/*
 * $LynxId: LYHistory.c,v 1.94 2021/06/09 22:55:43 tom Exp $
 */
#include <HTUtils.h>
#include <HTTP.h>
#include <GridText.h>
#include <HTAlert.h>
#include <HText.h>
#include <LYGlobalDefs.h>
#include <LYUtils.h>
#include <LYHistory.h>
#include <LYPrint.h>
#include <LYDownload.h>
#include <LYOptions.h>
#include <LYKeymap.h>
#include <LYList.h>
#include <LYShowInfo.h>
#include <LYStrings.h>
#include <LYCharUtils.h>
#include <LYCharSets.h>
#include <LYrcFile.h>
#ifdef DISP_PARTIAL
#include <LYMainLoop.h>
#endif

#ifdef DIRED_SUPPORT
#include <LYUpload.h>
#include <LYLocal.h>
#endif /* DIRED_SUPPORT */

#include <LYexit.h>
#include <LYLeaks.h>
#include <HTCJK.h>

HTList *Visited_Links = NULL;	/* List of safe popped docs. */
int Visited_Links_As = VISITED_LINKS_AS_LATEST | VISITED_LINKS_REVERSE;

static VisitedLink *PrevVisitedLink = NULL;	/* NULL on auxiliary */
static VisitedLink *PrevActiveVisitedLink = NULL;	/* Last non-auxillary */
static VisitedLink Latest_first;
static VisitedLink Latest_last;
static VisitedLink *Latest_tree;
static VisitedLink *First_tree;
static VisitedLink *Last_by_first;

int nhist_extra;

#ifdef LY_FIND_LEAKS
static int already_registered_free_messages_stack = 0;
static int already_registered_clean_all_history = 0;
#endif

#ifdef LY_FIND_LEAKS
/*
 * Utility for freeing the list of visited links.  - FM
 */
static void Visited_Links_free(void)
{
    VisitedLink *vl;
    HTList *cur = Visited_Links;

    PrevVisitedLink = NULL;
    PrevActiveVisitedLink = NULL;
    if (!cur)
	return;

    while (NULL != (vl = (VisitedLink *) HTList_nextObject(cur))) {
	FREE(vl->address);
	FREE(vl->title);
	FREE(vl);
    }
    HTList_delete(Visited_Links);
    Visited_Links = NULL;
    Latest_last.prev_latest = &Latest_first;
    Latest_first.next_latest = &Latest_last;
    Last_by_first = Latest_tree = First_tree = 0;
    return;
}
#endif /* LY_FIND_LEAKS */

#ifdef DEBUG
static void trace_history(const char *tag)
{
    if (TRACE) {
	CTRACE((tfp, "HISTORY %s %d/%u (%d extra)\n",
		tag, nhist, size_history, nhist_extra));
	CTRACE_FLUSH(tfp);
    }
}
#else
#define trace_history(tag)	/* nothing */
#endif /* DEBUG */

/*
 * Utility for listing visited links, making any repeated links the most
 * current in the list.  - FM
 */
void LYAddVisitedLink(DocInfo *doc)
{
    VisitedLink *tmp;
    HTList *cur;
    const char *title = (doc->title ? doc->title : NO_TITLE);

    if (isEmpty(doc->address)) {
	PrevVisitedLink = NULL;
	return;
    }

    /*
     * Exclude POST or HEAD replies, and bookmark, menu or list files.  - FM
     */
    if (doc->post_data || doc->isHEAD || doc->bookmark ||
	(			/* special url or a temp file */
	    (!StrNCmp(doc->address, "LYNX", 4) ||
	     !StrNCmp(doc->address, "file://localhost/", 17)))) {
	int related = 1;	/* First approximation only */

	if (LYIsUIPage(doc->address, UIP_HISTORY) ||
	    LYIsUIPage(doc->address, UIP_VLINKS) ||
	    LYIsUIPage(doc->address, UIP_SHOWINFO) ||
	    isLYNXMESSAGES(doc->address) ||
	    ((related = 0) != 0) ||
#ifdef DIRED_SUPPORT
	    LYIsUIPage(doc->address, UIP_DIRED_MENU) ||
	    LYIsUIPage(doc->address, UIP_UPLOAD_OPTIONS) ||
	    LYIsUIPage(doc->address, UIP_PERMIT_OPTIONS) ||
#endif /* DIRED_SUPPORT */
	    LYIsUIPage(doc->address, UIP_PRINT_OPTIONS) ||
	    LYIsUIPage(doc->address, UIP_DOWNLOAD_OPTIONS) ||
	    LYIsUIPage(doc->address, UIP_OPTIONS_MENU) ||
	    isLYNXEDITMAP(doc->address) ||
	    isLYNXKEYMAP(doc->address) ||
	    LYIsUIPage(doc->address, UIP_LIST_PAGE) ||
#ifdef USE_ADDRLIST_PAGE
	    LYIsUIPage(doc->address, UIP_ADDRLIST_PAGE) ||
#endif
	    LYIsUIPage(doc->address, UIP_CONFIG_DEF) ||
	    LYIsUIPage(doc->address, UIP_LYNXCFG) ||
	    isLYNXCOOKIE(doc->address) ||
	    LYIsUIPage(doc->address, UIP_TRACELOG)) {
	    if (!related)
		PrevVisitedLink = NULL;
	    return;
	}
    }

