/**
 * 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());

	// 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);
	}
}


}
}
}