CsvParser.java

package org.sigmah.server.servlet.exporter.utils;

/*
 * #%L
 * Sigmah
 * %%
 * Copyright (C) 2010 - 2016 URD
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import java.util.ArrayList;
import java.util.List;

public class CsvParser {

	private boolean hasNext = true;

	private final char separator;

	private final char quotechar;

	private final char escape;

	private String[] csvLines;

	private int lineCount;

	public static final int INITIAL_READ_SIZE = 64;

	/**
	 * The default escape character to use if none is supplied to the constructor.
	 */
	public static final char DEFAULT_ESCAPE_CHARACTER = '\\';

	public CsvParser() {
		this.separator = CsvBuilder.DEFAULT_SEPARATOR;
		this.quotechar = CsvBuilder.DEFAULT_QUOTE_CHARACTER;
		this.escape = DEFAULT_ESCAPE_CHARACTER;
	}

	/*
	 * Parses CSV string returns list of arrays which represents each line of CSV
	 */
	public List<String[]> parseCsv(String csvString) {
		hasNext = true;
		csvLines = csvString.split(CsvBuilder.DEFAULT_LINE_END);
		lineCount = 0;

		List<String[]> allElements = new ArrayList<String[]>();
		while (hasNext) {
			String[] nextLineAsTokens = readNext();
			if (nextLineAsTokens != null)
				allElements.add(nextLineAsTokens);
		}
		return allElements;

	}

	private String[] readNext() {

		String nextLine = getNextLine();
		return hasNext ? parseLine(nextLine) : null;
	}

	private String getNextLine() {

		String nextLine = null;

		if (lineCount <= csvLines.length - 1) {
			nextLine = csvLines[lineCount++];
		}

		if (nextLine == null) {
			hasNext = false;
		}
		return hasNext ? nextLine : null;
	}

	/**
	 * Parses an incoming String and returns an array of elements.
	 * 
	 * @param nextLine
	 *          the string to parse
	 * @return the comma-tokenized list of elements, or null if nextLine is null
	 */
	private String[] parseLine(String nextLine) {

		if (nextLine == null) {
			return null;
		}

		List<String> tokensOnThisLine = new ArrayList<String>();
		StringBuilder sb = new StringBuilder(INITIAL_READ_SIZE);
		boolean inQuotes = false;
		do {
			if (inQuotes) {
				// continuing a quoted section, reappend newline
				sb.append("\n");
				nextLine = getNextLine();
				if (nextLine == null)
					break;
			}
			for (int i = 0; i < nextLine.length(); i++) {

				char c = nextLine.charAt(i);
				if (c == this.escape) {
					if (isEscapable(nextLine, inQuotes, i)) {
						sb.append(nextLine.charAt(i + 1));
						i++;
					} else {
						i++; // ignore the escape
					}
				} else if (c == quotechar) {
					if (isEscapedQuote(nextLine, inQuotes, i)) {
						sb.append(nextLine.charAt(i + 1));
						i++;
					} else {
						inQuotes = !inQuotes;
						// the tricky case of an embedded quote in the middle: a,bc"d"ef,g
						if (i > 2 // not on the beginning of the line
							&& nextLine.charAt(i - 1) != this.separator // not at the beginning of an escape sequence
							&& nextLine.length() > (i + 1)
							&& nextLine.charAt(i + 1) != this.separator // not at the end of an escape sequence
						) {
							sb.append(c);
						}
					}
				} else if (c == separator && !inQuotes) {
					tokensOnThisLine.add(sb.toString());
					sb = new StringBuilder(INITIAL_READ_SIZE); // start work on next token
				} else {
					sb.append(c);
				}
			}
		} while (inQuotes);
		tokensOnThisLine.add(sb.toString());
		return tokensOnThisLine.toArray(new String[0]);

	}

	/**
	 * precondition: the current character is a quote or an escape
	 * 
	 * @param nextLine
	 *          the current line
	 * @param inQuotes
	 *          true if the current context is quoted
	 * @param i
	 *          current index in line
	 * @return true if the following character is a quote
	 */
	private boolean isEscapedQuote(String nextLine, boolean inQuotes, int i) {
		return inQuotes // we are in quotes, therefore there can be escaped quotes in here.
			&& nextLine.length() > (i + 1) // there is indeed another character to check.
			&& nextLine.charAt(i + 1) == quotechar;
	}

	/**
	 * precondition: the current character is an escape
	 * 
	 * @param nextLine
	 *          the current line
	 * @param inQuotes
	 *          true if the current context is quoted
	 * @param i
	 *          current index in line
	 * @return true if the following character is a quote
	 */
	private boolean isEscapable(String nextLine, boolean inQuotes, int i) {
		return inQuotes // we are in quotes, therefore there can be escaped quotes in here.
			&& nextLine.length() > (i + 1) // there is indeed another character to check.
			&& (nextLine.charAt(i + 1) == quotechar || nextLine.charAt(i + 1) == this.escape);
	}

}