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#ifndef lint
static char *RCSid = "$Id: help.c,v 3.26 92/03/24 22:34:24 woo Exp Locker: woo $";
#endif

/* GNUPLOT - help.c */
/*
 * Copyright (C) 1986, 1987, 1990, 1991, 1992   Thomas Williams, Colin Kelley
 *
 * Permission to use, copy, and distribute this software and its
 * documentation for any purpose with or without fee is hereby granted, 
 * provided that the above copyright notice appear in all copies and 
 * that both that copyright notice and this permission notice appear 
 * in supporting documentation.
 *
 * Permission to modify the software is granted, but not the right to
 * distribute the modified code.  Modifications are to be distributed 
 * as patches to released version.
 *  
 * This software is provided "as is" without express or implied warranty.
 * 
 *
 * AUTHORS
 * 
 *   Original Software:
 *     Thomas Williams,  Colin Kelley.
 * 
 *   Gnuplot 2.0 additions:
 *       Russell Lang, Dave Kotz, John Campbell.
 *
 *   Gnuplot 3.0 additions:
 *       Gershon Elber and many others.
 * 
 * Send your comments or suggestions to 
 *  info-gnuplot@ames.arc.nasa.gov.
 * This is a mailing list; to join it send a note to 
 *  info-gnuplot-request@ames.arc.nasa.gov.  
 * Send bug reports to
 *  bug-gnuplot@ames.arc.nasa.gov.
 */

#include <stdio.h>

extern int errno;

extern int strcmp();
extern int strlen();
extern char *strcpy();
extern char *strncpy();
extern char *strcat();
extern char *strncat();
extern char *getenv();
extern FILE *fopen();
extern char *malloc();

extern int instring();

#define	SAME	0	/* for strcmp() */

#include "help.h"	/* values passed back */

/* help -- help subsystem that understands defined keywords
**
** Looks for the desired keyword in the help file at runtime, so you
** can give extra help or supply local customizations by merely editing
** the help file.
**
** The original (single-file) idea and algorithm is by John D. Johnson,
** Hewlett-Packard Company.  Thanx and a tip of the Hatlo hat!
**
** Much extension by David Kotz for use in gnutex, and then in gnuplot.
** Added output paging support, both unix and builtin. Rewrote completely
** to read helpfile into memory, avoiding reread of help file. 12/89.
**
** Modified by Russell Lang to avoid reading completely into memory
** if MSDOS defined.  This uses much less memory.  6/91
**
** The help file looks like this (the question marks are really in column 1):
**
** 	?topic
** 	This line is printed when the user wants help on "topic".
** 	?keyword
** 	?Keyword
** 	?KEYWORD
** 	These lines will be printed on the screen if the user wanted
** 	help on "keyword", "Keyword", or "KEYWORD".  No casefolding is
**	done on the keywords.
** 	?subject
** 	?alias
** 	This line is printed for help on "subject" and "alias".
** 	?
**	??
** 	Since there is a null keyword for this line, this section
** 	is printed when the user wants general help (when a help
** 	keyword isn't given).  A command summary is usually here.
**	Notice that the null keyword is equivalent to a "?" keyword
**	here, because of the '?' and '??' topic lines above.
**   If multiple keywords are given, the first is considered the 
**   'primary' keyword. This affects a listing of available topics.
** 	?last-subject
** 	Note that help sections are terminated by the start of the next
** 	'?' entry or by EOF.  So you can't have a leading '?' on a line
** 	of any help section.  You can re-define the magic character to
**	recognize in column 1, though, if '?' is too useful.  (Try ^A.)
*/

