/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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 com.google.common.hash;

import java.io.OutputStream;
import java.io.Serializable;
import java.nio.charset.Charset;

import javax.annotation.Nullable;

import com.google.common.annotations.Beta;
import com.google.common.base.Preconditions;

/**
 * Funnels for common types. All implementations are serializable.
 *
 * @author Dimitris Andreou
 * @since 11.0
 */
@Beta
public final class Funnels {
	private Funnels() {
	}

	/**
	 * Returns a funnel that extracts the bytes from a {@code byte} array.
	 */
	public static Funnel<byte[]> byteArrayFunnel() {
		return ByteArrayFunnel.INSTANCE;
	}

	private enum ByteArrayFunnel implements Funnel<byte[]> {
		INSTANCE;

		public void funnel(byte[] from, PrimitiveSink into) {
			into.putBytes(from);
		}

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

	/**
	 * Returns a funnel that extracts the characters from a {@code CharSequence}, a
	 * character at a time, without performing any encoding. If you need to use a
	 * specific encoding, use {@link Funnels#stringFunnel(Charset)} instead.
	 *
	 * @since 15.0 (since 11.0 as {@code Funnels.stringFunnel()}.
	 */
	public static Funnel<CharSequence> unencodedCharsFunnel() {
		return UnencodedCharsFunnel.INSTANCE;
	}

	private enum UnencodedCharsFunnel implements Funnel<CharSequence> {
		INSTANCE;

		public void funnel(CharSequence from, PrimitiveSink into) {
			into.putUnencodedChars(from);
		}

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

	/**
	 * Returns a funnel that encodes the characters of a {@code CharSequence} with
	 * the specified {@code Charset}.
	 *
	 * @since 15.0
	 */
	public static Funnel<CharSequence> stringFunnel(Charset charset) {
		return new StringCharsetFunnel(charset);
	}

	private static class StringCharsetFunnel implements Funnel<CharSequence>, Serializable {
		private final Charset charset;

		StringCharsetFunnel(Charset charset) {
			this.charset = Preconditions.checkNotNull(charset);
		}

		public void funnel(CharSequence from, PrimitiveSink into) {
			into.putString(from, charset);
		}

		@Override
		public String toString() {
			return "Funnels.stringFunnel(" + charset.name() + ")";
		}

		@Override
		public boolean equals(@Nullable Object o) {
			if (o instanceof StringCharsetFunnel) {
				StringCharsetFunnel funnel = (StringCharsetFunnel) o;
				return this.charset.equals(funnel.charset);
			}
			return false;
		}

		@Override
		public int hashCode() {
			return StringCharsetFunnel.class.hashCode() ^ charset.hashCode();
		}

		Object writeReplace() {
			return new SerializedForm(charset);
		}

		private static class SerializedForm implements Serializable {
			private final String charsetCanonicalName;

			SerializedForm(Charset charset) {
				this.charsetCanonicalName = charset.name();
			}

			private Object readResolve() {
				return stringFunnel(Charset.forName(charsetCanonicalName));
			}

			private static final long serialVersionUID = 0;
		}
	}

	/**
	 * Returns a funnel for integers.
	 *
	 * @since 13.0
	 */
	public static Funnel<Integer> integerFunnel() {
		return IntegerFunnel.INSTANCE;
	}

	private enum IntegerFunnel implements Funnel<Integer> {
		INSTANCE;

		public void funnel(Integer from, PrimitiveSink into) {
			into.putInt(from);
		}

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

	/**
	 * Returns a funnel that processes an {@code Iterable} by funneling its elements
	 * in iteration order with the specified funnel. No separators are added between
	 * the elements.
	 *
	 * @since 15.0
	 */
	public static <E> Funnel<Iterable<? extends E>> sequentialFunnel(Funnel<E> elementFunnel) {
		return new SequentialFunnel<E>(elementFunnel);
	}

	private static class SequentialFunnel<E> implements Funnel<Iterable<? extends E>>, Serializable {
		private final Funnel<E> elementFunnel;

		SequentialFunnel(Funnel<E> elementFunnel) {
			this.elementFunnel = Preconditions.checkNotNull(elementFunnel);
		}

		public void funnel(Iterable<? extends E> from, PrimitiveSink into) {
			for (E e : from) {
				elementFunnel.funnel(e, into);
			}
		}

		@Override
		public String toString() {
			return "Funnels.sequentialFunnel(" + elementFunnel + ")";
		}

		@Override
		public boolean equals(@Nullable Object o) {
			if (o instanceof SequentialFunnel) {
				SequentialFunnel<?> funnel = (SequentialFunnel<?>) o;
				return elementFunnel.equals(funnel.elementFunnel);
			}
			return false;
		}

		@Override
		public int hashCode() {
			return SequentialFunnel.class.hashCode() ^ elementFunnel.hashCode();
		}
	}

	/**
	 * Returns a funnel for longs.
	 * 
	 * @since 13.0
	 */
	public static Funnel<Long> longFunnel() {
		return LongFunnel.INSTANCE;
	}

	private enum LongFunnel implements Funnel<Long> {
		INSTANCE;

		public void funnel(Long from, PrimitiveSink into) {
			into.putLong(from);
		}

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

	/**
	 * Wraps a {@code PrimitiveSink} as an {@link OutputStream}, so it is easy to
	 * {@link Funnel#funnel funnel} an object to a {@code PrimitiveSink} if there is
	 * already a way to write the contents of the object to an {@code OutputStream}.
	 * 
	 * <p>
	 * The {@code close} and {@code flush} methods of the returned
	 * {@code OutputStream} do nothing, and no method throws {@code IOException}.
	 * 
	 * @since 13.0
	 */
	public static OutputStream asOutputStream(PrimitiveSink sink) {
		return new SinkAsStream(sink);
	}

	private static class SinkAsStream extends OutputStream {
		final PrimitiveSink sink;

		SinkAsStream(PrimitiveSink sink) {
			this.sink = Preconditions.checkNotNull(sink);
		}

		@Override
		public void write(int b) {
			sink.putByte((byte) b);
		}

		@Override
		public void write(byte[] bytes) {
			sink.putBytes(bytes);
		}

		@Override
		public void write(byte[] bytes, int off, int len) {
			sink.putBytes(bytes, off, len);
		}

		@Override
		public String toString() {
			return "Funnels.asOutputStream(" + sink + ")";
		}
	}
}
