/*****************************************************************************
 * Copyright (C) Codehaus.org                                                *
 * ------------------------------------------------------------------------- *
 * 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.                                            *
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package net.ion.rosetta;

import java.util.concurrent.atomic.AtomicReference;

import net.ion.rosetta.util.Checks;

/**
 * Delegates to the {@link Parser} object stored in a {@link AtomicReference} dynamically when parsing.
 * 
 * @author Ben Yu
 */
final class LazyParser<T> extends Parser<T> {
	private final AtomicReference<Parser<T>> ref;

	LazyParser(AtomicReference<Parser<T>> ref) {
		this.ref = ref;
	}

	@Override
	boolean apply(ParseContext ctxt) {
		return deref().apply(ctxt);
	}

	private Parser<T> deref() {
		Parser<T> p = ref.get();
		Checks.checkNotNullState(p, "Uninitialized lazy parser reference. Did you forget to call set() on the reference?");
		return p;
	}

	@Override
	public String toString() {
		return "lazy";
	}
}