001/*
002 * This file is part of the JDrupes non-blocking HTTP Codec
003 * Copyright (C) 2017 Michael N. Lipp
004 *
005 * This program is free software; you can redistribute it and/or modify it 
006 * under the terms of the GNU Lesser General Public License as published
007 * by the Free Software Foundation; either version 3 of the License, or 
008 * (at your option) any later version.
009 *
010 * This program is distributed in the hope that it will be useful, but 
011 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
012 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
013 * License for more details.
014 *
015 * You should have received a copy of the GNU Lesser General Public License along 
016 * with this program; if not, see <http://www.gnu.org/licenses/>.
017 */
018
019package org.jdrupes.httpcodec.types;
020
021import java.text.ParseException;
022
023/**
024 * Implemented by classes that convert between a value and its 
025 * string representation in the HTTP header field.
026 * 
027 * @param <T> the type to be converted
028 */
029public interface Converter<T> {
030
031    /**
032     * Returns the representation of this value in a header field.
033     * 
034     * @param value the value to be converted
035     * @return the representation
036     */
037    String asFieldValue(T value);
038
039    /**
040     * Returns the string representation of this header field as it 
041     * appears in an HTTP message. Note that the returned string may 
042     * span several lines (may contain CR/LF), if the converter is a
043     * {@link MultiValueConverter} with separate values, but never 
044     * has a trailing CR/LF.
045     *
046     * @param fieldName the field name
047     * @param value the value
048     * @return the field as it occurs in a header
049     */
050    default String asHeaderField(String fieldName, T value) {
051        return fieldName + ": " + asFieldValue(value);
052    }
053
054    /**
055     * Parses the given text and returns the parsed value.
056     * 
057     * @param text the value from the header field
058     * @return the parsed value
059     * @throws ParseException if the value cannot be parsed
060     */
061    T fromFieldValue(String text) throws ParseException;
062}