package org.junit.internal;

import java.lang.reflect.Array;
import java.util.Arrays;

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.
/**
 * 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 AssertionError is thrown with the given message. If expecteds and
actuals are null, they are considered equal.
Params:
message – the identifying message for the AssertionError ( null okay)
expecteds – Object array or array of arrays (multi-dimensional array) with
expected values.
actuals – Object array or array of arrays (multi-dimensional array) with
actual values/**
     * 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 {
        arrayEquals(message, expecteds, actuals, true);
    }

    private void arrayEquals(String message, Object expecteds, Object actuals, boolean outer)
            throws ArrayComparisonFailure {
        if (expecteds == actuals
            || Arrays.deepEquals(new Object[] {expecteds}, new Object[] {actuals})) {
            // The reflection-based loop below is potentially very slow, especially for primitive
            // arrays. The deepEquals check allows us to circumvent it in the usual case where
            // the arrays are exactly equal.
            return;
        }
        String header = message == null ? "" : message + ": ";

        // Only include the user-provided message in the outer exception.
        String exceptionMessage = outer ? header : "";

        if (expecteds == null) {
            Assert.fail(exceptionMessage + "expected array was null");
        }
        if (actuals == null) {
            Assert.fail(exceptionMessage + "actual array was null");
        }

        int actualsLength = Array.getLength(actuals);
        int expectedsLength = Array.getLength(expecteds);
        if (actualsLength != expectedsLength) {
            header += "array lengths differed, expected.length="
                    + expectedsLength + " actual.length=" + actualsLength + "; ";
        }
        int prefixLength = Math.min(actualsLength, expectedsLength);

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

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

        if (actualsLength != expectedsLength) {
            Object expected = getToStringableArrayElement(expecteds, expectedsLength, prefixLength);
            Object actual = getToStringableArrayElement(actuals, actualsLength, prefixLength);
            try {
                Assert.assertEquals(expected, actual);
            } catch (AssertionError e) {
                throw new ArrayComparisonFailure(header, e, prefixLength);
            }
        }
    }

    private static final Object END_OF_ARRAY_SENTINEL = objectWithToString("end of array");

    private Object getToStringableArrayElement(Object array, int length, int index) {
        if (index < length) {
            Object element = Array.get(array, index);
            if (isArray(element)) {
                return objectWithToString(componentTypeName(element.getClass()) + "[" + Array.getLength(element) + "]");
            } else {
                return element;
            }
        } else {
            return END_OF_ARRAY_SENTINEL;
        }
    }

    private static Object objectWithToString(final String string) {
        return new Object() {
            @Override
            public String toString() {
                return string;
            }
        };
    }

    private String componentTypeName(Class<?> arrayClass) {
        Class<?> componentType = arrayClass.getComponentType();
        if (componentType.isArray()) {
            return componentTypeName(componentType) + "[]";
        } else {
            return componentType.getName();
        }
    }

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

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