/*
 *  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 org.codehaus.groovy.control.io;

import org.codehaus.groovy.control.CompilerConfiguration;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URI;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

/**
 *  A ReaderSource for source files.
 */
public class FileReaderSource extends AbstractReaderSource {
    private final File file;  // The File from which we produce Readers.
    private final Charset UTF8 = StandardCharsets.UTF_8;

   /**
    *  Creates the ReaderSource from a File descriptor.
    * @param file script source file
    * @param configuration configuration for compiling source
    */
    public FileReaderSource( File file, CompilerConfiguration configuration ) {
       super( configuration );
        this.file = file;
    }

    /**
     * Returns the underlying source file.
     *
     * @return the backing file
     */
    public File getFile() {
        return file;
    }

    /**
    *  Returns a new Reader on the underlying source object.
    */
    @Override
    public Reader getReader() throws IOException {
       // we want to remove the BOM windows adds from a file if the encoding is UTF-8
       // in other cases we depend on the charsets
       Charset cs = Charset.forName(configuration.getSourceEncoding());
       InputStream in = new BufferedInputStream(new FileInputStream(file));
       if (UTF8.name().equalsIgnoreCase(cs.name())) {
           in.mark(3);
           boolean hasBOM = true;
           try {
               int i = in.read();
               hasBOM &= i == 0xEF;
               i = in.read();
               hasBOM &= i == 0xBB;
               i = in.read();
               hasBOM &= i == 0xFF;
           } catch (IOException ioe) {
               hasBOM= false;
           }
           if (!hasBOM) in.reset();
       }
       return new InputStreamReader( in, cs );
    }

    /**
     * Returns a URI for the file of this source.
     *
     * @return URI for the file of this source.
     */
    @Override
    public URI getURI() {
        return file.toURI();
    }

}
