LazyObjectMap.java

package com.github.czyzby.kiwi.util.gdx.collection.lazy;

import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.ObjectMap;
import com.badlogic.gdx.utils.ObjectSet;
import com.github.czyzby.kiwi.util.gdx.asset.lazy.provider.ArrayObjectProvider;
import com.github.czyzby.kiwi.util.gdx.asset.lazy.provider.MapObjectProvider;
import com.github.czyzby.kiwi.util.gdx.asset.lazy.provider.ObjectProvider;
import com.github.czyzby.kiwi.util.gdx.asset.lazy.provider.SetObjectProvider;

/** An unordered map. This implementation is a cuckoo hash map using 3 hashes, random walking, and a small stash for
 * problematic keys. Null keys are not allowed. Null values are allowed. No allocation is done except when growing the
 * table size. <br>
 * <br>
 * This map performs very fast get, containsKey, and remove (typically O(1), worst case O(log(n))). Put may be a bit
 * slower, depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have
 * to rehash to the next higher POT size. <br>
 * <br>
 * Thanks to the passed ObjectProvider, this map can initiate object on every get(key) call if the key is not present in
 * the map. This implementation is especially useful for maps of other collections (like arrays), where you usually keep
 * a lot of similarly created object instances without the need of varying constructor parameters. Maps of common
 * collections can be easily constructed with static helper methods of this class.
 *
 * @author Nathan Sweet
 * @author MJ */
public class LazyObjectMap<Key, Value> extends ObjectMap<Key, Value> {
    private ObjectProvider<? extends Value> provider;

    /** Creates a new map with an initial capacity of 32 and a load factor of 0.8. This map will hold 25 items before
     * growing the backing table.
     *
     * @param provider creates new object on get(key) calls if the key is not present in the map. */
    public LazyObjectMap(final ObjectProvider<? extends Value> provider) {
        super();
        this.provider = provider;
    }

    /** Creates a new map with a load factor of 0.8. This map will hold initialCapacity * 0.8 items before growing the
     * backing table.
     *
     * @param provider creates new object on get(key) calls if the key is not present in the map. */
    public LazyObjectMap(final ObjectProvider<? extends Value> provider, final int initialCapacity) {
        super(initialCapacity);
        this.provider = provider;
    }

    /** Creates a new map with the specified initial capacity and load factor. This map will hold initialCapacity *
     * loadFactor items before growing the backing table.
     *
     * @param provider creates new object on get(key) calls if the key is not present in the map. */
    public LazyObjectMap(final ObjectProvider<? extends Value> provider, final int initialCapacity,
            final float loadFactor) {
        super(initialCapacity, loadFactor);
        this.provider = provider;
    }

    /** Creates a new map identical to the specified map.
     *
     * @param provider creates new object on get(key) calls if the key is not present in the map. */
    public LazyObjectMap(final ObjectProvider<? extends Value> provider,
            final ObjectMap<? extends Key, ? extends Value> map) {
        super(map);
        this.provider = provider;
    }

    /** Creates a new map identical to the specified map. */
    public LazyObjectMap(final LazyObjectMap<? extends Key, ? extends Value> map) {
        super(map);
        this.provider = map.provider;
    }

    /** @param provider creates new object on get(key) calls if the key is not present in the map.
     * @return new lazy map instance. */
    public static <Key, Value> LazyObjectMap<Key, Value> newMap(final ObjectProvider<? extends Value> provider) {
        return new LazyObjectMap<Key, Value>(provider);
    }

    /** @return a new lazy map that provides empty, non-typed arrays. */
    public static <Key, Value> LazyObjectMap<Key, Array<Value>> newMapOfArrays() {
        final ObjectProvider<Array<Value>> provider = ArrayObjectProvider.getProvider();
        return newMap(provider);
    }

    /** @return a new lazy map that provides empty object sets. */
    public static <Key, Value> LazyObjectMap<Key, ObjectSet<Value>> newMapOfSets() {
        final ObjectProvider<ObjectSet<Value>> provider = SetObjectProvider.getProvider();
        return newMap(provider);
    }

    /** @return a new lazy map that provides empty object maps. */
    public static <Key, MapKey, MapValue> LazyObjectMap<Key, ObjectMap<MapKey, MapValue>> newMapOfMaps() {
        final ObjectProvider<ObjectMap<MapKey, MapValue>> provider = MapObjectProvider.getProvider();
        return newMap(provider);
    }

    /** @param keysAndValues pairs of keys and values.
     * @param provider creates new object on get(key) calls if the key is not present in the map.
     * @return a new LazyObjectMap created with the passed keys and values.
     * @throws IllegalArgumentException if keys and values total amount is not even.
     * @throws ClassCastException if received unexpected object type. */
    @SuppressWarnings("unchecked")
    public static <Key, Value> LazyObjectMap<Key, Value> of(final ObjectProvider<? extends Value> provider,
            final Object... keysAndValues) {
        if (keysAndValues.length % 2 != 0) {
            throw new IllegalArgumentException("Keys and values have to be passed in pairs.");
        }
        final LazyObjectMap<Key, Value> map = new LazyObjectMap<Key, Value>(provider);
        for (int index = 0; index < keysAndValues.length; index += 2) {
            map.put((Key) keysAndValues[index], (Value) keysAndValues[index + 1]);
        }
        return map;
    }

    /** @param provider creates new object on get(key) calls if the key is not present in the map.
     * @return a new LazyObjectMap created with the keys and values stored in passed map. */
    public static <Key, Value> LazyObjectMap<Key, Value> copyOf(
            final ObjectMap<? extends Key, ? extends Value> objectMap, final ObjectProvider<? extends Value> provider) {
        return new LazyObjectMap<Key, Value>(provider, objectMap);
    }

    /** @return a new LazyObjectMap created with the keys and values stored in passed map. */
    public static <Key, Value> LazyObjectMap<Key, Value> copyOf(
            final LazyObjectMap<? extends Key, ? extends Value> lazyMap) {
        return new LazyObjectMap<Key, Value>(lazyMap);
    }

    @Override
    public Value get(final Key key) {
        Value value = super.get(key);
        if (value == null) {
            value = provider.provide();
            put(key, value);
        }
        return value;
    }

    /** LazyObjectMap initiates values on access. No need for default values, as nulls are impossible as long as the
     * provided is correctly implemented and nulls are not put into the map. */
    @Override
    @Deprecated
    public Value get(final Key key, final Value defaultValue) {
        return super.get(key, defaultValue);
    }

    /** @return provider that produces new instances of objects on get(key) calls with unknown keys. */
    public ObjectProvider<? extends Value> getProvider() {
        return provider;
    }

    /** @param provider produces new instances of objects on get(key) calls with unknown keys. */
    public void setProvider(final ObjectProvider<? extends Value> provider) {
        this.provider = provider;
    }
}