#define	KEYFLAG	'?'	/* leading char in help file topic lines */

/*
** Calling sequence:
**	int result;		# 0 == success
**	char *keyword;		# topic to give help on
**	char *pathname;		# path of help file
**      int subtopics;		# set to TRUE if only subtopics to be listed
**				# returns TRUE if subtopics were found
**	result = help(keyword, pathname, &subtopics);
** Sample:
**	cmd = "search\n";
**	helpfile = "/usr/local/lib/program/program.help";
**	subtopics = FALSE;
**	if (help(cmd, helpfile, &subtopics) != H_FOUND)
**		printf("Sorry, no help for %s", cmd);
**
**
** Speed this up by replacing the stdio calls with open/close/read/write.
*/
#ifdef	WDLEN
#  define	PATHSIZE	WDLEN
#else
#  define	PATHSIZE	BUFSIZ
#endif

typedef int boolean;
#ifndef TRUE
#define TRUE (1)
#define FALSE (0)
#endif

typedef struct line_s LINEBUF;
struct line_s {
    char *line;			/* the text of this line */
    LINEBUF *next;			/* the next line */
};

typedef struct linkey_s LINKEY;
struct linkey_s {
    char *key;				/* the name of this key */
    long pos;			    /* ftell position */
    LINEBUF *text;			/* the text for this key */
    boolean primary;		/* TRUE -> is a primary name for a text block */
    LINKEY *next;			/* the next key in linked list */
};

typedef struct key_s KEY;
struct key_s {
    char *key;				/* the name of this key */
    long pos;			    /* ftell position */
    LINEBUF *text;			/* the text for this key */
    boolean primary;		/* TRUE -> is a primary name for a text block */
};
static LINKEY *keylist = NULL;	/* linked list of keys */
static KEY *keys = NULL;		/* array of keys */
static int keycount = 0;		/* number of keys */
static FILE *helpfp = NULL;

static int LoadHelp();
static void sortkeys();
static int keycomp();
static LINEBUF *storeline();
static LINKEY *storekey();
static KEY *FindHelp();
static boolean Ambiguous();

/* Help output */
static void PrintHelp();
static void ShowSubtopics();
static void StartOutput();
static void OutLine();
static void EndOutput();
static FILE *outfile;		/* for unix pager, if any */
static int pagelines;		/* count for builtin pager */
#define SCREENSIZE 24		/* lines on screen (most have at least 24) */

/* help:
 * print a help message 
 * also print available subtopics, if subtopics is TRUE
 */
help(keyword, path, subtopics)
	char *keyword;		/* on this topic */
	char *path;			/* from this file */
	boolean *subtopics;	/* (in) - subtopics only? */
						/* (out) - are there subtopics? */
{
    static char oldpath[PATHSIZE] = "";	/* previous help file */
    int status;			/* result of LoadHelp */
    KEY *key;			/* key that matches keyword */

    /*
	** Load the help file if necessary (say, first time we enter this routine,
	** or if the help file changes from the last time we were called).
	** Also may occur if in-memory copy was freed.
	** Calling routine may access errno to determine cause of H_ERROR.
	*/
    errno = 0;
    if (strncmp(oldpath, path, PATHSIZE) != SAME)
	 FreeHelp();
    if (keys == NULL) {
	   status = LoadHelp(path);
	   if (status == H_ERROR)
		return(status);

	   /* save the new path in oldpath */
	   if (strlen(path) < PATHSIZE)
		(void) strcpy(oldpath, path);
	   else {				/* not enough room in oldpath, sigh */
		  (void) strncpy(oldpath, path, PATHSIZE - 1);
		  oldpath[PATHSIZE - 1] = '\0';
	   }
    }

    /* look for the keyword in the help file */
    key = FindHelp(keyword);
    if (key != NULL) {
	   /* found the keyword: print help and return */
	   PrintHelp(key, subtopics);
	   status = H_FOUND;
    } else {
	   status = H_NOTFOUND;
    }

    return(status);
}

/* we only read the file once, into memory
 * except for MSDOS when we don't read all the file -
 * just the keys and location of the text
 */
static int
LoadHelp(path)
	char *path;
{
    LINKEY *key;			/* this key */
    long pos;				/* ftell location within help file */
    char buf[BUFSIZ];		/* line from help file */
    LINEBUF *head;			/* head of text list  */
    LINEBUF *firsthead = NULL;
    boolean primary;		/* first ? line of a set is primary */
    boolean flag;

    if ((helpfp = fopen(path, "r")) == NULL) {
	   /* can't open help file, so error exit */
	   return (H_ERROR);
    }