    if (!Visited_Links) {
	Visited_Links = HTList_new();
#ifdef LY_FIND_LEAKS
	atexit(Visited_Links_free);
#endif
	Latest_last.prev_latest = &Latest_first;
	Latest_first.next_latest = &Latest_last;
	Latest_last.next_latest = NULL;		/* Find bugs quick! */
	Latest_first.prev_latest = NULL;
	Last_by_first = Latest_tree = First_tree = NULL;
    }

    cur = Visited_Links;
    while (NULL != (tmp = (VisitedLink *) HTList_nextObject(cur))) {
	if (!strcmp(NonNull(tmp->address),
		    NonNull(doc->address))) {
	    PrevVisitedLink = PrevActiveVisitedLink = tmp;
	    /* Already visited.  Update the last-visited info. */
	    if (tmp->next_latest == &Latest_last)	/* optimization */
		return;

	    /* Remove from "latest" chain */
	    tmp->prev_latest->next_latest = tmp->next_latest;
	    tmp->next_latest->prev_latest = tmp->prev_latest;

	    /* Insert at the end of the "latest" chain */
	    Latest_last.prev_latest->next_latest = tmp;
	    tmp->prev_latest = Latest_last.prev_latest;
	    tmp->next_latest = &Latest_last;
	    Latest_last.prev_latest = tmp;
	    return;
	}
    }

    if ((tmp = typecalloc(VisitedLink)) == NULL)
	outofmem(__FILE__, "LYAddVisitedLink");

    StrAllocCopy(tmp->address, doc->address);
    LYformTitle(&(tmp->title), title);

    /* First-visited chain */
    HTList_appendObject(Visited_Links, tmp);	/* At end */
    tmp->prev_first = Last_by_first;
    Last_by_first = tmp;

    /* Tree structure */
    if (PrevVisitedLink) {
	VisitedLink *a = PrevVisitedLink;
	VisitedLink *b = a->next_tree;
	int l = PrevVisitedLink->level;

	/* Find last on the deeper levels */
	while (b && b->level > l)
	    a = b, b = b->next_tree;

	if (!b)			/* a == Latest_tree */
	    Latest_tree = tmp;
	tmp->next_tree = a->next_tree;
	a->next_tree = tmp;

	tmp->level = PrevVisitedLink->level + 1;
    } else {
	if (Latest_tree)
	    Latest_tree->next_tree = tmp;
	tmp->level = 0;
	tmp->next_tree = NULL;
	Latest_tree = tmp;
    }
    PrevVisitedLink = PrevActiveVisitedLink = tmp;
    if (!First_tree)
	First_tree = tmp;

    /* "latest" chain */
    Latest_last.prev_latest->next_latest = tmp;
    tmp->prev_latest = Latest_last.prev_latest;
    tmp->next_latest = &Latest_last;
    Latest_last.prev_latest = tmp;

    return;
}

/*
 * Returns true if this is a page that we would push onto the stack if not
 * forced.  If docurl is NULL, only the title is considered; otherwise also
 * check the URL whether it is (likely to be) a generated special page.
 */
BOOLEAN LYwouldPush(const char *title,
		    const char *docurl)
{
    BOOLEAN rc = FALSE;

    /*
     * All non-pushable generated pages have URLs that begin with
     * "file://localhost/" and end with HTML_SUFFIX.  - kw
     */
    if (docurl) {
	size_t ulen;

	if (StrNCmp(docurl, "file://localhost/", 17) != 0 ||
	    (ulen = strlen(docurl)) <= strlen(HTML_SUFFIX) ||
	    strcmp(docurl + ulen - strlen(HTML_SUFFIX), HTML_SUFFIX) != 0) {
	    /*
	     * If it is not a local HTML file, it may be a Web page that
	     * accidentally has the same title.  So return TRUE now.  - kw
	     */
	    return TRUE;
	}
    }

    if (docurl) {
	rc = (BOOLEAN)
	    !(LYIsUIPage(docurl, UIP_HISTORY)
	      || LYIsUIPage(docurl, UIP_PRINT_OPTIONS)
#ifdef DIRED_SUPPORT
	      || LYIsUIPage(docurl, UIP_DIRED_MENU)
	      || LYIsUIPage(docurl, UIP_UPLOAD_OPTIONS)
	      || LYIsUIPage(docurl, UIP_PERMIT_OPTIONS)
#endif /* DIRED_SUPPORT */
	    );
    } else {
	rc = (BOOLEAN)
	    !(!strcmp(title, HISTORY_PAGE_TITLE)
	      || !strcmp(title, PRINT_OPTIONS_TITLE)
#ifdef DIRED_SUPPORT
	      || !strcmp(title, DIRED_MENU_TITLE)
	      || !strcmp(title, UPLOAD_OPTIONS_TITLE)
	      || !strcmp(title, PERMIT_OPTIONS_TITLE)
#endif /* DIRED_SUPPORT */
	    );
    }
    return rc;
}

