AggCustom.java example

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.expr.aggregate;

import java.util.Locale;
import java.util.Objects;

import org.apache.jena.atlas.io.IndentedLineBuffer;
import org.apache.jena.graph.Node;
import org.apache.jena.query.QueryExecException;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.expr.E_Function;
import org.apache.jena.sparql.expr.Expr;
import org.apache.jena.sparql.expr.ExprList;
import org.apache.jena.sparql.expr.NodeValue;
import org.apache.jena.sparql.function.FunctionEnv;
import org.apache.jena.sparql.serializer.SerializationContext;
import org.apache.jena.sparql.sse.writers.WriterExpr;
import org.apache.jena.sparql.util.ExprUtils;
import org.apache.jena.sparql.util.FmtUtils ;

/**
 * Syntax element and framework execution for custom aggregates.
 */
public class AggCustom extends AggregatorBase {
    // See also ExprAggregator

    private final String iri;

    public AggCustom(String iri, boolean distinct, ExprList exprs) {
        super("AGG", distinct, exprs);
        this.iri = iri;
    }

    @Override
    public Aggregator copy(ExprList exprs) {
        return new AggCustom(iri, isDistinct, exprs);
    }

    @Override
    public String asSparqlExpr(SerializationContext sCxt) {
        IndentedLineBuffer x = new IndentedLineBuffer();
        if ( !AggregateRegistry.isRegistered(iri) ) {
            // If not registered and if parsed in again not registered, it becomes a
            // function.
            // AGG <iri>(...) syntax. It can't have been legal SPARQL 1.1 unless it got
            // unregistered in which case all bets are off anyway.
            x.append(getName());
            x.append(" ");
        }

        String uriStr = FmtUtils.stringForURI(iri, sCxt) ;
        x.append(uriStr) ;
        x.append("(");
        if ( isDistinct )
            x.append("DISTINCT ");
        x.incIndent();
        ExprUtils.fmtSPARQL(x, getExprList(), sCxt);
        x.decIndent();
        x.append(")");
        return x.asString();
    }

    @Override
    public String toPrefixString() {
        IndentedLineBuffer x = new IndentedLineBuffer();
        x.append("(");
        x.append(getName().toLowerCase(Locale.ROOT));
        x.append(" <");
        x.append(iri);
        x.append("> ");
        x.incIndent();

        if ( isDistinct )
            x.append("distinct ");
        boolean first = true;
        for ( Expr e : getExprList() ) {
            if ( !first )
                x.append(" ");
            first = false;
            WriterExpr.output(x, e, null);
            first = false;
        }
        x.decIndent();
        x.append(")");
        return x.asString();
    }

    @Override
    public Accumulator createAccumulator() {
        AccumulatorFactory f = AggregateRegistry.getAccumulatorFactory(iri);
        if ( f == null )
            throw new QueryExecException("Unregistered aggregate: " + iri);
        return f.createAccumulator(this, isDistinct);
    }

    @Override
    public Node getValueEmpty() {
        return AggregateRegistry.getNoGroupValue(iri);
    }

    @Override
    public Expr getExpr() {
        if ( exprList.size() == 0 )
            return null;
        else
            return exprList.get(0);
    }

    public String getIRI() {
        return iri;
    }

    @Override
    public int hashCode() {
        if ( !AggregateRegistry.isRegistered(iri) ) {
            return asFunction().hashCode();
        }
        return HC_AggCustom ^ getExprList().hashCode() ^ iri.hashCode();
    }

    private E_Function asFunction() {
        return new E_Function(iri, exprList);
    }

    @Override
    public boolean equals(Aggregator other, boolean bySyntax) {
        if ( other == null )
            return false;
        if ( this == other )
            return true;

        if ( !AggregateRegistry.isRegistered(iri) ) {
            E_Function f1 = asFunction();
            if ( !(other instanceof AggCustom) )
                return false;
            E_Function f2 = ((AggCustom)other).asFunction();
            return f1.equals(f2, bySyntax);
        }

        if ( !(other instanceof AggCustom) )
            return false;
        AggCustom agg = (AggCustom)other;
        return Objects.equals(this.iri, agg.iri) && this.isDistinct == agg.isDistinct
               && this.getExprList().equals(agg.getExprList(), bySyntax);
    }

    public static Accumulator createAccNull() {
        return new AccCustom();
    }

    // ---- Accumulator
    private static class AccCustom implements Accumulator {
        private int nBindings = 0;

        public AccCustom() {}

        @Override
        public void accumulate(Binding binding, FunctionEnv functionEnv) {
            nBindings++;
        }

        @Override
        public NodeValue getValue() {
            return null;
        }
    }

}