/* $OpenBSD$ */

/*

 * Copyright (c) 2019 Nicholas Marriott <nicholas.marriott@gmail.com>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER

 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING

 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include <sys/types.h>

#include <errno.h>

#include <signal.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include "tmux.h"

/*

 * Set up the environment and create a new window and pane or a new pane.

 *

 * We need to set up the following items:

 *

 * - history limit, comes from the session;

 *

 * - base index, comes from the session;

 *

 * - current working directory, may be specified - if it isn't it comes from

 *   either the client or the session;

 *

 * - PATH variable, comes from the client if any, otherwise from the session

 *   environment;

 *

 * - shell, comes from default-shell;

 *

 * - termios, comes from the session;

 *

 * - remaining environment, comes from the session.

 */

static void

spawn_log(const char *from, struct spawn_context *sc)

{

  struct session    *s = sc->s;

  struct winlink    *wl = sc->wl;

  struct window_pane  *wp0 = sc->wp0;

  const char    *name = cmdq_get_name(sc->item);

  char       tmp[128];

  log_debug("%s: %s, flags=%#x", from, name, sc->flags);

  if (wl != NULL && wp0 != NULL)

    xsnprintf(tmp, sizeof tmp, "wl=%d wp0=%%%u", wl->idx, wp0->id);

  else if (wl != NULL)

    xsnprintf(tmp, sizeof tmp, "wl=%d wp0=none", wl->idx);

  else if (wp0 != NULL)

    xsnprintf(tmp, sizeof tmp, "wl=none wp0=%%%u", wp0->id);

  else

    xsnprintf(tmp, sizeof tmp, "wl=none wp0=none");

  log_debug("%s: s=$%u %s idx=%d", from, s->id, tmp, sc->idx);

  log_debug("%s: name=%s", from, sc->name == NULL ? "none" : sc->name);

}

struct winlink *

spawn_window(struct spawn_context *sc, char **cause)

{

  struct cmdq_item  *item = sc->item;

  struct client   *c = cmdq_get_client(item);

  struct session    *s = sc->s;

  struct window   *w;

  struct window_pane  *wp;

  struct winlink    *wl;

  int      idx = sc->idx;

  u_int      sx, sy, xpixel, ypixel;

  spawn_log(__func__, sc);

  /*

   * If the window already exists, we are respawning, so destroy all the

   * panes except one.

   */

  if (sc->flags & SPAWN_RESPAWN) {

    w = sc->wl->window;

    if (~sc->flags & SPAWN_KILL) {

      TAILQ_FOREACH(wp, &w->panes, entry) {

        if (wp->fd != -1)

          break;

      }

      if (wp != NULL) {

        xasprintf(cause, "window %s:%d still active",

            s->name, sc->wl->idx);

        return (NULL);

      }

    }

    sc->wp0 = TAILQ_FIRST(&w->panes);

    TAILQ_REMOVE(&w->panes, sc->wp0, entry);

    layout_free(w);

    window_destroy_panes(w);

    TAILQ_INSERT_HEAD(&w->panes, sc->wp0, entry);

    window_pane_resize(sc->wp0, w->sx, w->sy);

    layout_init(w, sc->wp0);

    w->active = NULL;

    window_set_active_pane(w, sc->wp0, 0);

  }

  /*

   * Otherwise we have no window so we will need to create one. First

   * check if the given index already exists and destroy it if so.

   */

  if ((~sc->flags & SPAWN_RESPAWN) && idx != -1) {

    wl = winlink_find_by_index(&s->windows, idx);

    if (wl != NULL && (~sc->flags & SPAWN_KILL)) {

      xasprintf(cause, "index %d in use", idx);

      return (NULL);

    }

    if (wl != NULL) {

      /*

       * Can't use session_detach as it will destroy session

       * if this makes it empty.

