package datomic.samples;

import datomic.Peer;

import datomic.Connection;

import java.util.Collection;

import java.util.Iterator;

import java.util.UUID;

public class Fns {

/**

* Returns single item in the collection, null if collection empty, throws if collection

* has more than one item.

*/

public static Object solo(Object c) {

if (c == null) return null;

Iterator it = ((Collection)c).iterator();

if (!it.hasNext()) return null;

Object result = it.next();

if (it.hasNext()) throw new RuntimeException("Expected one item, got more than one");

return result;

}

/**

* Connection to a fresh in-memory Datomic database.

* @return

*/

public static Connection scratchConnection() {

String uri = "datomic:mem://" + UUID.randomUUID();

Peer.createDatabase(uri);

return Peer.connect(uri);

}

public static void printQueryResult(Collection coll) {

System.out.println(coll);

}

}