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Give each client a name. This defaults to the tty name as before but
falls back to an alternative if the tty name is not available. This is
clearer than overloading the client ttyname member and allows us to
remove the path stored in the tty struct, it should always be the same
as the client.

/* $OpenBSD: format.c,v 1.124 2017/04/05 10:49:46 nicm Exp $ */

/*
 * Copyright (c) 2011 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 <sys/wait.h>

#include <ctype.h>
#include <errno.h>
#include <libgen.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "tmux.h"

/*
 * Build a list of key-value pairs and use them to expand #{key} entries in a
 * string.
 */

struct format_entry;
typedef void (*format_cb)(struct format_tree *, struct format_entry *);

static void	 format_job_callback(struct job *);
static char	*format_job_get(struct format_tree *, const char *);
static void	 format_job_timer(int, short, void *);

static void	 format_cb_host(struct format_tree *, struct format_entry *);
static void	 format_cb_host_short(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_pid(struct format_tree *, struct format_entry *);
static void	 format_cb_session_alerts(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_window_layout(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_window_visible_layout(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_start_command(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_current_command(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_history_bytes(struct format_tree *,
		     struct format_entry *);
static void	 format_cb_pane_tabs(struct format_tree *,
		     struct format_entry *);

static char	*format_find(struct format_tree *, const char *, int);
static void	 format_add_cb(struct format_tree *, const char *, format_cb);
static void	 format_add_tv(struct format_tree *, const char *,
		     struct timeval *);
static int	 format_replace(struct format_tree *, const char *, size_t,
		     char **, size_t *, size_t *);

static void	 format_defaults_session(struct format_tree *,
		     struct session *);
static void	 format_defaults_client(struct format_tree *, struct client *);
static void	 format_defaults_winlink(struct format_tree *, struct session *,
		     struct winlink *);

/* Entry in format job tree. */
struct format_job {
	u_int			 tag;
	const char		*cmd;
	const char		*expanded;

	time_t			 last;
	char			*out;

	struct job		*job;
	int			 status;

	RB_ENTRY(format_job)	 entry;
};

/* Format job tree. */
static struct event format_job_event;
static int format_job_cmp(struct format_job *, struct format_job *);
static RB_HEAD(format_job_tree, format_job) format_jobs = RB_INITIALIZER();
RB_GENERATE_STATIC(format_job_tree, format_job, entry, format_job_cmp);

/* Format job tree comparison function. */
static int
format_job_cmp(struct format_job *fj1, struct format_job *fj2)
{
	if (fj1->tag < fj2->tag)
		return (-1);
	if (fj1->tag > fj2->tag)
		return (1);
	return (strcmp(fj1->cmd, fj2->cmd));
}

/* Format modifiers. */
#define FORMAT_TIMESTRING 0x1
#define FORMAT_BASENAME 0x2
#define FORMAT_DIRNAME 0x4
#define FORMAT_SUBSTITUTE 0x8

/* Entry in format tree. */
struct format_entry {
	char			*key;
	char			*value;
	time_t			 t;
	format_cb		 cb;
	RB_ENTRY(format_entry)	 entry;
};

/* Format entry tree. */
struct format_tree {
	struct window		*w;
	struct session		*s;
	struct window_pane	*wp;

	u_int			 tag;
	int			 flags;

	RB_HEAD(format_entry_tree, format_entry) tree;
};
static int format_entry_cmp(struct format_entry *, struct format_entry *);
RB_GENERATE_STATIC(format_entry_tree, format_entry, entry, format_entry_cmp);

/* Format entry tree comparison function. */
static int
format_entry_cmp(struct format_entry *fe1, struct format_entry *fe2)
{
	return (strcmp(fe1->key, fe2->key));
}

/* Single-character uppercase aliases. */
static const char *format_upper[] = {
	NULL,		/* A */
	NULL,		/* B */
	NULL,		/* C */
	"pane_id",	/* D */
	NULL,		/* E */
	"window_flags",	/* F */
	NULL,		/* G */
	"host",		/* H */
	"window_index",	/* I */
	NULL,		/* J */
	NULL,		/* K */
	NULL,		/* L */
	NULL,		/* M */
	NULL,		/* N */
	NULL,		/* O */
	"pane_index",	/* P */
	NULL,		/* Q */
	NULL,		/* R */
	"session_name",	/* S */
	"pane_title",	/* T */
	NULL,		/* U */
	NULL,		/* V */
	"window_name",	/* W */
	NULL,		/* X */
	NULL,		/* Y */
	NULL 		/* Z */
};

