/*
 *  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/>.
 */

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

#include <sys/select.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>

#include "l_util.h"

#if LUA_VERSION_NUM < 502
#define lua_rawlen lua_objlen
#endif

static int get_fd(lua_State *L)
{
  if(!lua_istable(L, -1))
    return -1;

  lua_pushliteral(L, "fd");
  lua_gettable(L, -2);
  int fd = luaL_checkint(L, -1);
  lua_pop(L, 1);
  return fd;
}

static int collect_fds(lua_State *L, int table_idx, fd_set* fds, int max_fd)
{
  FD_ZERO(fds);
  int i;
  for(i = 1;;i++) {
    int fd;
    lua_pushinteger(L, i);
    lua_gettable(L, table_idx);
    if(lua_isnil(L,-1)) {
      lua_pop(L, 1);
      break;
    }
    fd = get_fd(L);
    if(fd >= 0) {
      FD_SET(fd, fds);
      max_fd = fd > max_fd ? fd : max_fd;
    }
    lua_pop(L,1);
  }
  return max_fd;
}

static void return_fds(lua_State *L, int table_idx, fd_set* fds)
{
  lua_newtable(L);
  int i, j = 1;
  for(i = 1;;i++) {
    int fd;
    lua_pushinteger(L, i);
    lua_gettable(L, table_idx);
    if(lua_isnil(L,-1)) {
      lua_pop(L, 1);
      break;
    }
    fd = get_fd(L);
    if(fd >= 0 && FD_ISSET(fd, fds)) {
      lua_pushinteger(L, j++);
      lua_insert(L, -2);
      lua_settable(L, -3);
    }
    else
      lua_pop(L,1);
  }
}

static int l_util_select(lua_State *L)
{
  if(!lua_istable(L, 1))
    luaL_error(L, "table expected as first argument");
  if(!lua_istable(L, 2))
    luaL_error(L, "table expected as second argument");
  int ms = luaL_optint(L, 3, -1);

  fd_set readables, writeables;
  int max_fd = collect_fds(L, 1, &readables, 0);
  max_fd = collect_fds(L, 2, &writeables, max_fd);

  struct timeval tv;
  struct timeval* timeout = NULL;
  if(ms >= 0) {
    tv.tv_sec = ms / 1000;
    tv.tv_usec = (ms % 1000) * 1000;
    timeout = &tv;
  }
  int ret = select(max_fd+1, &readables, &writeables, NULL, timeout);
  if(ret <= 0) {
    lua_pushnil(L);
    lua_pushnil(L);
    if(!ret)
      lua_pushliteral(L, "timeout");
    else if(errno == EINTR)
      lua_pushliteral(L, "signal");
    else
      lua_pushstring(L, strerror(errno)); // FIXXXXXME: strerror is not threadsafe!!!
    return 3;
  }
  return_fds(L, 1, &readables);
  return_fds(L, 2, &writeables);
  return 2;
}

static char** table_to_argv(lua_State *L, const char* script, int index)
{
  size_t n = 0;
  if(lua_istable(L, index))
    n = lua_rawlen(L, index);

  char** my_ptrptr = malloc((n+2)*sizeof(char*));
  if(!my_ptrptr)
    return NULL;

  my_ptrptr[n+1] = NULL;
  my_ptrptr[0] = strdup(script);
  if(!my_ptrptr[0]) {
    free(my_ptrptr);
    return NULL;
  }

  int i;
  for(i = 1; i <= n; ++i) {
    lua_pushinteger(L, i);
    lua_gettable(L, index);
    my_ptrptr[i] = strdup(luaL_checkstring(L, -1));
    lua_pop(L, 1);
    if(!my_ptrptr[i]) {
      i--;
      for(; i >= 0; --i)
        free(my_ptrptr[i]);

      free(my_ptrptr);
      return NULL;
    }
  }

  return my_ptrptr;
}

static char** table_to_evp(lua_State *L, int index)
{
  if(!lua_istable(L, index))
    return NULL;

  size_t n = lua_rawlen(L, index);
  char** my_ptrptr = malloc((n+1)*sizeof(char*));
  if(!my_ptrptr)
    return NULL;

  int i;
  for(i = 0; i < n; ++i) {
    lua_pushinteger(L, i+1);
    lua_gettable(L, index);
    my_ptrptr[i] = strdup(luaL_checkstring(L, -1));
    lua_pop(L, 1);
    if(!my_ptrptr[i]) {
      i--;
      for(; i >= 0; --i)
        free(my_ptrptr[i]);

      free(my_ptrptr);
      return NULL;
    }
  }
  my_ptrptr[n] = NULL;
  return my_ptrptr;
}

void free_ptrptr(char** ptrptr)
{
  if(!ptrptr)
    return;