/*
 * Free post-data for 'DocInfo'
 */
void LYFreePostData(DocInfo *doc)
{
    BStrFree(doc->post_data);
    FREE(doc->post_content_type);
}

/*
 * Free strings associated with a 'DocInfo' struct.
 */
void LYFreeDocInfo(DocInfo *doc)
{
    FREE(doc->title);
    FREE(doc->address);
    FREE(doc->bookmark);
    LYFreePostData(doc);
}

/*
 * Free the information in the last history entry.
 */
static void clean_extra_history(void)
{
    trace_history("clean_extra_history");
    nhist += nhist_extra;
    while (nhist_extra > 0) {
	nhist--;
	LYFreeDocInfo(&HDOC(nhist));
	nhist_extra--;
    }
    trace_history("...clean_extra_history");
}

/*
 * Free the entire history stack, for auditing memory leaks.
 */
#ifdef LY_FIND_LEAKS
static void clean_all_history(void)
{
    trace_history("clean_all_history");
    clean_extra_history();
    while (nhist > 0) {
	nhist--;
	LYFreeDocInfo(&HDOC(nhist));
    }
    trace_history("...clean_all_history");
}
#endif

/* FIXME What is the relationship to are_different() from the mainloop?! */
static int are_identical(HistInfo * doc, DocInfo *doc1)
{
    return (STREQ(doc1->address, doc->hdoc.address)
	    && BINEQ(doc1->post_data, doc->hdoc.post_data)
	    && !strcmp(NonNull(doc1->bookmark),
		       NonNull(doc->hdoc.bookmark))
	    && doc1->isHEAD == doc->hdoc.isHEAD);
}

void LYAllocHistory(unsigned entries)
{
    CTRACE((tfp, "LYAllocHistory %u vs %u\n", entries, size_history));
    if (entries + 1 >= size_history) {
	size_t want;
	unsigned save = size_history;

	size_history += (entries + 2) * 2;
	want = ((size_t) size_history) * sizeof(*history);

	if (history == 0) {
	    history = typecallocn(HistInfo, want);
	} else {
	    history = typeRealloc(HistInfo, history, want);
	    memset(&history[save], 0, size_history - save);
	}
	if (history == 0)
	    outofmem(__FILE__, "LYAllocHistory");
    }
    CTRACE((tfp, "...LYAllocHistory %u vs %u\n", entries, size_history));
}

/*
 * Push the current filename, link and line number onto the history list.
 */
int LYpush(DocInfo *doc, int force_push)
{
    /*
     * Don't push NULL file names.
     */
    if (*doc->address == '\0')
	return 0;

    /*
     * Check whether this is a document we don't push unless forced.  - FM
     */
    if (!force_push) {
	/*
	 * Don't push the history, printer, or download lists.
	 */
	if (!LYwouldPush(doc->title, doc->address)) {
	    if (!LYforce_no_cache)
		LYoverride_no_cache = TRUE;
	    return 0;
	}
    }

    /*
     * If file is identical to one before it, don't push it.
     * But do not duplicate it if there is only one on the stack,
     * note that HDOC() starts from 0, so nhist should be > 0.
     */
    if (nhist >= 1 && are_identical(&(history[nhist - 1]), doc)) {
	if (HDOC(nhist - 1).internal_link == doc->internal_link) {
	    /* But it is nice to have the last position remembered!
	       - kw */
	    HDOC(nhist - 1).link = doc->link;
	    HDOC(nhist - 1).line = doc->line;
	    return 0;
	}
    }

    /*
     * If file is identical to the current document, just move the pointer.
     */
    if (nhist_extra >= 1 && are_identical(&(history[nhist]), doc)) {
	HDOC(nhist).link = doc->link;
	HDOC(nhist).line = doc->line;
	nhist_extra--;
	LYAllocHistory((unsigned) nhist);
	nhist++;
	trace_history("LYpush: just move the cursor");
	return 1;
    }

    clean_extra_history();
#ifdef LY_FIND_LEAKS
    if (!already_registered_clean_all_history) {
	already_registered_clean_all_history = 1;
	atexit(clean_all_history);
    }
#endif

    /*
     * OK, push it...
     */
    LYAllocHistory((unsigned) nhist);
    HDOC(nhist).link = doc->link;
    HDOC(nhist).line = doc->line;

    HDOC(nhist).title = NULL;
    LYformTitle(&(HDOC(nhist).title), doc->title);

    HDOC(nhist).address = NULL;
    StrAllocCopy(HDOC(nhist).address, doc->address);

    HDOC(nhist).post_data = NULL;
    BStrCopy(HDOC(nhist).post_data, doc->post_data);

    HDOC(nhist).post_content_type = NULL;
    StrAllocCopy(HDOC(nhist).post_content_type, doc->post_content_type);

    HDOC(nhist).bookmark = NULL;
    StrAllocCopy(HDOC(nhist).bookmark, doc->bookmark);

    HDOC(nhist).isHEAD = doc->isHEAD;
    HDOC(nhist).safe = doc->safe;