/* Single-character lowercase aliases. */
static const char *format_lower[] = {
	NULL,		/* a */
	NULL,		/* b */
	NULL,		/* c */
	NULL,		/* d */
	NULL,		/* e */
	NULL,		/* f */
	NULL,		/* g */
	"host_short",	/* h */
	NULL,		/* i */
	NULL,		/* j */
	NULL,		/* k */
	NULL,		/* l */
	NULL,		/* m */
	NULL,		/* n */
	NULL,		/* o */
	NULL,		/* p */
	NULL,		/* q */
	NULL,		/* r */
	NULL,		/* s */
	NULL,		/* t */
	NULL,		/* u */
	NULL,		/* v */
	NULL,		/* w */
	NULL,		/* x */
	NULL,		/* y */
	NULL		/* z */
};

/* Format job callback. */
static void
format_job_callback(struct job *job)
{
	struct format_job	*fj = job->data;
	char			*line, *buf;
	size_t			 len;
	struct client		*c;

	fj->job = NULL;
	free(fj->out);

	buf = NULL;
	if ((line = evbuffer_readline(job->event->input)) == NULL) {
		len = EVBUFFER_LENGTH(job->event->input);
		buf = xmalloc(len + 1);
		if (len != 0)
			memcpy(buf, EVBUFFER_DATA(job->event->input), len);
		buf[len] = '\0';
	} else
		buf = line;
	fj->out = buf;

	if (fj->status) {
		TAILQ_FOREACH(c, &clients, entry)
		    server_status_client(c);
		fj->status = 0;
	}

	log_debug("%s: %s: %s", __func__, fj->cmd, fj->out);
}

/* Find a job. */
static char *
format_job_get(struct format_tree *ft, const char *cmd)
{
	struct format_job	 fj0, *fj;
	time_t			 t;
	char			*expanded;
	int			 force;

	fj0.tag = ft->tag;
	fj0.cmd = cmd;
	if ((fj = RB_FIND(format_job_tree, &format_jobs, &fj0)) == NULL) {
		fj = xcalloc(1, sizeof *fj);
		fj->tag = ft->tag;
		fj->cmd = xstrdup(cmd);
		fj->expanded = NULL;

		xasprintf(&fj->out, "<'%s' not ready>", fj->cmd);

		RB_INSERT(format_job_tree, &format_jobs, fj);
	}

	expanded = format_expand(ft, cmd);
	if (fj->expanded == NULL || strcmp(expanded, fj->expanded) != 0) {
		free((void *)fj->expanded);
		fj->expanded = xstrdup(expanded);
		force = 1;
	} else
		force = (ft->flags & FORMAT_FORCE);

	t = time(NULL);
	if (fj->job == NULL && (force || fj->last != t)) {
		fj->job = job_run(expanded, NULL, NULL, format_job_callback,
		    NULL, fj);
		if (fj->job == NULL) {
			free(fj->out);
			xasprintf(&fj->out, "<'%s' didn't start>", fj->cmd);
		}
		fj->last = t;
	}

	if (ft->flags & FORMAT_STATUS)
		fj->status = 1;

	free(expanded);
	return (format_expand(ft, fj->out));
}

/* Remove old jobs. */
static void
format_job_timer(__unused int fd, __unused short events, __unused void *arg)
{
	struct format_job	*fj, *fj1;
	time_t			 now;
	struct timeval		 tv = { .tv_sec = 60 };

	now = time(NULL);
	RB_FOREACH_SAFE(fj, format_job_tree, &format_jobs, fj1) {
		if (fj->last > now || now - fj->last < 3600)
			continue;
		RB_REMOVE(format_job_tree, &format_jobs, fj);

		log_debug("%s: %s", __func__, fj->cmd);

		if (fj->job != NULL)
			job_free(fj->job);

		free((void *)fj->expanded);
		free((void *)fj->cmd);
		free(fj->out);

		free(fj);
	}

	evtimer_del(&format_job_event);
	evtimer_add(&format_job_event, &tv);
}

/* Callback for host. */
static void
format_cb_host(__unused struct format_tree *ft, struct format_entry *fe)
{
	char host[HOST_NAME_MAX + 1];

	if (gethostname(host, sizeof host) != 0)
		fe->value = xstrdup("");
	else
		fe->value = xstrdup(host);
}

/* Callback for host_short. */
static void
format_cb_host_short(__unused struct format_tree *ft, struct format_entry *fe)
{
	char host[HOST_NAME_MAX + 1], *cp;

	if (gethostname(host, sizeof host) != 0)
		fe->value = xstrdup("");
	else {
		if ((cp = strchr(host, '.')) != NULL)
			*cp = '\0';
		fe->value = xstrdup(host);
	}
}

/* Callback for pid. */
static void
format_cb_pid(__unused struct format_tree *ft, struct format_entry *fe)
{
	xasprintf(&fe->value, "%ld", (long)getpid());
}

/* Callback for session_alerts. */
static void
format_cb_session_alerts(struct format_tree *ft, struct format_entry *fe)
{
	struct session	*s = ft->s;
	struct winlink	*wl;
	char		 alerts[256], tmp[16];

	if (s == NULL)
		return;

