/*
 *  rhdropbox
 *
 *  Copyright (C) 2009 Christian Pointner <equinox@helsinki.at>
 *
 *  This file is part of rhdropbox.
 *
 *  rhdropbox 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.
 *
 *  rhdropbox 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 rhdropbox. If not, see <http://www.gnu.org/licenses/>.
 */

#include "datatypes.h"

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

#include "sysexec.h"
#include "log.h"

void child_list_init(child_list_t* list)
{
  if(!list)
    return;
  
  list->first_ = NULL;
}

void child_list_clear(child_list_t* list)
{
  if(!list)
    return;

  while(list->first_) {
    child_list_element_t* tmp;
    tmp = list->first_;
    list->first_ = tmp->next_;
    if(tmp->script_)
      free(tmp->script_);
    free(tmp);
  }
}

int child_list_add(child_list_t* list, pid_t pid, const char* script, int err_fd)
{
  if(!list)
    return -1;

  if(!list->first_) {
    list->first_ = malloc(sizeof(child_list_element_t));
    if(!list->first_)
      return -2;

    list->first_->next_ = 0;
    list->first_->pid_ = pid;
    list->first_->err_fd_ = err_fd;
    list->first_->script_ = strdup(script);
    if(!list->first_->script_) {
      free(list->first_);
      list->first_ = NULL;
      return -2;
    }
  }
  else {
    child_list_element_t* tmp = list->first_;
    while(tmp->next_)
      tmp = tmp->next_;

    tmp->next_  = malloc(sizeof(child_list_element_t));
    if(!tmp->next_)
      return -2;

    tmp->next_->next_ = 0;
    tmp->next_->pid_ = pid;
    tmp->next_->err_fd_ = err_fd;
    tmp->next_->script_ = strdup(script);
    if(!tmp->next_->script_) {
      free(tmp->next_);
      tmp->next_ = NULL;
      return -2;
    }
  }
  return 0;
}

void child_list_rm(child_list_t* list, pid_t pid)
{
  if(!list)
    return;
  
  child_list_element_t* tmp = NULL;
  if(list->first_->pid_ == pid) {
    tmp = list->first_;
    list->first_ = list->first_->next_;
    
    if(tmp->script_)
      free(tmp->script_);
    free(tmp);
    return;
  }

  child_list_element_t* prev = list->first_;
  tmp = list->first_->next_;
  while(tmp) {
    if(tmp->pid_ == pid) {
      prev->next_ = tmp->next_;

      if(tmp->script_)
        free(tmp->script_);
      free(tmp);
      return;      
    }
    prev = tmp;
    tmp = tmp->next_;
  }
}

child_list_element_t* child_list_find(child_list_t* list, pid_t pid)
{
  if(!list)
    return NULL;
  
  child_list_element_t* tmp = list->first_;
  while(tmp) {
    if(tmp->pid_ == pid)
      return tmp;
    tmp = tmp->next_;
  }
  
  return NULL;
}

int rh_exec(const char* script, char* const argv[], char* const evp[], child_list_t* child_lst)
{
  if(!script)
    return -1;

  int pipefd[2];
  if(pipe(pipefd) == -1) {
    log_printf(ERROR, "executing script '%s' pipe() error: %s", script, strerror(errno));
    return -1;
  }

  pid_t pid;
  pid = fork();
  if(pid == -1) {
    log_printf(ERROR, "executing script '%s' fork() error: %s", script, strerror(errno));
    return -1;
  }

  if(!pid) {
    int fd;
    for (fd=getdtablesize();fd>=0;--fd) // close all file descriptors
      if(fd != pipefd[1]) close(fd);

    fd = open("/dev/null",O_RDWR);        // stdin
    if(fd == -1)
      log_printf(WARNING, "can't open stdin");
    else {
      if(dup(fd) == -1)   // stdout
        log_printf(WARNING, "can't open stdout");
      if(dup(fd) == -1)   // stderr
        log_printf(WARNING, "can't open stderr");
    }
    execve(script, argv, evp);
        // if execve returns, an error occurred, but logging doesn't work 
        // because we closed all file descriptors, so just write errno to
        // pipe and call exit
    write(pipefd[1], (void*)(&errno), sizeof(errno));
    exit(-1);
  }
  close(pipefd[1]);

  log_printf(INFO, "called script '%s' with pid %d", script, pid);
  return child_list_add(child_lst, pid, script, pipefd[0]);
}

int rh_waitpid(child_list_t* child_lst)
{
  int status = 0;
  pid_t pid = waitpid(-1, &status, WNOHANG);
  if(!pid || (pid < 0 && errno == ECHILD))
    return 0;
  if(pid < 0) {
    log_printf(ERROR, "waitpid returned with error: %s", strerror(errno));
    return pid;
  }

  child_list_element_t* child = child_list_find(child_lst, pid);
  if(!child) {
    log_printf(ERROR, "waitpid returned unknown child pid (%d)", pid);
    return 0;
  }

  fd_set rfds;
  FD_ZERO(&rfds);
  FD_SET(child->err_fd_, &rfds);
  struct timeval tv = { 0 , 0 };
  if(select(child->err_fd_+1, &rfds, NULL, NULL, &tv) == 1) {
    int err = 0;
    if(read(child->err_fd_, (void*)(&err), sizeof(err)) >= sizeof(err)) {
      log_printf(INFO, "script '%s' exec() error: %s", child->script_, strerror(err));
      close(child->script_);
      return -1;
    }
  }
  if(WIFEXITED(status))
    log_printf(INFO, "script '%s' (pid %d) returned %d", child->script_, child->pid_, WEXITSTATUS(status));
  else if(WIFSIGNALED(status))
    log_printf(INFO, "script '%s' (pid %d) terminated after signal %d", child->script_, child->pid_, WTERMSIG(status));
  else
    log_printf(INFO, "executing script '%s' (pid %d): unkown error", child->script_, child->pid_);

  close(child->err_fd_);
  return status;
}