/**

 * 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 <stdexcept>

#include <mutex>

#include <shared_mutex>

#include <iomanip>

#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/cli/RelpipeCLIException.h>

#include "Configuration.h"

#include "HTTPServer.h"

namespace relpipe {

namespace tr {

namespace httpd {

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

private:

	std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encoding than UTF-8

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

	std::mutex relationalWriterMutex;

	Configuration configuration;

	std::shared_ptr<HTTPServer> httpServer;

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

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

	size_t currentAttributeIndex = 0;

	size_t currentRecordNumber = 1;

	class RequestMatcher {

	public:

		std::regex method = std::regex(".*");

		std::regex url = std::regex(".*");

		virtual ~RequestMatcher() = default;

		bool matches(const std::string& method, const std::string& url) const {

			bool result = true;

			result &= std::regex_match(method, this->method);

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

			return result;

		}

	};

	class HeaderTemplate {

	public:

		std::string name;

		std::string value;

		HeaderTemplate() {

		}

		HeaderTemplate(std::string name, std::string value) : name(name), value(value) {

		}

		virtual ~HeaderTemplate() = default;

	};

	class GlobalHeaderTemplate : public HeaderTemplate, public RequestMatcher {

	} headerTemplate;

	std::vector<GlobalHeaderTemplate> headerTemplates;

	class ResponseTemplate : public RequestMatcher {

	public:

		std::string body;

		uint16_t code = 200;

		std::vector<HeaderTemplate> headers;

	} responseTemplate;

	std::vector<ResponseTemplate> responseTemplates;

	std::mutex templatesMutex; // TODO: read-write lock (for responseTemplates and headerTemplates)

	class RequestHandler : public HTTPServer::RequestHandler {

	private:

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

		std::mutex* relationalWriterMutex;

		std::vector<ResponseTemplate>* responseTemplates;

		std::vector<GlobalHeaderTemplate>* headerTemplates;

		std::mutex* templatesMutex;

		void writeExchange(const HTTPServer::Request& request, const HTTPServer::Response& response) {

			std::wstring_convert < codecvt_utf8<wchar_t>> convertor; // TODO: support also other encoding than UTF-8

			std::lock_guard<std::mutex> lock(*relationalWriterMutex);

			auto exchangeId = convertor.from_bytes(generateExchangeId());

			// TODO: multiple modes:

			// a) interleaved (current)

			// b) write exchanges immediatelly + cache headers and flush them at the end

			// TODO: data types

			// TODO: support multiple encodings

			relationalWriter->startRelation(L"exchange",{

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

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

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

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

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

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

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

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

			}, true);

			relationalWriter->writeAttribute(exchangeId);

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

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

			relationalWriter->writeAttribute(bodyToText(convertor, request.body));

			relationalWriter->writeAttribute(bodyToHex(convertor, request.body));

			relationalWriter->writeAttribute(bodyToText(convertor, response.body));

			relationalWriter->writeAttribute(bodyToHex(convertor, response.body));

			relationalWriter->writeAttribute(std::to_wstring(response.code));

			relationalWriter->startRelation(L"header",{

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

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

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

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

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

			}, true);

			for (const HTTPServer::Header& h : request.header) {

				relationalWriter->writeAttribute(exchangeId);

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

				relationalWriter->writeAttribute(L"request");

				relationalWriter->writeAttribute(convertor.from_bytes(h.name));

				relationalWriter->writeAttribute(convertor.from_bytes(h.value));

			}

			for (const HTTPServer::Header& h : response.header) {

				relationalWriter->writeAttribute(exchangeId);

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

				relationalWriter->writeAttribute(L"response");

				relationalWriter->writeAttribute(convertor.from_bytes(h.name));

				relationalWriter->writeAttribute(convertor.from_bytes(h.value));

			}

		}

		relpipe::common::type::StringX bodyToText(std::wstring_convert < codecvt_utf8<wchar_t>>&convertor, 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(std::wstring_convert < codecvt_utf8<wchar_t>>&convertor, 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());

		}

		std::string generateExchangeId() {

			char buffer[37];

			uuid_t uuid;

			uuid_generate_random(uuid);

			// uuid_generate_time(uuid);

			uuid_unparse_lower(uuid, buffer);

			return buffer;

		}

	public:

