/*
 * Copyright (C) 2002-2017 Sebastiano Vigna
 *
 * Licensed 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 PACKAGE;

import it.unimi.dsi.fastutil.Function;

/** A class providing static methods and objects that do useful things with type-specific functions.
 *
 * @see it.unimi.dsi.fastutil.Function
 * @see java.util.Collections
 */

public final class FUNCTIONS {

	private FUNCTIONS() {}

	/** An immutable class representing an empty type-specific function.
	 *
	 * <p>This class may be useful to implement your own in case you subclass
	 * a type-specific function.
	 */

	public static class EmptyFunction KEY_VALUE_GENERIC extends ABSTRACT_FUNCTION KEY_VALUE_GENERIC implements java.io.Serializable, Cloneable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected EmptyFunction() {}

		@Override
		public VALUE_GENERIC_TYPE GET_VALUE(final KEY_TYPE k) { return VALUE_NULL; }

		@Override
		public boolean containsKey(final KEY_TYPE k) { return false; }

		@Override
		public VALUE_GENERIC_TYPE defaultReturnValue()  { return VALUE_NULL; }

		@Override
		public void defaultReturnValue(final VALUE_GENERIC_TYPE defRetValue)  { throw new UnsupportedOperationException(); }

		@Override
		public int size() { return 0; }

		@Override
		public void clear() {}

		@Override
		public Object clone() { return EMPTY_FUNCTION; }

		@Override
		public int hashCode() { return 0; }

		@Override
		public boolean equals(final Object o) {
			if (! (o instanceof Function)) return false;
			return ((Function<?,?>)o).size() == 0;
		}

		@Override
		public String toString() { return "{}"; }

		private Object readResolve() { return EMPTY_FUNCTION; }
	}


	/** An empty type-specific function (immutable). It is serializable and cloneable. */

	SUPPRESS_WARNINGS_KEY_VALUE_RAWTYPES
	public static final EmptyFunction EMPTY_FUNCTION = new EmptyFunction();


	/** An immutable class representing a type-specific singleton function.	Note
	 *  that the default return value is still settable.
	 *
	 * <p>Note that albeit the function is immutable, its default return value may be changed.
	 *
	 * <p>This class may be useful to implement your own in case you subclass
	 * a type-specific function.
	 */

	public static class Singleton KEY_VALUE_GENERIC extends ABSTRACT_FUNCTION KEY_VALUE_GENERIC implements java.io.Serializable, Cloneable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final KEY_GENERIC_TYPE key;
		protected final VALUE_GENERIC_TYPE value;

		protected Singleton(final KEY_GENERIC_TYPE key, final VALUE_GENERIC_TYPE value) {
			this.key = key;
			this.value = value;
		}

		@Override
		public boolean containsKey(final KEY_TYPE k) { return KEY_EQUALS(key, k); }

		@Override
		public VALUE_GENERIC_TYPE GET_VALUE(final KEY_TYPE k) { return KEY_EQUALS(key, k) ? value : defRetValue; }

		@Override
		public int size() { return 1; }

		@Override
		public Object clone() { return this; }
	}

	/** Returns a type-specific immutable function containing only the specified pair.
	 * The returned function is serializable and cloneable.
	 *
	 * <p>Note that albeit the returned function is immutable, its default return value may be changed.
	 *
	 * @param key the only key of the returned function.
	 * @param value the only value of the returned function.
	 * @return a type-specific immutable function containing just the pair {@code &lt;key,value&gt;}.
	 */

	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC singleton(final KEY_GENERIC_TYPE key, VALUE_GENERIC_TYPE value) {
		return new Singleton KEY_VALUE_GENERIC_DIAMOND(key, value);
	}

#if KEYS_PRIMITIVE || VALUES_PRIMITIVE

	/** Returns a type-specific immutable function containing only the specified pair. The returned function is serializable and cloneable.
	 *
	 * <p>Note that albeit the returned function is immutable, its default return value may be changed.
	 *
	 * @param key the only key of the returned function.
	 * @param value the only value of the returned function.
	 * @return a type-specific immutable function containing just the pair {@code &lt;key,value&gt;}.
	 */

