com.hotels.styx.server.routing.antlr.AntlrConditionParser Maven / Gradle / Ivy

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/**
 * Copyright (C) 2013-2017 Expedia Inc.
 *
 * Licensed 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 com.hotels.styx.server.routing.antlr;

import com.hotels.styx.server.routing.Condition;
import com.hotels.styx.server.routing.ConditionLexer;
import com.hotels.styx.server.routing.ConditionParser;
import org.antlr.v4.runtime.ANTLRInputStream;
import org.antlr.v4.runtime.BaseErrorListener;
import org.antlr.v4.runtime.CommonTokenStream;
import org.antlr.v4.runtime.RecognitionException;
import org.antlr.v4.runtime.Recognizer;

import java.util.HashMap;
import java.util.Map;

/**
 * A {@link Condition} parser based on ANLR.
 */
public class AntlrConditionParser implements Condition.Parser {
    private final ExpressionVisitor expressionVisitor;

    public AntlrConditionParser(Builder builder) {
        this.expressionVisitor = new ExpressionVisitor(builder.zeroArgumentFunctions, builder.oneArgumentFunctions);
    }

    @Override
    public Condition parse(String condition) {
        ConditionParser parser = new ConditionParser(
                new CommonTokenStream(new ConditionLexer(new ANTLRInputStream(condition))));
        parser.addErrorListener(new BaseErrorListener() {
            @Override
            public void syntaxError(Recognizer recognizer, Object offendingSymbol, int line, int charPositionInLine, String msg, RecognitionException e) {
                throw new DslSyntaxError(line, charPositionInLine, msg, e);
            }
        });

        return new AntlrCondition(expressionVisitor.visit(parser.expression()));
    }

    /**
     * Builder for {@link AntlrConditionParser}.
     */
    public static class Builder {
        private final Map zeroArgumentFunctions = new HashMap<>();
        private final Map oneArgumentFunctions = new HashMap<>();

        public Builder registerFunction(String name, Function0 function0) {
            zeroArgumentFunctions.put(name, function0);
            return this;
        }

        public Builder registerFunction(String name, Function1 function1) {
            oneArgumentFunctions.put(name, function1);
            return this;
        }

        public AntlrConditionParser build() {
            return new AntlrConditionParser(this);
        }
    }
}