  int i;
  for(i = 0; ptrptr[i]; ++i)
    free(ptrptr[i]);

  free(ptrptr);
}

static void child_add(lua_State *L, pid_t pid, int fd)
{
  lua_getglobal(L, LUA_UTILLIBNAME);
  lua_getfield(L, -1, LUA_UTILCHLIDRENNAME);
  lua_remove(L, -2);
  lua_newtable(L);
  lua_pushinteger(L, pid);
  lua_setfield(L, -2, "pid");
  lua_pushinteger(L, fd);
  lua_setfield(L, -2, "errfd");
  lua_pushinteger(L, pid);
  lua_pushvalue(L, -2);
  lua_settable(L, -4);
  lua_remove(L, -2);
}

static void child_remove(lua_State *L, pid_t pid)
{
  lua_getglobal(L, LUA_UTILLIBNAME);
  lua_getfield(L, -1, LUA_UTILCHLIDRENNAME);
  lua_pushinteger(L, pid);
  lua_pushnil(L);
  lua_settable(L, -3);
  lua_pop(L, 2);
}

static int child_find(lua_State *L, pid_t pid)
{
  lua_getglobal(L, LUA_UTILLIBNAME);
  lua_getfield(L, -1, LUA_UTILCHLIDRENNAME);
  lua_pushinteger(L, pid);
  lua_gettable(L, -2);
  if(lua_isnil(L, -1)) {
    lua_pop(L, 3);
    return -1;
  }
  lua_getfield(L, -1, "errfd");
  int fd = luaL_checkint(L, -1);
  lua_pop(L, 1);
  lua_remove(L, -2);
  lua_remove(L, -3);
  return fd;
}

static void prepare_fds(lua_State *L, int *child_stdio, int pipefd)
{
  int fd;
  for (fd=getdtablesize();fd>=0;--fd) // close all file descriptors
    if(fd != pipefd && fd != child_stdio[0] && fd != child_stdio[1] && fd != child_stdio[2]) close(fd);
  fcntl(pipefd, F_SETFD, FD_CLOEXEC);

  int i, ret;
  for(i = 0; i<3; ++i) {
    if(child_stdio[i] >= 0) {
      fd = dup2(child_stdio[i], i);
      if(fd == -1) {
        ret = write(pipefd, (void*)(&errno), sizeof(errno));
        lua_close(L);
        exit(ret);
      }
      close(child_stdio[i]);
    }
  }
}

static int l_util_exec(lua_State *L)
{
  const char* script = luaL_checkstring(L, 1);
  int child_stdio[3];
  child_stdio[0] = luaL_optint(L, 4, -1);
  child_stdio[1] = luaL_optint(L, 5, -1);
  child_stdio[2] = luaL_optint(L, 6, -1);

  int pipefd[2];
  if(pipe(pipefd) == -1) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno)); // FIXXXXXME: strerror is not threadsafe!!!
    return 2;
  }

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

  if(!pid) {
    prepare_fds(L, child_stdio, pipefd[1]);

    char** argv = table_to_argv(L, script, 2);
    char** evp = table_to_evp(L, 3);
    if(!argv) {
      int err = ENOMEM;
      int ret = write(pipefd[1], (void*)(&err), sizeof(err));
      free_ptrptr(evp);
      lua_close(L);
      exit(ret);
    }

    execve(script, argv, evp);
    int ret = write(pipefd[1], (void*)(&errno), sizeof(errno));
    free_ptrptr(argv);
    free_ptrptr(evp);
    lua_close(L);
    exit(ret);
  }
  close(pipefd[1]);
  child_add(L, pid, pipefd[0]);
  return 1;
}

static int l_util_waitpid(lua_State *L)
{
  int status = 0;
  pid_t pid = waitpid(-1, &status, WNOHANG);
  if(!pid || (pid < 0 && (errno == ECHILD))) {
    lua_pushnil(L);
    return 1;
  }
  if(pid < 0) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno)); // FIXXXXXME: strerror is not threadsafe!!!
    return 2;
  }

  int errfd = child_find(L, pid);
  if(errfd != -1) {
    child_remove(L, pid);
    int err = 0;
    if(read(errfd, (void*)(&err), sizeof(err)) >= sizeof(err)) {
      lua_pushliteral(L, "error");
      lua_pushstring(L, strerror(err)); // FIXXXXXME: strerror is not threadsafe!!!
      close(errfd);
      return 3;
    }
    close(errfd);
  } else {
    lua_pushnil(L);
    lua_pushliteral(L, "unknown child pid returned");
    return 2;
  }
  if(WIFEXITED(status)) {
    lua_pushliteral(L, "exit");
    lua_pushinteger(L, WEXITSTATUS(status));
  }
  else if(WIFSIGNALED(status)) {
    lua_pushliteral(L, "signal");
    lua_pushinteger(L, WTERMSIG(status));
  }
  else {
    lua_pushliteral(L, "unknown");
    lua_pushnil(L);
  }
  return 3;
}

