prompt.c

/*
 * Copyright (C) 1984-2023  Mark Nudelman
 *
 * You may distribute under the terms of either the GNU General Public
 * License or the Less License, as specified in the README file.
 *
 * For more information, see the README file.
 */


/*
 * Prompting and other messages.
 * There are three flavors of prompts, SHORT, MEDIUM and LONG,
 * selected by the -m/-M options.
 * There is also the "equals message", printed by the = command.
 * A prompt is a message composed of various pieces, such as the 
 * name of the file being viewed, the percentage into the file, etc.
 */

#include "less.h"
#include "position.h"

extern int pr_type;
extern lbool new_file;
extern int linenums;
extern int hshift;
extern int sc_height;
extern int jump_sline;
extern int less_is_more;
extern int header_lines;
extern IFILE curr_ifile;
#if EDITOR
extern constant char *editor;
extern constant char *editproto;
#endif

/*
 * Prototypes for the three flavors of prompts.
 * These strings are expanded by pr_expand().
 */
static constant char s_proto[] =
  "?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\\: %x..%t";
static constant char m_proto[] =
  "?n?f%f .?m(%T %i of %m) ..?e(END) ?x- Next\\: %x.:?pB%pB\\%:byte %bB?s/%s...%t";
static constant char M_proto[] =
  "?f%f .?n?m(%T %i of %m) ..?ltlines %lt-%lb?L/%L. :byte %bB?s/%s. .?e(END) ?x- Next\\: %x.:?pB%pB\\%..%t";
static constant char e_proto[] =
  "?f%f .?m(%T %i of %m) .?ltlines %lt-%lb?L/%L. .byte %bB?s/%s. ?e(END) :?pB%pB\\%..%t";
static constant char h_proto[] =
  "HELP -- ?eEND -- Press g to see it again:Press RETURN for more., or q when done";
static constant char w_proto[] =
  "Waiting for data";
static constant char more_proto[] =
  "--More--(?eEND ?x- Next\\: %x.:?pB%pB\\%:byte %bB?s/%s...%t)";

public char *prproto[3];
public char constant *eqproto = e_proto;
public char constant *hproto = h_proto;
public char constant *wproto = w_proto;

static char message[PROMPT_SIZE];
static char *mp;

/*
 * Initialize the prompt prototype strings.
 */
public void init_prompt(void)
{
	prproto[0] = save(s_proto);
	prproto[1] = save(less_is_more ? more_proto : m_proto);
	prproto[2] = save(M_proto);
	eqproto = save(e_proto);
	hproto = save(h_proto);
	wproto = save(w_proto);
}

/*
 * Append a string to the end of the message.
 */
static void ap_str(constant char *s)
{
	size_t len;

	len = strlen(s);
	if (mp + len >= message + PROMPT_SIZE)
		len = ptr_diff(message, mp) + PROMPT_SIZE - 1;
	strncpy(mp, s, len);
	mp += len;
	*mp = '\0';
}

/*
 * Append a character to the end of the message.
 */
static void ap_char(char c)
{
	char buf[2];

	buf[0] = c;
	buf[1] = '\0';
	ap_str(buf);
}

/*
 * Append a POSITION (as a decimal integer) to the end of the message.
 */
static void ap_pos(POSITION pos)
{
	char buf[INT_STRLEN_BOUND(pos) + 2];

	postoa(pos, buf, 10);
	ap_str(buf);
}

/*
 * Append a line number to the end of the message.
 */
static void ap_linenum(LINENUM linenum)
{
	char buf[INT_STRLEN_BOUND(linenum) + 2];

	linenumtoa(linenum, buf, 10);
	ap_str(buf);
}

/*
 * Append an integer to the end of the message.
 */
static void ap_int(int num)
{
	char buf[INT_STRLEN_BOUND(num) + 2];

	inttoa(num, buf, 10);
	ap_str(buf);
}

/*
 * Append a question mark to the end of the message.
 */
static void ap_quest(void)
{
	ap_str("?");
}

/*
 * Return the "current" byte offset in the file.
 */
static POSITION curr_byte(int where)
{
	POSITION pos;

	pos = position(where);
	while (pos == NULL_POSITION && where >= 0 && where < sc_height-1)
		pos = position(++where);
	if (pos == NULL_POSITION)
		pos = ch_length();
	return (pos);
}

