/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/

#include	<circogen/blockpath.h>
#include	<circogen/circular.h>
#include	<circogen/edgelist.h>
#include	<stddef.h>
#include	<stdbool.h>
#include	<stdint.h>
#include	<util/agxbuf.h>
#include	<util/alloc.h>
#include	<util/list.h>

/* The code below lays out a single block on a circle.
 */

/* We use the unused fields order and to_orig in cloned nodes and edges */
#define ORIGE(e)  (ED_to_orig(e))

/* clone_graph:
 * Create two copies of the argument graph
 * One is a subgraph, the other is an actual copy since we will be
 * adding edges to it.
 *
 * @param state Context containing a counter to use for graph copy naming
 */
static Agraph_t *clone_graph(Agraph_t *ing, Agraph_t **xg, circ_state *state) {
    Agraph_t *clone;
    Agraph_t *xclone;
    Agnode_t *n;
    Agnode_t *xn;
    Agnode_t *xh;
    Agedge_t *e;
    Agedge_t *xe;
    agxbuf gname = {0};

    agxbprint(&gname, "_clone_%d", state->graphCopyCount++);
    clone = agsubg(ing, agxbuse(&gname), 1);
    agbindrec(clone, "Agraphinfo_t", sizeof(Agraphinfo_t), true);	//node custom data
    agxbprint(&gname, "_clone_%d", state->graphCopyCount++);
    xclone = agopen(agxbuse(&gname), ing->desc, NULL);
    agxbfree(&gname);
    for (n = agfstnode(ing); n; n = agnxtnode(ing, n)) {
	agsubnode(clone,n,1);
	xn = agnode(xclone, agnameof(n),1);
        agbindrec(xn, "Agnodeinfo_t", sizeof(Agnodeinfo_t), true);	//node custom data
	CLONE(n) = xn;
    }

    for (n = agfstnode(ing); n; n = agnxtnode(ing, n)) {
	xn = CLONE(n);
	for (e = agfstout(ing, n); e; e = agnxtout(ing, e)) {
	    agsubedge(clone,e,1);
	    xh = CLONE(aghead(e));
	    xe = agedge(xclone, xn, xh, NULL, 1);
	    agbindrec(xe, "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);	//node custom data
	    ORIGE(xe) = e;
	    DEGREE(xn) += 1;
	    DEGREE(xh) += 1;
	}
    }
    *xg = xclone;
    return clone;
}

typedef LIST(Agnode_t *) deglist_t;

/// comparison function for sorting nodes by degree, descending
static int cmpDegree(const void *x, const void *y) {
  Agnode_t *const *a = x;
  Agnode_t *const *b = y;
  if (DEGREE(*a) < DEGREE(*b)) {
    return 1;
  }
  if (DEGREE(*a) > DEGREE(*b)) {
    return -1;
  }
  return 0;
}

/// Add nodes to deg_list, storing them by descending degree.
static deglist_t getList(Agraph_t *g) {
    deglist_t dl = {0};
    Agnode_t *n;

    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
	LIST_APPEND(&dl, n);
    }
    LIST_SORT(&dl, cmpDegree);
    return dl;
}

static void find_pair_edges(Agraph_t * g, Agnode_t * n, Agraph_t * outg)
{
    int edge_cnt = 0;

    const int node_degree = DEGREE(n);
    LIST(Agnode_t *) neighbors_with = {0};
    LIST(Agnode_t *) neighbors_without = {0};

    for (Agedge_t *e = agfstedge(g, n); e; e = agnxtedge(g, e, n)) {
	Agnode_t *n1 = aghead(e);
	if (n1 == n)
	    n1 = agtail(e);
	bool has_pair_edge = false;
	for (Agedge_t *ep = agfstedge(g, n); ep; ep = agnxtedge(g, ep, n)) {
	    if (ep == e)
		continue;
	    Agnode_t *n2 = aghead(ep);
	    if (n2 == n)
		n2 = agtail(ep);
	    Agedge_t *const ex = agfindedge(g, n1, n2);
	    if (ex) {
		has_pair_edge = true;
		if ((uintptr_t)n1 < (uintptr_t)n2) { // count edge only once
		    edge_cnt++;
		    if (ORIGE(ex)) {
			agdelete(outg, ORIGE(ex));
			ORIGE(ex) = 0;	/* delete only once */
		    }
		}
	    }
	}
	if (has_pair_edge) {
	    LIST_APPEND(&neighbors_with, n1);
	} else {
	    LIST_APPEND(&neighbors_without, n1);
	}
    }