    HDOC(nhist).internal_link = FALSE;	/* by default */
    history[nhist].intern_seq_start = -1;	/* by default */
    if (doc->internal_link) {
	/* Now some tricky stuff: if the caller thinks that the doc
	   to push was the result of following an internal
	   (fragment) link, we check whether we believe it.
	   It is only accepted as valid if the immediately preceding
	   item on the history stack is actually the same document
	   except for fragment and location info.  I.e. the Parent
	   Anchors are the same.
	   Also of course this requires that this is not the first
	   history item. - kw */
	if (nhist > 0) {
	    DocAddress WWWDoc;
	    HTParentAnchor *thisparent, *thatparent = NULL;

	    WWWDoc.address = doc->address;
	    WWWDoc.post_data = doc->post_data;
	    WWWDoc.post_content_type = doc->post_content_type;
	    WWWDoc.bookmark = doc->bookmark;
	    WWWDoc.isHEAD = doc->isHEAD;
	    WWWDoc.safe = doc->safe;
	    thisparent =
		HTAnchor_findAddress(&WWWDoc);
	    /* Now find the ParentAnchor for the previous history
	     * item - kw
	     */
	    if (thisparent) {
		/* If the last-pushed item is a LYNXIMGMAP but THIS one
		 * isn't, compare the physical URLs instead. - kw
		 */
		if (isLYNXIMGMAP(HDOC(nhist - 1).address) &&
		    !isLYNXIMGMAP(doc->address)) {
		    WWWDoc.address = HDOC(nhist - 1).address + LEN_LYNXIMGMAP;
		    /*
		     * If THIS item is a LYNXIMGMAP but the last-pushed one
		     * isn't, fake it by using THIS item's address for
		     * thatparent... - kw
		     */
		} else if (isLYNXIMGMAP(doc->address) &&
			   !isLYNXIMGMAP(HDOC(nhist - 1).address)) {
		    char *temp = NULL;

		    StrAllocCopy(temp, STR_LYNXIMGMAP);
		    StrAllocCat(temp, doc->address + LEN_LYNXIMGMAP);
		    WWWDoc.address = temp;
		    WWWDoc.post_content_type = HDOC(nhist - 1).post_content_type;
		    WWWDoc.bookmark = HDOC(nhist - 1).bookmark;
		    WWWDoc.isHEAD = HDOC(nhist - 1).isHEAD;
		    WWWDoc.safe = HDOC(nhist - 1).safe;
		    thatparent =
			HTAnchor_findAddress(&WWWDoc);
		    FREE(temp);
		} else {
		    WWWDoc.address = HDOC(nhist - 1).address;
		}
		if (!thatparent) {	/* if not yet done */
		    WWWDoc.post_data = HDOC(nhist - 1).post_data;
		    WWWDoc.post_content_type = HDOC(nhist - 1).post_content_type;
		    WWWDoc.bookmark = HDOC(nhist - 1).bookmark;
		    WWWDoc.isHEAD = HDOC(nhist - 1).isHEAD;
		    WWWDoc.safe = HDOC(nhist - 1).safe;
		    thatparent =
			HTAnchor_findAddress(&WWWDoc);
		}
		/* In addition to equality of the ParentAnchors, require
		 * that IF we have a HTMainText (i.e., it wasn't just
		 * HTuncache'd by mainloop), THEN it has to be consistent
		 * with what we are trying to push.
		 *
		 * This may be overkill...  - kw
		 */
		if (thatparent == thisparent &&
		    (!HTMainText || HTMainAnchor == thisparent)
		    ) {
		    HDOC(nhist).internal_link = TRUE;
		    history[nhist].intern_seq_start =
			history[nhist - 1].intern_seq_start >= 0 ?
			history[nhist - 1].intern_seq_start : nhist - 1;
		    CTRACE((tfp, "\nLYpush: pushed as internal link, OK\n"));
		}
	    }
	}
	if (!HDOC(nhist).internal_link) {
	    CTRACE((tfp, "\nLYpush: push as internal link requested, %s\n",
		    "but didn't check out!"));
	}
    }
    CTRACE((tfp, "\nLYpush[%d]: address:%s\n        title:%s\n",
	    nhist, doc->address, doc->title));
    nhist++;
    return 1;
}

/*
 * Pop the previous filename, link and line number from the history list.
 */
void LYpop(DocInfo *doc)
{
    if (nhist > 0) {
	clean_extra_history();
	nhist--;

	LYFreeDocInfo(doc);

	*doc = HDOC(nhist);

#ifdef DISP_PARTIAL
	/* assume we pop the 'doc' to show it soon... */
	LYSetNewline(doc->line);	/* reinitialize */
#endif /* DISP_PARTIAL */
	CTRACE((tfp, "LYpop[%d]: address:%s\n     title:%s\n",
		nhist, doc->address, doc->title));
    }
}

/*
 * Move to the previous filename, link and line number from the history list.
 */
void LYhist_prev(DocInfo *doc)
{
    trace_history("LYhist_prev");
    if (nhist > 0 && (nhist_extra || (unsigned) nhist < size_history)) {
	nhist--;
	nhist_extra++;
	LYpop_num(nhist, doc);
	trace_history("...LYhist_prev");
    }
}

