/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * VIM - Vi IMproved	by Bram Moolenaar
 *
 * Do ":help uganda"  in Vim to read copying and usage conditions.
 * Do ":help credits" in Vim to see a list of people who contributed.
 * See README.txt for an overview of the Vim source code.
 */

/*
 * evalbuffer.c: Buffer related builtin functions
 */

#include "vim.h"

#if defined(FEAT_EVAL) || defined(PROTO)
/*
 * Mark references in functions of buffers.
 */
    int
set_ref_in_buffers(int copyID)
{
    int		abort = FALSE;
    buf_T	*bp;

    FOR_ALL_BUFFERS(bp)
    {
	listener_T *lnr;
	typval_T tv;

	for (lnr = bp->b_listener; !abort && lnr != NULL; lnr = lnr->lr_next)
	{
	    if (lnr->lr_callback.cb_partial != NULL)
	    {
		tv.v_type = VAR_PARTIAL;
		tv.vval.v_partial = lnr->lr_callback.cb_partial;
		abort = abort || set_ref_in_item(&tv, copyID, NULL, NULL);
	    }
	}
# ifdef FEAT_JOB_CHANNEL
	if (!abort && bp->b_prompt_callback.cb_partial != NULL)
	{
	    tv.v_type = VAR_PARTIAL;
	    tv.vval.v_partial = bp->b_prompt_callback.cb_partial;
	    abort = abort || set_ref_in_item(&tv, copyID, NULL, NULL);
	}
	if (!abort && bp->b_prompt_interrupt.cb_partial != NULL)
	{
	    tv.v_type = VAR_PARTIAL;
	    tv.vval.v_partial = bp->b_prompt_interrupt.cb_partial;
	    abort = abort || set_ref_in_item(&tv, copyID, NULL, NULL);
	}
# endif
	if (abort)
	    break;
    }
    return abort;
}

    buf_T *
buflist_find_by_name(char_u *name, int curtab_only)
{
    int		save_magic;
    char_u	*save_cpo;
    buf_T	*buf;

    // Ignore 'magic' and 'cpoptions' here to make scripts portable
    save_magic = p_magic;
    p_magic = TRUE;
    save_cpo = p_cpo;
    p_cpo = empty_option;

    buf = buflist_findnr(buflist_findpat(name, name + STRLEN(name),
						    TRUE, FALSE, curtab_only));

    p_magic = save_magic;
    p_cpo = save_cpo;
    return buf;
}

/*
 * Find a buffer by number or exact name.
 */
    buf_T *
find_buffer(typval_T *avar)
{
    buf_T	*buf = NULL;

    if (avar->v_type == VAR_NUMBER)
	buf = buflist_findnr((int)avar->vval.v_number);
    else if (in_vim9script() && check_for_string_arg(avar, 0) == FAIL)
	return NULL;
    else if (avar->v_type == VAR_STRING && avar->vval.v_string != NULL)
    {
	buf = buflist_findname_exp(avar->vval.v_string);
	if (buf == NULL)
	{
	    // No full path name match, try a match with a URL or a "nofile"
	    // buffer, these don't use the full path.
	    FOR_ALL_BUFFERS(buf)
		if (buf->b_fname != NULL
			&& (path_with_url(buf->b_fname)
#ifdef FEAT_QUICKFIX
			    || bt_nofilename(buf)
#endif
			   )
			&& STRCMP(buf->b_fname, avar->vval.v_string) == 0)
		    break;
	}
    }
    return buf;
}

/*
 * If there is a window for "curbuf", make it the current window.
 */
    static void
find_win_for_curbuf(void)
{
    wininfo_T *wip;

    FOR_ALL_BUF_WININFO(curbuf, wip)
    {
	if (wip->wi_win != NULL)
	{
	    curwin = wip->wi_win;
	    break;
	}
    }
}

