/***********************************************************************
 *               Copyright (C) 1995 Joe English
 *                   Freely redistributable
 ***********************************************************************
 *
 * relation.c,v 1.11 1999/07/18 06:40:06 joe Exp
 *
 * Author:	Joe English
 * Created: 	25 Oct 1995
 * Description:	Implementation of ILINKs and RELATIONS.
 *
 * 1999/07/18 06:40:06
 * 1.11
 */

#include <stdlib.h>
#include <stdio.h>

#include "project.h"
#include "strmgt.h"
#include "esis.h"
#include "strmap.h"
#include "pile.h"
#include "esisp.h"

/* Organization:
 *
 * RELATION nodes appear in the attribute list of the document root.
 *	name:		relation name
 *	children:	ILINK nodes
 *	next,prev:	next/previous attribute/relation/entity/etc.
 *	link:		points to last ILINK node.
 *
 * ILINK node structure:
 *	name:		relation name
 *	parent: 	parent relation
 *	children:	LINKEND nodes
 *	next,prev:	next/previous ilink in relation
 *	reference:	origin of link
 *
 * LINKEND node structure:
 *	name:		anchor name
 *	parent: 	containing ILINK node
 *	reference:	anchor node
 *	next,prev:	next/previous anchor in link
 *
 * All the LINKEND nodes which reference a particular tree node
 * are stored in a circular linked list, chained by the 'link'
 * field.   The 'link' field of the tree node points to the tail of
 * this list.
 */

/*
 * Constructors:
 */
static ESISNode find_relation(ESISNode node, ESISToken relname)
{
    ESISNode nd = esis_docroot(node);
    for (nd = nd->attributes; nd; nd = nd->next)
	if (nd->type == EN_RELATION && nd->name == relname)
	    return nd;
    return 0;
}

static ESISNode find_linkend(ESISNode ilink, ESISToken anchname)
{
    ESISNode linkend = ilink->children;
    while (linkend)
    {
	if (linkend->name == anchname)
	    break;
	linkend = linkend->next;
    }
    return linkend;
}

int esis_define_relation(
	ESISDocument doc,
	const char *relname,
	int nanchors,
	char **anchnames)
{
    ESISNode rel;
    ESISToken name = ucintern(relname);

    if (find_relation(doc->rootnode, name))
	return 0;

    rel = esis_create_node(EN_RELATION, name, doc->rootnode, NULL, 1);

    /* %%% do something about anchor names ... */

    return 1;
}

ESISNode esis_create_ilink(ESISDocument doc, ESISToken relname, ESISNode origin)
{
    ESISNode rel, ilink;

    rel = find_relation(doc->rootnode,relname);
    if (!rel)
	return 0;

    rel->link = ilink = esis_create_node(
	EN_ILINK, relname,
	rel, rel->link, 0);

    ilink->reference = origin;

    return ilink;
}

int esis_set_linkend(ESISNode ilink, ESISToken anchname, ESISNode anchor)
{
    ESISNode linkend = find_linkend(ilink, anchname);

    if (!linkend)
    {
	linkend = esis_create_node(
		EN_LINKEND,
		anchname,
		ilink, NULL, 0);
    }
    if (linkend->reference)
	return 0;
    linkend->reference = anchor;

    /* Add to circular linked list: */
    if (anchor->link)
    {
	linkend->link = anchor->link->link;
	anchor->link->link = linkend;
	anchor->link = linkend;
    } else
    {
	anchor->link = linkend->link = linkend;
    }

    return 1;
}

ESISNode esis_relation_first(ESISNode node, ESISToken relname)
{
    ESISNode rel = find_relation(node, relname);
    return rel ? rel->children : 0;
}

ESISNode esis_relation_next(ESISNode ilink)
{
    if (ilink->type != EN_ILINK)
	return 0;
    return ilink->next;
}

ESISNode esis_first_ilink(
	ESISNode origin,
	ESISToken relname,
	ESISToken anchname)
{
    ESISNode tail = origin->link;
    ESISNode linkend;
    ASSERT(relname == ucintern(relname), "Uninterned relname");
    ASSERT(anchname == ucintern(anchname), "Uninterned anchname");

    if (!tail) return 0;
    linkend = tail->link;	/* head of cll */

    while (linkend)
    {
	ASSERT(linkend->type == EN_LINKEND
	   && linkend->parent->type == EN_ILINK,
	   "Botched ilink structure");
	if (linkend->name == anchname && linkend->parent->name == relname)
	    return linkend->parent;
	linkend = (linkend == tail) ? 0 : linkend->link;
    }
    return 0;
}

ESISNode esis_next_ilink(
	ESISNode origin,
	ESISToken relname,
	ESISToken anchname,
	ESISNode ilink)
{
    ESISNode linkend;

    ASSERT(ilink->type == EN_ILINK, "Not an ILINK node");
    linkend = find_linkend(ilink, anchname);
    while (linkend != origin->link)
    {
	linkend = linkend->link;
	ASSERT(linkend->type == EN_LINKEND
	   && linkend->parent->type == EN_ILINK,
	   "Botched ilink structure");
	if (linkend->name == anchname && linkend->parent->name == relname)
	    return linkend->parent;
    }
    return 0;
}

ESISNode esis_ilink_anchor(ESISNode ilink, ESISToken anchname)
{
    ESISNode linkend;
    if (ilink->type != EN_ILINK)
	return 0;
    linkend = find_linkend(ilink, anchname);
    return linkend ? linkend->reference : 0;
}

ESISNode esis_ilink_origin(ESISNode ilink)
{
    if (ilink->type == EN_ILINK)
	return ilink->reference;
    return NULL;
}