	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC singleton(final KEY_GENERIC_CLASS key, final VALUE_GENERIC_CLASS value) {
		return new Singleton KEY_VALUE_GENERIC_DIAMOND(KEY_CLASS2TYPE(key), VALUE_CLASS2TYPE(value));
	}

#endif


	/** A synchronized wrapper class for functions. */

	public static class SynchronizedFunction KEY_VALUE_GENERIC implements FUNCTION KEY_VALUE_GENERIC, java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final FUNCTION KEY_VALUE_GENERIC function;
		protected final Object sync;

		protected SynchronizedFunction(final FUNCTION KEY_VALUE_GENERIC f, final Object sync) {
			if (f == null) throw new NullPointerException();
			this.function = f;
			this.sync = sync;
		}

		protected SynchronizedFunction(final FUNCTION KEY_VALUE_GENERIC f) {
			if (f == null) throw new NullPointerException();
			this.function = f;
			this.sync = this;
		}

#ifdef JDK_PRIMITIVE_FUNCTION

#if KEY_WIDENED
		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
#endif
		@Override
		public VALUE_GENERIC_TYPE_WIDENED JDK_PRIMITIVE_FUNCTION_APPLY(KEY_GENERIC_TYPE_WIDENED operand) { synchronized(sync) { return function.JDK_PRIMITIVE_FUNCTION_APPLY(operand); } }

#endif

#if KEYS_PRIMITIVE || VALUES_PRIMITIVE
		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
#endif
		@Override
		public VALUE_GENERIC_CLASS apply(final KEY_GENERIC_CLASS key) { synchronized (sync) { return function.apply(key); } }

		@Override
		public int size() { synchronized(sync) { return function.size(); } }

		@Override
		public VALUE_GENERIC_TYPE defaultReturnValue()  { synchronized(sync) { return function.defaultReturnValue(); } }

		@Override
		public void defaultReturnValue(final VALUE_GENERIC_TYPE defRetValue)  { synchronized(sync) { function.defaultReturnValue(defRetValue); } }

		@Override
		public boolean containsKey(final KEY_TYPE k) { synchronized(sync) { return function.containsKey(k); } }

#if KEYS_PRIMITIVE

		@Deprecated
		@Override
		public boolean containsKey(final Object k) { synchronized(sync) { return function.containsKey(k); } }

#endif

		@Override
		public VALUE_GENERIC_TYPE put(final KEY_GENERIC_TYPE k, final VALUE_GENERIC_TYPE v) { synchronized(sync) { return function.put(k, v); } }

		@Override
		public VALUE_GENERIC_TYPE GET_VALUE(final KEY_TYPE k) { synchronized(sync) { return function.GET_VALUE(k); } }

		@Override
		public VALUE_GENERIC_TYPE REMOVE_VALUE(final KEY_TYPE k) { synchronized(sync) { return function.REMOVE_VALUE(k); } }

		@Override
		public void clear() { synchronized(sync) { function.clear(); } }

#if KEYS_PRIMITIVE || VALUES_PRIMITIVE

		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS put(final KEY_GENERIC_CLASS k, final VALUE_GENERIC_CLASS v) { synchronized(sync) { return function.put(k, v); } }

		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS get(final Object k) { synchronized(sync) { return function.get(k); } }

		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS remove(final Object k) { synchronized(sync) { return function.remove(k); } }

#endif

		@Override
		public int hashCode() { synchronized(sync) { return function.hashCode(); } }

		@Override
		public boolean equals(final Object o) {
			if (o == this) return true;
			synchronized(sync) { return function.equals(o); }
		}

		@Override
		public String toString() { synchronized(sync) { return function.toString(); } }

		private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
			synchronized(sync) { s.defaultWriteObject(); }
		}
	}

