/*
 * 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.apache.flink.api.java.io;

import java.io.IOException;
import java.nio.charset.Charset;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.io.DelimitedInputFormat;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.core.fs.Path;

@PublicEvolving
public class TextInputFormat extends DelimitedInputFormat<String> {
	
	private static final long serialVersionUID = 1L;
	
	/**
	 * Code of \r, used to remove \r from a line when the line ends with \r\n
	 */
	private static final byte CARRIAGE_RETURN = (byte) '\r';

	/**
	 * Code of \n, used to identify if \n is used as delimiter
	 */
	private static final byte NEW_LINE = (byte) '\n';
	
	
	/**
	 * The name of the charset to use for decoding.
	 */
	private String charsetName = "UTF-8";
	
	// --------------------------------------------------------------------------------------------
	
	public TextInputFormat(Path filePath) {
		super(filePath, null);
	}
	
	// --------------------------------------------------------------------------------------------	
	
	public String getCharsetName() {
		return charsetName;
	}
	
	public void setCharsetName(String charsetName) {
		if (charsetName == null) {
			throw new IllegalArgumentException("Charset must not be null.");
		}
		
		this.charsetName = charsetName;
	}
	
	// --------------------------------------------------------------------------------------------

	@Override
	public void configure(Configuration parameters) {
		super.configure(parameters);
		
		if (charsetName == null || !Charset.isSupported(charsetName)) {
			throw new RuntimeException("Unsupported charset: " + charsetName);
		}
	}

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

	@Override
	public String readRecord(String reusable, byte[] bytes, int offset, int numBytes) throws IOException {
		//Check if \n is used as delimiter and the end of this line is a \r, then remove \r from the line
		if (this.getDelimiter() != null && this.getDelimiter().length == 1 
				&& this.getDelimiter()[0] == NEW_LINE && offset+numBytes >= 1 
				&& bytes[offset+numBytes-1] == CARRIAGE_RETURN){
			numBytes -= 1;
		}
		
		return new String(bytes, offset, numBytes, this.charsetName);
	}
	
	// --------------------------------------------------------------------------------------------
	
	@Override
	public String toString() {
		return "TextInputFormat (" + getFilePath() + ") - " + this.charsetName;
	}
}