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HTTP server implementing a REST-style protocol
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/*******************************************************************************
 * Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Distribution License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *******************************************************************************/
package org.eclipse.rdf4j.common.webapp.util;

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

import org.eclipse.rdf4j.common.text.StringUtil;

/**
 * An element in an HTTP header value. An HTTP header element has a value and zero or more parameters consisting of a
 * key and a value. An example header element is audio/*; q=0.2.
 */
public class HeaderElement {

	/*----------------*
	 * Static methods *
	 *----------------*/

	public static HeaderElement parse(String encodedValue) {
		HeaderElement result = new HeaderElement();

		List tokens = HttpServerUtil.splitHeaderString(encodedValue, ';');

		if (!tokens.isEmpty()) {
			// First token is the value of the header element
			String token = tokens.get(0);

			// Remove any whitespace and double quotes from the token
			token = StringUtil.trimDoubleQuotes(token.trim());

			result.setValue(token);

			// Add parameters to the header element
			for (int i = 1; i < tokens.size(); i++) {
				token = (String) tokens.get(i);

				int splitIdx = token.indexOf('=');

				if (splitIdx == -1) {
					// No value, only key
					token = StringUtil.trimDoubleQuotes(token.trim());

					// Ignore empty parameters
					if (!token.isEmpty()) {
						result.addParameter(token);
					}
				} else {
					String key = token.substring(0, splitIdx).trim();
					String value = token.substring(splitIdx + 1).trim();
					value = StringUtil.trimDoubleQuotes(value);
					result.addParameter(key, value);
				}
			}
		}

		return result;
	}

	/*-----------*
	 * Variables *
	 *-----------*/

	private String value;

	private final List parameters;

	/*--------------*
	 * Constructors *
	 *--------------*/

	public HeaderElement() {
		this("");
	}

	public HeaderElement(String value) {
		setValue(value);
		parameters = new ArrayList<>();
	}

	/*---------*
	 * Methods *
	 *---------*/

	public String getValue() {
		return value;
	}

	public void setValue(String value) {
		this.value = value;
	}

	public int getParameterCount() {
		return parameters.size();
	}

	public Parameter getParameter(int i) {
		return parameters.get(i);
	}

	public Parameter getParameter(String key) {
		for (int i = 0; i < parameters.size(); i++) {
			Parameter param = parameters.get(i);
			if (param.getKey().equals(key)) {
				return param;
			}
		}

		return null;
	}

	public String getParameterValue(String key) {
		Parameter param = getParameter(key);

		if (param != null) {
			return param.getValue();
		}

		return null;
	}

	public List getParameters() {
		return Collections.unmodifiableList(parameters);
	}

	public void addParameter(String key) {
		addParameter(key, null);
	}

	public void addParameter(String key, String value) {
		addParameter(new Parameter(key, value));
	}

	public void addParameter(Parameter param) {
		parameters.add(param);
	}

	public Parameter removeParameter(int idx) {
		return parameters.remove(idx);
	}

	public boolean removeParameter(Parameter param) {
		return parameters.remove(param);
	}

	@Override
	public boolean equals(Object obj) {
		if (obj instanceof HeaderElement) {
			HeaderElement other = (HeaderElement) obj;

			return value.equals(other.getValue()) && parameters.equals(other.getParameters());
		}

		return false;
	}

	@Override
	public int hashCode() {
		return value.hashCode();
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder(32);
		sb.append(value);

		for (int i = 0; i < parameters.size(); i++) {
			Parameter param = parameters.get(i);

			sb.append("; ");
			sb.append(param.toString());
		}

		return sb.toString();
	}
}