/*
 * Return the value of a prototype conditional.
 * A prototype string may include conditionals which consist of a 
 * question mark followed by a single letter.
 * Here we decode that letter and return the appropriate boolean value.
 */
static lbool cond(char c, int where)
{
	POSITION len;

	switch (c)
	{
	case 'a': /* Anything in the message yet? */
		return (mp > message);
	case 'b': /* Current byte offset known? */
		return (curr_byte(where) != NULL_POSITION);
	case 'c':
		return (hshift != 0);
	case 'e': /* At end of file? */
		return (eof_displayed());
	case 'f': /* Filename known? */
	case 'g':
		return (strcmp(get_filename(curr_ifile), "-") != 0);
	case 'l': /* Line number known? */
	case 'd': /* Same as l */
		if (!linenums)
			return FALSE;
		return (currline(where) != 0);
	case 'L': /* Final line number known? */
	case 'D': /* Final page number known? */
		return (linenums && ch_length() != NULL_POSITION);
	case 'm': /* More than one file? */
#if TAGS
		return (ntags() ? (ntags() > 1) : (nifile() > 1));
#else
		return (nifile() > 1);
#endif
	case 'n': /* First prompt in a new file? */
#if TAGS
		return (ntags() ? TRUE : new_file ? TRUE : FALSE);
#else
		return (new_file ? TRUE : FALSE);
#endif
	case 'p': /* Percent into file (bytes) known? */
		return (curr_byte(where) != NULL_POSITION && ch_length() > 0);
	case 'P': /* Percent into file (lines) known? */
		return (currline(where) != 0 &&
				(len = ch_length()) > 0 &&
				find_linenum(len) != 0);
	case 's': /* Size of file known? */
	case 'B':
		return (ch_length() != NULL_POSITION);
	case 'x': /* Is there a "next" file? */
#if TAGS
		if (ntags())
			return (FALSE);
#endif
		return (next_ifile(curr_ifile) != NULL_IFILE);
	}
	return (FALSE);
}

/*
 * Decode a "percent" prototype character.
 * A prototype string may include various "percent" escapes;
 * that is, a percent sign followed by a single letter.
 * Here we decode that letter and take the appropriate action,
 * usually by appending something to the message being built.
 */
static void protochar(char c, int where)
{
	POSITION pos;
	POSITION len;
	int n;
	LINENUM linenum;
	LINENUM last_linenum;
	IFILE h;
	char *s;

#undef  PAGE_NUM
#define PAGE_NUM(linenum)  ((((linenum) - 1) / (sc_height - header_lines - 1)) + 1)

	switch (c)
	{
	case 'b': /* Current byte offset */
		pos = curr_byte(where);
		if (pos != NULL_POSITION)
			ap_pos(pos);
		else
			ap_quest();
		break;
	case 'c':
		ap_int(hshift);
		break;
	case 'd': /* Current page number */
		linenum = currline(where);
		if (linenum > 0 && sc_height > header_lines + 1)
			ap_linenum(PAGE_NUM(linenum));
		else
			ap_quest();
		break;
	case 'D': /* Final page number */
		/* Find the page number of the last byte in the file (len-1). */
		len = ch_length();
		if (len == NULL_POSITION)
			ap_quest();
		else if (len == 0)
			/* An empty file has no pages. */
			ap_linenum(0);
		else
		{
			linenum = find_linenum(len - 1);
			if (linenum <= 0)
				ap_quest();
			else 
				ap_linenum(PAGE_NUM(linenum));
		}
		break;
#if EDITOR
	case 'E': /* Editor name */
		ap_str(editor);
		break;
#endif
	case 'f': /* File name */
		ap_str(get_filename(curr_ifile));
		break;
	case 'F': /* Last component of file name */
		ap_str(last_component(get_filename(curr_ifile)));
		break;
	case 'g': /* Shell-escaped file name */
		s = shell_quote(get_filename(curr_ifile));
		ap_str(s);
		free(s);
		break;
	case 'i': /* Index into list of files */
#if TAGS
		if (ntags())
			ap_int(curr_tag());
		else
#endif
			ap_int(get_index(curr_ifile));
		break;
	case 'l': /* Current line number */
		linenum = currline(where);
		if (linenum != 0)
			ap_linenum(vlinenum(linenum));
		else
			ap_quest();
		break;
	case 'L': /* Final line number */
		len = ch_length();
		if (len == NULL_POSITION || len == ch_zero() ||
		    (linenum = find_linenum(len)) <= 0)
			ap_quest();
		else
			ap_linenum(vlinenum(linenum-1));
		break;
	case 'm': /* Number of files */
#if TAGS
		n = ntags();
		if (n)
			ap_int(n);
		else
#endif
			ap_int(nifile());
		break;
	case 'p': /* Percent into file (bytes) */
		pos = curr_byte(where);
		len = ch_length();
		if (pos != NULL_POSITION && len > 0)
			ap_int(percentage(pos,len));
		else
			ap_quest();
		break;
	case 'P': /* Percent into file (lines) */
		linenum = currline(where);
		if (linenum == 0 ||
		    (len = ch_length()) == NULL_POSITION || len == ch_zero() ||
		    (last_linenum = find_linenum(len)) <= 0)
			ap_quest();
		else
			ap_int(percentage(linenum, last_linenum));
		break;
	case 's': /* Size of file */
	case 'B':
		len = ch_length();
		if (len != NULL_POSITION)
			ap_pos(len);
		else
			ap_quest();
		break;
	case 't': /* Truncate trailing spaces in the message */
		while (mp > message && mp[-1] == ' ')
			mp--;
		*mp = '\0';
		break;
	case 'T': /* Type of list */
#if TAGS
		if (ntags())
			ap_str("tag");
		else
#endif
			ap_str("file");
		break;
	case 'x': /* Name of next file */
		h = next_ifile(curr_ifile);
		if (h != NULL_IFILE)
			ap_str(get_filename(h));
		else
			ap_quest();
		break;
	}
}

