/*
 *  gcsd
 *
 *  gcsd the generic command sequencer daemon can be used to serialize
 *  commands sent over various paralell communication channels to a
 *  single command output. It can be seen as a multiplexer for any
 *  kind of communication between a single resource and various clients
 *  which want to submit commands to it or query information from it.
 *  gcsd is written in C and Lua. The goal is to provide an easy to
 *  understand high level API based on Lua which can be used to
 *  implement the business logic of the so formed multiplexer daemon.
 *
 *
 *  Copyright (C) 2009-2010 Markus Grueneis <gimpf@spreadspace.org>
 *                          Christian Pointner <equinox@spreadspace.org>
 *
 *  This file is part of gcsd.
 *
 *  gcsd 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.
 *
 *  gcsd 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 gcsd. If not, see <http://www.gnu.org/licenses/>.
 */

#define _GNU_SOURCE
#include <stdio.h>

#include <lua.h>
#include <lauxlib.h>

#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>
#include <fcntl.h>
#include <netinet/tcp.h>

#include "l_tcp.h"

#include "datatypes.h"
#include "log.h"

typedef struct {
  socklen_t len_;
  struct sockaddr_storage addr_;
} tcp_endpoint_t;
#define LUA_TCP_UDATA_NAME "tcp_endpoint_t"


static tcp_endpoint_t* newtcpendudata(lua_State *L)
{
  tcp_endpoint_t* end = (tcp_endpoint_t*)lua_newuserdata(L, sizeof(tcp_endpoint_t));
  memset(end, 0, sizeof(*end));
  luaL_newmetatable(L, LUA_TCP_UDATA_NAME);
  lua_setmetatable(L, -2);
  return end;
}

static char* tcp_endpoint_to_string(tcp_endpoint_t* e)
{
  char addrstr[INET6_ADDRSTRLEN + 1], portstr[6], *ret;
  char addrport_sep = ':';

  switch(e->addr_.ss_family)
  {
  case AF_INET: addrport_sep = ':'; break;
  case AF_INET6: addrport_sep = '.'; break;
  case AF_UNSPEC: return NULL;
  default: return strdup("unknown address type");
  }

  int errcode  = getnameinfo((struct sockaddr *)&(e->addr_), e->len_, addrstr, sizeof(addrstr), portstr, sizeof(portstr), NI_NUMERICHOST | NI_NUMERICSERV);
  if (errcode != 0) return NULL;
  int len = asprintf(&ret, "%s%c%s", addrstr, addrport_sep ,portstr);
  if(len == -1) return NULL;
  return ret;
}

static struct addrinfo* tcp_resolve_endpoint(const char* addr, const char* port, int af, int passive)
{
  struct addrinfo hints, *res;
  res = NULL;
  memset (&hints, 0, sizeof (hints));
  hints.ai_socktype = SOCK_STREAM;
  if(passive)
    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
  switch(af) {
  case 4: hints.ai_family = AF_INET; break;
  case 6: hints.ai_family = AF_INET6; break;
  default: hints.ai_family = AF_UNSPEC; break;
  }

  int errcode = getaddrinfo(addr, port, &hints, &res);
  if(errcode != 0 || !res) {
    log_printf(ERROR, "tcp: resolver error: %s", errcode ? gai_strerror(errcode):"no address found!");
    return NULL;
  }

  return res;
}

static int init_listener(tcp_endpoint_t* end)
{
  int fd = socket(end->addr_.ss_family, SOCK_STREAM, 0);
  if(fd < 0) {
    log_printf(ERROR, "tcp: error on opening socket: %s", strerror(errno));
    return -1;
  }

  int on = 1;
  int ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
  if(ret) {
    log_printf(ERROR, "tcp: error on setsockopt(): %s", strerror(errno));
    return -1;
  }
  if(end->addr_.ss_family == AF_INET6) {
    if(setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &on, sizeof(on)))
      log_printf(WARNING, "tcp: failed to set IPV6_V6ONLY socket option: %s", strerror(errno));
  }

  char* ls = tcp_endpoint_to_string(end);
  ret = bind(fd, (struct sockaddr *)&(end->addr_), end->len_);
  if(ret) {
    log_printf(ERROR, "tcp: error on bind(%s): %s", ls ? ls:"", strerror(errno));
    if(ls) free(ls);
    return -1;
  }
  free(ls);