    int diff = node_degree - 1 - edge_cnt;
    if (diff > 0) {
	if ((size_t)diff < LIST_SIZE(&neighbors_without)) {
	    for (size_t mark = 0; mark + 1 < LIST_SIZE(&neighbors_without); mark += 2) {
		Agnode_t *const tp = LIST_GET(&neighbors_without, mark);
		Agnode_t *const hp = LIST_GET(&neighbors_without, mark + 1);
		agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);   // edge custom data
		DEGREE(tp)++;
		DEGREE(hp)++;
		diff--;
	    }

	    for (size_t mark = 2; diff > 0; ++mark, --diff) {
		Agnode_t *const tp = LIST_GET(&neighbors_without, 0);
		Agnode_t *const hp = LIST_GET(&neighbors_without, mark);
		agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);   // edge custom data
		DEGREE(tp)++;
		DEGREE(hp)++;
	    }
	}

	else if ((size_t)diff == LIST_SIZE(&neighbors_without)) {
	    Agnode_t *const tp =
	      LIST_IS_EMPTY(&neighbors_with) ? NULL : LIST_GET(&neighbors_with, 0);
	    for (size_t mark = 0; mark < LIST_SIZE(&neighbors_without); mark++) {
		Agnode_t *const hp = LIST_GET(&neighbors_without, mark);
		agbindrec(agedge(g, tp, hp, NULL, 1), "Agedgeinfo_t", sizeof(Agedgeinfo_t), true);	//node custom data
		if (tp != NULL) {
		    DEGREE(tp)++;
		}
		DEGREE(hp)++;
	    }
	}
    }

    LIST_FREE(&neighbors_without);
    LIST_FREE(&neighbors_with);
}

/// Create layout skeleton of ing. Why is returned graph connected?
///
/// @param state Context containing a counter to use for graph copy naming
static Agraph_t *remove_pair_edges(Agraph_t *ing, circ_state *state) {
    int nodeCount;
    Agraph_t *outg;
    Agraph_t *g;
    Agnode_t *currnode, *adjNode;
    Agedge_t *e;

    outg = clone_graph(ing, &g, state);
    nodeCount = agnnodes(g);
    deglist_t dl = getList(g);

    for (int counter = 0; counter < nodeCount - 3; ++counter) {
	currnode = LIST_IS_EMPTY(&dl) ? NULL : LIST_POP_BACK(&dl);

	/* Remove all adjacent nodes since they have to be reinserted */
	for (e = agfstedge(g, currnode); e; e = agnxtedge(g, e, currnode)) {
	    adjNode = aghead(e);
	    if (currnode == adjNode)
		adjNode = agtail(e);
	    LIST_REMOVE(&dl, adjNode);
	}

	find_pair_edges(g, currnode, outg);

	for (e = agfstedge(g, currnode); e; e = agnxtedge(g, e, currnode)) {
	    adjNode = aghead(e);
	    if (currnode == adjNode)
		adjNode = agtail(e);

	    DEGREE(adjNode)--;
	    LIST_APPEND(&dl, adjNode);
	}
	LIST_SORT(&dl, cmpDegree);

	agdelete(g, currnode);
    }

    agclose(g);
    LIST_FREE(&dl);
    return outg;
}

static void
measure_distance(Agnode_t * n, Agnode_t * ancestor, int dist,
		 Agnode_t * change)
{
    Agnode_t *parent;

    parent = TPARENT(ancestor);
    if (parent == NULL)
	return;

    dist++;