/*
 * Set line or list of lines in buffer "buf" to "lines".
 * Any type is allowed and converted to a string.
 */
    static void
set_buffer_lines(
	buf_T	    *buf,
	linenr_T    lnum_arg,
	int	    append,
	typval_T    *lines,
	typval_T    *rettv)
{
    linenr_T    lnum = lnum_arg + (append ? 1 : 0);
    char_u	*line = NULL;
    list_T	*l = NULL;
    listitem_T	*li = NULL;
    long	added = 0;
    linenr_T	append_lnum;
    buf_T	*curbuf_save = NULL;
    win_T	*curwin_save = NULL;
    int		is_curbuf = buf == curbuf;

    // When using the current buffer ml_mfp will be set if needed.  Useful when
    // setline() is used on startup.  For other buffers the buffer must be
    // loaded.
    if (buf == NULL || (!is_curbuf && buf->b_ml.ml_mfp == NULL) || lnum < 1)
    {
	rettv->vval.v_number = 1;	// FAIL
	return;
    }

    if (!is_curbuf)
    {
	curbuf_save = curbuf;
	curwin_save = curwin;
	curbuf = buf;
	find_win_for_curbuf();
    }

    if (append)
	// appendbufline() uses the line number below which we insert
	append_lnum = lnum - 1;
    else
	// setbufline() uses the line number above which we insert, we only
	// append if it's below the last line
	append_lnum = curbuf->b_ml.ml_line_count;

    if (lines->v_type == VAR_LIST)
    {
	l = lines->vval.v_list;
	if (l == NULL || list_len(l) == 0)
	{
	    // set proper return code
	    if (lnum > curbuf->b_ml.ml_line_count)
		rettv->vval.v_number = 1;	// FAIL
	    goto done;
	}
	CHECK_LIST_MATERIALIZE(l);
	li = l->lv_first;
    }
    else
	line = typval_tostring(lines, FALSE);

    // default result is zero == OK
    for (;;)
    {
	if (l != NULL)
	{
	    // list argument, get next string
	    if (li == NULL)
		break;
	    vim_free(line);
	    line = typval_tostring(&li->li_tv, FALSE);
	    li = li->li_next;
	}

	rettv->vval.v_number = 1;	// FAIL
	if (line == NULL || lnum > curbuf->b_ml.ml_line_count + 1)
	    break;

	// When coming here from Insert mode, sync undo, so that this can be
	// undone separately from what was previously inserted.
	if (u_sync_once == 2)
	{
	    u_sync_once = 1; // notify that u_sync() was called
	    u_sync(TRUE);
	}

	if (!append && lnum <= curbuf->b_ml.ml_line_count)
	{
	    // Existing line, replace it.
	    // Removes any existing text properties.
	    if (u_savesub(lnum) == OK && ml_replace_len(
		      lnum, line, (colnr_T)STRLEN(line) + 1, TRUE, TRUE) == OK)
	    {
		changed_bytes(lnum, 0);
		if (is_curbuf && lnum == curwin->w_cursor.lnum)
		    check_cursor_col();
		rettv->vval.v_number = 0;	// OK
	    }
	}
	else if (added > 0 || u_save(lnum - 1, lnum) == OK)
	{
	    // append the line
	    ++added;
	    if (ml_append(lnum - 1, line, (colnr_T)0, FALSE) == OK)
		rettv->vval.v_number = 0;	// OK
	}

	if (l == NULL)			// only one string argument
	    break;
	++lnum;
    }
    vim_free(line);

    if (added > 0)
    {
	win_T	    *wp;
	tabpage_T   *tp;

	appended_lines_mark(append_lnum, added);

	// Only adjust the cursor for buffers other than the current, unless it
	// is the current window.  For curbuf and other windows it has been
	// done in mark_adjust_internal().
	FOR_ALL_TAB_WINDOWS(tp, wp)
	    if (wp->w_buffer == buf
		    && (wp->w_buffer != curbuf || wp == curwin)
		    && wp->w_cursor.lnum > append_lnum)
		wp->w_cursor.lnum += added;
	check_cursor_col();
	update_topline();
    }

done:
    if (!is_curbuf)
    {
	curbuf = curbuf_save;
	curwin = curwin_save;
    }
}