    /*
	** The help file is open.  Look in there for the keyword.
	*/
    (void) fgets(buf, BUFSIZ - 1, helpfp);
    while (!feof(helpfp)) {
	   /*
	    ** Make an entry for each synonym keyword
	    */
	   primary = TRUE;
	   while (buf[0] == KEYFLAG) {
		  key = storekey(buf+1);	/* store this key */
	      key->primary = primary;
	      key->text = NULL;			/* fill in with real value later */
	      key->pos = 0;				/* fill in with real value later */
		  primary = FALSE;
		  pos = ftell(helpfp);
		  if (fgets(buf, BUFSIZ - 1, helpfp) == (char *)NULL)
		    break;
	   }
	   /*
	    ** Now store the text for this entry.
	    ** buf already contains the first line of text.
	    */
#ifndef MSDOS
	   firsthead = storeline(buf);
	   head = firsthead;
#endif
	   while ( (fgets(buf, BUFSIZ - 1, helpfp) != (char *)NULL)
		&& (buf[0] != KEYFLAG) ){
#ifndef MSDOS
		  /* save text line */
		  head->next = storeline(buf);
		  head = head->next;
#endif
	   }
	   /* make each synonym key point to the same text */
	   do {
	      key->pos = pos;
	      key->text = firsthead;
	      flag = key->primary;
	      key = key->next;
	   } while ( flag!=TRUE  &&  key!=NULL );
    }
#ifndef MSDOS
    (void) fclose(helpfp);
#endif

    /* we sort the keys so we can use binary search later */
    sortkeys();
	return(H_FOUND); /* ok */
}

/* make a new line buffer and save this string there */
static LINEBUF *
storeline(text)
	char *text;
{
    LINEBUF *new;

    new = (LINEBUF *)malloc(sizeof(LINEBUF));
    if (new == NULL)
	 int_error("not enough memory to store help file", -1);
    if (text != NULL) {
	   new->line = (char *) malloc((unsigned int)(strlen(text)+1));
	   if (new->line == NULL)
		int_error("not enough memory to store help file", -1);
	   (void) strcpy(new->line, text);
    } else
	 new->line = NULL;

    new->next = NULL;

    return(new);
}

/* Add this keyword to the keys list, with the given text */
static LINKEY *
storekey(key)
	char *key;
{
    LINKEY *new;

    key[strlen(key)-1] = '\0'; /* cut off \n  */

    new = (LINKEY *)malloc(sizeof(LINKEY));
    if (new == NULL)
	 int_error("not enough memory to store help file", -1);
    new->key = (char *) malloc((unsigned int)(strlen(key)+1));
    if (new->key == NULL)
	 int_error("not enough memory to store help file", -1);
    (void) strcpy(new->key, key);

    /* add to front of list */
    new->next = keylist;
    keylist = new;
    keycount++;
	return(new);
}

/* we sort the keys so we can use binary search later */
/* We have a linked list of keys and the number.
 * to sort them we need an array, so we reform them into an array,
 * and then throw away the list.
 */
static void
sortkeys()
{
    LINKEY *p,*n;			/* pointers to linked list */
    int i;				/* index into key array */
    
    /* allocate the array */
    keys = (KEY *)malloc((unsigned int)((keycount+1) * sizeof(KEY)));
    if (keys == NULL)
	 int_error("not enough memory to store help file", -1);
    
    /* copy info from list to array, freeing list */
    for (p = keylist, i = 0; p != NULL; p = n, i++) {
	   keys[i].key = p->key;
	   keys[i].pos = p->pos;
	   keys[i].text = p->text;
	   keys[i].primary = p->primary;
	   n = p->next;
	   free( (char *)p );
    }

    /* a null entry to terminate subtopic searches */
    keys[keycount].key = NULL;
    keys[keycount].pos = 0;
    keys[keycount].text = NULL;

