/*
 * Copyright 2002-2023 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 org.springframework.util;

import java.io.ByteArrayInputStream;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.file.Files;

import org.springframework.lang.Nullable;

/**
 * Simple utility methods for file and stream copying. All copy methods use a block size
 * of 4096 bytes, and close all affected streams when done. A variation of the copy
 * methods from this class that leave streams open can be found in {@link StreamUtils}.
 *
 * <p>Mainly for use within the framework, but also useful for application code.
 *
 * @author Juergen Hoeller
 * @author Hyunjin Choi
 * @since 06.10.2003
 * @see StreamUtils
 * @see FileSystemUtils
 */
public abstract class FileCopyUtils {

	/**
	 * The default buffer size used when copying bytes.
	 */
	public static final int BUFFER_SIZE = StreamUtils.BUFFER_SIZE;


	//---------------------------------------------------------------------
	// Copy methods for java.io.File
	//---------------------------------------------------------------------

	/**
	 * Copy the contents of the given input File to the given output File.
	 * @param in the file to copy from
	 * @param out the file to copy to
	 * @return the number of bytes copied
	 * @throws IOException in case of I/O errors
	 */
	public static int copy(File in, File out) throws IOException {
		Assert.notNull(in, "No input File specified");
		Assert.notNull(out, "No output File specified");
		return copy(Files.newInputStream(in.toPath()), Files.newOutputStream(out.toPath()));
	}

	/**
	 * Copy the contents of the given byte array to the given output File.
	 * @param in the byte array to copy from
	 * @param out the file to copy to
	 * @throws IOException in case of I/O errors
	 */
	public static void copy(byte[] in, File out) throws IOException {
		Assert.notNull(in, "No input byte array specified");
		Assert.notNull(out, "No output File specified");
		copy(new ByteArrayInputStream(in), Files.newOutputStream(out.toPath()));
	}

	/**
	 * Copy the contents of the given input File into a new byte array.
	 * @param in the file to copy from
	 * @return the new byte array that has been copied to
	 * @throws IOException in case of I/O errors
	 */
	public static byte[] copyToByteArray(File in) throws IOException {
		Assert.notNull(in, "No input File specified");
		return copyToByteArray(Files.newInputStream(in.toPath()));
	}


	//---------------------------------------------------------------------
	// Copy methods for java.io.InputStream / java.io.OutputStream
	//---------------------------------------------------------------------

	/**
	 * Copy the contents of the given InputStream to the given OutputStream.
	 * Closes both streams when done.
	 * @param in the stream to copy from
	 * @param out the stream to copy to
	 * @return the number of bytes copied
	 * @throws IOException in case of I/O errors
	 */
	public static int copy(InputStream in, OutputStream out) throws IOException {
		Assert.notNull(in, "No InputStream specified");
		Assert.notNull(out, "No OutputStream specified");

		try (in; out) {
			int count = (int) in.transferTo(out);
			out.flush();
			return count;
		}
	}

	/**
	 * Copy the contents of the given byte array to the given OutputStream.
	 * Closes the stream when done.
	 * @param in the byte array to copy from
	 * @param out the OutputStream to copy to
	 * @throws IOException in case of I/O errors
	 */
	public static void copy(byte[] in, OutputStream out) throws IOException {
		Assert.notNull(in, "No input byte array specified");
		Assert.notNull(out, "No OutputStream specified");

		try {
			out.write(in);
		}
		finally {
			close(out);
		}
	}

	/**
	 * Copy the contents of the given InputStream into a new byte array.
	 * Closes the stream when done.
	 * @param in the stream to copy from (may be {@code null} or empty)
	 * @return the new byte array that has been copied to (possibly empty)
	 * @throws IOException in case of I/O errors
	 */
	public static byte[] copyToByteArray(@Nullable InputStream in) throws IOException {
		if (in == null) {
			return new byte[0];
		}

		try (in) {
			return in.readAllBytes();
		}
	}


	//---------------------------------------------------------------------
	// Copy methods for java.io.Reader / java.io.Writer
	//---------------------------------------------------------------------

	/**
	 * Copy the contents of the given Reader to the given Writer.
	 * Closes both when done.
	 * @param in the Reader to copy from
	 * @param out the Writer to copy to
	 * @return the number of characters copied
	 * @throws IOException in case of I/O errors
	 */
	public static int copy(Reader in, Writer out) throws IOException {
		Assert.notNull(in, "No Reader specified");
		Assert.notNull(out, "No Writer specified");

		try {
			int charCount = 0;
			char[] buffer = new char[BUFFER_SIZE];
			int charsRead;
			while ((charsRead = in.read(buffer)) != -1) {
				out.write(buffer, 0, charsRead);
				charCount += charsRead;
			}
			out.flush();
			return charCount;
		}
		finally {
			close(in);
			close(out);
		}
	}

	/**
	 * Copy the contents of the given String to the given Writer.
	 * Closes the writer when done.
	 * @param in the String to copy from
	 * @param out the Writer to copy to
	 * @throws IOException in case of I/O errors
	 */
	public static void copy(String in, Writer out) throws IOException {
		Assert.notNull(in, "No input String specified");
		Assert.notNull(out, "No Writer specified");

		try {
			out.write(in);
		}
		finally {
			close(out);
		}
	}

	/**
	 * Copy the contents of the given Reader into a String.
	 * Closes the reader when done.
	 * @param in the reader to copy from (may be {@code null} or empty)
	 * @return the String that has been copied to (possibly empty)
	 * @throws IOException in case of I/O errors
	 */
	public static String copyToString(@Nullable Reader in) throws IOException {
		if (in == null) {
			return "";
		}

		StringWriter out = new StringWriter(BUFFER_SIZE);
		copy(in, out);
		return out.toString();
	}

	/**
	 * Attempt to close the supplied {@link Closeable}, silently swallowing any
	 * exceptions.
	 * @param closeable the {@code Closeable} to close
	 */
	private static void close(Closeable closeable) {
		try {
			closeable.close();
		}
		catch (IOException ex) {
			// ignore
		}
	}

}
