package org.richfaces.taglib;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

class TypedCollections {

    /**
     * Dynamically check that the members of the collection are all instances of
     * the given type (or null).
     */
    private static boolean checkCollectionMembers(Collection<?> c, Class<?> type) {
	for (Object element : c) {
	    if (element != null && !type.isInstance(element)) {
		return false;
	    }
	}
	return true;
    }

    /**
     * Dynamically check that the members of the collection are all instances of
     * the given type (or null), and that the collection itself is of the given
     * collection type.
     * 
     * @param <E>
     *                the collection's element type
     * @param c
     *                the collection to cast
     * @param type
     *                the class of the collection's element type.
     * @return the dynamically-type checked collection.
     * @throws java.lang.ClassCastException
     */
    @SuppressWarnings("unchecked")
    static <E, TypedC extends Collection<E>> TypedC dynamicallyCastCollection(
	    Collection<?> c, Class<E> type, Class<TypedC> collectionType) {
	if (c == null)
	    return null;
	if (!collectionType.isInstance(c))
	    throw new ClassCastException(c.getClass().getName());
	assert checkCollectionMembers(c, type) : "The collection contains members with a type other than "
		+ type.getName();

	return collectionType.cast(c);
    }

    /**
     * Dynamically check that the members of the list are all instances of the
     * given type (or null).
     * 
     * @param <E>
     *                the list's element type
     * @param list
     *                the list to cast
     * @param type
     *                the class of the list's element type.
     * @return the dynamically-type checked list.
     * @throws java.lang.ClassCastException
     */
    @SuppressWarnings("unchecked")
    static <E> List<E> dynamicallyCastList(List<?> list, Class<E> type) {
	return dynamicallyCastCollection(list, type, List.class);
    }

    /**
     * Dynamically check that the members of the set are all instances of the
     * given type (or null).
     * 
     * @param <E>
     *                the set's element type
     * @param set
     *                the set to cast
     * @param type
     *                the class of the set's element type.
     * @return the dynamically-type checked set.
     * @throws java.lang.ClassCastException
     */
    @SuppressWarnings("unchecked")
    static <E> Set<E> dynamicallyCastSet(Set<?> set, Class<E> type) {
	return dynamicallyCastCollection(set, type, Set.class);
    }

    /**
     * Dynamically check that the keys and values in the map are all instances
     * of the correct types (or null).
     * 
     * @param <K>
     *                the map's key type
     * @param <V>
     *                the map's value type
     * @param map
     *                the map to cast
     * @param keyType
     *                the class of the map's key type.
     * @param keyType
     *                the class of the map's key type.
     * @return the dynamically-type checked map.
     * @throws java.lang.ClassCastException
     */
    @SuppressWarnings("unchecked")
    static <K, V> Map<K, V> dynamicallyCastMap(Map<?, ?> map, Class<K> keyType,
	    Class<V> valueType) {
	if (map == null) {
	    return null;
	}
	assert checkCollectionMembers(map.keySet(), keyType) : "The map contains keys with a type other than "
		+ keyType.getName();
	assert checkCollectionMembers(map.values(), valueType) : "The map contains values with a type other than "
		+ valueType.getName();

	return (Map<K, V>) map;
    }
}