       */

      wl->flags &= ~WINLINK_ALERTFLAGS;

      notify_session_window("window-unlinked", s, wl->window);

      winlink_stack_remove(&s->lastw, wl);

      winlink_remove(&s->windows, wl);

      if (s->curw == wl) {

        s->curw = NULL;

        sc->flags &= ~SPAWN_DETACHED;

      }

    }

  }

  /* Then create a window if needed. */

  if (~sc->flags & SPAWN_RESPAWN) {

    if (idx == -1)

      idx = -1 - options_get_number(s->options, "base-index");

    if ((sc->wl = winlink_add(&s->windows, idx)) == NULL) {

      xasprintf(cause, "couldn't add window %d", idx);

      return (NULL);

    }

    default_window_size(sc->tc, s, NULL, &sx, &sy, &xpixel, &ypixel,

        -1);

    if ((w = window_create(sx, sy, xpixel, ypixel)) == NULL) {

      winlink_remove(&s->windows, sc->wl);

      xasprintf(cause, "couldn't create window %d", idx);

      return (NULL);

    }

    if (s->curw == NULL)

      s->curw = sc->wl;

    sc->wl->session = s;

    w->latest = sc->tc;

    winlink_set_window(sc->wl, w);

  } else

    w = NULL;

  sc->flags |= SPAWN_NONOTIFY;

  /* Spawn the pane. */

  wp = spawn_pane(sc, cause);

  if (wp == NULL) {

    if (~sc->flags & SPAWN_RESPAWN)

      winlink_remove(&s->windows, sc->wl);

    return (NULL);

  }

  /* Set the name of the new window. */

  if (~sc->flags & SPAWN_RESPAWN) {

    free(w->name);

    if (sc->name != NULL) {

      w->name = format_single(item, sc->name, c, s, NULL,

          NULL);

      options_set_number(w->options, "automatic-rename", 0);

    } else

      w->name = default_window_name(w);

  }

  /* Switch to the new window if required. */

  if (~sc->flags & SPAWN_DETACHED)

    session_select(s, sc->wl->idx);

  /* Fire notification if new window. */

  if (~sc->flags & SPAWN_RESPAWN)

    notify_session_window("window-linked", s, w);

  session_group_synchronize_from(s);

  return (sc->wl);

}

struct window_pane *

spawn_pane(struct spawn_context *sc, char **cause)

{

  struct cmdq_item   *item = sc->item;

  struct cmd_find_state  *target = cmdq_get_target(item);

  struct client    *c = cmdq_get_client(item);

  struct session     *s = sc->s;

  struct window    *w = sc->wl->window;

  struct window_pane   *new_wp;

  struct environ     *child;

  struct environ_entry   *ee;

  char      **argv, *cp, **argvp, *argv0, *cwd, *new_cwd;

  char        path[PATH_MAX];

  const char     *cmd, *tmp, *home = find_home();

  const char     *actual_cwd = NULL;

  int       argc;

  u_int       idx;

  struct termios      now;

  u_int       hlimit;

  struct winsize      ws;

  sigset_t      set, oldset;

  key_code      key;

  spawn_log(__func__, sc);

  /*

   * Work out the current working directory. If respawning, use

   * the pane's stored one unless specified.

   */

  if (sc->cwd != NULL) {

    cwd = format_single(item, sc->cwd, c, target->s, NULL, NULL);

    if (*cwd != '/') {

      xasprintf(&new_cwd, "%s%s%s",

          server_client_get_cwd(c, target->s),

          *cwd != '\0' ? "/" : "", cwd);

      free(cwd);

      cwd = new_cwd;

    }

  } else if (~sc->flags & SPAWN_RESPAWN)

    cwd = xstrdup(server_client_get_cwd(c, target->s));

  else

    cwd = NULL;

  /*

   * If we are respawning then get rid of the old process. Otherwise

   * either create a new cell or assign to the one we are given.

   */

  hlimit = options_get_number(s->options, "history-limit");

  if (sc->flags & SPAWN_RESPAWN) {

    if (sc->wp0->fd != -1 && (~sc->flags & SPAWN_KILL)) {

      window_pane_index(sc->wp0, &idx);

      xasprintf(cause, "pane %s:%d.%u still active",

          s->name, sc->wl->idx, idx);

      free(cwd);

      return (NULL);

    }

    if (sc->wp0->fd != -1) {

      bufferevent_free(sc->wp0->event);

      close(sc->wp0->fd);

    }

    window_pane_reset_mode_all(sc->wp0);

    screen_reinit(&sc->wp0->base);

    input_free(sc->wp0->ictx);

    sc->wp0->ictx = NULL;

    new_wp = sc->wp0;

    new_wp->flags &= ~(PANE_STATUSREADY|PANE_STATUSDRAWN);

  } else if (sc->lc == NULL) {

    new_wp = window_add_pane(w, NULL, hlimit, sc->flags);

    layout_init(w, new_wp);

  } else {

    new_wp = window_add_pane(w, sc->wp0, hlimit, sc->flags);

    if (sc->flags & SPAWN_ZOOM)

      layout_assign_pane(sc->lc, new_wp, 1);

    else

      layout_assign_pane(sc->lc, new_wp, 0);

  }

  /*

   * Now we have a pane with nothing running in it ready for the new

   * process. Work out the command and arguments and store the working

   * directory.

