#ifndef _GRAPH_H
#define _GRAPH_H

#include "collections.h"

typedef struct graph* Graph;

int graph_size(Graph graph);

BitSet graph_newNodeSet(Graph graph, int arena);

Graph graph_new(void);

BitSet graph_children(Graph graph, int parent);

BitSet graph_parents(Graph graph, int child);

int graph_addNode(Graph graph, void* data);

void graph_addEdge(Graph graph, int from, int to);

void graph_close(Graph graph, void* (* merge)(void* node1, void* node2));

void* graph_node(Graph graph, int index);

/** ensure all nodes are non-null and parents and children bitsets match. */
void integrity(Graph graph);

#endif