/*
 * Called before calling LYhist_prev().
 */
void LYhist_prev_register(DocInfo *doc)
{
    trace_history("LYhist_prev_register");
    if (nhist > 1) {
	if (nhist_extra) {	/* Make something to return back */
	    /* Store the new position */
	    HDOC(nhist).link = doc->link;
	    HDOC(nhist).line = doc->line;
	} else if (LYpush(doc, 0)) {
	    nhist--;
	    nhist_extra++;
	}
	trace_history("...LYhist_prev_register");
    }
}

/*
 * Move to the next filename, link and line number from the history.
 */
int LYhist_next(DocInfo *doc, DocInfo *newdoc)
{
    if (nhist_extra <= 1)	/* == 1 when we are the last one */
	return 0;
    /* Store the new position */
    HDOC(nhist).link = doc->link;
    HDOC(nhist).line = doc->line;
    LYAllocHistory((unsigned) nhist);
    nhist++;
    nhist_extra--;
    LYpop_num(nhist, newdoc);
    return 1;
}

/*
 * Pop the specified hist entry, link and line number from the history list but
 * don't actually remove the entry, just return it.
 * (This procedure is badly named :)
 */
void LYpop_num(int number,
	       DocInfo *doc)
{
    if (number >= 0 && (nhist + nhist_extra) > number) {
	doc->link = HDOC(number).link;
	doc->line = HDOC(number).line;
	StrAllocCopy(doc->title, HDOC(number).title);
	StrAllocCopy(doc->address, HDOC(number).address);
	BStrCopy(doc->post_data, HDOC(number).post_data);
	StrAllocCopy(doc->post_content_type, HDOC(number).post_content_type);
	StrAllocCopy(doc->bookmark, HDOC(number).bookmark);
	doc->isHEAD = HDOC(number).isHEAD;
	doc->safe = HDOC(number).safe;
	doc->internal_link = HDOC(number).internal_link;	/* ?? */
#ifdef DISP_PARTIAL
	/* assume we pop the 'doc' to show it soon... */
	LYSetNewline(doc->line);	/* reinitialize */
#endif /* DISP_PARTIAL */
	if (TRACE) {
	    CTRACE((tfp, "LYpop_num(%d)\n", number));
	    CTRACE((tfp, "  link    %d\n", doc->link));
	    CTRACE((tfp, "  line    %d\n", doc->line));
	    CTRACE((tfp, "  title   %s\n", NonNull(doc->title)));
	    CTRACE((tfp, "  address %s\n", NonNull(doc->address)));
	}
    }
}

/*
 * This procedure outputs the history buffer into a temporary file.
 */
int showhistory(char **newfile)
{
    static char tempfile[LY_MAXPATH] = "\0";
    char *Title = NULL;
    int x = 0;
    FILE *fp0;

    if ((fp0 = InternalPageFP(tempfile, TRUE)) == 0)
	return (-1);

    LYLocalFileToURL(newfile, tempfile);

    LYforce_HTML_mode = TRUE;	/* force this file to be HTML */
    LYforce_no_cache = TRUE;	/* force this file to be new */

    BeginInternalPage(fp0, HISTORY_PAGE_TITLE, HISTORY_PAGE_HELP);

    fprintf(fp0, "<p align=right> <a href=\"%s\">[%s]</a>\n",
	    STR_LYNXMESSAGES, STATUSLINES_TITLE);

    fprintf(fp0, "<pre>\n");

    fprintf(fp0, "<em>%s</em>\n", gettext("You selected:"));
    for (x = nhist + nhist_extra - 1; x >= 0; x--) {
	/*
	 * The number of the document in the hist stack, its title in a link,
	 * and its address.  - FM
	 */
	if (HDOC(x).title != NULL) {
	    StrAllocCopy(Title, HDOC(x).title);
	    LYEntify(&Title, TRUE);
	    LYTrimLeading(Title);
	    LYTrimTrailing(Title);
	    if (*Title == '\0')
		StrAllocCopy(Title, NO_TITLE);
	} else {
	    StrAllocCopy(Title, NO_TITLE);
	}
	fprintf(fp0,
		"%s<em>%d</em>. <tab id=t%d><a href=\"%s%d\">%s</a>\n",
		(x > 99 ? "" : x < 10 ? "  " : " "),
		x, x, STR_LYNXHIST, x, Title);
	if (HDOC(x).address != NULL) {
	    StrAllocCopy(Title, HDOC(x).address);
	    LYEntify(&Title, TRUE);
	} else {
	    StrAllocCopy(Title, gettext("(no address)"));
	}
	if (HDOC(x).internal_link) {
	    if (history[x].intern_seq_start == history[nhist - 1].intern_seq_start)
		StrAllocCat(Title, gettext(" (internal)"));
	    else
		StrAllocCat(Title, gettext(" (was internal)"));
	}
	fprintf(fp0, "<tab to=t%d>%s\n", x, Title);
    }
    fprintf(fp0, "</pre>\n");
    EndInternalPage(fp0);