	*alerts = '\0';
	RB_FOREACH(wl, winlinks, &s->windows) {
		if ((wl->flags & WINLINK_ALERTFLAGS) == 0)
			continue;
		xsnprintf(tmp, sizeof tmp, "%u", wl->idx);

		if (*alerts != '\0')
			strlcat(alerts, ",", sizeof alerts);
		strlcat(alerts, tmp, sizeof alerts);
		if (wl->flags & WINLINK_ACTIVITY)
			strlcat(alerts, "#", sizeof alerts);
		if (wl->flags & WINLINK_BELL)
			strlcat(alerts, "!", sizeof alerts);
		if (wl->flags & WINLINK_SILENCE)
			strlcat(alerts, "~", sizeof alerts);
	}
	fe->value = xstrdup(alerts);
}

/* Callback for window_layout. */
static void
format_cb_window_layout(struct format_tree *ft, struct format_entry *fe)
{
	struct window	*w = ft->w;

	if (w == NULL)
		return;

	if (w->saved_layout_root != NULL)
		fe->value = layout_dump(w->saved_layout_root);
	else
		fe->value = layout_dump(w->layout_root);
}

/* Callback for window_visible_layout. */
static void
format_cb_window_visible_layout(struct format_tree *ft, struct format_entry *fe)
{
	struct window	*w = ft->w;

	if (w == NULL)
		return;

	fe->value = layout_dump(w->layout_root);
}

/* Callback for pane_start_command. */
static void
format_cb_start_command(struct format_tree *ft, struct format_entry *fe)
{
	struct window_pane	*wp = ft->wp;

	if (wp == NULL)
		return;

	fe->value = cmd_stringify_argv(wp->argc, wp->argv);
}

/* Callback for pane_current_command. */
static void
format_cb_current_command(struct format_tree *ft, struct format_entry *fe)
{
	struct window_pane	*wp = ft->wp;
	char			*cmd;

	if (wp == NULL)
		return;

	cmd = get_proc_name(wp->fd, wp->tty);
	if (cmd == NULL || *cmd == '\0') {
		free(cmd);
		cmd = cmd_stringify_argv(wp->argc, wp->argv);
		if (cmd == NULL || *cmd == '\0') {
			free(cmd);
			cmd = xstrdup(wp->shell);
		}
	}
	fe->value = parse_window_name(cmd);
	free(cmd);
}

/* Callback for history_bytes. */
static void
format_cb_history_bytes(struct format_tree *ft, struct format_entry *fe)
{
	struct window_pane	*wp = ft->wp;
	struct grid		*gd;
	struct grid_line	*gl;
	unsigned long long	 size;
	u_int			 i;

	if (wp == NULL)
		return;
	gd = wp->base.grid;

	size = 0;
	for (i = 0; i < gd->hsize; i++) {
		gl = &gd->linedata[i];
		size += gl->cellsize * sizeof *gl->celldata;
		size += gl->extdsize * sizeof *gl->extddata;
	}
	size += gd->hsize * sizeof *gd->linedata;

	xasprintf(&fe->value, "%llu", size);
}

/* Callback for pane_tabs. */
static void
format_cb_pane_tabs(struct format_tree *ft, struct format_entry *fe)
{
	struct window_pane	*wp = ft->wp;
	struct evbuffer		*buffer;
	u_int			 i;
	int			 size;

	if (wp == NULL)
		return;

	buffer = evbuffer_new();
	for (i = 0; i < wp->base.grid->sx; i++) {
		if (!bit_test(wp->base.tabs, i))
			continue;

		if (EVBUFFER_LENGTH(buffer) > 0)
			evbuffer_add(buffer, ",", 1);
		evbuffer_add_printf(buffer, "%u", i);
	}
	size = EVBUFFER_LENGTH(buffer);
	xasprintf(&fe->value, "%.*s", size, EVBUFFER_DATA(buffer));
	evbuffer_free(buffer);
}

/* Merge a format tree. */
static void
format_merge(struct format_tree *ft, struct format_tree *from)
{
	struct format_entry	*fe;

	RB_FOREACH(fe, format_entry_tree, &from->tree) {
		if (fe->value != NULL)
			format_add(ft, fe->key, "%s", fe->value);
	}
}

/* Create a new tree. */
struct format_tree *
format_create(struct cmdq_item *item, int tag, int flags)
{
	struct format_tree	*ft;

	if (!event_initialized(&format_job_event)) {
		evtimer_set(&format_job_event, format_job_timer, NULL);
		format_job_timer(-1, 0, NULL);
	}

	ft = xcalloc(1, sizeof *ft);
	RB_INIT(&ft->tree);

	ft->tag = tag;
	ft->flags = flags;

	format_add_cb(ft, "host", format_cb_host);
	format_add_cb(ft, "host_short", format_cb_host_short);
	format_add_cb(ft, "pid", format_cb_pid);
	format_add(ft, "socket_path", "%s", socket_path);
	format_add_tv(ft, "start_time", &start_time);

	if (item != NULL && item->cmd != NULL)
		format_add(ft, "command", "%s", item->cmd->entry->name);
	if (item != NULL && item->formats != NULL)
		format_merge(ft, item->formats);

	return (ft);
}

/* Free a tree. */
void
format_free(struct format_tree *ft)
{
	struct format_entry	*fe, *fe1;