/*
 * "append(lnum, string/list)" function
 */
    void
f_append(typval_T *argvars, typval_T *rettv)
{
    linenr_T	lnum;

    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
	return;

    lnum = tv_get_lnum(&argvars[0]);
    set_buffer_lines(curbuf, lnum, TRUE, &argvars[1], rettv);
}

/*
 * Set or append lines to a buffer.
 */
    static void
buf_set_append_line(typval_T *argvars, typval_T *rettv, int append)
{
    linenr_T	lnum;
    buf_T	*buf;

    if (in_vim9script()
	    && (check_for_buffer_arg(argvars, 0) == FAIL
		|| check_for_lnum_arg(argvars, 1) == FAIL
		|| check_for_string_or_number_or_list_arg(argvars, 2) == FAIL))
	return;

    buf = tv_get_buf(&argvars[0], FALSE);
    if (buf == NULL)
	rettv->vval.v_number = 1; // FAIL
    else
    {
	lnum = tv_get_lnum_buf(&argvars[1], buf);
	set_buffer_lines(buf, lnum, append, &argvars[2], rettv);
    }
}

/*
 * "appendbufline(buf, lnum, string/list)" function
 */
    void
f_appendbufline(typval_T *argvars, typval_T *rettv)
{
    buf_set_append_line(argvars, rettv, TRUE);
}

/*
 * "bufadd(expr)" function
 */
    void
f_bufadd(typval_T *argvars, typval_T *rettv)
{
    char_u *name;

    if (in_vim9script() && check_for_string_arg(argvars, 0) == FAIL)
	return;

    name = tv_get_string(&argvars[0]);
    rettv->vval.v_number = buflist_add(*name == NUL ? NULL : name, 0);
}

/*
 * "bufexists(expr)" function
 */
    void
f_bufexists(typval_T *argvars, typval_T *rettv)
{
    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
	return;

    rettv->vval.v_number = (find_buffer(&argvars[0]) != NULL);
}

/*
 * "buflisted(expr)" function
 */
    void
f_buflisted(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;

    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
	return;

    buf = find_buffer(&argvars[0]);
    rettv->vval.v_number = (buf != NULL && buf->b_p_bl);
}

/*
 * "bufload(expr)" function
 */
    void
f_bufload(typval_T *argvars, typval_T *rettv UNUSED)
{
    buf_T	*buf;

    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
	return;

    buf = get_buf_arg(&argvars[0]);
    if (buf != NULL)
	buffer_ensure_loaded(buf);
}

/*
 * "bufloaded(expr)" function
 */
    void
f_bufloaded(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;

    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
	return;

    buf = find_buffer(&argvars[0]);
    rettv->vval.v_number = (buf != NULL && buf->b_ml.ml_mfp != NULL);
}

/*
 * "bufname(expr)" function
 */
    void
f_bufname(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;
    typval_T	*tv = &argvars[0];

    if (in_vim9script() && check_for_opt_buffer_arg(argvars, 0) == FAIL)
	return;

    if (tv->v_type == VAR_UNKNOWN)
	buf = curbuf;
    else
	buf = tv_get_buf_from_arg(tv);
    rettv->v_type = VAR_STRING;
    if (buf != NULL && buf->b_fname != NULL)
	rettv->vval.v_string = vim_strsave(buf->b_fname);
    else
	rettv->vval.v_string = NULL;
}

/*
 * "bufnr(expr)" function
 */
    void
f_bufnr(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;
    int		error = FALSE;
    char_u	*name;

    if (in_vim9script()
	    && (check_for_opt_buffer_arg(argvars, 0) == FAIL
		|| (argvars[0].v_type != VAR_UNKNOWN
		    && check_for_opt_bool_arg(argvars, 1) == FAIL)))
	return;

    if (argvars[0].v_type == VAR_UNKNOWN)
	buf = curbuf;
    else
	buf = tv_get_buf_from_arg(&argvars[0]);

