Added an input range interface to MongoCursor. This is a redo of pull #…

…172.

The range interface is added directly to MongoCursor in the version instead
of introducing an extra range type. Original pull by Михаил Страшун (Dicebot).

source/vibe/db/mongo/cursor.d

@@ -47,7 +47,11 @@ struct MongoCursor {
 
 		Throws: An exception if there is a query or communication error.
 	*/
-	bool empty() { return m_data ? !m_data.hasNext() : true; }
+	@property bool empty() { return m_data ? m_data.empty() : true; }
+
+	@property Bson front() { return m_data.front; }
+
+	void popFront() { m_data.popFront(); }
 
 	/**
 		Iterates over all remaining documents.
@@ -58,8 +62,9 @@ struct MongoCursor {
 	{
 		if( !m_data ) return 0;
 
-		while( m_data.hasNext() ){
-			auto doc = m_data.getNext();
+		while( !m_data.empty ){
+			auto doc = m_data.front;
+			m_data.popFront();
 			if( auto ret = del(doc) )
 				return ret;
 		}
@@ -75,9 +80,10 @@ struct MongoCursor {
 	{
 		if( !m_data ) return 0;
 
-		while( m_data.hasNext() ){
-			auto idx = m_data.getNextIndex();
-			auto doc = m_data.getNext();
+		while( !m_data.empty ){
+			auto idx = m_data.index;
+			auto doc = m_data.front;
+			m_data.popFront();
 			if( auto ret = del(idx, doc) )
 				return ret;
 		}
@@ -110,26 +116,34 @@ private class MongoCursorData {
 		handleReply(first_chunk);
 	}
 
-	bool hasNext(){
+	@property bool empty()
+	{
 		if( m_currentDoc < m_documents.length )
-			return true;
-		if( m_cursor == 0 )
 			return false;
+		if( m_cursor == 0 )
+			return true;
 
 		auto conn = m_client.lockConnection();
 		auto reply = conn.getMore(m_collection, m_nret, m_cursor);
 		handleReply(reply);
-		return m_currentDoc < m_documents.length;
+		return m_currentDoc >= m_documents.length;
 	}
 
-	size_t getNextIndex(){
-		enforce(hasNext(), "Cursor has no more data.");
+	@property size_t index()
+	{
+		enforce(!empty(), "Cursor has no more data.");
 		return m_offset + m_currentDoc;
 	}
 
-	Bson getNext(){
-		enforce(hasNext(), "Cursor has no more data.");
-		return m_documents[m_currentDoc++];
+	@property Bson front()
+	{
+		enforce(!empty(), "Cursor has no more data.");
+		return m_documents[m_currentDoc];
+	}
+
+	void popFront()
+	{
+		m_currentDoc++;
 	}
 
 	private void destroy()

tests/source/tests/mongodb.d

@@ -16,13 +16,23 @@ void test_mongodb_general()
 	coll.insert([ "key1" : "value1", "key2" : "value2"]);
 	coll.update(["key1" : "value1"], [ "key1" : "value1", "key2" : "1337"]);
 	assert(coll.database.getLastError().n == 1);
-	auto data = coll.find(["key1" : true]);
-	foreach (doc; data)
-	{
-	    assert(doc.length == 1);
-	    assert(doc.key2.get!string() == "1337");
-	}
+	auto data = coll.findOne(["key1" : "value1"]);
+	assert(!data.isNull());
+	assert(data.key2.get!string() == "1337");
 	coll.database.fsync();
 	auto logBson = client.getDatabase("admin").getLog("global");
 	assert(!logBson.isNull());
+
+	// testing cursor range interface
+	coll.remove();
+	coll.insert(["key1" : "value1"]);
+	coll.insert(["key1" : "value2"]);
+	coll.insert(["key1" : "value2"]);
+	auto data1 = coll.find(["key1" : "value1"]);
+	auto data2 = coll.find(["key1" : "value2"]);
+
+	import std.range;
+	auto converted = zip(data1, data2).map!( a => a[0].key1.get!string() ~ a[1].key1.get!string() )();
+	assert(!converted.empty);
+	assert(converted.front == "value1value2");
 }