	RB_FOREACH_SAFE(fe, format_entry_tree, &ft->tree, fe1) {
		RB_REMOVE(format_entry_tree, &ft->tree, fe);
		free(fe->value);
		free(fe->key);
		free(fe);
	}

	free(ft);
}

/* Add a key-value pair. */
void
format_add(struct format_tree *ft, const char *key, const char *fmt, ...)
{
	struct format_entry	*fe;
	struct format_entry	*fe_now;
	va_list			 ap;

	fe = xmalloc(sizeof *fe);
	fe->key = xstrdup(key);

	fe_now = RB_INSERT(format_entry_tree, &ft->tree, fe);
	if (fe_now != NULL) {
		free(fe->key);
		free(fe);
		free(fe_now->value);
		fe = fe_now;
	}

	fe->cb = NULL;
	fe->t = 0;

	va_start(ap, fmt);
	xvasprintf(&fe->value, fmt, ap);
	va_end(ap);
}

/* Add a key and time. */
static void
format_add_tv(struct format_tree *ft, const char *key, struct timeval *tv)
{
	struct format_entry	*fe;
	struct format_entry	*fe_now;

	fe = xmalloc(sizeof *fe);
	fe->key = xstrdup(key);

	fe_now = RB_INSERT(format_entry_tree, &ft->tree, fe);
	if (fe_now != NULL) {
		free(fe->key);
		free(fe);
		free(fe_now->value);
		fe = fe_now;
	}

	fe->cb = NULL;
	fe->t = tv->tv_sec;

	fe->value = NULL;
}

/* Add a key and function. */
static void
format_add_cb(struct format_tree *ft, const char *key, format_cb cb)
{
	struct format_entry	*fe;
	struct format_entry	*fe_now;

	fe = xmalloc(sizeof *fe);
	fe->key = xstrdup(key);

	fe_now = RB_INSERT(format_entry_tree, &ft->tree, fe);
	if (fe_now != NULL) {
		free(fe->key);
		free(fe);
		free(fe_now->value);
		fe = fe_now;
	}

	fe->cb = cb;
	fe->t = 0;

	fe->value = NULL;
}

/* Find a format entry. */
static char *
format_find(struct format_tree *ft, const char *key, int modifiers)
{
	struct format_entry	*fe, fe_find;
	struct environ_entry	*envent;
	static char		 s[64];
	struct options_entry	*o;
	const char		*found;
	int			 idx;
	char			*copy, *saved;

	if (~modifiers & FORMAT_TIMESTRING) {
		o = options_parse_get(global_options, key, &idx, 0);
		if (o == NULL && ft->w != NULL)
			o = options_parse_get(ft->w->options, key, &idx, 0);
		if (o == NULL)
			o = options_parse_get(global_w_options, key, &idx, 0);
		if (o == NULL && ft->s != NULL)
			o = options_parse_get(ft->s->options, key, &idx, 0);
		if (o == NULL)
			o = options_parse_get(global_s_options, key, &idx, 0);
		if (o != NULL) {
			found = options_tostring(o, idx, 1);
			goto found;
		}
	}
	found = NULL;

	fe_find.key = (char *) key;
	fe = RB_FIND(format_entry_tree, &ft->tree, &fe_find);
	if (fe != NULL) {
		if (modifiers & FORMAT_TIMESTRING) {
			if (fe->t == 0)
				return (NULL);
			ctime_r(&fe->t, s);
			s[strcspn(s, "\n")] = '\0';
			found = s;
			goto found;
		}
		if (fe->t != 0) {
			xsnprintf(s, sizeof s, "%lld", (long long)fe->t);
			found = s;
			goto found;
		}
		if (fe->value == NULL && fe->cb != NULL)
			fe->cb(ft, fe);
		found = fe->value;
		goto found;
	}

	if (~modifiers & FORMAT_TIMESTRING) {
		envent = NULL;
		if (ft->s != NULL)
			envent = environ_find(ft->s->environ, key);
		if (envent == NULL)
			envent = environ_find(global_environ, key);
		if (envent != NULL) {
			found = envent->value;
			goto found;
		}
	}

	return (NULL);

found:
	if (found == NULL)
		return (NULL);
	copy = xstrdup(found);
	if (modifiers & FORMAT_BASENAME) {
		saved = copy;
		copy = xstrdup(basename(saved));
		free(saved);
	}
	if (modifiers & FORMAT_DIRNAME) {
		saved = copy;
		copy = xstrdup(dirname(saved));
		free(saved);
	}
	return (copy);
}