/*
 * Skip a false conditional.
 * When a false condition is found (either a false IF or the ELSE part 
 * of a true IF), this routine scans the prototype string to decide
 * where to resume parsing the string.
 * We must keep track of nested IFs and skip them properly.
 */
static constant char * skipcond(constant char *p)
{
	int iflevel;

	/*
	 * We came in here after processing a ? or :,
	 * so we start nested one level deep.
	 */
	iflevel = 1;

	for (;;) switch (*++p)
	{
	case '?':
		/*
		 * Start of a nested IF.
		 */
		iflevel++;
		break;
	case ':':
		/*
		 * Else.
		 * If this matches the IF we came in here with,
		 * then we're done.
		 */
		if (iflevel == 1)
			return (p);
		break;
	case '.':
		/*
		 * Endif.
		 * If this matches the IF we came in here with,
		 * then we're done.
		 */
		if (--iflevel == 0)
			return (p);
		break;
	case '\\':
		/*
		 * Backslash escapes the next character.
		 */
		if (p[1] != '\0')
			++p;
		break;
	case '\0':
		/*
		 * Whoops.  Hit end of string.
		 * This is a malformed conditional, but just treat it
		 * as if all active conditionals ends here.
		 */
		return (p-1);
	}
	/*NOTREACHED*/
}

/*
 * Decode a char that represents a position on the screen.
 */
static constant char * wherechar(char constant *p, int *wp)
{
	switch (*p)
	{
	case 'b': case 'd': case 'l': case 'p': case 'P':
		switch (*++p)
		{
		case 't':   *wp = TOP;                  break;
		case 'm':   *wp = MIDDLE;               break;
		case 'b':   *wp = BOTTOM;               break;
		case 'B':   *wp = BOTTOM_PLUS_ONE;      break;
		case 'j':   *wp = sindex_from_sline(jump_sline); break;
		default:    *wp = TOP;  p--;            break;
		}
	}
	return (p);
}

/*
 * Construct a message based on a prototype string.
 */
public constant char * pr_expand(constant char *proto)
{
	constant char *p;
	char c;
	int where;

	mp = message;

	if (*proto == '\0')
		return ("");

	for (p = proto;  *p != '\0';  p++)
	{
		switch (*p)
		{
		default: /* Just put the character in the message */
			ap_char(*p);
			break;
		case '\\': /* Backslash escapes the next character */
			if (p[1] != '\0')
				ap_char(*++p);
			break;
		case '?': /* Conditional (IF) */
			if ((c = *++p) == '\0')
				--p;
			else
			{
				where = 0;
				p = wherechar(p, &where);
				if (!cond(c, where))
					p = skipcond(p);
			}
			break;
		case ':': /* ELSE */
			p = skipcond(p);
			break;
		case '.': /* ENDIF */
			break;
		case '%': /* Percent escape */
			if ((c = *++p) == '\0')
				--p;
			else
			{
				where = 0;
				p = wherechar(p, &where);
				protochar(c, where);
			}
			break;
		}
	}

	if (mp == message)
		return ("");
	return (message);
}

/*
 * Return a message suitable for printing by the "=" command.
 */
public constant char * eq_message(void)
{
	return (pr_expand(eqproto));
}

/*
 * Return a prompt.
 * This depends on the prompt type (SHORT, MEDIUM, LONG), etc.
 * If we can't come up with an appropriate prompt, return NULL
 * and the caller will prompt with a colon.
 */
public constant char * pr_string(void)
{
	constant char *prompt;
	int type;

	type = (!less_is_more) ? pr_type : pr_type ? 0 : 1;
	prompt = pr_expand((ch_getflags() & CH_HELPFILE) ?
				hproto : prproto[type]);
	new_file = FALSE;
	return (prompt);
}

/*
 * Return a message suitable for printing while waiting in the F command.
 */
public constant char * wait_message(void)
{
	return (pr_expand(wproto));
}