/// \file procs.cpp
/// Contains generic functions for managing processes.

#include "defines.h"
#include "procs.h"
#include <signal.h>
#include <string.h>
#include <sys/types.h>

#if defined(__FreeBSD__) || defined(__APPLE__) || defined(__MACH__)
#include <sys/wait.h>
#else
#include <wait.h>
#endif
#include "timing.h"
#include <errno.h>
#include <fcntl.h>
#include <iostream>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>

std::set<pid_t> Util::Procs::plist;
std::set<int> Util::Procs::socketList;
bool Util::Procs::handler_set = false;
bool Util::Procs::thread_handler = false;
tthread::mutex Util::Procs::plistMutex;
tthread::thread *Util::Procs::reaper_thread = 0;

/// Local-only function. Attempts to reap child and returns current running status.
bool Util::Procs::childRunning(pid_t p){
  int status;
  pid_t ret = waitpid(p, &status, WNOHANG);
  if (ret == p){
    tthread::lock_guard<tthread::mutex> guard(plistMutex);
    int exitcode = -1;
    if (WIFEXITED(status)){
      exitcode = WEXITSTATUS(status);
    }else if (WIFSIGNALED(status)){
      exitcode = -WTERMSIG(status);
    }
    if (plist.count(ret)){
      HIGH_MSG("Process %d fully terminated with code %d", ret, exitcode);
      plist.erase(ret);
    }else{
      HIGH_MSG("Child process %d exited with code %d", ret, exitcode);
    }
    return false;
  }
  if (ret < 0 && errno == EINTR){return childRunning(p);}
  return !kill(p, 0);
}

/// sends sig 0 to process (pid). returns true if process is running
bool Util::Procs::isRunning(pid_t pid){
  return !kill(pid, 0);
}

/// Called at exit of any program that used a Start* function.
/// Waits up to 1 second, then sends SIGINT signal to all managed processes.
/// After that waits up to 5 seconds for children to exit, then sends SIGKILL to
/// all remaining children. Waits one more second for cleanup to finish, then exits.
void Util::Procs::exit_handler(){
  if (!handler_set){return;}
  int waiting = 0;
  std::set<pid_t> listcopy;
  {
    tthread::lock_guard<tthread::mutex> guard(plistMutex);
    listcopy = plist;
    thread_handler = false;
  }
  if (reaper_thread){
    reaper_thread->join();
    delete reaper_thread;
    reaper_thread = 0;
  }
  std::set<pid_t>::iterator it;
  if (listcopy.empty()){return;}

  // wait up to 0.5 second for applications to shut down
  while (!listcopy.empty() && waiting <= 25){
    for (it = listcopy.begin(); it != listcopy.end(); it++){
      if (!childRunning(*it)){
        listcopy.erase(it);
        break;
      }
      if (!listcopy.empty()){
        Util::wait(20);
        ++waiting;
      }
    }
  }
  if (listcopy.empty()){return;}

  INFO_MSG("Sending SIGINT and waiting up to 10 seconds for %d children to terminate.",
           (int)listcopy.size());
  waiting = 0;
  // wait up to 10 seconds for applications to shut down
  while (!listcopy.empty() && waiting <= 500){
    bool doWait = true;
    for (it = listcopy.begin(); it != listcopy.end(); it++){
      if (!childRunning(*it)){
        listcopy.erase(it);
        doWait = false;
        break;
      }
    }
    if (doWait && !listcopy.empty()){
      if ((waiting % 50) == 0){
        for (it = listcopy.begin(); it != listcopy.end(); it++){
          INFO_MSG("SIGINT %d", *it);
          kill(*it, SIGINT);
        }
      }
      Util::wait(20);
      ++waiting;
    }
  }
  if (listcopy.empty()){return;}

  ERROR_MSG("Sending SIGKILL to remaining %d children", (int)listcopy.size());
  // send sigkill to all remaining
  if (!listcopy.empty()){
    for (it = listcopy.begin(); it != listcopy.end(); it++){
      INFO_MSG("SIGKILL %d", *it);
      kill(*it, SIGKILL);
    }
  }

