Attributes.java

package com.smartandroid.sa.tag.nodes;

import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.smartandroid.sa.tag.helper.Validate;

/**
 * The attributes of an Element.
 * <p/>
 * Attributes are treated as a map: there can be only one value associated with
 * an attribute key.
 * <p/>
 * Attribute key and value comparisons are done case insensitively, and keys are
 * normalised to lower-case.
 * 
 * @author Jonathan Hedley, jonathan@hedley.net
 */
public class Attributes implements Iterable<Attribute>, Cloneable {
	protected static final String dataPrefix = "data-";

	private LinkedHashMap<String, Attribute> attributes = null;

	// linked hash map to preserve insertion order.
	// null be default as so many elements have no attributes -- saves a good
	// chunk of memory

	/**
	 * Get an attribute value by key.
	 * 
	 * @param key
	 *            the attribute key
	 * @return the attribute value if set; or empty string if not set.
	 * @see #hasKey(String)
	 */
	public String get(String key) {
		Validate.notEmpty(key);

		if (attributes == null)
			return "";

		Attribute attr = attributes.get(key.toLowerCase());
		return attr != null ? attr.getValue() : "";
	}

	/**
	 * Set a new attribute, or replace an existing one by key.
	 * 
	 * @param key
	 *            attribute key
	 * @param value
	 *            attribute value
	 */
	public void put(String key, String value) {
		Attribute attr = new Attribute(key, value);
		put(attr);
	}

	/**
	 * Set a new attribute, or replace an existing one by key.
	 * 
	 * @param attribute
	 *            attribute
	 */
	public void put(Attribute attribute) {
		Validate.notNull(attribute);
		if (attributes == null)
			attributes = new LinkedHashMap<String, Attribute>(2);
		attributes.put(attribute.getKey(), attribute);
	}

	/**
	 * Remove an attribute by key.
	 * 
	 * @param key
	 *            attribute key to remove
	 */
	public void remove(String key) {
		Validate.notEmpty(key);
		if (attributes == null)
			return;
		attributes.remove(key.toLowerCase());
	}

	/**
	 * Tests if these attributes contain an attribute with this key.
	 * 
	 * @param key
	 *            key to check for
	 * @return true if key exists, false otherwise
	 */
	public boolean hasKey(String key) {
		return attributes != null && attributes.containsKey(key.toLowerCase());
	}

	/**
	 * Get the number of attributes in this set.
	 * 
	 * @return size
	 */
	public int size() {
		if (attributes == null)
			return 0;
		return attributes.size();
	}

	/**
	 * Add all the attributes from the incoming set to this set.
	 * 
	 * @param incoming
	 *            attributes to add to these attributes.
	 */
	public void addAll(Attributes incoming) {
		if (incoming.size() == 0)
			return;
		if (attributes == null)
			attributes = new LinkedHashMap<String, Attribute>(incoming.size());
		attributes.putAll(incoming.attributes);
	}

	public Iterator<Attribute> iterator() {
		return asList().iterator();
	}

	/**
	 * Get the attributes as a List, for iteration. Do not modify the keys of
	 * the attributes via this view, as changes to keys will not be recognised
	 * in the containing set.
	 * 
	 * @return an view of the attributes as a List.
	 */
	public List<Attribute> asList() {
		if (attributes == null)
			return Collections.emptyList();

		List<Attribute> list = new ArrayList<Attribute>(attributes.size());
		for (Map.Entry<String, Attribute> entry : attributes.entrySet()) {
			list.add(entry.getValue());
		}
		return Collections.unmodifiableList(list);
	}

	/**
	 * Retrieves a filtered view of attributes that are HTML5 custom data
	 * attributes; that is, attributes with keys starting with {@code data-}.
	 * 
	 * @return map of custom data attributes.
	 */
	public Map<String, String> dataset() {
		return new Dataset();
	}

	/**
	 * Get the HTML representation of these attributes.
	 * 
	 * @return HTML
	 */
	public String html() {
		StringBuilder accum = new StringBuilder();
		html(accum, (new Document("")).outputSettings()); // output settings a
															// bit funky, but
															// this html()
															// seldom used
		return accum.toString();
	}

	void html(StringBuilder accum, Document.OutputSettings out) {
		if (attributes == null)
			return;

		for (Map.Entry<String, Attribute> entry : attributes.entrySet()) {
			Attribute attribute = entry.getValue();
			accum.append(" ");
			attribute.html(accum, out);
		}
	}

	public String toString() {
		return html();
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof Attributes))
			return false;

		Attributes that = (Attributes) o;

		if (attributes != null ? !attributes.equals(that.attributes)
				: that.attributes != null)
			return false;

		return true;
	}

	@Override
	public int hashCode() {
		return attributes != null ? attributes.hashCode() : 0;
	}

	@Override
	public Attributes clone() {
		if (attributes == null)
			return new Attributes();

		Attributes clone;
		try {
			clone = (Attributes) super.clone();
		} catch (CloneNotSupportedException e) {
			throw new RuntimeException(e);
		}
		clone.attributes = new LinkedHashMap<String, Attribute>(
				attributes.size());
		for (Attribute attribute : this)
			clone.attributes.put(attribute.getKey(), attribute.clone());
		return clone;
	}

	private class Dataset extends AbstractMap<String, String> {

		private Dataset() {
			if (attributes == null)
				attributes = new LinkedHashMap<String, Attribute>(2);
		}

		public Set<Entry<String, String>> entrySet() {
			return new EntrySet();
		}

		@Override
		public String put(String key, String value) {
			String dataKey = dataKey(key);
			String oldValue = hasKey(dataKey) ? attributes.get(dataKey)
					.getValue() : null;
			Attribute attr = new Attribute(dataKey, value);
			attributes.put(dataKey, attr);
			return oldValue;
		}

		private class EntrySet extends AbstractSet<Map.Entry<String, String>> {
			public Iterator<Map.Entry<String, String>> iterator() {
				return new DatasetIterator();
			}

			public int size() {
				int count = 0;
				Iterator iter = new DatasetIterator();
				while (iter.hasNext())
					count++;
				return count;
			}
		}

		private class DatasetIterator implements
				Iterator<Map.Entry<String, String>> {
			private Iterator<Attribute> attrIter = attributes.values()
					.iterator();
			private Attribute attr;

			public boolean hasNext() {
				while (attrIter.hasNext()) {
					attr = attrIter.next();
					if (attr.isDataAttribute())
						return true;
				}
				return false;
			}

			public Entry<String, String> next() {
				return new Attribute(attr.getKey().substring(
						dataPrefix.length()), attr.getValue());
			}

			public void remove() {
				attributes.remove(attr.getKey());
			}
		}
	}

	private static String dataKey(String key) {
		return dataPrefix + key;
	}
}