    /* check parent to see if it has other leaf paths at greater distance
       than the context node.
       set the path/distance of the leaf at this ancestor node */

    if (DISTONE(parent) == 0) {
	LEAFONE(parent) = n;
	DISTONE(parent) = dist;
    } else if (dist > DISTONE(parent)) {
	if (LEAFONE(parent) != change) {
	    if (!DISTTWO(parent) || LEAFTWO(parent) != change)
		change = LEAFONE(parent);
	    LEAFTWO(parent) = LEAFONE(parent);
	    DISTTWO(parent) = DISTONE(parent);
	}
	LEAFONE(parent) = n;
	DISTONE(parent) = dist;
    } else if (dist > DISTTWO(parent)) {
	LEAFTWO(parent) = n;
	DISTTWO(parent) = dist;
	return;
    } else
	return;

    measure_distance(n, parent, dist, change);
}

/// Find and return longest path in tree.
static nodelist_t find_longest_path(Agraph_t *tree) {
    Agnode_t *n;
    Agedge_t *e;
    Agnode_t *common = 0;
    int maxlength = 0;
    int length;

    if (agnnodes(tree) == 1) {
	nodelist_t beginPath = {0};
	n = agfstnode(tree);
	LIST_APPEND(&beginPath, n);
	SET_ONPATH(n);
	return beginPath;
    }

    for (n = agfstnode(tree); n; n = agnxtnode(tree, n)) {
	int count = 0;
	for (e = agfstedge(tree, n); e; e = agnxtedge(tree, e, n)) {
	    count++;
	}
	if (count == 1)
	    measure_distance(n, n, 0, NULL);
    }

    /* find the branch node rooted at the longest path */
    for (n = agfstnode(tree); n; n = agnxtnode(tree, n)) {
	length = DISTONE(n) + DISTTWO(n);
	if (length > maxlength) {
	    common = n;
	    maxlength = length;
	}
    }

    nodelist_t beginPath = {0};
    for (n = LEAFONE(common); n != common; n = TPARENT(n)) {
	LIST_APPEND(&beginPath, n);
	SET_ONPATH(n);
    }
    LIST_APPEND(&beginPath, common);
    SET_ONPATH(common);

    if (DISTTWO(common)) {	/* 2nd path might be empty */
	nodelist_t endPath = {0};
	for (n = LEAFTWO(common); n != common; n = TPARENT(n)) {
	    LIST_APPEND(&endPath, n);
	    SET_ONPATH(n);
	}
	reverseAppend(&beginPath, &endPath);
    }

    return beginPath;
}

/// Simple depth first search, adding traversed edges to tree.
static void dfs(Agraph_t * g, Agnode_t * n, Agraph_t * tree)
{
    Agedge_t *e;
    Agnode_t *neighbor;

    SET_VISITED(n);
    for (e = agfstedge(g, n); e; e = agnxtedge(g, e, n)) {
	neighbor = aghead(e);
	if (neighbor == n)
	    neighbor = agtail(e);

	if (!VISITED(neighbor)) {
	    /* add the edge to the dfs tree */
	    agsubedge(tree,e,1);
	    TPARENT(neighbor) = n;
	    dfs(g, neighbor, tree);
	}
    }
}

/// Construct spanning forest of g as subgraph
///
/// @param state Context containing a counter to use for spanning tree naming
static Agraph_t *spanning_tree(Agraph_t *g, circ_state *state) {
    Agnode_t *n;
    Agraph_t *tree;
    agxbuf gname = {0};

    agxbprint(&gname, "_span_%d", state->spanningTreeCount++);
    tree = agsubg(g, agxbuse(&gname), 1);
    agxbfree(&gname);
    agbindrec(tree, "Agraphinfo_t", sizeof(Agraphinfo_t), true);	//node custom data

    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
	agsubnode(tree,n,1);
	DISTONE(n) = 0;
	DISTTWO(n) = 0;
	UNSET_VISITED(n);
    }

    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
	if (!VISITED(n)) {
	    TPARENT(n) = NULL;
	    dfs(g, n, tree);
	}
    }

    return tree;
}

/// Add induced edges.
static void block_graph(Agraph_t * g, block_t * sn)
{
    Agnode_t *n;
    Agedge_t *e;
    Agraph_t *subg = sn->sub_graph;