	/** Returns a synchronized type-specific function backed by the given type-specific function.
	 *
	 * @param f the function to be wrapped in a synchronized function.
	 * @return a synchronized view of the specified function.
	 * @see java.util.Collections#synchronizedMap(java.util.Map)
	 */
	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC synchronize(final FUNCTION KEY_VALUE_GENERIC f) { return new SynchronizedFunction KEY_VALUE_GENERIC_DIAMOND(f); }

	/** Returns a synchronized type-specific function backed by the given type-specific function, using an assigned object to synchronize.
	 *
	 * @param f the function to be wrapped in a synchronized function.
	 * @param sync an object that will be used to synchronize the access to the function.
	 * @return a synchronized view of the specified function.
	 * @see java.util.Collections#synchronizedMap(java.util.Map)
	 */

	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC synchronize(final FUNCTION KEY_VALUE_GENERIC f, final Object sync) { return new SynchronizedFunction KEY_VALUE_GENERIC_DIAMOND(f, sync); }



	/** An unmodifiable wrapper class for functions. */

	public static class UnmodifiableFunction KEY_VALUE_GENERIC extends ABSTRACT_FUNCTION KEY_VALUE_GENERIC implements java.io.Serializable {

		private static final long serialVersionUID = -7046029254386353129L;

		protected final FUNCTION KEY_VALUE_GENERIC function;

		protected UnmodifiableFunction(final FUNCTION KEY_VALUE_GENERIC f) {
			if (f == null) throw new NullPointerException();
			this.function = f;
		}

		@Override
		public int size() { return function.size(); }

		@Override
		public VALUE_GENERIC_TYPE defaultReturnValue()  { return function.defaultReturnValue(); }

		@Override
		public void defaultReturnValue(final VALUE_GENERIC_TYPE defRetValue)  { throw new UnsupportedOperationException(); }

		@Override
		public boolean containsKey(final KEY_TYPE k) { return function.containsKey(k); }

		@Override
		public VALUE_GENERIC_TYPE put(final KEY_GENERIC_TYPE k, final VALUE_GENERIC_TYPE v) { throw new UnsupportedOperationException(); }

		@Override
		public VALUE_GENERIC_TYPE GET_VALUE(final KEY_TYPE k) { return function.GET_VALUE(k); }

		@Override
		public VALUE_GENERIC_TYPE REMOVE_VALUE(final KEY_TYPE k) { throw new UnsupportedOperationException(); }

		@Override
		public void clear() { throw new UnsupportedOperationException(); }

#if KEYS_PRIMITIVE || VALUES_PRIMITIVE
		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS put(final KEY_GENERIC_CLASS k, final VALUE_GENERIC_CLASS v) { throw new UnsupportedOperationException(); }

		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS get(final Object k) { return function.get(k); }

		/** {@inheritDoc}
		 * @deprecated Please use the corresponding type-specific method instead. */
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS remove(final Object k) { throw new UnsupportedOperationException(); }
#endif

		@Override
		public int hashCode() { return function.hashCode(); }

		@Override
		public boolean equals(Object o) { return o == this || function.equals(o); }

		@Override
		public String toString() { return function.toString(); }
	}

	/** Returns an unmodifiable type-specific function backed by the given type-specific function.
	 *
	 * @param f the function to be wrapped in an unmodifiable function.
	 * @return an unmodifiable view of the specified function.
	 * @see java.util.Collections#unmodifiableMap(java.util.Map)
	 */
	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC unmodifiable(final FUNCTION KEY_VALUE_GENERIC f) { return new UnmodifiableFunction KEY_VALUE_GENERIC_DIAMOND(f); }


