/* $OpenBSD: spawn.c,v 1.35 2025/12/08 08:04:35 nicm Exp $ */

/*
 * 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 <paths.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <util.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;
        }

        /*
         * 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;
        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:
        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);
}