/*

 * Lua polling library

 * Copyright (C) 2017-2018 Kim Alvefur

 *

 * This project is MIT licensed. Please see the

 * COPYING file in the source package for more information.

 *

 */

#include <unistd.h>

#include <string.h>

#include <errno.h>

#ifdef __linux__

#define USE_EPOLL

#endif

#ifdef USE_EPOLL

#include <sys/epoll.h>

#ifndef MAX_EVENTS

#define MAX_EVENTS 64

#endif

#else

#include <sys/select.h>

#endif

#include <lualib.h>

#include <lauxlib.h>

#ifdef USE_EPOLL

#define STATE_MT "util.poll<epoll>"

#else

#define STATE_MT "util.poll<select>"

#endif

#if (LUA_VERSION_NUM == 501)

#define luaL_setmetatable(L, tname) luaL_getmetatable(L, tname); lua_setmetatable(L, -2)

#endif

#if (LUA_VERSION_NUM < 504)

#define luaL_pushfail lua_pushnil

#endif

/*

 * Structure to keep state for each type of API

 */

typedef struct Lpoll_state {

	int processed;

#ifdef USE_EPOLL

	int epoll_fd;

	struct epoll_event events[MAX_EVENTS];

#else

	fd_set wantread;

	fd_set wantwrite;

	fd_set readable;

	fd_set writable;

	fd_set all;

	fd_set err;

#endif

} Lpoll_state;

/*

 * Add an FD to be watched

 */

static int Ladd(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	int fd = luaL_checkinteger(L, 2);

	int wantread = lua_toboolean(L, 3);

	int wantwrite = lua_toboolean(L, 4);

	if(fd < 0) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(EBADF));

		lua_pushinteger(L, EBADF);

		return 3;

	}

#ifdef USE_EPOLL

	struct epoll_event event;

	event.data.fd = fd;

	event.events = (wantread ? EPOLLIN : 0) | (wantwrite ? EPOLLOUT : 0);

	event.events |= EPOLLERR | EPOLLHUP | EPOLLRDHUP;

	int ret = epoll_ctl(state->epoll_fd, EPOLL_CTL_ADD, fd, &event);

	if(ret < 0) {

		ret = errno;

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ret));

		lua_pushinteger(L, ret);

		return 3;

	}

	lua_pushboolean(L, 1);

	return 1;

#else

	if(fd > FD_SETSIZE) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(EBADF));

		lua_pushinteger(L, EBADF);

		return 3;

	}

	if(FD_ISSET(fd, &state->all)) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(EEXIST));

		lua_pushinteger(L, EEXIST);

		return 3;

	}

	FD_CLR(fd, &state->readable);

	FD_CLR(fd, &state->writable);

	FD_CLR(fd, &state->err);

	FD_SET(fd, &state->all);

	if(wantread) {

		FD_SET(fd, &state->wantread);

	}

	else {

		FD_CLR(fd, &state->wantread);

	}

	if(wantwrite) {

		FD_SET(fd, &state->wantwrite);

	}

	else {

		FD_CLR(fd, &state->wantwrite);

	}

	lua_pushboolean(L, 1);

	return 1;

#endif

}

/*

 * Set events to watch for, readable and/or writable

 */

static int Lset(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	int fd = luaL_checkinteger(L, 2);

#ifdef USE_EPOLL

	int wantread = lua_toboolean(L, 3);

	int wantwrite = lua_toboolean(L, 4);

	struct epoll_event event;

	event.data.fd = fd;

	event.events = (wantread ? EPOLLIN : 0) | (wantwrite ? EPOLLOUT : 0);

	event.events |= EPOLLERR | EPOLLHUP | EPOLLRDHUP;

	int ret = epoll_ctl(state->epoll_fd, EPOLL_CTL_MOD, fd, &event);

	if(ret == 0) {

		lua_pushboolean(L, 1);

		return 1;

	}

	else {

		ret = errno;

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ret));

		lua_pushinteger(L, ret);

		return 3;

	}

#else

	if(!FD_ISSET(fd, &state->all)) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ENOENT));

		lua_pushinteger(L, ENOENT);

		return 3;

	}

	if(!lua_isnoneornil(L, 3)) {

		if(lua_toboolean(L, 3)) {

			FD_SET(fd, &state->wantread);

		}

		else {

			FD_CLR(fd, &state->wantread);

		}

	}

	if(!lua_isnoneornil(L, 4)) {

		if(lua_toboolean(L, 4)) {

			FD_SET(fd, &state->wantwrite);

		}

		else {

			FD_CLR(fd, &state->wantwrite);

		}

	}

	lua_pushboolean(L, 1);

	return 1;

#endif

}

/*

 * Remove FDs

 */

static int Ldel(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	int fd = luaL_checkinteger(L, 2);

#ifdef USE_EPOLL

	struct epoll_event event;

	event.data.fd = fd;

	int ret = epoll_ctl(state->epoll_fd, EPOLL_CTL_DEL, fd, &event);

	if(ret == 0) {

		lua_pushboolean(L, 1);

		return 1;