    // If the buffer isn't found and the second argument is not zero create a
    // new buffer.
    if (buf == NULL
	    && argvars[1].v_type != VAR_UNKNOWN
	    && tv_get_bool_chk(&argvars[1], &error) != 0
	    && !error
	    && (name = tv_get_string_chk(&argvars[0])) != NULL
	    && !error)
	buf = buflist_new(name, NULL, (linenr_T)1, 0);

    if (buf != NULL)
	rettv->vval.v_number = buf->b_fnum;
    else
	rettv->vval.v_number = -1;
}

    static void
buf_win_common(typval_T *argvars, typval_T *rettv, int get_nr)
{
    win_T	*wp;
    int		winnr = 0;
    buf_T	*buf;

    if (in_vim9script() && check_for_buffer_arg(argvars, 0) == FAIL)
	return;

    buf = tv_get_buf_from_arg(&argvars[0]);
    FOR_ALL_WINDOWS(wp)
    {
	++winnr;
	if (wp->w_buffer == buf)
	    break;
    }
    rettv->vval.v_number = (wp != NULL ? (get_nr ? winnr : wp->w_id) : -1);
}

/*
 * "bufwinid(nr)" function
 */
    void
f_bufwinid(typval_T *argvars, typval_T *rettv)
{
    buf_win_common(argvars, rettv, FALSE);
}

/*
 * "bufwinnr(nr)" function
 */
    void
f_bufwinnr(typval_T *argvars, typval_T *rettv)
{
    buf_win_common(argvars, rettv, TRUE);
}

/*
 * "deletebufline()" function
 */
    void
f_deletebufline(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;
    linenr_T	first, last;
    linenr_T	lnum;
    long	count;
    int		is_curbuf;
    buf_T	*curbuf_save = NULL;
    win_T	*curwin_save = NULL;
    tabpage_T	*tp;
    win_T	*wp;

    if (in_vim9script()
	    && (check_for_buffer_arg(argvars, 0) == FAIL
		|| check_for_lnum_arg(argvars, 1) == FAIL
		|| check_for_opt_lnum_arg(argvars, 2) == FAIL))
	return;

    buf = tv_get_buf(&argvars[0], FALSE);
    if (buf == NULL)
    {
	rettv->vval.v_number = 1; // FAIL
	return;
    }
    is_curbuf = buf == curbuf;

    first = tv_get_lnum_buf(&argvars[1], buf);
    if (argvars[2].v_type != VAR_UNKNOWN)
	last = tv_get_lnum_buf(&argvars[2], buf);
    else
	last = first;

    if (buf->b_ml.ml_mfp == NULL || first < 1
			   || first > buf->b_ml.ml_line_count || last < first)
    {
	rettv->vval.v_number = 1;	// FAIL
	return;
    }

    if (!is_curbuf)
    {
	curbuf_save = curbuf;
	curwin_save = curwin;
	curbuf = buf;
	find_win_for_curbuf();
    }
    if (last > curbuf->b_ml.ml_line_count)
	last = curbuf->b_ml.ml_line_count;
    count = last - first + 1;

    // When coming here from Insert mode, sync undo, so that this can be
    // undone separately from what was previously inserted.
    if (u_sync_once == 2)
    {
	u_sync_once = 1; // notify that u_sync() was called
	u_sync(TRUE);
    }

    if (u_save(first - 1, last + 1) == FAIL)
    {
	rettv->vval.v_number = 1;	// FAIL
    }
    else
    {
	for (lnum = first; lnum <= last; ++lnum)
	    ml_delete_flags(first, ML_DEL_MESSAGE);