   */

  if (sc->argc == 0 && (~sc->flags & SPAWN_RESPAWN)) {

    cmd = options_get_string(s->options, "default-command");

    if (cmd != NULL && *cmd != '\0') {

      argc = 1;

      argv = (char **)&cmd;

    } else {

      argc = 0;

      argv = NULL;

    }

  } else {

    argc = sc->argc;

    argv = sc->argv;

  }

  if (cwd != NULL) {

    free(new_wp->cwd);

    new_wp->cwd = cwd;

  }

  /*

   * Replace the stored arguments if there are new ones. If not, the

   * existing ones will be used (they will only exist for respawn).

   */

  if (argc > 0) {

    cmd_free_argv(new_wp->argc, new_wp->argv);

    new_wp->argc = argc;

    new_wp->argv = cmd_copy_argv(argc, argv);

  }

  /* Create an environment for this pane. */

  child = environ_for_session(s, 0);

  if (sc->environ != NULL)

    environ_copy(sc->environ, child);

  environ_set(child, "TMUX_PANE", 0, "%%%u", new_wp->id);

  /*

   * Then the PATH environment variable. The session one is replaced from

   * the client if there is one because otherwise running "tmux new

   * myprogram" wouldn't work if myprogram isn't in the session's path.

   */

  if (c != NULL && c->session == NULL) { /* only unattached clients */

    ee = environ_find(c->environ, "PATH");

    if (ee != NULL)

      environ_set(child, "PATH", 0, "%s", ee->value);

  }

  if (environ_find(child, "PATH") == NULL)

    environ_set(child, "PATH", 0, "%s", _PATH_DEFPATH);

  /* Then the shell. If respawning, use the old one. */

  if (~sc->flags & SPAWN_RESPAWN) {

    tmp = options_get_string(s->options, "default-shell");

    if (!checkshell(tmp))

      tmp = _PATH_BSHELL;

    free(new_wp->shell);

    new_wp->shell = xstrdup(tmp);

  }

  environ_set(child, "SHELL", 0, "%s", new_wp->shell);

  /* Log the arguments we are going to use. */

  log_debug("%s: shell=%s", __func__, new_wp->shell);

  if (new_wp->argc != 0) {

    cp = cmd_stringify_argv(new_wp->argc, new_wp->argv);

    log_debug("%s: cmd=%s", __func__, cp);

    free(cp);

  }

  log_debug("%s: cwd=%s", __func__, new_wp->cwd);

  cmd_log_argv(new_wp->argc, new_wp->argv, "%s", __func__);

  environ_log(child, "%s: environment ", __func__);

  /* Initialize the window size. */

  memset(&ws, 0, sizeof ws);

  ws.ws_col = screen_size_x(&new_wp->base);

  ws.ws_row = screen_size_y(&new_wp->base);

  ws.ws_xpixel = w->xpixel * ws.ws_col;

  ws.ws_ypixel = w->ypixel * ws.ws_row;

  /* Block signals until fork has completed. */

  sigfillset(&set);

  sigprocmask(SIG_BLOCK, &set, &oldset);

  /* If the command is empty, don't fork a child process. */

  if (sc->flags & SPAWN_EMPTY) {

    new_wp->flags |= PANE_EMPTY;

    new_wp->base.mode &= ~MODE_CURSOR;

    new_wp->base.mode |= MODE_CRLF;

    goto complete;

  }

    /* Store current working directory and change to new one. */

  if (getcwd(path, sizeof path) != NULL) {

    if (chdir(new_wp->cwd) == 0)

      actual_cwd = new_wp->cwd;

    else if (home != NULL && chdir(home) == 0)

      actual_cwd = home;

    else if (chdir("/") == 0)

      actual_cwd = "/";

  }

  /* Fork the new process. */

  new_wp->pid = fdforkpty(ptm_fd, &new_wp->fd, new_wp->tty, NULL, &ws);

  if (new_wp->pid == -1) {

    xasprintf(cause, "fork failed: %s", strerror(errno));

    new_wp->fd = -1;

    if (~sc->flags & SPAWN_RESPAWN) {

      server_client_remove_pane(new_wp);

      layout_close_pane(new_wp);

      window_remove_pane(w, new_wp);

    }

    sigprocmask(SIG_SETMASK, &oldset, NULL);

    environ_free(child);

    return (NULL);

  }

  /*

   * In the parent process, everything is done now. Change the working

   * directory back.

