/**
 * 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 <sstream>
#include <iostream>

#include <curl/curl.h>

#include "HTTPClient.h"


namespace relpipe {
namespace tr {
namespace http {

class HTTPClient::HTTPClientImpl {
public:
	CURL* curl;
	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 (ch == ':') {
				current = &value;
				for (char space = responseHeaders.get(); responseHeaders.good() && responseHeaders.peek() == ' '; space = 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() {
	return new HTTPClient(new HTTPClient::HTTPClientImpl(curl_easy_init()));
}

HTTPClient::~HTTPClient() {
	curl_easy_cleanup(impl->curl);
	delete impl;
}

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

	// TODO: set request method

	// 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());

	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;
	});

	// do HTTP call
	curl_easy_perform(impl->curl);

	// 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;
}


}
}
}