/*
 * 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.commons.math.analysis.integration;

import org.apache.commons.math.ConvergingAlgorithmImpl;
import org.apache.commons.math.MathRuntimeException;
import org.apache.commons.math.analysis.UnivariateRealFunction;

/**
 * Provide a default implementation for several generic functions.
 * 
 * @version $Revision$ $Date$
 * @since 1.2
 */
public abstract class UnivariateRealIntegratorImpl extends ConvergingAlgorithmImpl implements UnivariateRealIntegrator {

	/** Serializable version identifier. */
	private static final long serialVersionUID = 6248808456637441533L;

	/** minimum number of iterations */
	protected int minimalIterationCount;

	/** default minimum number of iterations */
	protected int defaultMinimalIterationCount;

	/** indicates whether an integral has been computed */
	protected boolean resultComputed = false;

	/** the last computed integral */
	protected double result;

	/**
	 * The integrand functione.
	 * 
	 * @deprecated as of 2.0 the integrand function is passed as an argument to
	 *             the
	 *             {@link #integrate(UnivariateRealFunction, double, double)}method.
	 */
	@Deprecated
	protected UnivariateRealFunction f;

	/**
	 * Construct an integrator with given iteration count and accuracy.
	 * 
	 * @param f
	 *            the integrand function
	 * @param defaultMaximalIterationCount
	 *            maximum number of iterations
	 * @throws IllegalArgumentException
	 *             if f is null or the iteration limits are not valid
	 * @deprecated as of 2.0 the integrand function is passed as an argument to
	 *             the
	 *             {@link #integrate(UnivariateRealFunction, double, double)}method.
	 */
	@Deprecated
	protected UnivariateRealIntegratorImpl(final UnivariateRealFunction f, final int defaultMaximalIterationCount)
			throws IllegalArgumentException {
		super(defaultMaximalIterationCount, 1.0e-15);
		if (f == null) {
			throw MathRuntimeException.createIllegalArgumentException("function is null");
		}

		this.f = f;

		// parameters that are problem specific
		setRelativeAccuracy(1.0e-6);
		this.defaultMinimalIterationCount = 3;
		this.minimalIterationCount = defaultMinimalIterationCount;

		verifyIterationCount();
	}

	/**
	 * Construct an integrator with given iteration count and accuracy.
	 * 
	 * @param defaultMaximalIterationCount
	 *            maximum number of iterations
	 * @throws IllegalArgumentException
	 *             if f is null or the iteration limits are not valid
	 */
	protected UnivariateRealIntegratorImpl(final int defaultMaximalIterationCount) throws IllegalArgumentException {
		super(defaultMaximalIterationCount, 1.0e-15);

		// parameters that are problem specific
		setRelativeAccuracy(1.0e-6);
		this.defaultMinimalIterationCount = 3;
		this.minimalIterationCount = defaultMinimalIterationCount;

		verifyIterationCount();
	}

	/**
	 * Access the last computed integral.
	 * 
	 * @return the last computed integral
	 * @throws IllegalStateException
	 *             if no integral has been computed
	 */
	public double getResult() throws IllegalStateException {
		if (resultComputed) {
			return result;
		} else {
			throw MathRuntimeException.createIllegalStateException("no result available");
		}
	}

	/**
	 * Convenience function for implementations.
	 * 
	 * @param result
	 *            the result to set
	 * @param iterationCount
	 *            the iteration count to set
	 */
	protected final void setResult(double result, int iterationCount) {
		this.result = result;
		this.iterationCount = iterationCount;
		this.resultComputed = true;
	}

	/**
	 * Convenience function for implementations.
	 */
	protected final void clearResult() {
		this.iterationCount = 0;
		this.resultComputed = false;
	}

	/** {@inheritDoc} */
	public void setMinimalIterationCount(int count) {
		minimalIterationCount = count;
	}

	/** {@inheritDoc} */
	public int getMinimalIterationCount() {
		return minimalIterationCount;
	}

	/** {@inheritDoc} */
	public void resetMinimalIterationCount() {
		minimalIterationCount = defaultMinimalIterationCount;
	}

	/**
	 * Verifies that the endpoints specify an interval.
	 * 
	 * @param lower
	 *            lower endpoint
	 * @param upper
	 *            upper endpoint
	 * @throws IllegalArgumentException
	 *             if not interval
	 */
	protected void verifyInterval(double lower, double upper) throws IllegalArgumentException {
		if (lower >= upper) {
			throw MathRuntimeException
					.createIllegalArgumentException("endpoints do not specify an interval: [{0}, {1}]", lower, upper);
		}
	}

	/**
	 * Verifies that the upper and lower limits of iterations are valid.
	 * 
	 * @throws IllegalArgumentException
	 *             if not valid
	 */
	protected void verifyIterationCount() throws IllegalArgumentException {
		if ((minimalIterationCount <= 0) || (maximalIterationCount <= minimalIterationCount)) {
			throw MathRuntimeException.createIllegalArgumentException("invalid iteration limits: min={0}, max={1}",
					minimalIterationCount, maximalIterationCount);
		}
	}
}