    LYCloseTempFP(fp0);
    FREE(Title);
    return (0);
}

/*
 * This function makes the history page seem like any other type of file since
 * more info is needed than can be provided by the normal link structure.  We
 * saved out the history number to a special URL.
 *
 * The info looks like:  LYNXHIST:#
 */
BOOLEAN historytarget(DocInfo *newdoc)
{
    int number;
    DocAddress WWWDoc;
    HTParentAnchor *tmpanchor;
    HText *text;
    BOOLEAN treat_as_intern = FALSE;

    if ((!newdoc || !newdoc->address) ||
	strlen(newdoc->address) < 10 || !isdigit(UCH(*(newdoc->address + 9))))
	return (FALSE);

    if ((number = atoi(newdoc->address + 9)) > nhist + nhist_extra || number < 0)
	return (FALSE);

    /*
     * Optimization: assume we came from the History Page,
     * so never return back - always a new version next time.
     * But check first whether HTMainText is really the History
     * Page document - in some obscure situations this may not be
     * the case.  If HTMainText seems to be a History Page document,
     * also check that it really hasn't been pushed. - LP, kw
     */
    if (HTMainText && nhist > 0 &&
	!strcmp(HTLoadedDocumentTitle(), HISTORY_PAGE_TITLE) &&
	LYIsUIPage3(HTLoadedDocumentURL(), UIP_HISTORY, 0) &&
	strcmp(HTLoadedDocumentURL(), HDOC(nhist - 1).address)) {
	HTuncache_current_document();	/* don't waste the cache */
    }

    LYpop_num(number, newdoc);
    if (((newdoc->internal_link &&
	  history[number].intern_seq_start == history[nhist - 1].intern_seq_start)
	 || (number < nhist - 1 &&
	     HDOC(nhist - 1).internal_link &&
	     number == history[nhist - 1].intern_seq_start))
	&& !(LYforce_no_cache == TRUE && LYoverride_no_cache == FALSE)) {
	if (track_internal_links) {
	    LYforce_no_cache = FALSE;
	    LYinternal_flag = TRUE;
	    newdoc->internal_link = TRUE;
	    treat_as_intern = TRUE;
	}
    } else {
	newdoc->internal_link = FALSE;
    }
    /*
     * If we have POST content, and have LYresubmit_posts set or have no_cache
     * set or do not still have the text cached, ask the user whether to
     * resubmit the form.  - FM
     */
    if (newdoc->post_data != NULL) {
	WWWDoc.address = newdoc->address;
	WWWDoc.post_data = newdoc->post_data;
	WWWDoc.post_content_type = newdoc->post_content_type;
	WWWDoc.bookmark = newdoc->bookmark;
	WWWDoc.isHEAD = newdoc->isHEAD;
	WWWDoc.safe = newdoc->safe;
	tmpanchor = HTAnchor_findAddress(&WWWDoc);
	text = (HText *) HTAnchor_document(tmpanchor);
	if (((((LYresubmit_posts == TRUE) ||
	       (LYforce_no_cache == TRUE &&
		LYoverride_no_cache == FALSE)) &&
	      !(treat_as_intern && !reloading)) ||
	     text == NULL) &&
	    (isLYNXIMGMAP(newdoc->address) ||
	     HTConfirm(CONFIRM_POST_RESUBMISSION) == TRUE)) {
	    LYforce_no_cache = TRUE;
	    LYoverride_no_cache = FALSE;
	} else if (text != NULL) {
	    LYforce_no_cache = FALSE;
	    LYoverride_no_cache = TRUE;
	} else {
	    HTInfoMsg(CANCELLED);
	    return (FALSE);
	}
    }

    if (number != 0)
	StrAllocCat(newdoc->title, gettext(" (From History)"));
    return (TRUE);
}

/*
 * This procedure outputs the Visited Links list into a temporary file.  - FM
 * Returns links's number to make active (1-based), or 0 if not required.
 */
int LYShowVisitedLinks(char **newfile)
{
    static char tempfile[LY_MAXPATH] = "\0";
    char *Title = NULL;
    char *Address = NULL;
    int x, tot;
    FILE *fp0;
    VisitedLink *vl;
    HTList *cur = Visited_Links;
    int offset;
    int ret = 0;
    const char *arrow, *post_arrow;

    if (!cur)
	return (-1);

    if ((fp0 = InternalPageFP(tempfile, TRUE)) == 0)
	return (-1);

    LYLocalFileToURL(newfile, tempfile);
    LYRegisterUIPage(*newfile, UIP_VLINKS);

    LYforce_HTML_mode = TRUE;	/* force this file to be HTML */
    LYforce_no_cache = TRUE;	/* force this file to be new */

    BeginInternalPage(fp0, VISITED_LINKS_TITLE, VISITED_LINKS_HELP);