	FOR_ALL_TAB_WINDOWS(tp, wp)
	    if (wp->w_buffer == buf)
	    {
		if (wp->w_cursor.lnum > last)
		    wp->w_cursor.lnum -= count;
		else if (wp->w_cursor.lnum> first)
		    wp->w_cursor.lnum = first;
		if (wp->w_cursor.lnum > wp->w_buffer->b_ml.ml_line_count)
		    wp->w_cursor.lnum = wp->w_buffer->b_ml.ml_line_count;
	    }
	check_cursor_col();
	deleted_lines_mark(first, count);
    }

    if (!is_curbuf)
    {
	curbuf = curbuf_save;
	curwin = curwin_save;
    }
}

/*
 * Returns buffer options, variables and other attributes in a dictionary.
 */
    static dict_T *
get_buffer_info(buf_T *buf)
{
    dict_T	*dict;
    tabpage_T	*tp;
    win_T	*wp;
    list_T	*windows;

    dict = dict_alloc();
    if (dict == NULL)
	return NULL;

    dict_add_number(dict, "bufnr", buf->b_fnum);
    dict_add_string(dict, "name", buf->b_ffname);
    dict_add_number(dict, "lnum", buf == curbuf ? curwin->w_cursor.lnum
						     : buflist_findlnum(buf));
    dict_add_number(dict, "linecount", buf->b_ml.ml_line_count);
    dict_add_number(dict, "loaded", buf->b_ml.ml_mfp != NULL);
    dict_add_number(dict, "listed", buf->b_p_bl);
    dict_add_number(dict, "changed", bufIsChanged(buf));
    dict_add_number(dict, "changedtick", CHANGEDTICK(buf));
    dict_add_number(dict, "hidden",
			    buf->b_ml.ml_mfp != NULL && buf->b_nwindows == 0);

    // Get a reference to buffer variables
    dict_add_dict(dict, "variables", buf->b_vars);

    // List of windows displaying this buffer
    windows = list_alloc();
    if (windows != NULL)
    {
	FOR_ALL_TAB_WINDOWS(tp, wp)
	    if (wp->w_buffer == buf)
		list_append_number(windows, (varnumber_T)wp->w_id);
	dict_add_list(dict, "windows", windows);
    }

#ifdef FEAT_PROP_POPUP
    // List of popup windows displaying this buffer
    windows = list_alloc();
    if (windows != NULL)
    {
	FOR_ALL_POPUPWINS(wp)
	    if (wp->w_buffer == buf)
		list_append_number(windows, (varnumber_T)wp->w_id);
	FOR_ALL_TABPAGES(tp)
	    FOR_ALL_POPUPWINS_IN_TAB(tp, wp)
		if (wp->w_buffer == buf)
		    list_append_number(windows, (varnumber_T)wp->w_id);

	dict_add_list(dict, "popups", windows);
    }
#endif

#ifdef FEAT_SIGNS
    if (buf->b_signlist != NULL)
    {
	// List of signs placed in this buffer
	list_T	*signs = list_alloc();
	if (signs != NULL)
	{
	    get_buffer_signs(buf, signs);
	    dict_add_list(dict, "signs", signs);
	}
    }
#endif

#ifdef FEAT_VIMINFO
    dict_add_number(dict, "lastused", buf->b_last_used);
#endif

    return dict;
}

/*
 * "getbufinfo()" function
 */
    void
f_getbufinfo(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf = NULL;
    buf_T	*argbuf = NULL;
    dict_T	*d;
    int		filtered = FALSE;
    int		sel_buflisted = FALSE;
    int		sel_bufloaded = FALSE;
    int		sel_bufmodified = FALSE;

    if (rettv_list_alloc(rettv) != OK)
	return;

    if (in_vim9script()
	    && check_for_opt_buffer_or_dict_arg(argvars, 0) == FAIL)
	return;