   */

  if (new_wp->pid != 0) {

    if (actual_cwd != NULL &&

        chdir(path) != 0 &&

        (home == NULL || chdir(home) != 0))

      chdir("/");

    goto complete;

  }

#if defined(HAVE_SYSTEMD) && defined(ENABLE_CGROUPS)

  /*

   * Move the child process into a new cgroup for systemd-oomd isolation.

   */

  if (systemd_move_to_new_cgroup(cause) < 0) {

    log_debug("%s: moving pane to new cgroup failed: %s",

        __func__, *cause);

    free (*cause);

  }

#endif

  /*

   * Child process. Set PWD to the working directory.

   */

  if (actual_cwd != NULL)

    environ_set(child, "PWD", 0, "%s", actual_cwd);

  /*

   * Update terminal escape characters from the session if available and

   * force VERASE to tmux's backspace.

   */

  if (tcgetattr(STDIN_FILENO, &now) != 0)

    _exit(1);

  if (s->tio != NULL)

    memcpy(now.c_cc, s->tio->c_cc, sizeof now.c_cc);

  key = options_get_number(global_options, "backspace");

  if (key >= 0x7f)

    now.c_cc[VERASE] = '\177';

  else

    now.c_cc[VERASE] = key;

#ifdef IUTF8

  now.c_iflag |= IUTF8;

#endif

  if (tcsetattr(STDIN_FILENO, TCSANOW, &now) != 0)

    _exit(1);

  /* Clean up file descriptors and signals and update the environment. */

  proc_clear_signals(server_proc, 1);

  closefrom(STDERR_FILENO + 1);

  sigprocmask(SIG_SETMASK, &oldset, NULL);

  log_close();

  environ_push(child);

  /*

   * If given multiple arguments, use execvp(). Copy the arguments to

   * ensure they end in a NULL.

   */

  if (new_wp->argc != 0 && new_wp->argc != 1) {

    argvp = cmd_copy_argv(new_wp->argc, new_wp->argv);

    execvp(argvp[0], argvp);

    _exit(1);

  }

  /*

   * If one argument, pass it to $SHELL -c. Otherwise create a login

   * shell.

   */

  cp = strrchr(new_wp->shell, '/');

  if (new_wp->argc == 1) {

    tmp = new_wp->argv[0];

    if (cp != NULL && cp[1] != '\0')

      xasprintf(&argv0, "%s", cp + 1);

    else

      xasprintf(&argv0, "%s", new_wp->shell);

    execl(new_wp->shell, argv0, "-c", tmp, (char *)NULL);

    _exit(1);

  }

  if (cp != NULL && cp[1] != '\0')

    xasprintf(&argv0, "-%s", cp + 1);

  else

    xasprintf(&argv0, "-%s", new_wp->shell);

  execl(new_wp->shell, argv0, (char *)NULL);

  _exit(1);

complete:

#ifdef HAVE_UTEMPTER

  if (~new_wp->flags & PANE_EMPTY) {

    xasprintf(&cp, "tmux(%lu).%%%u", (long)getpid(), new_wp->id);

    utempter_add_record(new_wp->fd, cp);

    kill(getpid(), SIGCHLD);

    free(cp);

  }

#endif

  new_wp->flags &= ~PANE_EXITED;

  sigprocmask(SIG_SETMASK, &oldset, NULL);

  window_pane_set_event(new_wp);

  environ_free(child);

  if (sc->flags & SPAWN_RESPAWN)

    return (new_wp);

  if ((~sc->flags & SPAWN_DETACHED) || w->active == NULL) {

    if (sc->flags & SPAWN_NONOTIFY)

      window_set_active_pane(w, new_wp, 0);

    else

      window_set_active_pane(w, new_wp, 1);

  }

  if (~sc->flags & SPAWN_NONOTIFY)

    notify_window("window-layout-changed", w);

  return (new_wp);

}