/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.alibaba.csp.sentinel.util.io;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;

/**
 * Copy from apache commons-io.
 */
public final class FileUtil {

    private FileUtil() {
    }

    // -----------------------------------------------------------------------

    /**
     * Opens a {@link FileInputStream} for the specified file, providing better
     * error messages than simply calling <code>new FileInputStream(file)</code>.
     * <p>
     * At the end of the method either the stream will be successfully opened, or an
     * exception will have been thrown.
     * <p>
     * An exception is thrown if the file does not exist. An exception is thrown if the
     * file object exists but is a directory. An exception is thrown if the file exists
     * but cannot be read.
     *
     * @param file the file to open for input, must not be {@code null}
     * @return a new {@link FileInputStream} for the specified file
     * @throws FileNotFoundException if the file does not exist
     * @throws IOException if the file object is a directory
     * @throws IOException if the file cannot be read
     * @since 1.3
     */
    public static FileInputStream openInputStream(final File file) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file + "' exists but is a directory");
            }
            if (!file.canRead()) {
                throw new IOException("File '" + file + "' cannot be read");
            }
        } else {
            throw new FileNotFoundException("File '" + file + "' does not exist");
        }
        return new FileInputStream(file);
    }

    // -----------------------------------------------------------------------

    /**
     * Reads the contents of a file into a String. The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     */
    public static String readFileToString(final File file, final Charset encoding)
        throws IOException {
        try (InputStream in = openInputStream(file)) {
            return IOUtil.toString(in, Charsets.toCharset(encoding));
        }
    }

    /**
     * Reads the contents of a file into a String. The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     * @throws java.nio.charset.UnsupportedCharsetException thrown instead of
     * {@link java.io .UnsupportedEncodingException} in version 2.2 if the encoding is not
     * supported.
     */
    public static String readFileToString(final File file, final String encoding)
        throws IOException {
        return readFileToString(file, Charsets.toCharset(encoding));
    }

    /**
     * Reads the contents of a file into a String using the default encoding for the VM.
     * The file is always closed.
     *
     * @param file the file to read, must not be {@code null}
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     * @deprecated 2.5 use {@link #readFileToString(File, String)} instead (and specify
     * the appropriate encoding)
     */
    @Deprecated
    public static String readFileToString(final File file) throws IOException {
        return readFileToString(file, Charset.defaultCharset());
    }

}
