/** LWS-releated functions.
 *
 * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
 * @copyright 2014-2020, Institute for Automation of Complex Power Systems, EONERC
 * @license GNU General Public License (version 3)
 *
 * VILLASnode
 *
 * 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, either version 3 of the License, or
 * any later version.
 *
 * 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 <libwebsockets.h>
#include <cstring>

#include <villas/node/config.h>
#include <villas/utils.hpp>
#include <villas/web.hpp>
#include <villas/api.hpp>
#include <villas/api/session.hpp>
#include <villas/node/exceptions.hpp>
#include <villas/nodes/websocket.hpp>

using namespace villas;
using namespace villas::node;

/* Forward declarations */
lws_callback_function websocket_protocol_cb;

/** List of libwebsockets protocols. */
lws_protocols protocols[] = {
 	{
 		.name = "http",
 		.callback = lws_callback_http_dummy,
 		.per_session_data_size = 0,
 		.rx_buffer_size = 1024
 	},
#ifdef WITH_API
	{
		.name = "http-api",
		.callback = api::Session::protocolCallback,
		.per_session_data_size = sizeof(api::Session),
		.rx_buffer_size = 1024
	},
#endif /* WITH_API */
#ifdef WITH_NODE_WEBSOCKET
	{
		.name = "live",
		.callback = websocket_protocol_cb,
		.per_session_data_size = sizeof(websocket_connection),
		.rx_buffer_size = 0
	},
#endif /* WITH_NODE_WEBSOCKET */
	{
		.name = nullptr /* terminator */
	}
};

/** List of libwebsockets mounts. */
static lws_http_mount mounts[] = {
#ifdef WITH_API
	{
		.mount_next =		&mounts[1],	/* linked-list "next" */
		.mountpoint =		"/api/v2",	/* mountpoint URL */
		.origin =		"http-api",	/* protocol */
		.def =			nullptr,
		.protocol =		"http-api",
		.cgienv =		nullptr,
		.extra_mimetypes =	nullptr,
		.interpret =		nullptr,
		.cgi_timeout =		0,
		.cache_max_age =	0,
		.auth_mask =		0,
		.cache_reusable =	0,
		.cache_revalidate =	0,
		.cache_intermediaries =	0,
		.origin_protocol =	LWSMPRO_CALLBACK, /* dynamic */
		.mountpoint_len =	7		/* char count */
	},
#endif /* WITH_API */
	{
		.mount_next =		nullptr,
		.mountpoint =		"/",
		.origin =		nullptr,
		.def =			"/index.html",
		.protocol =		nullptr,
		.cgienv =		nullptr,
		.extra_mimetypes =	nullptr,
		.interpret =		nullptr,
		.cgi_timeout =		0,
		.cache_max_age =	0,
		.auth_mask =		0,
		.cache_reusable =	0,
		.cache_revalidate =	0,
		.cache_intermediaries = 0,
		.origin_protocol =	LWSMPRO_FILE,
		.mountpoint_len =	1
	}
};

/** List of libwebsockets extensions. */
static const lws_extension extensions[] = {
#ifdef LWS_DEFLATE_FOUND
	{
		.name = "permessage-deflate",
		.callback = lws_extension_callback_pm_deflate,
		.client_offer = "permessage-deflate"
	},
	{
		.name = "deflate-frame",
		.callback = lws_extension_callback_pm_deflate,
		.client_offer = "deflate_frame"
	},
#endif /* LWS_DEFLATE_FOUND */
	{ nullptr /* terminator */ }
};

void Web::lwsLogger(int lws_lvl, const char *msg) {
	char *nl;

	nl = (char *) strchr(msg, '\n');
	if (nl)
		*nl = 0;

	/* Decrease severity for some errors. */
	if (strstr(msg, "Unable to open") == msg)
		lws_lvl = LLL_WARN;

