/**

 * 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/>.

 */

#include <string>

#include <sstream>

#include <iostream>

#include <curl/curl.h>

#include "HTTPClient.h"

namespace relpipe {

namespace tr {

namespace http {

class HTTPClient::HTTPClientImpl {

public:

	CURL* curl;

	char curlErrorBuffer[CURL_ERROR_SIZE];

	std::stringstream responseBody;

	std::stringstream responseHeaders;

	HTTPClientImpl(CURL* curl) : curl(curl) {

	}

	std::vector<std::string> getResponseHeaders() {

		std::vector<std::string> heathers;

		std::stringstream name;

		std::stringstream value;

		std::stringstream* current = &name;

		for (char ch = responseHeaders.get(); responseHeaders.good(); ch = responseHeaders.get()) {

			if (current == &name && ch == ':') {

				current = &value;

				while (responseHeaders.good() && responseHeaders.peek() == ' ') responseHeaders.get(); // skip spaces

			} else if (ch == '\n') {

				if (name.tellp() > 0 && current == &value) {

					heathers.push_back(name.str());

					heathers.push_back(value.str());

				} else if (name.tellp() > 0 && current == &value) {

					// TODO: usually "HTTP/1.1 200 OK" → extract HTTP version and message?

				}

				name = std::stringstream();

				value = std::stringstream();

				current = &name;

			} else if (ch == '\r') {

				// ignore

			} else {

				current->put(ch);

			}

		}

		return heathers;

	}

};

class CurlList {

private:

	curl_slist* list = nullptr;

public:

	CurlList() = default;

	CurlList(const HTTPClient&) = delete;

	CurlList& operator=(const CurlList&) = delete;

	virtual ~CurlList() {

		curl_slist_free_all(list);

	}

	void append(std::string item) {

		list = curl_slist_append(list, item.c_str());

	}

	curl_slist* getList() {

		return list;

	}

};

HTTPClient* HTTPClient::open() {

	HTTPClient::HTTPClientImpl* impl = new HTTPClient::HTTPClientImpl(curl_easy_init());

	typedef size_t(*CurlWriteCallback)(char*, size_t, size_t, HTTPClient::HTTPClientImpl*);

	// set response body callback

	curl_easy_setopt(impl->curl, CURLOPT_WRITEDATA, impl);

	curl_easy_setopt(impl->curl, CURLOPT_WRITEFUNCTION, (CurlWriteCallback)[](char* buffer, size_t size, size_t nmemb, HTTPClient::HTTPClientImpl * impl)->size_t {

		size_t r = size * nmemb;

		impl->responseBody.write(buffer, r);

		return r;

	});

	// set response headers callback

	curl_easy_setopt(impl->curl, CURLOPT_HEADERDATA, impl);

	curl_easy_setopt(impl->curl, CURLOPT_HEADERFUNCTION, (CurlWriteCallback)[](char* buffer, size_t size, size_t nmemb, HTTPClient::HTTPClientImpl * impl)->size_t {

		size_t r = size * nmemb;

		impl->responseHeaders.write(buffer, r);

		return r;

	});

	// set the error buffer

	curl_easy_setopt(impl->curl, CURLOPT_ERRORBUFFER, impl->curlErrorBuffer);

	// enable HTTP and HTTPS only

	curl_easy_setopt(impl->curl, CURLOPT_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);

	// disable protocol guesswork

	curl_easy_setopt(impl->curl, CURLOPT_DEFAULT_PROTOCOL, "no-default-protocol-specify-http-or-https-explicitly-in-url");

	// TODO: automatic decompression of response bodies

	// curl_easy_setopt(impl->curl, CURLOPT_ACCEPT_ENCODING, "");

	// curl_easy_setopt(impl->curl, CURLOPT_HTTP_CONTENT_DECODING, 1L);

	// curl_easy_setopt(impl->curl, CURLOPT_HTTP_TRANSFER_DECODING, 1L);

	return new HTTPClient(impl);

}

HTTPClient::~HTTPClient() {

	curl_easy_cleanup(impl->curl);

	delete impl;

}

const HTTPClient::Response HTTPClient::exchange(const Request& request) {

	HTTPClient::Response response;

	// set request method

	std::string method;

	if (request.method == Method::DELETE) method = "DELETE";

	else if (request.method == Method::GET) method = "GET";

	else if (request.method == Method::HEAD) method = "HEAD";

	else if (request.method == Method::PATCH) method = "PATCH";

	else if (request.method == Method::POST) method = "POST";

	else if (request.method == Method::PUT) method = "PUT";

	else throw std::invalid_argument("Unsupported HTTP method: " + std::to_string((int) request.method));

	curl_easy_setopt(impl->curl, CURLOPT_CUSTOMREQUEST, method.c_str());

	if (request.method == Method::HEAD) curl_easy_setopt(impl->curl, CURLOPT_NOBODY, 1L);

	// set URL

	curl_easy_setopt(impl->curl, CURLOPT_URL, request.url.c_str());

	// set request headers

	CurlList requestHeders;

	for (size_t i = 0; i < request.headers.size(); i += 2) requestHeders.append(request.headers[i] + ": " + request.headers[i + 1]); // TODO: validate, no CR/LF...

	curl_easy_setopt(impl->curl, CURLOPT_HTTPHEADER, requestHeders.getList());

	if (request.body.size()) {

	}

	// clear the error buffer

	impl->curlErrorBuffer[0] = 0;

	// do HTTP call

	CURLcode result = curl_easy_perform(impl->curl);

	if (result == CURLE_OK) {

		// response code and fill the result object

		curl_easy_getinfo(impl->curl, CURLINFO_RESPONSE_CODE, &response.responseCode);

		response.headers = impl->getResponseHeaders();

		response.body = impl->responseBody.str();

		impl->responseBody = std::stringstream();

		return response;

	} else {

		throw Exception(curl_easy_strerror(result), impl->curlErrorBuffer);

	}

}

}

}

}