#ifndef NO_OPTION_FORMS
    fprintf(fp0, "<form action=\"%s\" method=\"post\">\n", STR_LYNXOPTIONS);
    LYMenuVisitedLinks(fp0, FALSE);
    fprintf(fp0, "<input type=\"submit\" value=\"Accept Changes\">\n");
    fprintf(fp0, "</form>\n");
    fprintf(fp0, "<P>\n");
#endif

    fprintf(fp0, "<pre>\n");
    fprintf(fp0, "<em>%s</em>\n",
	    gettext("You visited (POSTs, bookmark, menu and list files excluded):"));
    if (Visited_Links_As & VISITED_LINKS_REVERSE)
	tot = x = HTList_count(Visited_Links);
    else
	tot = x = -1;

    if (Visited_Links_As & VISITED_LINKS_AS_TREE) {
	vl = First_tree;
    } else if (Visited_Links_As & VISITED_LINKS_AS_LATEST) {
	if (Visited_Links_As & VISITED_LINKS_REVERSE)
	    vl = Latest_last.prev_latest;
	else
	    vl = Latest_first.next_latest;
	if (vl == &Latest_last || vl == &Latest_first)
	    vl = NULL;
    } else {
	if (Visited_Links_As & VISITED_LINKS_REVERSE)
	    vl = Last_by_first;
	else
	    vl = (VisitedLink *) HTList_nextObject(cur);
    }
    while (NULL != vl) {
	/*
	 * The number of the document (most recent highest), its title in a
	 * link, and its address.  - FM
	 */
	post_arrow = arrow = "";
	if (Visited_Links_As & VISITED_LINKS_REVERSE)
	    x--;
	else
	    x++;
	if (vl == PrevActiveVisitedLink) {
	    if (Visited_Links_As & VISITED_LINKS_REVERSE)
		ret = tot - x + 2;
	    else
		ret = x + 3;
	}
	if (vl == PrevActiveVisitedLink) {
	    post_arrow = "<A NAME=current></A>";
	    /* Otherwise levels 0 and 1 look the same when with arrow: */
	    arrow = (vl->level && (Visited_Links_As & VISITED_LINKS_AS_TREE))
		? "==>" : "=>";
	    StrAllocCat(*newfile, "#current");
	}
	if (Visited_Links_As & VISITED_LINKS_AS_TREE) {
	    offset = 2 * vl->level;
	    if (offset > 24)
		offset = (offset + 24) / 2;
	    if (offset > LYcols * 3 / 4)
		offset = LYcols * 3 / 4;
	} else
	    offset = (x > 99 ? 0 : x < 10 ? 2 : 1);
	if (non_empty(vl->title)) {
	    StrAllocCopy(Title, vl->title);
	    LYEntify(&Title, TRUE);
	    LYTrimLeading(Title);
	    LYTrimTrailing(Title);
	    if (*Title == '\0')
		StrAllocCopy(Title, NO_TITLE);
	} else {
	    StrAllocCopy(Title, NO_TITLE);
	}
	if (non_empty(vl->address)) {
	    StrAllocCopy(Address, vl->address);
	    LYEntify(&Address, FALSE);
	    fprintf(fp0,
		    "%-*s%s<em>%d</em>. <tab id=t%d><a href=\"%s\">%s</a>\n",
		    offset, arrow, post_arrow,
		    x, x, Address, Title);
	} else {
	    fprintf(fp0,
		    "%-*s%s<em>%d</em>. <tab id=t%d><em>%s</em>\n",
		    offset, arrow, post_arrow,
		    x, x, Title);
	}
	if (Address != NULL) {
	    StrAllocCopy(Address, vl->address);
	    LYEntify(&Address, TRUE);
	}
	fprintf(fp0, "<tab to=t%d>%s\n", x,
		((Address != NULL) ? Address : gettext("(no address)")));
	if (Visited_Links_As & VISITED_LINKS_AS_TREE)
	    vl = vl->next_tree;
	else if (Visited_Links_As & VISITED_LINKS_AS_LATEST) {
	    if (Visited_Links_As & VISITED_LINKS_REVERSE)
		vl = vl->prev_latest;
	    else
		vl = vl->next_latest;
	    if (vl == &Latest_last || vl == &Latest_first)
		vl = NULL;
	} else {
	    if (Visited_Links_As & VISITED_LINKS_REVERSE)
		vl = vl->prev_first;
	    else
		vl = (VisitedLink *) HTList_nextObject(cur);
	}
    }
    fprintf(fp0, "</pre>\n");
    EndInternalPage(fp0);

    LYCloseTempFP(fp0);
    FREE(Title);
    FREE(Address);
    return (ret);
}

/*
 * Keep cycled buffer for statusline messages.
 * But allow user to change how big it will be from userdefs.h
 */
#ifndef STATUSBUFSIZE
#define STATUSBUFSIZE   40
#endif

int status_buf_size = STATUSBUFSIZE;

static char **buffstack;
static int topOfStack = 0;

#ifdef LY_FIND_LEAKS
static void free_messages_stack(void)
{
    if (buffstack != 0) {
	topOfStack = status_buf_size;

	while (--topOfStack >= 0) {
	    FREE(buffstack[topOfStack]);
	}
	FREE(buffstack);
    }
}
#endif

static void to_stack(char *str)
{
    /*
     * Cycle buffer:
     */
    if (topOfStack >= status_buf_size) {
	topOfStack = 0;
    }

    /*
     * Register string.
     */
    if (buffstack == 0)
	buffstack = typecallocn(char *, (size_t) status_buf_size);

    FREE(buffstack[topOfStack]);
    buffstack[topOfStack] = str;
    topOfStack++;
#ifdef LY_FIND_LEAKS
    if (!already_registered_free_messages_stack) {
	already_registered_free_messages_stack = 1;
	atexit(free_messages_stack);
    }
#endif
    if (topOfStack >= status_buf_size) {
	topOfStack = 0;
    }
}