    /* sort the array */
    /* note that it only moves objects of size (two pointers + long + int) */
    /* it moves no strings */
    qsort((char *)keys, keycount, sizeof(KEY), keycomp);
}

static int
keycomp(a, b)
	KEY *a,*b;
{
    return (strcmp(a->key, b->key));
}

/* Free the help file from memory. */
/* May be called externally if space is needed */
void
FreeHelp()
{
    int i;				/* index into keys[] */
    LINEBUF *t, *next;

    if (keys == NULL)
	 return;

    for (i = 0; i < keycount; i++) {
	   free( (char *)keys[i].key );
	   if (keys[i].primary)   /* only try to release text once! */
	   for (t = keys[i].text; t != NULL; t = next) {
		  free( (char *)t->line );
		  next = t->next;
		  free( (char *)t );
	   }
    }
    free( (char *)keys );
    keys = NULL;
    keycount = 0;
#ifdef MSDOS
    (void) fclose(helpfp);
#endif
}

/* FindHelp:
 *  Find the key that matches the keyword.
 *  The keys[] array is sorted by key.
 *  We could use a binary search, but a linear search will aid our
 *  attempt to allow abbreviations. We search for the first thing that
 *  matches all the text we're given. If not an exact match, then
 *  it is an abbreviated match, and there must be no other abbreviated
 *  matches -- for if there are, the abbreviation is ambiguous. 
 *  We print the ambiguous matches in that case, and return not found.
 */
static KEY *				/* NULL if not found */
FindHelp(keyword)
	char *keyword;			/* string we look for */
{
    KEY *key;
    int len = strlen(keyword);
    int compare;

    for (key = keys, compare = 1; key->key != NULL && compare > 0; key++) {
	   compare = strncmp(keyword, key->key, len);
	   if (compare == 0)	/* we have a match! */
		if (!Ambiguous(key, len)) {
		    /* non-ambiguous abbreviation */
		    (void) strcpy(keyword, key->key); /* give back the full spelling */
		    return(key);		/* found!! */
		}
    }

    /* not found, or ambiguous */
    return(NULL);
}

/* Ambiguous:
 * Check the key for ambiguity up to the given length.
 * It is ambiguous if it is not a complete string and there are other
 * keys following it with the same leading substring.
 */
static boolean
Ambiguous(key, len)
	KEY *key;
	int len;
{
    char *first;
    char *prev;
    boolean status = FALSE;	/* assume not ambiguous */
    int compare;
    int sublen;

    if (key->key[len] == '\0')
	 return(FALSE);
    
    for (prev = first = key->key, compare = 0, key++;
	    key->key != NULL && compare == 0; key++) {
	   compare = strncmp(first, key->key, len);
	   if (compare == 0) {
		  /* So this key matches the first one, up to len.
		   * But is it different enough from the previous one
		   * to bother printing it as a separate choice?
		   */
		  sublen = instring(prev+len, ' ');
		  if (strncmp(key->key, prev, len+sublen) != 0) {
			 /* yup, this is different up to the next space */
			 if (!status) {
				/* first one we have printed is special */
				fprintf(stderr, 
					   "Ambiguous request '%.*s'; possible matches:\n",
					   len, first);
				fprintf(stderr, "\t%s\n", prev);
				status = TRUE;
			 }
			 fprintf(stderr, "\t%s\n", key->key);
			 prev = key->key;
		  }
	   }
    }
    
    return(status);
}

/* PrintHelp:
 * print the text for key
 */
static void
PrintHelp(key, subtopics)
	KEY *key;
	boolean *subtopics;		/* (in) - subtopics only? */
						/* (out) - are there subtopics? */
{
    LINEBUF *t;
#ifdef MSDOS
    char buf[BUFSIZ];		/* line from help file */
#endif