/* Skip until comma. */
static char *
format_skip(char *s)
{
	int	brackets = 0;

	for (; *s != '\0'; s++) {
		if (*s == '{')
			brackets++;
		if (*s == '}')
			brackets--;
		if (*s == ',' && brackets == 0)
			break;
	}
	if (*s == '\0')
		return (NULL);
	return (s);
}

/* Return left and right alternatives separated by commas. */
static int
format_choose(char *s, char **left, char **right)
{
	char	*cp;

	cp = format_skip(s);
	if (cp == NULL)
		return (-1);
	*cp = '\0';

	*left = s;
	*right = cp + 1;
	return (0);
}

/* Is this true? */
static int
format_true(const char *s)
{
	if (s != NULL && *s != '\0' && (s[0] != '0' || s[1] != '\0'))
		return (1);
	return (0);
}

/*
 * Replace a key/value pair in buffer. #{blah} is expanded directly,
 * #{?blah,a,b} is replace with a if blah exists and is nonzero else b.
 */
static int
format_replace(struct format_tree *ft, const char *key, size_t keylen,
    char **buf, size_t *len, size_t *off)
{
	char		*copy, *copy0, *endptr, *ptr, *found, *new, *value;
	char		*from = NULL, *to = NULL, *left, *right;
	size_t		 valuelen, newlen, fromlen, tolen, used;
	long		 limit = 0;
	int		 modifiers = 0, compare = 0;

	/* Make a copy of the key. */
	copy0 = copy = xmalloc(keylen + 1);
	memcpy(copy, key, keylen);
	copy[keylen] = '\0';

	/* Is there a length limit or whatnot? */
	switch (copy[0]) {
	case '!':
		if (copy[1] == '=' && copy[2] == ':') {
			compare = -1;
			copy += 3;
			break;
		}
		break;
	case '=':
		if (copy[1] == '=' && copy[2] == ':') {
			compare = 1;
			copy += 3;
			break;
		}
		errno = 0;
		limit = strtol(copy + 1, &endptr, 10);
		if (errno == ERANGE && (limit == LONG_MIN || limit == LONG_MAX))
			break;
		if (*endptr != ':')
			break;
		copy = endptr + 1;
		break;
	case 'b':
		if (copy[1] != ':')
			break;
		modifiers |= FORMAT_BASENAME;
		copy += 2;
		break;
	case 'd':
		if (copy[1] != ':')
			break;
		modifiers |= FORMAT_DIRNAME;
		copy += 2;
		break;
	case 't':
		if (copy[1] != ':')
			break;
		modifiers |= FORMAT_TIMESTRING;
		copy += 2;
		break;
	case 's':
		if (copy[1] != '/')
			break;
		from = copy + 2;
		for (copy = from; *copy != '\0' && *copy != '/'; copy++)
			/* nothing */;
		if (copy[0] != '/' || copy == from) {
			copy = copy0;
			break;
		}
		copy[0] = '\0';
		to = copy + 1;
		for (copy = to; *copy != '\0' && *copy != '/'; copy++)
			/* nothing */;
		if (copy[0] != '/' || copy[1] != ':') {
			copy = copy0;
			break;
		}
		copy[0] = '\0';

		modifiers |= FORMAT_SUBSTITUTE;
		copy += 2;
		break;
	}

	/* Is this a comparison or a conditional? */
	if (compare != 0) {
		/* Comparison: compare comma-separated left and right. */
		if (format_choose(copy, &left, &right) != 0)
			goto fail;
		left = format_expand(ft, left);
		right = format_expand(ft, right);
		if (compare == 1 && strcmp(left, right) == 0)
			value = xstrdup("1");
		else if (compare == -1 && strcmp(left, right) != 0)
			value = xstrdup("1");
		else
			value = xstrdup("0");
		free(right);
		free(left);
	} else if (*copy == '?') {
		/* Conditional: check first and choose second or third. */
		ptr = format_skip(copy);
		if (ptr == NULL)
			goto fail;
		*ptr = '\0';

		found = format_find(ft, copy + 1, modifiers);
		if (found == NULL)
			found = format_expand(ft, copy + 1);
		if (format_choose(ptr + 1, &left, &right) != 0)
			goto fail;

		if (format_true(found))
			value = format_expand(ft, left);
		else
			value = format_expand(ft, right);
		free(found);
	} else {
		/* Neither: look up directly. */
		value = format_find(ft, copy, modifiers);
		if (value == NULL)
			value = xstrdup("");
	}

	/* Perform substitution if any. */
	if (modifiers & FORMAT_SUBSTITUTE) {
		fromlen = strlen(from);
		tolen = strlen(to);

		newlen = strlen(value) + 1;
		copy = new = xmalloc(newlen);
		for (ptr = value; *ptr != '\0'; /* nothing */) {
			if (strncmp(ptr, from, fromlen) != 0) {
				*new++ = *ptr++;
				continue;
			}
			used = new - copy;

			newlen += tolen;
			copy = xrealloc(copy, newlen);

			new = copy + used;
			memcpy(new, to, tolen);

			new += tolen;
			ptr += fromlen;
		}
		*new = '\0';
		free(value);
		value = copy;
	}

