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Core building blocks and API for the Metal library.
There is a newer version: 10.0.0
/*
 * Copyright 2013-2016 Netherlands Forensic Institute
 *
 * 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 io.parsingdata.metal.token;

import static io.parsingdata.metal.Util.checkNotNull;
import static io.parsingdata.metal.data.ParseResult.failure;
import static io.parsingdata.metal.data.ParseResult.success;

import java.io.IOException;

import io.parsingdata.metal.data.Environment;
import io.parsingdata.metal.data.ImmutableList;
import io.parsingdata.metal.data.ParseResult;
import io.parsingdata.metal.encoding.Encoding;
import io.parsingdata.metal.expression.value.OptionalValue;
import io.parsingdata.metal.expression.value.ValueExpression;

/**
 * A {@link Token} that specifies a bounded repetition of a token.
 * 
 * A RepN consists of a token (a {@link Token}) and an
 * n (a {@link ValueExpression}). First n is
 * evaluated. Parsing fails if it does not evaluate to a single value. The
 * token is then parsed for an amount of times equal to the evaluated value of
 * n. RepN succeeds if this succeeds.
 *
 * @see Rep
 * @see ValueExpression
 */
public class RepN extends Token {

    public final Token token;
    public final ValueExpression n;

    public RepN(final String name, final Token token, final ValueExpression n, final Encoding encoding) {
        super(name, encoding);
        this.token = checkNotNull(token, "token");
        this.n = checkNotNull(n, "n");
    }

    @Override
    protected ParseResult parseImpl(final String scope, final Environment environment, final Encoding encoding) throws IOException {
        final ImmutableList counts = n.eval(environment, encoding);
        if (counts.size != 1 || !counts.head.isPresent()) {
            return failure(environment);
        }
        final ParseResult result = iterate(scope, environment.addBranch(this), encoding, counts.head.get().asNumeric().longValue());
        if (result.succeeded) {
            return success(result.environment.closeBranch());
        }
        return failure(environment);
    }

    private ParseResult iterate(final String scope, final Environment environment, final Encoding encoding, final long count) throws IOException {
        if (count <= 0) {
            return success(environment);
        }
        final ParseResult result = token.parse(scope, environment, encoding);
        if (result.succeeded) {
            return iterate(scope, result.environment, encoding, count - 1);
        }
        return failure(environment);
    }

    @Override
    public String toString() {
        return getClass().getSimpleName() + "(" + makeNameFragment() + token + "," + n + ")";
    }

}