#if KEYS_PRIMITIVE || VALUES_PRIMITIVE
	/** An adapter for mapping generic total functions to partial primitive functions. */

	public static class PrimitiveFunction KEY_VALUE_GENERIC implements FUNCTION KEY_VALUE_GENERIC {
		protected final java.util.function.Function<? super KEY_GENERIC_CLASS, ? extends VALUE_GENERIC_CLASS> function;

		protected PrimitiveFunction(java.util.function.Function<? super KEY_GENERIC_CLASS, ? extends VALUE_GENERIC_CLASS> function) {
			this.function = function;
		}

#if KEYS_PRIMITIVE
		@Override
		public boolean containsKey(KEY_GENERIC_TYPE key) { return function.apply(KEY2OBJ(key)) != null; }
#endif

		SUPPRESS_WARNINGS_KEY_UNCHECKED
#if KEYS_PRIMITIVE
		@Deprecated
#endif
		@Override
		public boolean containsKey(Object key) {
#if KEYS_PRIMITIVE
			if (key == null) return false;
#endif
			return function.apply(KEY_CLASS_CAST (key)) != null;
		}

		SUPPRESS_WARNINGS_KEY_UNCHECKED
		@Override
		public VALUE_GENERIC_TYPE GET_VALUE(KEY_TYPE key) {
			VALUE_GENERIC_CLASS v = function.apply(KEY_GENERIC_CAST KEY2OBJ(key));
#if VALUES_PRIMITIVE
			if (v == null) return defaultReturnValue();
#else
			if (v == null) return null;
#endif
			return VALUE_CLASS2TYPE(v);
		}

		SUPPRESS_WARNINGS_KEY_UNCHECKED
		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS get(Object key) {
#if KEYS_PRIMITIVE
			if (key == null) return null;
#endif
			return function.apply(KEY_CLASS_CAST key);
		}

		@Deprecated
		@Override
		public VALUE_GENERIC_CLASS put(final KEY_GENERIC_CLASS key, final VALUE_GENERIC_CLASS value) { throw new UnsupportedOperationException(); }
	}

	/** Returns a (partial) type-specific function based on the given total generic function.
	 * <p>The returned function contains all keys which are not mapped to {@code null}. If the function already
	 * is a primitive function, it is returned without changes.
	 * <p><strong>Warning</strong>: If the given function is a &ldquo;widened&rdquo; primitive function (e.g. an
	 * {@code Int2IntFunction} given to {@code Short2ShortFunctions}), it still is wrapped into a proxy,
	 * decreasing performance.
	 *
	 * @param f the function to be converted to a type-specific function.
	 * @return a primitive view of the specified function.
	 * @throws NullPointerException if {@code f} is null.
	 * @see PrimitiveFunction
	 * @since 8.1.0
	 */
	SUPPRESS_WARNINGS_KEY_VALUE_UNCHECKED
	public static KEY_VALUE_GENERIC FUNCTION KEY_VALUE_GENERIC primitive(final java.util.function.Function<? super KEY_GENERIC_CLASS, ? extends VALUE_GENERIC_CLASS> f) {
		java.util.Objects.requireNonNull(f);

		if (f instanceof FUNCTION) return (FUNCTION KEY_VALUE_GENERIC) f;
#if defined JDK_PRIMITIVE_FUNCTION
		if (f instanceof JDK_PRIMITIVE_FUNCTION)
#if KEYS_PRIMITIVE
#if VALUE_WIDENED
			return key -> VALUE_NARROWING(((JDK_PRIMITIVE_FUNCTION KEY_VALUE_GENERIC) f).JDK_PRIMITIVE_FUNCTION_APPLY(key));
#else
			return ((JDK_PRIMITIVE_FUNCTION KEY_VALUE_GENERIC) f)::JDK_PRIMITIVE_FUNCTION_APPLY;
#endif
#else
			return key -> VALUE_NARROWING(((JDK_PRIMITIVE_FUNCTION KEY_VALUE_GENERIC) f).JDK_PRIMITIVE_FUNCTION_APPLY((K)(key)));
#endif
#endif
		return new PrimitiveFunction KEY_VALUE_GENERIC_DIAMOND(f);
	}
#endif
}
