/** Lua expressions hook.
 *
 * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
 * @copyright 2014-2021, 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/>.
 *********************************************************************************/

#pragma once

#include <vector>
#include <mutex>

#include <villas/hook.hpp>

extern "C" {
	#include "lua.h"
};

namespace villas {
namespace node {

/* Forward declarations */
class LuaHook;

class LuaSignalExpression {

protected:
	int cookie;
	lua_State *L;

	std::string expression;

	json_t *cfg;

public:
	LuaSignalExpression(lua_State *L, json_t *json_sig);

	void prepare();

	void parseExpression(const std::string &expr);

	void evaluate(union signal_data *data, enum SignalType type);
};

class LuaHook : public Hook {

	friend LuaSignalExpression;

private:
	static const int SELF_REFERENCE = 55;

protected:
	std::string script;
	std::vector<LuaSignalExpression> expressions;

	struct vlist signalsProcessed; /**> Signals as emited by Lua process() function */
	struct vlist signalsExpressions; /**> Signals as emited by Lua expressions */

	lua_State *L;
	std::mutex mutex;

	bool useNames;
	bool hasExpressions;
	bool needsLocking;

	/* Function indizes */
	struct {
		int start;
		int stop;
		int restart;
		int process;
		int periodic;
		int prepare;
	} functions;

	void parseExpressions(json_t *json_sigs);

	void loadScript();
	void lookupFunctions();
	void setupEnvironment();

	/* Lua functions */

	int luaInfo(lua_State *L);
	int luaWarn(lua_State *L);
	int luaError(lua_State *L);
	int luaDebug(lua_State *L);

	int luaRegisterApiHandler(lua_State *L);

	typedef int (LuaHook::*mem_func)(lua_State * L);

	// This template wraps a member function into a C-style "free" function compatible with lua.
	template <mem_func func>
	static int
	dispatch(lua_State * L) {
		lua_rawgeti(L, LUA_REGISTRYINDEX, SELF_REFERENCE);
		void *vptr = lua_touserdata(L, -1);
		lua_pop(L, 1);

		LuaHook *ptr = static_cast<LuaHook*>(vptr);
		return ((*ptr).*func)(L);
	}

public:
	LuaHook(struct vpath *p, struct vnode *n, int fl, int prio, bool en = true);

	virtual ~LuaHook();

	virtual void parse(json_t *cfg);

	virtual void prepare();

	/** Periodically called by the main thread. */
	virtual void periodic();

	/** Called whenever a hook is started; before threads are created. */
	virtual void start();

	/** Called whenever a hook is stopped; after threads are destoyed. */
	virtual void stop();

	/** Called whenever a new simulation case is started. This is detected by a sequence no equal to zero. */
	virtual void restart();

	/** Called whenever a sample is processed. */
	virtual Reason process(sample *smp);
};


} /* namespace node */
} /* namespace villas */

/** @} */