	Logger logger = logging.get("lws");

	switch (lws_lvl) {
		case LLL_ERR:
			logger->error("{}", msg);
			break;

		case LLL_WARN:
			logger->warn("{}", msg);
			break;

		case LLL_NOTICE:
		case LLL_INFO:
			logger->info("{}", msg);
			break;

		default: /* Everything else is debug */
			logger->debug("{}", msg);
	}
}

void Web::worker()
{
	lws *wsi;

	logger->info("Started worker");

	while (running) {
		lws_service(context, 0);

		while (!writables.empty()) {
			wsi = writables.pop();

			lws_callback_on_writable(wsi);
		}
	}

	logger->info("Stopped worker");
}

Web::Web(Api *a) :
	state(State::INITIALIZED),
	logger(logging.get("web")),
	context(nullptr),
	vhost(nullptr),
	port(getuid() > 0 ? 8080 : 80),
	htdocs(WEB_PATH),
	api(a)
{
	/** @todo: Port to C++: add LLL_DEBUG and others if trace log level is activated */
	lws_set_log_level(LLL_ERR | LLL_WARN | LLL_NOTICE, lwsLogger);
}

int Web::parse(json_t *json)
{
	int ret, enabled = 1;
	const char *cert = nullptr;
	const char *pkey = nullptr;
	const char *htd = nullptr;
	json_error_t err;

	ret = json_unpack_ex(json, &err, JSON_STRICT, "{ s?: s, s?: s, s?: s, s?: i, s?: b }",
		"ssl_cert", &cert,
		"ssl_private_key", &pkey,
		"htdocs", &htd,
		"port", &port,
		"enabled", &enabled
	);
	if (ret)
		throw ConfigError(json, err, "node-config-http");

	if (cert)
		ssl_cert = cert;

	if (pkey)
		ssl_private_key = pkey;

	if (htd)
		htdocs = htd;

	if (!enabled)
		port = CONTEXT_PORT_NO_LISTEN;

	state = State::PARSED;

	return 0;
}

void Web::start()
{
	/* Start server */
	lws_context_creation_info ctx_info;

	memset(&ctx_info, 0, sizeof(ctx_info));

	ctx_info.port = port;
	ctx_info.protocols = protocols;
	ctx_info.extensions = extensions;
	ctx_info.ssl_cert_filepath = ssl_cert.empty() ? nullptr : ssl_cert.c_str();
	ctx_info.ssl_private_key_filepath = ssl_private_key.empty() ? nullptr : ssl_private_key.c_str();
	ctx_info.gid = -1;
	ctx_info.uid = -1;
	ctx_info.options = LWS_SERVER_OPTION_EXPLICIT_VHOSTS | LWS_SERVER_OPTION_DO_SSL_GLOBAL_INIT;
	ctx_info.user = (void *) this;
#if LWS_LIBRARY_VERSION_NUMBER <= 3000000
	/* See: https://github.com/warmcat/libwebsockets/issues/1249 */
	ctx_info.max_http_header_pool = 1024;
 #endif
	ctx_info.mounts = mounts;

	logger->info("Starting sub-system: htdocs={}", htdocs);

	/* update web root of mount point */
	mounts[ARRAY_LEN(mounts)-1].origin = htdocs.c_str();

	context = lws_create_context(&ctx_info);
	if (context == nullptr)
		throw RuntimeError("Failed to initialize server context");

	for (int tries = 10; tries > 0; tries--) {
		vhost = lws_create_vhost(context, &ctx_info);
		if (vhost)
			break;

		ctx_info.port++;
		logger->warn("WebSocket: failed to setup vhost. Trying another port: {}", ctx_info.port);
	}

	if (vhost == nullptr)
		throw RuntimeError("Failed to initialize virtual host");

	/* Start thread */
	running = true;
	thread = std::thread(&Web::worker, this);

	state = State::STARTED;
}

void Web::stop()
{
	assert(state == State::STARTED);

	logger->info("Stopping sub-system");

	running = false;
	lws_cancel_service(context);
	thread.join();

	lws_context_destroy(context);

	state = State::STOPPED;
}

void Web::callbackOnWritable(lws *wsi)
{
	writables.push(wsi);
	lws_cancel_service(context);
}