    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
	for (e = agfstout(g, n); e; e = agnxtout(g, e)) {
	    if (BLOCK(aghead(e)) == sn)
		agsubedge(subg,e,1);
	}
    }
}

static int count_all_crossings(nodelist_t * list, Agraph_t * subg)
{
    edgelist *openEdgeList = init_edgelist();
    Agnode_t *n;
    Agedge_t *e;
    int crossings = 0;
    int order = 1;

    for (n = agfstnode(subg); n; n = agnxtnode(subg, n)) {
	for (e = agfstout(subg, n); e; e = agnxtout(subg, e)) {
	    EDGEORDER(e) = 0;
	}
    }

    for (size_t item = 0; item < LIST_SIZE(list); ++item) {
	n = LIST_GET(list, item);

	for (e = agfstedge(subg, n); e; e = agnxtedge(subg, e, n)) {
	    if (EDGEORDER(e) > 0) {
		edgelistitem *eitem;
		Agedge_t *ep;

		for (eitem = dtfirst(openEdgeList); eitem;
		     eitem = dtnext(openEdgeList, eitem)) {
		    ep = eitem->edge;
		    if (EDGEORDER(ep) > EDGEORDER(e)) {
			if (aghead(ep) != n && agtail(ep) != n)
			    crossings++;
		    }
		}
		remove_edge(openEdgeList, e);
	    }
	}

	for (e = agfstedge(subg, n); e; e = agnxtedge(subg, e, n)) {
	    if (EDGEORDER(e) == 0) {
		EDGEORDER(e) = order;
		add_edge(openEdgeList, e);
	    }
	}
	order++;
    }

    free_edgelist(openEdgeList);
    return crossings;
}

#define CROSS_ITER 10

/* Attempt to reduce edge crossings by moving nodes.
 * Original crossing count is in cnt; final count is returned there.
 * list is the original list; return the best list found.
 */
static nodelist_t reduce(nodelist_t list, Agraph_t *subg, int *cnt) {
    Agnode_t *curnode;
    Agedge_t *e;
    Agnode_t *neighbor;
    int crossings, j, newCrossings;

    crossings = *cnt;
    for (curnode = agfstnode(subg); curnode;
	 curnode = agnxtnode(subg, curnode)) {
	/*  move curnode next to its neighbors */
	for (e = agfstedge(subg, curnode); e;
	     e = agnxtedge(subg, e, curnode)) {
	    neighbor = agtail(e);
	    if (neighbor == curnode)
		neighbor = aghead(e);

	    for (j = 0; j < 2; j++) {
		nodelist_t listCopy;
		LIST_COPY(&listCopy, &list);
		insertNodelist(&list, curnode, neighbor, j);
		newCrossings = count_all_crossings(&list, subg);
		if (newCrossings < crossings) {
		    crossings = newCrossings;
		    LIST_FREE(&listCopy);
		    if (crossings == 0) {
			*cnt = 0;
			return list;
		    }
		} else {
		    LIST_FREE(&list);
		    list = listCopy;
		}
	    }
	}
    }
    *cnt = crossings;
    return list;
}

static nodelist_t reduce_edge_crossings(nodelist_t list, Agraph_t *subg) {
    int i, crossings, origCrossings;

    crossings = count_all_crossings(&list, subg);
    if (crossings == 0)
	return list;

    for (i = 0; i < CROSS_ITER; i++) {
	origCrossings = crossings;
	list = reduce(list, subg, &crossings);
	/* return if no crossings or no improvement */
	if (origCrossings == crossings || crossings == 0)
	    return list;
    }
    return list;
}

/// Return max dimension of nodes on list
static double largest_nodesize(nodelist_t * list)
{
    double size = 0;

    for (size_t item = 0; item < LIST_SIZE(list); ++item) {
	Agnode_t *n = ORIGN(LIST_GET(list, item));
	if (ND_width(n) > size)
	    size = ND_width(n);
	if (ND_height(n) > size)
	    size = ND_height(n);
    }
    return size;
}