  INFO_MSG("Waiting up to a second for %d children to terminate.", (int)listcopy.size());
  waiting = 0;
  // wait up to 1 second for applications to shut down
  while (!listcopy.empty() && waiting <= 50){
    for (it = listcopy.begin(); it != listcopy.end(); it++){
      if (!childRunning(*it)){
        listcopy.erase(it);
        break;
      }
      if (!listcopy.empty()){
        Util::wait(20);
        ++waiting;
      }
    }
  }
  if (listcopy.empty()){return;}
  FAIL_MSG("Giving up with %d children left.", (int)listcopy.size());
}

// Joins the reaper thread, if any, before a fork
void Util::Procs::fork_prepare(){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  if (handler_set){
    thread_handler = false;
    if (reaper_thread){
      reaper_thread->join();
      delete reaper_thread;
      reaper_thread = 0;
    }
  }
}

/// Restarts reaper thread if it was joined
void Util::Procs::fork_complete(){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  if (handler_set){
    thread_handler = true;
    reaper_thread = new tthread::thread(grim_reaper, 0);
  }
}

/// Sets up exit and childsig handlers.
/// Spawns grim_reaper. exit handler despawns grim_reaper
/// Called by every Start* function.
void Util::Procs::setHandler(){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  if (!handler_set){
    thread_handler = true;
    reaper_thread = new tthread::thread(grim_reaper, 0);
    struct sigaction new_action;
    new_action.sa_handler = childsig_handler;
    sigemptyset(&new_action.sa_mask);
    new_action.sa_flags = 0;
    sigaction(SIGCHLD, &new_action, NULL);
    atexit(exit_handler);
    handler_set = true;
  }
}

/// Thread that loops until thread_handler is false.
/// Reaps available children and then sleeps for a second.
/// Not done in signal handler so we can use a mutex to prevent race conditions.
void Util::Procs::grim_reaper(void *n){
  VERYHIGH_MSG("Grim reaper start");
  while (thread_handler){
    {
      tthread::lock_guard<tthread::mutex> guard(plistMutex);
      int status;
      pid_t ret = -1;
      while (ret != 0){
        ret = waitpid(-1, &status, WNOHANG);
        if (ret <= 0){// ignore, would block otherwise
          if (ret == 0 || errno != EINTR){break;}
          continue;
        }
        int exitcode;
        if (WIFEXITED(status)){
          exitcode = WEXITSTATUS(status);
        }else if (WIFSIGNALED(status)){
          exitcode = -WTERMSIG(status);
        }else{// not possible
          break;
        }
        if (plist.count(ret)){
          HIGH_MSG("Process %d fully terminated with code %d", ret, exitcode);
          plist.erase(ret);
        }else{
          HIGH_MSG("Child process %d exited with code %d", ret, exitcode);
        }
      }
    }
    Util::sleep(500);
  }
  VERYHIGH_MSG("Grim reaper stop");
}

/// Ignores everything. Separate thread handles waiting for children.
void Util::Procs::childsig_handler(int signum){
  return;
}

/// Runs the given command and returns the stdout output as a string.
std::string Util::Procs::getOutputOf(char *const *argv){
  std::string ret;
  int fin = 0, fout = -1, ferr = 0;
  pid_t myProc = StartPiped(argv, &fin, &fout, &ferr);
  while (childRunning(myProc)){Util::sleep(100);}
  FILE *outFile = fdopen(fout, "r");
  char *fileBuf = 0;
  size_t fileBufLen = 0;
  while (!(feof(outFile) || ferror(outFile)) && (getline(&fileBuf, &fileBufLen, outFile) != -1)){
    ret += fileBuf;
  }
  fclose(outFile);
  free(fileBuf);
  return ret;
}