  ret = listen(fd, 0);
  if(ret) {
    log_printf(ERROR, "tcp: error on listen(): %s", strerror(errno));
    if(ls) free(ls);
    return -1;
  }

  return fd;
}

static int l_tcp_server(lua_State *L)
{
  const char* addr = luaL_optstring(L, 1, "*");
  if(!strcmp(addr, "*") || !strlen(addr)) addr = NULL;
  const char* port = luaL_checkstring(L, 2);
  int af = luaL_optint(L, 3, 0);

  struct addrinfo *res = tcp_resolve_endpoint(addr, port, af, 1);
  if(!res) {
    lua_pushnil(L);
    lua_pushstring(L, "error at tcp-server initialization");
    return 2;
  }

  lua_newtable(L);
  int idx = 1;
  struct addrinfo* r = res;
  while(r) {
    lua_pushinteger(L, idx++);
    lua_newtable(L);

    lua_pushliteral(L, "local_end");
    tcp_endpoint_t* end = newtcpendudata(L);
    memcpy(&(end->addr_), r->ai_addr, r->ai_addrlen);
    end->len_ = r->ai_addrlen;
    lua_settable(L, -3);

    int fd = init_listener(end);
    if(fd < 0) {
      freeaddrinfo(res);
      lua_pushnil(L);
      lua_pushstring(L, "error at tcp-server initialization");
      return 2;
    }

    lua_pushliteral(L, "fd");
    lua_pushinteger(L, fd);
    lua_settable(L, -3);

    lua_settable(L, -3);
    r = r->ai_next;
  }
  freeaddrinfo(res);

  return 1;
}

static int l_tcp_accept(lua_State *L)
{
  int fd = luaL_checkint(L, 1);
  tcp_endpoint_t* remote_addr = newtcpendudata(L);
  remote_addr->len_ = sizeof(remote_addr->addr_);
  int new_client = accept(fd, (struct sockaddr *)&(remote_addr->addr_), &remote_addr->len_);
  if(new_client == -1) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno));
    return 2;
  }
  char* rs = tcp_endpoint_to_string(remote_addr);
  log_printf(INFO, "new client from %s (fd=%d)", rs ? rs:"(null)", new_client);
  if(rs) free(rs);

  lua_pushinteger(L, new_client);
  lua_insert(L, -2);
  return 2;
}

static int init_client(tcp_endpoint_t remote, tcp_endpoint_t source)
{
  int fd = socket(remote.addr_.ss_family, SOCK_STREAM, 0);
  if(fd < 0) {
    log_printf(INFO, "error on socket(): %s", strerror(errno));
    return -1;
  }

  int on = 1;
  if(setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on))) {
    log_printf(ERROR, "error on setsockopt(): %s", strerror(errno));
    close(fd);
    return -1;
  }

  if(fcntl(fd, F_SETFL, O_NONBLOCK)) {
    log_printf(ERROR, "error on fcntl(): %s", strerror(errno));
    close(fd);
    return -1;
  }

  if(source.addr_.ss_family != AF_UNSPEC) {
    if(bind(fd, (struct sockaddr *)&(source.addr_), source.len_)==-1) {
      log_printf(INFO, "error on bind(): %s", strerror(errno));
      close(fd);
      return -1;
    }
  }

  return fd;
}

static int l_tcp_client(lua_State *L)
{
  const char* raddr = luaL_checkstring(L, 1);
  const char* rport = luaL_checkstring(L, 2);
  int af = luaL_optint(L, 3, 0);
  const char* saddr = luaL_optstring(L, 4, NULL);

  tcp_endpoint_t remote, source;
  memset(&remote, 0, sizeof(tcp_endpoint_t));
  memset(&source, 0, sizeof(tcp_endpoint_t));
  source.addr_.ss_family = AF_UNSPEC;

  struct addrinfo *res = tcp_resolve_endpoint(raddr, rport, af, 0);
  if(!res) {
    lua_pushnil(L);
    lua_pushstring(L, "error at tcp-client initialization");
    return 2;
  }
  memcpy(&(remote.addr_), res->ai_addr, res->ai_addrlen);
  remote.len_ = res->ai_addrlen;
  freeaddrinfo(res);

  if(saddr) {
    res = tcp_resolve_endpoint(saddr, NULL, af, 0);
    if(!res) {
      lua_pushnil(L);
      lua_pushstring(L, "error at tcp-client initialization");
      return 2;
    }
    memcpy(&(source.addr_), res->ai_addr, res->ai_addrlen);
    source.len_ = res->ai_addrlen;
    freeaddrinfo(res);
  }

