr(getHeaderAttributePrefix().size());

	}

	void appendRequestHeader(const relpipe::common::type::StringX& name, const relpipe::common::type::StringX& value) {

		request.headers.push_back(convertor.to_bytes(name));

		request.headers.push_back(convertor.to_bytes(value));

	}

	relpipe::common::type::StringX generateRequestId() {

		char buffer[37];

		uuid_t uuid;

		uuid_generate_random(uuid);

		// uuid_generate_time(uuid);

		uuid_unparse_lower(uuid, buffer);

		return convertor.from_bytes(buffer);

	}

	relpipe::common::type::StringX bodyToText(const std::string& body, bool* validEncoding = nullptr) {

		try {

			if (validEncoding) *validEncoding = true;

			// TODO: use encoding from the HTTP response headers instead of the constant one?

			return convertor.from_bytes(body);

		} catch (...) {

			if (validEncoding) *validEncoding = false;

			std::stringstream filtered;

			for (char ch : body) filtered << (ch >= ' ' && ch < 127 ? ch : '.');

			return convertor.from_bytes(filtered.str());

		}

	}

	relpipe::common::type::StringX bodyToHex(const std::string& body) {

		std::stringstream hex;

		hex << std::hex << std::setfill('0') << std::hex;

		for (size_t i = 0, size = body.size(); i < size; i++) hex << std::setw(2) << (0xff & body[i]);

		return convertor.from_bytes(hex.str());

	}

public:

	HTTPHandler(shared_ptr<relpipe::writer::RelationalWriter> relationalWriter, Configuration configuration) : relationalWriter(relationalWriter), configuration(configuration) {

	}

	virtual ~HTTPHandler() {

	}

	void startRelation(relpipe::common::type::StringX name, std::vector<relpipe::reader::handlers::AttributeMetadata> attributes) override {

		writeHeaders(); // from previous relation

		currentRelationName = name;

		currentReaderMetadata = attributes;

		currentAttributeIndex = 0;

		if (currentRelationName == L"header") {

			// TODO: analyze header attributes

		} else if (currentRelationName == L"request") {

			relationalWriter->startRelation(L"response",{

				{L"request", relpipe::writer::TypeId::STRING},

				{L"url", relpipe::writer::TypeId::STRING},

				{L"text", relpipe::writer::TypeId::STRING},

				{L"data", relpipe::writer::TypeId::STRING},

				{L"text_valid", relpipe::writer::TypeId::BOOLEAN},

				{L"code", relpipe::writer::TypeId::INTEGER},

			}, true);

		}

	}

	void attribute(const relpipe::common::type::StringX& value) override {

		if (currentRelationName == L"header") headerAttribute(value);

		else if (currentRelationName == L"request") requestAttribute(value);

		else throw std::invalid_argument("Unsupported relation: " + convertor.to_bytes(currentRelationName));

	}

private:

	void headerAttribute(const relpipe::common::type::StringX& value) {

		auto attributeName = currentReaderMetadata[currentAttributeIndex].getAttributeName();

		if (attributeName == L"name") requestHeader.name = value;

		else if (attributeName == L"value") requestHeader.value = value;

		else if (attributeName == L"request") requestHeader.request = std::wregex(value.size() ? value : L".*"); // TODO: null instead of empty value (when supported)

		else if (attributeName == L"url") requestHeader.url = std::wregex(value.size() ? value : L".*"); // TODO: null instead of empty value (when supported)

		else throw std::invalid_argument("Unsupported attribute in the header relation: " + convertor.to_bytes(attributeName + L" = " + value));

		currentAttributeIndex++;

		if (currentAttributeIndex % currentReaderMetadata.size() == 0) {

			currentAttributeIndex = 0;

			requestHeaders.push_back(requestHeader);

			requestHeader = HeaderDefinition();

		}

	}

	void requestAttribute(const relpipe::common::type::StringX& value) {

		auto attributeName = currentReaderMetadata[currentAttributeIndex].getAttributeName();

		if (attributeName == L"id") requestId = value;

		else if (attributeName == L"url") request.url = convertor.to_bytes(value);

		else if (attributeName == L"method") request.method = parseMethod(value);

		else if (isHeaderAttribute(attributeName)) appendRequestHeader(fetchHeaderName(attributeName), value);

		else throw std::invalid_argument("Unsupported attribute in the header relation: " + convertor.to_bytes(attributeName + L" = " + value));

		currentAttributeIndex++;

		if (currentAttributeIndex % currentReaderMetadata.size() == 0) {

			currentAttributeIndex = 0;

			std::shared_ptr<HTTPClient> http(HTTPClient::open());

			if (requestId.empty()) requestId = generateRequestId();

			for (const HeaderDefinition& h : requestHeaders) if (h.matches(requestId, convertor.from_bytes(request.url))) appendRequestHeader(h.name, h.value);

			std::string body;

			relpipe::common::type::Integer responseCode = -1;

			try {

				HTTPClient::Response response = http->exchange(request);

				responseCode = response.responseCode;

				body = response.body;

				for (size_t i = 0; i < response.headers.size(); i += 2) {

					responseHeaders.push_back(requestId);

					responseHeaders.push_back(convertor.from_bytes(request.url));

					responseHeaders.push_back(convertor.from_bytes(response.headers[i]));

					responseHeaders.push_back(convertor.from_bytes(response.headers[i + 1]));

				}

			} catch (const HTTPClient::Exception& e) {

				body = e.getFullMessage();

				// TODO: move error message into separate attribute?

			}

			bool validText = false;

			relationalWriter->writeAttribute(requestId);

			relationalWriter->writeAttribute(convertor.from_bytes(request.url));

			relationalWriter->writeAttribute(bodyToText(body, &validText));

			relationalWriter->writeAttribute(bodyToHex(body)); // TODO: return as an octet-string (when supported) instead of hexadecimal

			relationalWriter->writeAttribute(&validText, typeid (validText));

			relationalWriter->writeAttribute(&responseCode, typeid (responseCode));

			request = HTTPClient::Request();

			requestId.clear();

		}

	}

public:

	void endOfPipe() {

		writeHeaders(); // from last relation

	}

};

}

}

}