/// Add n to list. By construction, n is not in list at start.
static void place_node(Agraph_t * g, Agnode_t * n, nodelist_t * list)
{
    Agedge_t *e;
    bool placed = false;
    nodelist_t neighbors = {0};

    for (e = agfstout(g, n); e; e = agnxtout(g, e)) {
	LIST_APPEND(&neighbors, aghead(e));
	SET_NEIGHBOR(aghead(e));
    }
    for (e = agfstin(g, n); e; e = agnxtin(g, e)) {
	LIST_APPEND(&neighbors, agtail(e));
	SET_NEIGHBOR(agtail(e));
    }

    /* Look for 2 neighbors consecutive on list */
    if (LIST_SIZE(&neighbors) >= 2) {
	for (size_t one = 0; one < LIST_SIZE(list); ++one) {
	    const size_t two = (one + 1) % LIST_SIZE(list);

	    if (NEIGHBOR(LIST_GET(list, one)) && NEIGHBOR(LIST_GET(list, two))) {
		appendNodelist(list, one + 1, n);
		placed = true;
		break;
	    }
	}
    }

    /* Find any neighbor on list */
    if (!placed && !LIST_IS_EMPTY(&neighbors)) {
	for (size_t one = 0; one < LIST_SIZE(list); ++one) {
	    if (NEIGHBOR(LIST_GET(list, one))) {
		appendNodelist(list, one + 1, n);
		placed = true;
		break;
	    }
	}
    }

    if (!placed)
	LIST_APPEND(list, n);

    for (size_t one = 0; one < LIST_SIZE(&neighbors); ++one)
	UNSET_NEIGHBOR(LIST_GET(&neighbors, one));
    LIST_FREE(&neighbors);
}

/// Add nodes not in list to list.
static void place_residual_nodes(Agraph_t * g, nodelist_t * list)
{
    Agnode_t *n;

    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
	if (!ONPATH(n))
	    place_node(g, n, list);
    }
}

/// @param state Context containing a counter to use for graph copy naming
nodelist_t layout_block(Agraph_t *g, block_t *sn, double min_dist,
                        circ_state *state) {
    Agraph_t *copyG, *tree, *subg;
    int k;
    double theta, radius;

    subg = sn->sub_graph;
    block_graph(g, sn);		/* add induced edges */

    copyG = remove_pair_edges(subg, state);

    tree = spanning_tree(copyG, state);
    nodelist_t longest_path = find_longest_path(tree);
    place_residual_nodes(subg, &longest_path);
    /* at this point, longest_path is a list of all nodes in the block */

    /* apply crossing reduction algorithms here */
    longest_path = reduce_edge_crossings(longest_path, subg);

    size_t N = LIST_SIZE(&longest_path);
    const double largest_node = largest_nodesize(&longest_path);
    /* N*(min_dist+largest_node) is roughly circumference of required circle */
    if (N == 1)
	radius = 0;
    else
	radius = (double)N * (min_dist + largest_node) / (2 * M_PI);

    for (size_t item = 0; item < LIST_SIZE(&longest_path); ++item) {
	Agnode_t *n = LIST_GET(&longest_path, item);
	if (ISPARENT(n)) {
	    /* QUESTION: Why is only one parent realigned? */
	    realignNodelist(&longest_path, item);
	    break;
	}
    }

    k = 0;
    for (size_t item = 0; item < LIST_SIZE(&longest_path); ++item) {
	Agnode_t *n = LIST_GET(&longest_path, item);
	POSITION(n) = k;
	PSI(n) = 0.0;
	theta = k * (2.0 * M_PI / (double)N);

	ND_pos(n)[0] = radius * cos(theta);
	ND_pos(n)[1] = radius * sin(theta);

	k++;
    }

    if (N == 1)
	sn->radius = largest_node / 2;
    else
	sn->radius = radius;
    sn->rad0 = sn->radius;

    /* initialize parent pos */
    sn->parent_pos = -1;

    agclose(copyG);
    return longest_path;
}

#ifdef DEBUG
void prTree(Agraph_t * g)
{
    Agnode_t *n;

    for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
	if (TPARENT(n)) {
			fprintf(stderr, "%s ", agnameof(n));
			fprintf(stderr, "-> %s\n", agnameof(TPARENT(n)));
		}
    }
}
#endif