	}

	else {

		ret = errno;

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ret));

		lua_pushinteger(L, ret);

		return 3;

	}

#else

	if(!FD_ISSET(fd, &state->all)) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ENOENT));

		lua_pushinteger(L, ENOENT);

		return 3;

	}

	FD_CLR(fd, &state->wantread);

	FD_CLR(fd, &state->wantwrite);

	FD_CLR(fd, &state->readable);

	FD_CLR(fd, &state->writable);

	FD_CLR(fd, &state->all);

	FD_CLR(fd, &state->err);

	lua_pushboolean(L, 1);

	return 1;

#endif

}

/*

 * Check previously manipulated event state for FDs ready for reading or writing

 */

static int Lpushevent(lua_State *L, struct Lpoll_state *state) {

#ifdef USE_EPOLL

	if(state->processed > 0) {

		state->processed--;

		struct epoll_event event = state->events[state->processed];

		lua_pushinteger(L, event.data.fd);

		lua_pushboolean(L, event.events & (EPOLLIN | EPOLLHUP | EPOLLRDHUP | EPOLLERR));

		lua_pushboolean(L, event.events & EPOLLOUT);

		return 3;

	}

#else

	for(int fd = state->processed + 1; fd < FD_SETSIZE; fd++) {

		if(FD_ISSET(fd, &state->readable) || FD_ISSET(fd, &state->writable) || FD_ISSET(fd, &state->err)) {

			lua_pushinteger(L, fd);

			lua_pushboolean(L, FD_ISSET(fd, &state->readable) | FD_ISSET(fd, &state->err));

			lua_pushboolean(L, FD_ISSET(fd, &state->writable));

			FD_CLR(fd, &state->readable);

			FD_CLR(fd, &state->writable);

			FD_CLR(fd, &state->err);

			state->processed = fd;

			return 3;

		}

	}

#endif

	return 0;

}

/*

 * Wait for event

 */

static int Lwait(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	int ret = Lpushevent(L, state);

	if(ret != 0) {

		return ret;

	}

	lua_Number timeout = luaL_checknumber(L, 2);

	luaL_argcheck(L, timeout >= 0, 1, "positive number expected");

#ifdef USE_EPOLL

	ret = epoll_wait(state->epoll_fd, state->events, MAX_EVENTS, timeout * 1000);

#else

	/*

	 * select(2) mutates the fd_sets passed to it so in order to not

	 * have to recreate it manually every time a copy is made.

	 */

	memcpy(&state->readable, &state->wantread, sizeof(fd_set));

	memcpy(&state->writable, &state->wantwrite, sizeof(fd_set));

	memcpy(&state->err, &state->all, sizeof(fd_set));

	struct timeval tv;

	tv.tv_sec = (time_t)timeout;

	tv.tv_usec = ((suseconds_t)(timeout * 1000000)) % 1000000;

	ret = select(FD_SETSIZE, &state->readable, &state->writable, &state->err, &tv);

#endif

	if(ret == 0) {

		/* Is this an error? */

		lua_pushnil(L);

		lua_pushstring(L, "timeout");

		return 2;

	}

	else if(ret < 0 && errno == EINTR) {

		/* Is this an error? */

		lua_pushnil(L);

		lua_pushstring(L, "signal");

		return 2;

	}

	else if(ret < 0) {

		ret = errno;

		luaL_pushfail(L);

		lua_pushstring(L, strerror(ret));

		lua_pushinteger(L, ret);

		return 3;

	}

	/*

	 * Search for the first ready FD and return it

	 */

#ifdef USE_EPOLL

	state->processed = ret;

#else

	state->processed = -1;

#endif

	return Lpushevent(L, state);

}

#ifdef USE_EPOLL

/*

 * Return Epoll FD

 */

static int Lgetfd(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	lua_pushinteger(L, state->epoll_fd);

	return 1;

}

/*

 * Close epoll FD

 */

static int Lgc(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	if(state->epoll_fd == -1) {

		return 0;

	}

	if(close(state->epoll_fd) == 0) {

		state->epoll_fd = -1;

	}

	else {

		lua_pushstring(L, strerror(errno));

		lua_error(L);

	}

	return 0;

}

#endif

/*

 * String representation

 */

static int Ltos(lua_State *L) {

	struct Lpoll_state *state = luaL_checkudata(L, 1, STATE_MT);

	lua_pushfstring(L, "%s: %p", STATE_MT, state);

	return 1;

}

/*

 * Create a new context

 */

static int Lnew(lua_State *L) {

	/* Allocate state */

	Lpoll_state *state = lua_newuserdata(L, sizeof(Lpoll_state));

	luaL_setmetatable(L, STATE_MT);

	/* Initialize state */

#ifdef USE_EPOLL

	state->epoll_fd = -1;

	state->processed = 0;

	int epoll_fd = epoll_create1(EPOLL_CLOEXEC);

	if(epoll_fd <= 0) {

		luaL_pushfail(L);

		lua_pushstring(L, strerror(errno));