/*
 *  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"

char** dup_ptrptr(char* const ptrptr[])
{
  if(!ptrptr)
    return NULL;

  int n = 0;
  while(ptrptr[n])
    n++;

  char** my_ptrptr;
  my_ptrptr = malloc((n+1)*sizeof(char*));
  if(!my_ptrptr)
    return NULL;

  int i;
  for(i = 0; i < n; ++i) {
    my_ptrptr[i] = strdup(ptrptr[i]); 
    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);
}

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);
  }
}

child_list_element_t* child_list_new(const char* script, char* const argv[], char* const evp[])
{
  child_list_element_t* new_child;

  new_child = malloc(sizeof(child_list_element_t));
  if(!new_child)
    return NULL;
  
  new_child->next_ = 0;
  new_child->pid_ = -1;
  new_child->err_fd_ = -1;
  new_child->running_ = 0;
  new_child->script_ = strdup(script);
  if(!new_child->script_) {
    free(new_child);
    return NULL;
  }
  
  new_child->argv_ = dup_ptrptr(argv);
  if(!new_child->argv_) {
    free(new_child->script_);
    free(new_child);
    return NULL;
    
  }
  
  new_child->evp_ = dup_ptrptr(evp);
  if(!new_child->evp_) {
    free_ptrptr(new_child->argv_);
    free(new_child->script_);
    free(new_child);
    return NULL;
  }
  return new_child;
}

child_list_element_t* child_list_add(child_list_t* list, const char* script, char* const argv[], char* const evp[])
{
  if(!list)
    return NULL;

  if(!list->first_) {
    list->first_ = child_list_new(script, argv, evp);
    return list->first_;
  }
  else {
    child_list_element_t* tmp = list->first_;
    while(tmp->next_)
      tmp = tmp->next_;

    tmp->next_  = child_list_new(script, argv, evp);
    return tmp->next_;
  }
}

void child_list_rm(child_list_t* list, child_list_element_t* child)
{
  if(!list || !child)
    return;

  if(child == list->first_) {
    list->first_ = list->first_->next_;
    free_ptrptr(child->argv_);
    free_ptrptr(child->evp_);
    if(child->script_)
      free(child->script_);
    free(child);
    return;
  }
  else {
    child_list_element_t* tmp = list->first_;
    while(tmp) {
      if(tmp->next_ == child) {
        tmp->next_ = tmp->next_->next_;
        free_ptrptr(child->argv_);
        free_ptrptr(child->evp_);
        if(child->script_)
          free(child->script_);
        free(child);
        return;
      }
      tmp = tmp->next_;
    }
  }
}

void child_list_rm_pid(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_;
    
    free_ptrptr(tmp->argv_);
    free_ptrptr(tmp->evp_);
    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_;

      free_ptrptr(tmp->argv_);
      free_ptrptr(tmp->evp_);
      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 child_list_num_running(child_list_t* list)
{
  int num = 0;

  if(!list)
    return 0;
  
  child_list_element_t* tmp = list->first_;
  for(;tmp;tmp=tmp->next_)
    if(tmp->running_) num++;
  
  return num;
}

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

  child_list_element_t* child = child_list_add(child_lst, script, argv, evp);
  if(!child)
    return -2;

  if(child_list_num_running(child_lst) >= opt->max_children_) {
    log_printf(INFO, "deferring script execution '%s'", script);
    return 0;
  }

  int ret = rh_exec_child(child);
  if(ret)
    child_list_rm(child_lst, child);

  return ret;
}

int rh_exec_child(child_list_element_t* child)
{
  if(!child || child->pid_ != -1)
    return -1;

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

  pid_t pid;
  pid = fork();
  if(pid == -1) {
    log_printf(ERROR, "executing script '%s' failed: fork() error: %s", child->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(child->script_, child->argv_, child->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]);

  child->pid_ = pid;
  child->err_fd_ = pipefd[0];
  child->running_ = 1;

  log_printf(INFO, "called script '%s' with pid %d", child->script_, child->pid_);

  return 0;
}

int rh_waitpid(child_list_t* child_lst, options_t* opt)
{
  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->err_fd_);
      child_list_rm_pid(child_lst, pid);
      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_);

  child_list_rm_pid(child_lst, pid);

  if(child_list_num_running(child_lst) < opt->max_children_)
    rh_exec_child(child_list_find(child_lst, -1));
  
  return status;
}