package org.junit.internal;

import java.lang.reflect.Array;

import org.junit.Assert;

/**
 * Defines criteria for finding two items "equal enough". Concrete subclasses
 * may demand exact equality, or, for example, equality within a given delta.
 */
public abstract class ComparisonCriteria {
    /**
     * Asserts that two arrays are equal, according to the criteria defined by
     * the concrete subclass. If they are not, an {@link AssertionError} is
     * thrown with the given message. If <code>expecteds</code> and
     * <code>actuals</code> are <code>null</code>, they are considered equal.
     *
     * @param message the identifying message for the {@link AssertionError} (
     * <code>null</code> okay)
     * @param expecteds Object array or array of arrays (multi-dimensional array) with
     * expected values.
     * @param actuals Object array or array of arrays (multi-dimensional array) with
     * actual values
     */
    public void arrayEquals(String message, Object expecteds, Object actuals)
            throws ArrayComparisonFailure {
        if (expecteds == actuals) {
            return;
        }
        String header = message == null ? "" : message + ": ";

        int expectedsLength = assertArraysAreSameLength(expecteds,
                actuals, header);

        for (int i = 0; i < expectedsLength; i++) {
            Object expected = Array.get(expecteds, i);
            Object actual = Array.get(actuals, i);

            if (isArray(expected) && isArray(actual)) {
                try {
                    arrayEquals(message, expected, actual);
                } catch (ArrayComparisonFailure e) {
                    e.addDimension(i);
                    throw e;
                }
            } else {
                try {
                    assertElementsEqual(expected, actual);
                } catch (AssertionError e) {
                    throw new ArrayComparisonFailure(header, e, i);
                }
            }
        }
    }

    private boolean isArray(Object expected) {
        return expected != null && expected.getClass().isArray();
    }

    private int assertArraysAreSameLength(Object expecteds,
            Object actuals, String header) {
        if (expecteds == null) {
            Assert.fail(header + "expected array was null");
        }
        if (actuals == null) {
            Assert.fail(header + "actual array was null");
        }
        int actualsLength = Array.getLength(actuals);
        int expectedsLength = Array.getLength(expecteds);
        if (actualsLength != expectedsLength) {
            Assert.fail(header + "array lengths differed, expected.length="
                    + expectedsLength + " actual.length=" + actualsLength);
        }
        return expectedsLength;
    }

    protected abstract void assertElementsEqual(Object expected, Object actual);
}