/*
 * Copyright 2013-present the original author or 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
 *
 *      https://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.alibaba.cloud.commons.io;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Collections;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * The Charsets constants, copy from apache commons-io.
 *
 * @author <a href="mailto:chenxilzx1@gmail.com">theonefx</a>
 */
public final class Charsets {

	private Charsets() {
	}

	/**
	 * Constructs a sorted map from canonical charset names to charset objects required of
	 * every implementation of the Java platform.
	 * <p>
	 * From the Java documentation
	 * <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
	 * Standard charsets</a>:
	 * </p>
	 *
	 * @return An immutable, case-insensitive map from canonical charset names to charset
	 * objects.
	 * @see Charset#availableCharsets()
	 */
	public static SortedMap<String, Charset> requiredCharsets() {
		// maybe cache?
		final TreeMap<String, Charset> m = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
		m.put(StandardCharsets.ISO_8859_1.name(), StandardCharsets.ISO_8859_1);
		m.put(StandardCharsets.US_ASCII.name(), StandardCharsets.US_ASCII);
		m.put(StandardCharsets.UTF_16.name(), StandardCharsets.UTF_16);
		m.put(StandardCharsets.UTF_16BE.name(), StandardCharsets.UTF_16BE);
		m.put(StandardCharsets.UTF_16LE.name(), StandardCharsets.UTF_16LE);
		m.put(StandardCharsets.UTF_8.name(), StandardCharsets.UTF_8);
		return Collections.unmodifiableSortedMap(m);
	}

	/**
	 * Returns the given Charset or the default Charset if the given Charset is null.
	 *
	 * @param charset A charset or null.
	 * @return the given Charset or the default Charset if the given Charset is null
	 */
	public static Charset toCharset(final Charset charset) {
		return charset == null ? Charset.defaultCharset() : charset;
	}

	/**
	 * Returns a Charset for the named charset. If the name is null, return the default
	 * Charset.
	 *
	 * @param charset The name of the requested charset, may be null.
	 * @return a Charset for the named charset
	 * @throws java.nio.charset.UnsupportedCharsetException If the named charset is unavailable
	 */
	public static Charset toCharset(final String charset) {
		return charset == null ? Charset.defaultCharset() : Charset.forName(charset);
	}

	/**
	 * CharEncodingISO Latin Alphabet No. 1, a.k.a. ISO-LATIN-1.
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset ISO_8859_1 = StandardCharsets.ISO_8859_1;

	/**
	 * <p>
	 * Seven-bit ASCII, also known as ISO646-US, also known as the Basic Latin block of
	 * the Unicode character set.
	 * </p>
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset US_ASCII = StandardCharsets.US_ASCII;

	/**
	 * <p>
	 * Sixteen-bit Unicode Transformation Format, The byte order specified by a mandatory
	 * initial byte-order mark (either order accepted on input, big-endian used on output)
	 * </p>
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset UTF_16 = StandardCharsets.UTF_16;

	/**
	 * <p>
	 * Sixteen-bit Unicode Transformation Format, big-endian byte order.
	 * </p>
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset UTF_16BE = StandardCharsets.UTF_16BE;

	/**
	 * <p>
	 * Sixteen-bit Unicode Transformation Format, little-endian byte order.
	 * </p>
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset UTF_16LE = StandardCharsets.UTF_16LE;

	/**
	 * <p>
	 * Eight-bit Unicode Transformation Format.
	 * </p>
	 * <p>
	 * Every implementation of the Java platform is required to support this character
	 * encoding.
	 * </p>
	 *
	 * @deprecated Use Java 7's {@link java.nio.charset.StandardCharsets}
	 * @see <a href=
	 * "https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">Standard
	 * charsets</a>
	 */
	@Deprecated
	public static final Charset UTF_8 = StandardCharsets.UTF_8;

}