  int fd = init_client(remote, source);
  if(fd < 0) {
    lua_pushnil(L);
    lua_pushstring(L, "error at tcp-client initialization");
    return 2;
  }

  lua_newtable(L);

  lua_pushliteral(L, "remote_end");
  tcp_endpoint_t* re = newtcpendudata(L);
  memcpy(re, &remote, sizeof(tcp_endpoint_t));
  lua_settable(L, -3);

  if(source.addr_.ss_family != AF_UNSPEC) {
    lua_pushliteral(L, "source_end");
    tcp_endpoint_t* se = newtcpendudata(L);
    memcpy(se, &source, sizeof(tcp_endpoint_t));
    lua_settable(L, -3);
  }

  lua_pushliteral(L, "fd");
  lua_pushinteger(L, fd);
  lua_settable(L, -3);

  if(connect(fd, (struct sockaddr *)&(remote.addr_), remote.len_)==-1) {
    if(errno == EINPROGRESS) {
      lua_pushboolean(L, 0);
      return 2;
    }

    close(fd);
    log_printf(INFO, "error on connect(): %s", strerror(errno));
    lua_pushnil(L);
    lua_pushstring(L, "connect() failed");
    return 2;
  }

  lua_pushboolean(L, 1);
  return 2;
}

static int l_tcp_connect(lua_State *L)
{
  int fd = luaL_checkint(L, 1);
  int error = 0;
  socklen_t len = sizeof(error);
  if(getsockopt(fd, SOL_SOCKET, SO_ERROR, &error, &len)==-1) {
    log_printf(ERROR, "error on getsockopt(): %s", strerror(errno));
    lua_pushnil(L);
    lua_pushstring(L, "can't read SO_ERROR");
    return 2;
  }
  if(error) {
    log_printf(ERROR, "error on connect(): %s", strerror(error));
    lua_pushnil(L);
    lua_pushstring(L, "connect() failed");
    return 2;
  }

  lua_pushboolean(L, 1);
  return 1;
}

static int l_tcp_recv(lua_State *L)
{
  int fd = luaL_checkint(L,1);
  size_t len = luaL_checkint(L,2);
  char* data = malloc(len);
  if(!data) {
    lua_pushnil(L);
    lua_pushstring(L, "bad alloc");
    return 2;
  }

  int ret = recv(fd, data, len, 0);

  if(ret == -1) {
    lua_pushnil(L);
// FIXXXXXME: strerror is not threadsafe!!!
    lua_pushstring(L, strerror(errno));
    free(data);
    return 2;
  }
  lua_pushlstring(L, data, ret);
  free(data);
  return 1;
}

static int l_tcp_send(lua_State *L)
{
  int fd = luaL_checkint(L,1);
  size_t len = 0;
  const char* data = luaL_checklstring(L, 2, &len);

  int ret = send(fd, data, len, 0);

  if(ret == -1) {
    lua_pushnil(L);
// FIXXXXXME: strerror is not threadsafe!!!
    lua_pushstring(L, strerror(errno));
    return 2;
  }
  lua_pushinteger(L, ret);
  return 1;
}

static int l_tcp_endtostring(lua_State *L)
{
  tcp_endpoint_t* e = (tcp_endpoint_t*)luaL_checkudata(L, 1, LUA_TCP_UDATA_NAME);
  char* es = tcp_endpoint_to_string(e);
  if(!es)
    luaL_error(L, "bad alloc");

  lua_pushstring(L, es);
  free(es);
  return 1;
}

static const struct luaL_Reg tcp_funcs [] = {
  { "server", l_tcp_server },
  { "accept", l_tcp_accept },
  { "client", l_tcp_client },
  { "connect", l_tcp_connect },
  { "recv", l_tcp_recv },
  { "send", l_tcp_send },
  { "endtostring", l_tcp_endtostring },
  { NULL, NULL }
};

LUALIB_API int luaopen_tcp(lua_State *L)
{
#if LUA_VERSION_NUM > 501
  lua_newtable(L);
  luaL_setfuncs(L, tcp_funcs, 0);
  lua_pushvalue(L, -1);
  lua_setglobal(L, LUA_TCPLIBNAME);
#else
  luaL_register(L, LUA_TCPLIBNAME, tcp_funcs);
#endif
  return 1;
}