	/* Truncate the value if needed. */
	if (limit > 0) {
		new = utf8_trimcstr(value, limit);
		free(value);
		value = new;
	} else if (limit < 0) {
		new = utf8_rtrimcstr(value, -limit);
		free(value);
		value = new;
	}

	/* Expand the buffer and copy in the value. */
	valuelen = strlen(value);
	while (*len - *off < valuelen + 1) {
		*buf = xreallocarray(*buf, 2, *len);
		*len *= 2;
	}
	memcpy(*buf + *off, value, valuelen);
	*off += valuelen;

	free(value);
	free(copy0);
	return (0);

fail:
	free(copy0);
	return (-1);
}

/* Expand keys in a template, passing through strftime first. */
char *
format_expand_time(struct format_tree *ft, const char *fmt, time_t t)
{
	struct tm	*tm;
	char		 s[2048];

	if (fmt == NULL || *fmt == '\0')
		return (xstrdup(""));

	tm = localtime(&t);

	if (strftime(s, sizeof s, fmt, tm) == 0)
		return (xstrdup(""));

	return (format_expand(ft, s));
}

/* Expand keys in a template. */
char *
format_expand(struct format_tree *ft, const char *fmt)
{
	char		*buf, *out;
	const char	*ptr, *s, *saved = fmt;
	size_t		 off, len, n, outlen;
	int     	 ch, brackets;

	if (fmt == NULL)
		return (xstrdup(""));

	len = 64;
	buf = xmalloc(len);
	off = 0;

	while (*fmt != '\0') {
		if (*fmt != '#') {
			while (len - off < 2) {
				buf = xreallocarray(buf, 2, len);
				len *= 2;
			}
			buf[off++] = *fmt++;
			continue;
		}
		fmt++;

		ch = (u_char) *fmt++;
		switch (ch) {
		case '(':
			brackets = 1;
			for (ptr = fmt; *ptr != '\0'; ptr++) {
				if (*ptr == '(')
					brackets++;
				if (*ptr == ')' && --brackets == 0)
					break;
			}
			if (*ptr != ')' || brackets != 0)
				break;
			n = ptr - fmt;

			if (ft->flags & FORMAT_NOJOBS)
				out = xstrdup("");
			else
				out = format_job_get(ft, xstrndup(fmt, n));
			outlen = strlen(out);

			while (len - off < outlen + 1) {
				buf = xreallocarray(buf, 2, len);
				len *= 2;
			}
			memcpy(buf + off, out, outlen);
			off += outlen;

			free(out);

			fmt += n + 1;
			continue;
		case '{':
			brackets = 1;
			for (ptr = fmt; *ptr != '\0'; ptr++) {
				if (*ptr == '{')
					brackets++;
				if (*ptr == '}' && --brackets == 0)
					break;
			}
			if (*ptr != '}' || brackets != 0)
				break;
			n = ptr - fmt;

			if (format_replace(ft, fmt, n, &buf, &len, &off) != 0)
				break;
			fmt += n + 1;
			continue;
		case '#':
			while (len - off < 2) {
				buf = xreallocarray(buf, 2, len);
				len *= 2;
			}
			buf[off++] = '#';
			continue;
		default:
			s = NULL;
			if (ch >= 'A' && ch <= 'Z')
				s = format_upper[ch - 'A'];
			else if (ch >= 'a' && ch <= 'z')
				s = format_lower[ch - 'a'];
			if (s == NULL) {
				while (len - off < 3) {
					buf = xreallocarray(buf, 2, len);
					len *= 2;
				}
				buf[off++] = '#';
				buf[off++] = ch;
				continue;
			}
			n = strlen(s);
			if (format_replace(ft, s, n, &buf, &len, &off) != 0)
				break;
			continue;
		}

		break;
	}
	buf[off] = '\0';

	log_debug("format '%s' -> '%s'", saved, buf);
	return (buf);
}

/* Expand a single string. */
char *
format_single(struct cmdq_item *item, const char *fmt, struct client *c,
    struct session *s, struct winlink *wl, struct window_pane *wp)
{
	struct format_tree	*ft;
	char			*expanded;

	ft = format_create(item, FORMAT_NONE, 0);
	format_defaults(ft, c, s, wl, wp);

	expanded = format_expand(ft, fmt);
	format_free(ft);
	return (expanded);
}

/* Set defaults for any of arguments that are not NULL. */
void
format_defaults(struct format_tree *ft, struct client *c, struct session *s,
    struct winlink *wl, struct window_pane *wp)
{
	if (s == NULL && c != NULL)
		s = c->session;
	if (wl == NULL && s != NULL)
		wl = s->curw;
	if (wp == NULL && wl != NULL)
		wp = wl->window->active;

	if (c != NULL)
		format_defaults_client(ft, c);
	if (s != NULL)
		format_defaults_session(ft, s);
	if (s != NULL && wl != NULL)
		format_defaults_winlink(ft, s, wl);
	if (wp != NULL)
		format_defaults_pane(ft, wp);
}