/// This function prepares a deque for getOutputOf and automatically inserts a NULL at the end of the char* const*
char *const *Util::Procs::dequeToArgv(std::deque<std::string> &argDeq){
  char **ret = (char **)malloc((argDeq.size() + 1) * sizeof(char *));
  for (int i = 0; i < argDeq.size(); i++){ret[i] = (char *)argDeq[i].c_str();}
  ret[argDeq.size()] = NULL;
  return ret;
}

std::string Util::Procs::getOutputOf(std::deque<std::string> &argDeq){
  std::string ret;
  char *const *argv = dequeToArgv(argDeq); // Note: Do not edit deque before executing command
  ret = getOutputOf(argv);
  return ret;
}

pid_t Util::Procs::StartPiped(std::deque<std::string> &argDeq, int *fdin, int *fdout, int *fderr){
  pid_t ret;
  char *const *argv = dequeToArgv(argDeq); // Note: Do not edit deque before executing command
  ret = Util::Procs::StartPiped(argv, fdin, fdout, fderr);
  return ret;
}

/// Starts a new process with given fds if the name is not already active.
/// \return 0 if process was not started, process PID otherwise.
/// \arg argv Command for this process.
/// \arg fdin Standard input file descriptor. If null, /dev/null is assumed. Otherwise, if arg
/// contains -1, a new fd is automatically allocated and written into this arg. Then the arg will be
/// used as fd. \arg fdout Same as fdin, but for stdout. \arg fdout Same as fdin, but for stderr.
pid_t Util::Procs::StartPiped(const char *const *argv, int *fdin, int *fdout, int *fderr){
  pid_t pid;
  int pipein[2], pipeout[2], pipeerr[2];
  setHandler();
  if (fdin && *fdin == -1 && pipe(pipein) < 0){
    ERROR_MSG("stdin pipe creation failed for process %s, reason: %s", argv[0], strerror(errno));
    return 0;
  }
  if (fdout && *fdout == -1 && pipe(pipeout) < 0){
    ERROR_MSG("stdout pipe creation failed for process %s, reason: %s", argv[0], strerror(errno));
    if (*fdin == -1){
      close(pipein[0]);
      close(pipein[1]);
    }
    return 0;
  }
  if (fderr && *fderr == -1 && pipe(pipeerr) < 0){
    ERROR_MSG("stderr pipe creation failed for process %s, reason: %s", argv[0], strerror(errno));
    if (*fdin == -1){
      close(pipein[0]);
      close(pipein[1]);
    }
    if (*fdout == -1){
      close(pipeout[0]);
      close(pipeout[1]);
    }
    return 0;
  }
  int devnull = -1;
  if (!fdin || !fdout || !fderr){
    devnull = open("/dev/null", O_RDWR);
    if (devnull == -1){
      ERROR_MSG("Could not open /dev/null for process %s, reason: %s", argv[0], strerror(errno));
      if (*fdin == -1){
        close(pipein[0]);
        close(pipein[1]);
      }
      if (*fdout == -1){
        close(pipeout[0]);
        close(pipeout[1]);
      }
      if (*fderr == -1){
        close(pipeerr[0]);
        close(pipeerr[1]);
      }
      return 0;
    }
  }
  pid = fork();
  if (pid == 0){// child
    handler_set = false;
    // Close all sockets in the socketList
    for (std::set<int>::iterator it = Util::Procs::socketList.begin();
         it != Util::Procs::socketList.end(); ++it){
      close(*it);
    }
    if (!fdin){
      dup2(devnull, STDIN_FILENO);
    }else if (*fdin == -1){
      close(pipein[1]); // close unused write end
      dup2(pipein[0], STDIN_FILENO);
      close(pipein[0]);
    }else if (*fdin != STDIN_FILENO){
      dup2(*fdin, STDIN_FILENO);
    }
    if (!fdout){
      dup2(devnull, STDOUT_FILENO);
    }else if (*fdout == -1){
      close(pipeout[0]); // close unused read end
      dup2(pipeout[1], STDOUT_FILENO);
      close(pipeout[1]);
    }else if (*fdout != STDOUT_FILENO){
      dup2(*fdout, STDOUT_FILENO);
    }
    if (!fderr){
      dup2(devnull, STDERR_FILENO);
    }else if (*fderr == -1){
      close(pipeerr[0]); // close unused read end
      dup2(pipeerr[1], STDERR_FILENO);
      close(pipeerr[1]);
    }else if (*fderr != STDERR_FILENO){
      dup2(*fderr, STDERR_FILENO);
    }
    if (fdin && *fdin != -1 && *fdin != STDIN_FILENO){close(*fdin);}
    if (fdout && *fdout != -1 && *fdout != STDOUT_FILENO){close(*fdout);}
    if (fderr && *fderr != -1 && *fderr != STDERR_FILENO){close(*fderr);}
    if (devnull != -1){close(devnull);}
    // Because execvp requires a char* const* and we have a const char* const*
    execvp(argv[0], (char *const *)argv);
    /*LTS-START*/
    char *trggr = getenv("MIST_TRIGGER");
    if (trggr && strlen(trggr)){
      ERROR_MSG("%s trigger failed to execute %s: %s", trggr, argv[0], strerror(errno));
      JSON::Value j;
      j["trigger_fail"] = trggr;
      Socket::UDPConnection uSock;
      uSock.SetDestination(UDP_API_HOST, UDP_API_PORT);
      uSock.SendNow(j.toString());
      std::cout << getenv("MIST_TRIG_DEF");
      exit(42);
    }
    /*LTS-END*/
    ERROR_MSG("execvp failed for process %s, reason: %s", argv[0], strerror(errno));
    exit(42);
  }else if (pid == -1){
    ERROR_MSG("fork failed for process %s, reason: %s", argv[0], strerror(errno));
    if (fdin && *fdin == -1){
      close(pipein[0]);
      close(pipein[1]);
    }
    if (fdout && *fdout == -1){
      close(pipeout[0]);
      close(pipeout[1]);
    }
    if (fderr && *fderr == -1){
      close(pipeerr[0]);
      close(pipeerr[1]);
    }
    if (devnull != -1){close(devnull);}
    return 0;
  }else{// parent
    {
      tthread::lock_guard<tthread::mutex> guard(plistMutex);
      plist.insert(pid);
    }
    HIGH_MSG("Piped process %s started, PID %d", argv[0], pid);
    if (devnull != -1){close(devnull);}
    if (fdin && *fdin == -1){
      close(pipein[0]); // close unused end end
      *fdin = pipein[1];
    }
    if (fdout && *fdout == -1){
      close(pipeout[1]); // close unused write end
      *fdout = pipeout[0];
    }
    if (fderr && *fderr == -1){
      close(pipeerr[1]); // close unused write end
      *fderr = pipeerr[0];
    }
  }
  return pid;
}