    // List of all the buffers or selected buffers
    if (argvars[0].v_type == VAR_DICT)
    {
	dict_T	*sel_d = argvars[0].vval.v_dict;

	if (sel_d != NULL)
	{
	    filtered = TRUE;
	    sel_buflisted = dict_get_bool(sel_d, (char_u *)"buflisted", FALSE);
	    sel_bufloaded = dict_get_bool(sel_d, (char_u *)"bufloaded", FALSE);
	    sel_bufmodified = dict_get_bool(sel_d, (char_u *)"bufmodified",
									FALSE);
	}
    }
    else if (argvars[0].v_type != VAR_UNKNOWN)
    {
	// Information about one buffer.  Argument specifies the buffer
	argbuf = tv_get_buf_from_arg(&argvars[0]);
	if (argbuf == NULL)
	    return;
    }

    // Return information about all the buffers or a specified buffer
    FOR_ALL_BUFFERS(buf)
    {
	if (argbuf != NULL && argbuf != buf)
	    continue;
	if (filtered && ((sel_bufloaded && buf->b_ml.ml_mfp == NULL)
			|| (sel_buflisted && !buf->b_p_bl)
			|| (sel_bufmodified && !buf->b_changed)))
	    continue;

	d = get_buffer_info(buf);
	if (d != NULL)
	    list_append_dict(rettv->vval.v_list, d);
	if (argbuf != NULL)
	    return;
    }
}

/*
 * Get line or list of lines from buffer "buf" into "rettv".
 * Return a range (from start to end) of lines in rettv from the specified
 * buffer.
 * If 'retlist' is TRUE, then the lines are returned as a Vim List.
 */
    static void
get_buffer_lines(
    buf_T	*buf,
    linenr_T	start,
    linenr_T	end,
    int		retlist,
    typval_T	*rettv)
{
    char_u	*p;

    if (retlist)
    {
	if (rettv_list_alloc(rettv) == FAIL)
	    return;
    }
    else
    {
	rettv->v_type = VAR_STRING;
	rettv->vval.v_string = NULL;
    }

    if (buf == NULL || buf->b_ml.ml_mfp == NULL || start < 0)
	return;

    if (!retlist)
    {
	if (start >= 1 && start <= buf->b_ml.ml_line_count)
	    p = ml_get_buf(buf, start, FALSE);
	else
	    p = (char_u *)"";
	rettv->vval.v_string = vim_strsave(p);
    }
    else
    {
	if (end < start)
	    return;

	if (start < 1)
	    start = 1;
	if (end > buf->b_ml.ml_line_count)
	    end = buf->b_ml.ml_line_count;
	while (start <= end)
	    if (list_append_string(rettv->vval.v_list,
				 ml_get_buf(buf, start++, FALSE), -1) == FAIL)
		break;
    }
}

/*
 * "getbufline()" function
 */
    void
f_getbufline(typval_T *argvars, typval_T *rettv)
{
    linenr_T	lnum = 1;
    linenr_T	end = 1;
    buf_T	*buf;

    if (in_vim9script()
	    && (check_for_buffer_arg(argvars, 0) == FAIL
		|| check_for_lnum_arg(argvars, 1) == FAIL
		|| check_for_opt_lnum_arg(argvars, 2) == FAIL))
	return;

    buf = tv_get_buf_from_arg(&argvars[0]);
    if (buf != NULL)
    {
	lnum = tv_get_lnum_buf(&argvars[1], buf);
	if (argvars[2].v_type == VAR_UNKNOWN)
	    end = lnum;
	else
	    end = tv_get_lnum_buf(&argvars[2], buf);
    }

    get_buffer_lines(buf, lnum, end, TRUE, rettv);
}

    type_T *
ret_f_getline(int argcount, type_T **argtypes UNUSED)
{
    return argcount == 1 ? &t_string : &t_list_string;
}