/* Set default format keys for a session. */
static void
format_defaults_session(struct format_tree *ft, struct session *s)
{
	struct session_group	*sg;

	ft->s = s;

	format_add(ft, "session_name", "%s", s->name);
	format_add(ft, "session_windows", "%u", winlink_count(&s->windows));
	format_add(ft, "session_width", "%u", s->sx);
	format_add(ft, "session_height", "%u", s->sy);
	format_add(ft, "session_id", "$%u", s->id);

	sg = session_group_contains(s);
	format_add(ft, "session_grouped", "%d", sg != NULL);
	if (sg != NULL)
		format_add(ft, "session_group", "%s", sg->name);

	format_add_tv(ft, "session_created", &s->creation_time);
	format_add_tv(ft, "session_last_attached", &s->last_attached_time);
	format_add_tv(ft, "session_activity", &s->activity_time);

	format_add(ft, "session_attached", "%u", s->attached);
	format_add(ft, "session_many_attached", "%d", s->attached > 1);

	format_add_cb(ft, "session_alerts", format_cb_session_alerts);
}

/* Set default format keys for a client. */
static void
format_defaults_client(struct format_tree *ft, struct client *c)
{
	struct session	*s;
	const char	*name;
	struct tty	*tty = &c->tty;
	const char	*types[] = TTY_TYPES;

	if (ft->s == NULL)
		ft->s = c->session;

	format_add(ft, "client_name", "%s", c->name);
	format_add(ft, "client_pid", "%ld", (long) c->pid);
	format_add(ft, "client_height", "%u", tty->sy);
	format_add(ft, "client_width", "%u", tty->sx);
	format_add(ft, "client_tty", "%s", c->ttyname);
	format_add(ft, "client_control_mode", "%d",
		!!(c->flags & CLIENT_CONTROL));

	if (tty->term_name != NULL)
		format_add(ft, "client_termname", "%s", tty->term_name);
	if (tty->term_name != NULL)
		format_add(ft, "client_termtype", "%s", types[tty->term_type]);

	format_add_tv(ft, "client_created", &c->creation_time);
	format_add_tv(ft, "client_activity", &c->activity_time);

	name = server_client_get_key_table(c);
	if (strcmp(c->keytable->name, name) == 0)
		format_add(ft, "client_prefix", "%d", 0);
	else
		format_add(ft, "client_prefix", "%d", 1);
	format_add(ft, "client_key_table", "%s", c->keytable->name);

	if (tty->flags & TTY_UTF8)
		format_add(ft, "client_utf8", "%d", 1);
	else
		format_add(ft, "client_utf8", "%d", 0);

	if (c->flags & CLIENT_READONLY)
		format_add(ft, "client_readonly", "%d", 1);
	else
		format_add(ft, "client_readonly", "%d", 0);

	s = c->session;
	if (s != NULL)
		format_add(ft, "client_session", "%s", s->name);
	s = c->last_session;
	if (s != NULL && session_alive(s))
		format_add(ft, "client_last_session", "%s", s->name);
}

/* Set default format keys for a window. */
void
format_defaults_window(struct format_tree *ft, struct window *w)
{
	ft->w = w;

	format_add_tv(ft, "window_activity", &w->activity_time);
	format_add(ft, "window_id", "@%u", w->id);
	format_add(ft, "window_name", "%s", w->name);
	format_add(ft, "window_width", "%u", w->sx);
	format_add(ft, "window_height", "%u", w->sy);
	format_add_cb(ft, "window_layout", format_cb_window_layout);
	format_add_cb(ft, "window_visible_layout",
	    format_cb_window_visible_layout);
	format_add(ft, "window_panes", "%u", window_count_panes(w));
	format_add(ft, "window_zoomed_flag", "%d",
	    !!(w->flags & WINDOW_ZOOMED));
}

/* Set default format keys for a winlink. */
static void
format_defaults_winlink(struct format_tree *ft, struct session *s,
    struct winlink *wl)
{
	struct window	*w = wl->window;
	char		*flags;

	if (ft->w == NULL)
		ft->w = wl->window;

	flags = window_printable_flags(s, wl);

	format_defaults_window(ft, w);

	format_add(ft, "window_index", "%d", wl->idx);
	format_add(ft, "window_flags", "%s", flags);
	format_add(ft, "window_active", "%d", wl == s->curw);