		RequestHandler(shared_ptr<relpipe::writer::RelationalWriter> relationalWriter, std::mutex* relationalWriterMutex, std::vector<ResponseTemplate>* responseTemplates, std::vector<GlobalHeaderTemplate>* headerTemplates, std::mutex* templatesMutex) :

		relationalWriter(relationalWriter), relationalWriterMutex(relationalWriterMutex), responseTemplates(responseTemplates), headerTemplates(headerTemplates), templatesMutex(templatesMutex) {

		}

		virtual ~RequestHandler() = default;

		const HTTPServer::Response handle(const HTTPServer::Request& request) override {

			HTTPServer::Response response;

			response.code = 404;

			response.body = "<h1>HTTP 404: Not Found</h1><p>(no response template matched)</p>";

			std::lock_guard<std::mutex> lock(*templatesMutex);

			for (ResponseTemplate t : *responseTemplates) {

				if (t.matches(request.method, request.url)) {

					response.code = t.code;

					response.body = t.body;

					// TODO: replace global header values with request-specific ones instead of appending?

					for (const GlobalHeaderTemplate& h : *headerTemplates) if (h.matches(request.method, request.url)) response.header.push_back(HTTPServer::Header(h.name, h.value));

					for (const HeaderTemplate& h : t.headers) response.header.push_back(HTTPServer::Header(h.name, h.value));

					break;

				}

			}

			writeExchange(request, response);

			return response;

		}

	};

	std::shared_ptr<RequestHandler> requestHandler = std::make_shared<RequestHandler>(relationalWriter, &relationalWriterMutex, &responseTemplates, &headerTemplates, &templatesMutex);

	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) {

		// TODO: recognize several modes: header.set.*, header.add.*, header.remove.*

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

	}

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

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

		if (attributeName == L"url") headerTemplate.url = std::regex(value.size() ? convertor.to_bytes(value) : ".*");

		else if (attributeName == L"method") headerTemplate.method = std::regex(value.size() ? convertor.to_bytes(value) : ".*");

		else if (attributeName == L"name") headerTemplate.name = convertor.to_bytes(value);

		else if (attributeName == L"value") headerTemplate.value = convertor.to_bytes(value); // TODO: header encoding?

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

		currentAttributeIndex++;

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

			std::lock_guard<std::mutex> lock(templatesMutex);

			currentAttributeIndex = 0;

			headerTemplates.push_back(headerTemplate);

			headerTemplate = GlobalHeaderTemplate();

		}

	}

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

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

		if (attributeName == L"url") responseTemplate.url = std::regex(value.size() ? convertor.to_bytes(value) : ".*");

		else if (attributeName == L"method") responseTemplate.method = std::regex(value.size() ? convertor.to_bytes(value) : ".*");

		else if (attributeName == L"code") responseTemplate.code = std::stoi(value);

		else if (attributeName == L"text") responseTemplate.body = convertor.to_bytes(value);

		else if (attributeName == L"data") responseTemplate.body = "TODO: read binary data: " + convertor.to_bytes(value); // TODO: read hex/binary request body

		else if (isHeaderAttribute(attributeName)) responseTemplate.headers.push_back(HeaderTemplate(convertor.to_bytes(fetchHeaderName(attributeName)), convertor.to_bytes(value))); // TODO: header encoding?

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

		currentAttributeIndex++;

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

			std::lock_guard<std::mutex> lock(templatesMutex);

			currentAttributeIndex = 0;

			responseTemplates.push_back(responseTemplate);

			responseTemplate = ResponseTemplate();

		}

	}

public:

	HttpdHandler(shared_ptr<relpipe::writer::RelationalWriter> relationalWriter, Configuration configuration, std::shared_ptr<HTTPServer> httpServer) : relationalWriter(relationalWriter), configuration(configuration), httpServer(httpServer) {

		httpServer->setRequestHandler(requestHandler);

	}

	virtual ~HttpdHandler() {

	}

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

		currentRelationName = name;

		currentReaderMetadata = attributes;

	}

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

		if (currentRelationName == L"header_template") headerTemplateAttribute(value);

		else if (currentRelationName == L"response_template") responseTemplateAttribute(value);

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

	}

	void endOfPipe() {

		sleep(60); // FIXME: run for configured interval or number of requests or forever (until some stop signal)

	}

};

}

}

}