/*
 * "getline(lnum, [end])" function
 */
    void
f_getline(typval_T *argvars, typval_T *rettv)
{
    linenr_T	lnum;
    linenr_T	end;
    int		retlist;

    if (in_vim9script()
	    && (check_for_lnum_arg(argvars, 0) == FAIL
		|| check_for_opt_lnum_arg(argvars, 1) == FAIL))
	return;

    lnum = tv_get_lnum(argvars);
    if (argvars[1].v_type == VAR_UNKNOWN)
    {
	end = 0;
	retlist = FALSE;
    }
    else
    {
	end = tv_get_lnum(&argvars[1]);
	retlist = TRUE;
    }

    get_buffer_lines(curbuf, lnum, end, retlist, rettv);
}

/*
 * "setbufline()" function
 */
    void
f_setbufline(typval_T *argvars, typval_T *rettv)
{
    buf_set_append_line(argvars, rettv, FALSE);
}

/*
 * "setline()" function
 */
    void
f_setline(typval_T *argvars, typval_T *rettv)
{
    linenr_T	lnum;

    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
	return;

    lnum = tv_get_lnum(&argvars[0]);
    set_buffer_lines(curbuf, lnum, FALSE, &argvars[1], rettv);
}
#endif  // FEAT_EVAL

#if defined(FEAT_JOB_CHANNEL) \
	|| defined(FEAT_PYTHON) || defined(FEAT_PYTHON3) \
	|| defined(PROTO)
/*
 * Make "buf" the current buffer.  restore_buffer() MUST be called to undo.
 * No autocommands will be executed.  Use aucmd_prepbuf() if there are any.
 */
    void
switch_buffer(bufref_T *save_curbuf, buf_T *buf)
{
    block_autocmds();
#ifdef FEAT_FOLDING
    ++disable_fold_update;
#endif
    set_bufref(save_curbuf, curbuf);
    --curbuf->b_nwindows;
    curbuf = buf;
    curwin->w_buffer = buf;
    ++curbuf->b_nwindows;
}

/*
 * Restore the current buffer after using switch_buffer().
 */
    void
restore_buffer(bufref_T *save_curbuf)
{
    unblock_autocmds();
#ifdef FEAT_FOLDING
    --disable_fold_update;
#endif
    // Check for valid buffer, just in case.
    if (bufref_valid(save_curbuf))
    {
	--curbuf->b_nwindows;
	curwin->w_buffer = save_curbuf->br_buf;
	curbuf = save_curbuf->br_buf;
	++curbuf->b_nwindows;
    }
}

/*
 * Find a window for buffer "buf".
 * If found OK is returned and "wp" and "tp" are set to the window and tabpage.
 * If not found FAIL is returned.
 */
    static int
find_win_for_buf(
    buf_T     *buf,
    win_T     **wp,
    tabpage_T **tp)
{
    FOR_ALL_TAB_WINDOWS(*tp, *wp)
	if ((*wp)->w_buffer == buf)
	    return OK;
    return FAIL;
}

/*
 * Find a window that contains "buf" and switch to it.
 * If there is no such window, use the current window and change "curbuf".
 * Caller must initialize save_curbuf to NULL.
 * restore_win_for_buf() MUST be called later!
 */
    void
switch_to_win_for_buf(
    buf_T	*buf,
    win_T	**save_curwinp,
    tabpage_T	**save_curtabp,
    bufref_T	*save_curbuf)
{
    win_T	*wp;
    tabpage_T	*tp;

    if (find_win_for_buf(buf, &wp, &tp) == FAIL)
	switch_buffer(save_curbuf, buf);
    else if (switch_win(save_curwinp, save_curtabp, wp, tp, TRUE) == FAIL)
    {
	restore_win(*save_curwinp, *save_curtabp, TRUE);
	switch_buffer(save_curbuf, buf);
    }
}

    void
restore_win_for_buf(
    win_T	*save_curwin,
    tabpage_T	*save_curtab,
    bufref_T	*save_curbuf)
{
    if (save_curbuf->br_buf == NULL)
	restore_win(save_curwin, save_curtab, TRUE);
    else
	restore_buffer(save_curbuf);
}
#endif