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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.rankingexpression.rule;
import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
import com.yahoo.searchlib.rankingexpression.RankingExpression;
import com.yahoo.searchlib.rankingexpression.Reference;
import com.yahoo.searchlib.rankingexpression.evaluation.Context;
import com.yahoo.searchlib.rankingexpression.evaluation.StringValue;
import com.yahoo.searchlib.rankingexpression.evaluation.Value;
import com.yahoo.tensor.TensorType;
import com.yahoo.tensor.evaluation.TypeContext;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.List;
import java.util.Optional;
/**
* A node referring either to a value in the context or to a named ranking expression function.
*
* @author bratseth
*/
public final class ReferenceNode extends CompositeNode {
private final Reference reference;
/* Creates a node with a simple identifier reference */
public ReferenceNode(String name) {
this.reference = Reference.fromIdentifier(name);
}
public ReferenceNode(String name, List<? extends ExpressionNode> arguments, String output) {
this.reference = new Reference(name,
arguments != null ? new Arguments(arguments) : new Arguments(),
output);
}
public ReferenceNode(Reference reference) {
this.reference = reference;
}
public String getName() {
return reference.name();
}
public int hashCode() {
return reference.hashCode();
}
/** Returns the arguments, never null */
public Arguments getArguments() { return reference.arguments(); }
/** Returns a copy of this where the arguments are replaced by the given arguments */
public ReferenceNode setArguments(List<ExpressionNode> arguments) {
return new ReferenceNode(reference.withArguments(new Arguments(arguments)));
}
/** Returns the specific output this references, or null if none specified */
public String getOutput() { return reference.output(); }
/** Returns a copy of this node with a modified output */
public ReferenceNode setOutput(String output) {
return new ReferenceNode(reference.withOutput(output));
}
/** Returns an empty list as this has no children */
@Override
public List<ExpressionNode> children() { return reference.arguments().expressions(); }
@Override
public StringBuilder toString(StringBuilder string, SerializationContext context, Deque<String> path, CompositeNode parent) {
// A reference to an identifier (function argument or bound variable)?
if (reference.isIdentifier() && context.getBinding(getName()) != null) {
// a bound identifier: replace by the value it is bound to
return string.append(context.getBinding(getName()));
}
// A reference to a function?
ExpressionFunction function = context.getFunction(getName());
if (function != null && function.arguments().size() == getArguments().size() && getOutput() == null) {
// a function reference: replace by the referenced function wrapped in rankingExpression
if (path == null)
path = new ArrayDeque<>();
String myPath = getName() + getArguments().expressions();
if (path.contains(myPath))
throw new IllegalStateException("Cycle in ranking expression function: " + path);
path.addLast(myPath);
ExpressionFunction.Instance instance = function.expand(context, getArguments().expressions(), path);
path.removeLast();
context.addFunctionSerialization(RankingExpression.propertyName(instance.getName()), instance.getExpressionString());
return string.append("rankingExpression(").append(instance.getName()).append(')');
}
// Not resolved in this context: output as-is
return reference.toString(string, context, path, parent);
}
/** Returns the reference of this node */
public Reference reference() { return reference; }
@Override
public TensorType type(TypeContext<Reference> context) {
TensorType type = null;
try {
type = context.getType(reference);
}
catch (IllegalArgumentException e) {
throw new IllegalArgumentException(reference + " is invalid", e);
}
if (type == null)
throw new IllegalArgumentException("Unknown feature '" + toString() + "'");
return type;
}
@Override
public Value evaluate(Context context) {
// TODO: Context should accept a Reference instead.
if (reference.isIdentifier())
return context.get(reference.name());
else
return context.get(getName(), getArguments(), getOutput());
}
@Override
public CompositeNode setChildren(List<ExpressionNode> newChildren) {
return setArguments(newChildren);
}
}
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