    StartOutput();

    if (subtopics == NULL || !*subtopics) {
#ifdef MSDOS
	   fseek(helpfp,key->pos,0);
	   while ( (fgets(buf, BUFSIZ - 1, helpfp) != (char *)NULL)
			&& (buf[0] != KEYFLAG) ) {
		  OutLine(buf);
	   }
#else
	   for (t = key->text; t != NULL; t = t->next)
		OutLine(t->line);		/* print text line */
#endif
    }

    ShowSubtopics(key, subtopics);
    OutLine("\n");

    EndOutput();
}

/* ShowSubtopics:
 *  Print a list of subtopic names
 */
#define PER_LINE 4

static void
ShowSubtopics(key, subtopics)
	KEY *key;				/* the topic */
	boolean *subtopics;		/* (out) are there any subtopics */
{
    int subt = 0;			/* printed any subtopics yet? */
    KEY *subkey;			/* subtopic key */
    int len;				/* length of key name */
    char line[BUFSIZ];		/* subtopic output line */
    char *start;			/* position of subname in key name */
    int sublen;			/* length of subname */
    int pos;
    char *prev = NULL;		/* the last thing we put on the list */

    *line = '\0';
    len = strlen(key->key);

    for (subkey = key+1; subkey->key != NULL; subkey++) {
	   if (strncmp(subkey->key, key->key, len) == 0) {
		  /* find this subtopic name */
		  start = subkey->key + len;
		  if (len > 0)
		    if (*start == ' ')
			 start++;		/* skip space */
		    else
			 break;		/* not the same topic after all  */
		  else			/* here we are looking for main topics */
		    if (!subkey->primary)
			 continue;	/* not a main topic */
		  sublen = instring(start, ' ');
		  if (prev == NULL || strncmp(start, prev, sublen) != 0) {
			 if (subt == 0) {
				subt++;
				if (len)
				  (void) sprintf(line, "\nSubtopics available for %s:\n", 
						key->key);
				else
				  (void) sprintf(line, "\nHelp topics available:\n");
				OutLine(line);
				*line = '\0';
				pos = 0;
			 }
			 if (pos == PER_LINE) {
				(void) strcat(line, "\n");
				OutLine(line);
				*line = '\0';
				pos = 0;
			 }
			 (void) strcat(line, "\t");
			 (void) strncat(line, start, sublen);
			 pos++;
			 prev = start;
		  }
	   } else {
		  /* new topic */
		  break;
	   }
    }
    
    /* put out the last line */
    if (subt > 0 && pos > 0) {
	   (void) strcat(line, "\n");
	   OutLine(line);
    }
    
/*
    if (subt == 0) {
	   OutLine("\n");
	   OutLine("No subtopics available\n");
    }
*/
    
    if (subtopics)
	 *subtopics = (subt != 0);
}


/* StartOutput:
 * Open a file pointer to a pipe to user's $PAGER, if there is one,
 * otherwise use our own pager.
 */
static void
StartOutput()
{
#ifdef unix
    char *pager_name = getenv("PAGER");
    extern FILE *popen();

    if (pager_name != NULL && *pager_name != '\0')
	 if ((outfile = popen(pager_name, "w")) != (FILE *)NULL)
	   return;			/* success */
    outfile = stderr;
    /* fall through to built-in pager */
#endif

    /* built-in pager */
    pagelines = 0;
}

/* write a line of help output  */
/* line should contain only one \n, at the end */
static void
OutLine(line)
	char *line;
{
    int c;				/* dummy input char */
#ifdef unix
    if (outfile != stderr) {
	   fputs(line, outfile);
	   return;
    }
#endif

    /* built-in dumb pager */
    /* leave room for prompt line */
    if (pagelines >= SCREENSIZE - 2) {
	   fprintf(stderr,"Press return for more: ");
	   do 
		c = getchar();
	   while (c != EOF && c != '\n');
	   pagelines = 0;
    }
    fputs(line, stderr);
    pagelines++;
}

static void
EndOutput()
{
#ifdef unix
    extern int pclose();

    if (outfile != stderr)
	 (void) pclose(outfile);
#endif
}
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