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Modules for reading and writing data in Formeta format

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/*
 * Copyright 2013, 2014 Deutsche Nationalbibliothek
 *
 * 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
 *
 *     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.metafacture.formeta.parser;

import org.metafacture.formeta.Formeta;
import org.metafacture.framework.FormatException;

/**
 * Context of the text parser. It stores the parsed text, maps escape sequences
 * to characters and handles the removal of trailing whitespace in unquoted
 * text.
 */
class TextParserContext {

    private static final String ESCAPABLE_CHARS = Formeta.WHITESPACE +
        Formeta.QUOT_CHAR +
        Formeta.ESCAPE_CHAR +
        Formeta.GROUP_START +
        Formeta.GROUP_END +
        Formeta.ITEM_SEPARATOR +
        Formeta.NAME_VALUE_SEPARATOR;

    private final StringBuilder text = new StringBuilder();

    private int lengthWithoutTrailingWs;
    private boolean quoted;

    TextParserContext() {
    }

    public String getText() {
        return text.substring(0, lengthWithoutTrailingWs);
    }

    public void setQuoted(final boolean quoted) {
        this.quoted = quoted;
    }

    public void appendChar(final char ch) {
        text.append(ch);
        if (quoted || !Formeta.isWhitespace(ch)) {
            lengthWithoutTrailingWs = text.length();
        }
    }

    public void appendEscapedChar(final char ch) {
        if (Formeta.NEWLINE_ESC_SEQ == ch) {
            text.append('\n');
        }
        else if (Formeta.CARRIAGE_RETURN_ESC_SEQ == ch) {
            text.append('\r');
        }
        else if (ESCAPABLE_CHARS.indexOf(ch) > -1) {
            text.append(ch);
        }
        else {
            throw new FormatException("invalid escape sequence: " + ch);
        }
        lengthWithoutTrailingWs = text.length();
    }

    public void reset() {
        text.delete(0, text.length());
        lengthWithoutTrailingWs = 0;
        quoted = false;
    }

}