public Expression Bind(PipelineExpression pipeline, EmbeddedPipelineBindingContext bindingContext, MethodCallExpression node, IEnumerable <Expression> arguments)
{
var sourceSerializer = pipeline.Projector.Serializer;
var accumulatorSerializer = sourceSerializer;
Expression seed;
LambdaExpression lambda;
var argumentCount = arguments.Count();
if (argumentCount == 1)
{
lambda = ExpressionHelper.GetLambda(arguments.Single());
seed = Expression.Constant(accumulatorSerializer.ValueType.GetDefaultValue());
}
else
{
seed = arguments.First();
accumulatorSerializer = bindingContext.GetSerializer(seed.Type, seed);
lambda = ExpressionHelper.GetLambda(arguments.ElementAt(1));
}
if (seed.NodeType == ExpressionType.Constant)
{
seed = new SerializedConstantExpression(((ConstantExpression)seed).Value, accumulatorSerializer);
}
var valueField = new FieldExpression("$value", accumulatorSerializer);
var thisField = new FieldExpression("$this", sourceSerializer);
bindingContext.AddExpressionMapping(lambda.Parameters[0], valueField);
bindingContext.AddExpressionMapping(lambda.Parameters[1], thisField);
var reducer = bindingContext.Bind(lambda.Body);
var serializer = bindingContext.GetSerializer(reducer.Type, reducer);
Expression finalizer = null;
string itemName = null;
if (argumentCount == 3)
{
lambda = ExpressionHelper.GetLambda(arguments.Last());
itemName = lambda.Parameters[0].Name;
var variable = new FieldExpression("$" + itemName, serializer);
bindingContext.AddExpressionMapping(lambda.Parameters[0], variable);
finalizer = bindingContext.Bind(lambda.Body);
serializer = bindingContext.GetSerializer(finalizer.Type, finalizer);
}
return(new PipelineExpression(
pipeline.Source,
new DocumentExpression(serializer),
new AggregateResultOperator(seed, reducer, finalizer, itemName, serializer)));
}
private BsonValue TranslateSerializedConstant(SerializedConstantExpression node)
{
return(node.SerializeValue(node.Type, node.Value));
}