/*
 * Dump statusline messages into the buffer.
 * Called from mainloop() when exit immediately with an error:
 * can not access startfile (first_file) so a couple of alert messages
 * will be very useful on exit.
 * (Don't expect everyone will look a trace log in case of difficulties:))
 */
void LYstatusline_messages_on_exit(char **buf)
{
    int i;

    if (buffstack != 0) {
	StrAllocCat(*buf, "\n");
	/* print messages in chronological order:
	 * probably a single message but let's do it.
	 */
	i = topOfStack - 1;
	while (++i < status_buf_size) {
	    if (buffstack[i] != NULL) {
		StrAllocCat(*buf, buffstack[i]);
		StrAllocCat(*buf, "\n");
	    }
	}
	i = -1;
	while (++i < topOfStack) {
	    if (buffstack[i] != NULL) {
		StrAllocCat(*buf, buffstack[i]);
		StrAllocCat(*buf, "\n");
	    }
	}
    }
}

void LYstore_message2(const char *message,
		      const char *argument)
{

    if (message != NULL) {
	char *temp = NULL;

	HTSprintf0(&temp, message, NonNull(argument));
	to_stack(temp);
    }
}

void LYstore_message(const char *message)
{
    if (message != NULL) {
	char *temp = NULL;

	StrAllocCopy(temp, message);
	to_stack(temp);
    }
}

/*     LYLoadMESSAGES
 *     --------------
 *     Create a text/html stream with a list of recent statusline messages.
 *     LYNXMESSAGES:/ internal page.
 *     [implementation based on LYLoadKeymap()].
 */

static int LYLoadMESSAGES(const char *arg GCC_UNUSED,
			  HTParentAnchor *anAnchor,
			  HTFormat format_out,
			  HTStream *sink)
{
    HTFormat format_in = WWW_HTML;
    HTStream *target = NULL;
    char *buf = NULL;
    int nummsg = 0;

    int i;
    char *temp = NULL;

    if (buffstack != 0) {
	i = status_buf_size;
	while (--i >= 0) {
	    if (buffstack[i] != NULL)
		nummsg++;
	}
    }

    /*
     * Set up the stream.  - FM
     */
    target = HTStreamStack(format_in, format_out, sink, anAnchor);

    if (target == NULL) {
	HTSprintf0(&buf, CANNOT_CONVERT_I_TO_O,
		   HTAtom_name(format_in), HTAtom_name(format_out));
	HTAlert(buf);
	FREE(buf);
	return (HT_NOT_LOADED);
    }
    anAnchor->no_cache = TRUE;

#define PUTS(buf)    (*target->isa->put_block)(target, buf, (int) strlen(buf))

    HTSprintf0(&buf, "<html>\n<head>\n");
    PUTS(buf);
    /*
     * This page is a list of messages in display character set.
     */
    HTSprintf0(&buf, "<META %s content=\"" STR_HTML ";charset=%s\">\n",
	       "http-equiv=\"content-type\"",
	       LYCharSet_UC[current_char_set].MIMEname);
    PUTS(buf);
    HTSprintf0(&buf, "<title>%s</title>\n</head>\n<body>\n",
	       STATUSLINES_TITLE);
    PUTS(buf);

    if (nummsg != 0) {
	HTSprintf0(&buf, "<ol>\n");
	PUTS(buf);
	/* print messages in reverse order: */
	i = topOfStack;
	while (--i >= 0) {
	    if (buffstack[i] != NULL) {
		StrAllocCopy(temp, buffstack[i]);
		LYEntify(&temp, TRUE);
		HTSprintf0(&buf, "<li value=%d> <em>%s</em>\n", nummsg, temp);
		nummsg--;
		PUTS(buf);
	    }
	}
	i = status_buf_size;
	while (--i >= topOfStack) {
	    if (buffstack[i] != NULL) {
		StrAllocCopy(temp, buffstack[i]);
		LYEntify(&temp, TRUE);
		HTSprintf0(&buf, "<li value=%d> <em>%s</em>\n", nummsg, temp);
		nummsg--;
		PUTS(buf);
	    }
	}
	FREE(temp);
	HTSprintf0(&buf, "</ol>\n</body>\n</html>\n");
    } else {
	HTSprintf0(&buf, "<p>%s\n</body>\n</html>\n",
		   gettext("(No messages yet)"));
    }
    PUTS(buf);

    (*target->isa->_free) (target);
    FREE(buf);
    return (HT_LOADED);
}

#ifdef GLOBALDEF_IS_MACRO
#define _LYMESSAGES_C_GLOBALDEF_1_INIT { "LYNXMESSAGES", LYLoadMESSAGES, 0}
GLOBALDEF(HTProtocol, LYLynxStatusMessages, _LYMESSAGES_C_GLOBALDEF_1_INIT);
#else
GLOBALDEF HTProtocol LYLynxStatusMessages =
{"LYNXMESSAGES", LYLoadMESSAGES, 0};
#endif /* GLOBALDEF_IS_MACRO */