static int l_util_pipe(lua_State *L)
{
  int pipefd[2];
  if(pipe(pipefd) == -1) {
    lua_pushnil(L);
    lua_pushstring(L, strerror(errno)); // FIXXXXXME: strerror is not threadsafe!!!
    return 2;
  }
  lua_pushinteger(L, pipefd[0]);
  lua_pushinteger(L, pipefd[1]);
  return 2;
}

static int l_util_kill(lua_State *L)
{
  int pid = luaL_checkint(L, 1);
  int sig = SIGTERM;

  if(lua_isnumber(L, 2)) {
    sig = luaL_checkint(L, 2);
  } else {
    const char* signame = luaL_optstring(L, 2, "TERM");
    if(!strcasecmp(signame, "HUP")) sig = SIGHUP;
    else if(!strcasecmp(signame, "INT")) sig = SIGINT;
    else if(!strcasecmp(signame, "QUIT")) sig = SIGQUIT;
    else if(!strcasecmp(signame, "ILL")) sig = SIGILL;
    else if(!strcasecmp(signame, "TRAP")) sig = SIGTRAP;
    else if(!strcasecmp(signame, "ABRT")) sig = SIGABRT;
    else if(!strcasecmp(signame, "IOT")) sig = SIGIOT;
    else if(!strcasecmp(signame, "BUS")) sig = SIGBUS;
    else if(!strcasecmp(signame, "FPE")) sig = SIGFPE;
    else if(!strcasecmp(signame, "KILL")) sig = SIGKILL;
    else if(!strcasecmp(signame, "USR1")) sig = SIGUSR1;
    else if(!strcasecmp(signame, "SEGV")) sig = SIGSEGV;
    else if(!strcasecmp(signame, "USR2")) sig = SIGUSR2;
    else if(!strcasecmp(signame, "PIPE")) sig = SIGPIPE;
    else if(!strcasecmp(signame, "ALRM")) sig = SIGALRM;
    else if(!strcasecmp(signame, "TERM")) sig = SIGTERM;
    else if(!strcasecmp(signame, "STKFLT")) sig = SIGSTKFLT;
    else if(!strcasecmp(signame, "CLD")) sig = SIGCLD;
    else if(!strcasecmp(signame, "CHLD")) sig = SIGCHLD;
    else if(!strcasecmp(signame, "CONT")) sig = SIGCONT;
    else if(!strcasecmp(signame, "STOP")) sig = SIGSTOP;
    else if(!strcasecmp(signame, "TSTP")) sig = SIGTSTP;
    else if(!strcasecmp(signame, "TTIN")) sig = SIGTTIN;
    else if(!strcasecmp(signame, "TTOU")) sig = SIGTTOU;
    else if(!strcasecmp(signame, "URG")) sig = SIGURG;
    else if(!strcasecmp(signame, "XCPU")) sig = SIGXCPU;
    else if(!strcasecmp(signame, "XFSZ")) sig = SIGXFSZ;
    else if(!strcasecmp(signame, "VTALRM")) sig = SIGVTALRM;
    else if(!strcasecmp(signame, "PROF")) sig = SIGPROF;
    else if(!strcasecmp(signame, "WINCH")) sig = SIGWINCH;
    else if(!strcasecmp(signame, "POLL")) sig = SIGPOLL;
    else if(!strcasecmp(signame, "IO")) sig = SIGIO;
    else if(!strcasecmp(signame, "PWR")) sig = SIGPWR;
    else if(!strcasecmp(signame, "SYS")) sig = SIGSYS;
    else if(!strcasecmp(signame, "UNUSED")) sig = SIGUNUSED;
    else {
      lua_pushnil(L);
      lua_pushliteral(L, "unknown signal");
      return 2;
    }
  }

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

static const struct luaL_Reg util_funcs [] = {
  { "select", l_util_select },
  { "exec", l_util_exec },
  { "waitpid", l_util_waitpid },
  { "pipe", l_util_pipe },
  { "kill", l_util_kill },
  { NULL, NULL }
};

LUALIB_API int luaopen_util(lua_State *L)
{
#if LUA_VERSION_NUM > 501
  lua_newtable(L);
  luaL_setfuncs(L, util_funcs, 0);
  lua_pushvalue(L, -1);
  lua_setglobal(L, LUA_UTILLIBNAME);
#else
  luaL_register(L, LUA_UTILLIBNAME, util_funcs);
#endif
  lua_newtable(L);
  lua_setfield(L, -2, LUA_UTILCHLIDRENNAME);
  return 1;
}