/// Stops the process with this pid, if running.
/// \arg name The PID of the process to stop.
void Util::Procs::Stop(pid_t name){
  kill(name, SIGTERM);
}

/// Stops the process with this pid, if running.
/// \arg name The PID of the process to murder.
void Util::Procs::Murder(pid_t name){
  kill(name, SIGKILL);
}

/// (Attempts to) stop all running child processes.
void Util::Procs::StopAll(){
  std::set<pid_t> listcopy;
  {
    tthread::lock_guard<tthread::mutex> guard(plistMutex);
    listcopy = plist;
  }
  std::set<pid_t>::iterator it;
  for (it = listcopy.begin(); it != listcopy.end(); it++){Stop(*it);}
}

/// Returns the number of active child processes.
int Util::Procs::Count(){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  return plist.size();
}

/// Returns true if a process with this PID is currently active.
bool Util::Procs::isActive(pid_t name){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  return (kill(name, 0) == 0);
}

/// Forget about the given PID, keeping it running on shutdown.
void Util::Procs::forget(pid_t pid){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  plist.erase(pid);
}

/// Remember the given PID, killing it on shutdown.
void Util::Procs::remember(pid_t pid){
  tthread::lock_guard<tthread::mutex> guard(plistMutex);
  plist.insert(pid);
}