	format_add(ft, "window_bell_flag", "%d",
	    !!(wl->flags & WINLINK_BELL));
	format_add(ft, "window_activity_flag", "%d",
	    !!(wl->flags & WINLINK_ACTIVITY));
	format_add(ft, "window_silence_flag", "%d",
	    !!(wl->flags & WINLINK_SILENCE));
	format_add(ft, "window_last_flag", "%d",
	    !!(wl == TAILQ_FIRST(&s->lastw)));
	format_add(ft, "window_linked", "%d", session_is_linked(s, wl->window));

	free(flags);
}

/* Set default format keys for a window pane. */
void
format_defaults_pane(struct format_tree *ft, struct window_pane *wp)
{
	struct grid	*gd = wp->base.grid;
	u_int		 idx;
	int  		 status, scroll_position;

	if (ft->w == NULL)
		ft->w = wp->window;
	ft->wp = wp;

	format_add(ft, "history_size", "%u", gd->hsize);
	format_add(ft, "history_limit", "%u", gd->hlimit);
	format_add_cb(ft, "history_bytes", format_cb_history_bytes);

	if (window_pane_index(wp, &idx) != 0)
		fatalx("index not found");
	format_add(ft, "pane_index", "%u", idx);

	format_add(ft, "pane_width", "%u", wp->sx);
	format_add(ft, "pane_height", "%u", wp->sy);
	format_add(ft, "pane_title", "%s", wp->base.title);
	format_add(ft, "pane_id", "%%%u", wp->id);
	format_add(ft, "pane_active", "%d", wp == wp->window->active);
	format_add(ft, "pane_input_off", "%d", !!(wp->flags & PANE_INPUTOFF));

	status = wp->status;
	if (wp->fd == -1 && WIFEXITED(status))
		format_add(ft, "pane_dead_status", "%d", WEXITSTATUS(status));
	format_add(ft, "pane_dead", "%d", wp->fd == -1);

	if (window_pane_visible(wp)) {
		format_add(ft, "pane_left", "%u", wp->xoff);
		format_add(ft, "pane_top", "%u", wp->yoff);
		format_add(ft, "pane_right", "%u", wp->xoff + wp->sx - 1);
		format_add(ft, "pane_bottom", "%u", wp->yoff + wp->sy - 1);
	}

	format_add(ft, "pane_in_mode", "%d", wp->screen != &wp->base);
	format_add(ft, "pane_synchronized", "%d",
	    !!options_get_number(wp->window->options, "synchronize-panes"));

	format_add(ft, "pane_tty", "%s", wp->tty);
	format_add(ft, "pane_pid", "%ld", (long) wp->pid);
	format_add_cb(ft, "pane_start_command", format_cb_start_command);
	format_add_cb(ft, "pane_current_command", format_cb_current_command);

	format_add(ft, "cursor_x", "%u", wp->base.cx);
	format_add(ft, "cursor_y", "%u", wp->base.cy);
	format_add(ft, "scroll_region_upper", "%u", wp->base.rupper);
	format_add(ft, "scroll_region_lower", "%u", wp->base.rlower);

	scroll_position = window_copy_scroll_position(wp);
	if (scroll_position != -1)
		format_add(ft, "scroll_position", "%d", scroll_position);

	format_add(ft, "alternate_on", "%d", wp->saved_grid ? 1 : 0);
	format_add(ft, "alternate_saved_x", "%u", wp->saved_cx);
	format_add(ft, "alternate_saved_y", "%u", wp->saved_cy);

	format_add(ft, "cursor_flag", "%d",
	    !!(wp->base.mode & MODE_CURSOR));
	format_add(ft, "insert_flag", "%d",
	    !!(wp->base.mode & MODE_INSERT));
	format_add(ft, "keypad_cursor_flag", "%d",
	    !!(wp->base.mode & MODE_KCURSOR));
	format_add(ft, "keypad_flag", "%d",
	    !!(wp->base.mode & MODE_KKEYPAD));
	format_add(ft, "wrap_flag", "%d",
	    !!(wp->base.mode & MODE_WRAP));

	format_add(ft, "mouse_any_flag", "%d",
	    !!(wp->base.mode & ALL_MOUSE_MODES));
	format_add(ft, "mouse_standard_flag", "%d",
	    !!(wp->base.mode & MODE_MOUSE_STANDARD));
	format_add(ft, "mouse_button_flag", "%d",
	    !!(wp->base.mode & MODE_MOUSE_BUTTON));
	format_add(ft, "mouse_all_flag", "%d",
	    !!(wp->base.mode & MODE_MOUSE_ALL));

	format_add_cb(ft, "pane_tabs", format_cb_pane_tabs);
}

/* Set default format keys for paste buffer. */
void
format_defaults_paste_buffer(struct format_tree *ft, struct paste_buffer *pb)
{
	size_t	 bufsize;
	char	*s;

	paste_buffer_data(pb, &bufsize);
	format_add(ft, "buffer_size", "%zu", bufsize);
	format_add(ft, "buffer_name", "%s", paste_buffer_name(pb));

	s = paste_make_sample(pb);
	format_add(ft, "buffer_sample", "%s", s);
	free(s);
}