package org.jsoup.nodes;

import java.util.Map;

import org.jsoup.helper.Validate;

/**
 * A single key + value attribute. Keys are trimmed and normalised to
 * lower-case.
 * 
 * @author Jonathan Hedley, jonathan@hedley.net
 */
public class Attribute implements Map.Entry<String, String>, Cloneable {
    private String key;
    private String value;

    /**
     * Create a new attribute from unencoded (raw) key and value.
     * 
     * @param key
     *            attribute key
     * @param value
     *            attribute value
     * @see #createFromEncoded
     */
    public Attribute(String key, String value) {
        Validate.notEmpty(key);
        Validate.notNull(value);
        this.key = key.trim().toLowerCase();
        this.value = value;
    }

    /**
     * Get the attribute key.
     * 
     * @return the attribute key
     */
    @Override
    public String getKey() {
        return key;
    }

    /**
     * Set the attribute key. Gets normalised as per the constructor method.
     * 
     * @param key
     *            the new key; must not be null
     */
    public void setKey(String key) {
        Validate.notEmpty(key);
        this.key = key.trim().toLowerCase();
    }

    /**
     * Get the attribute value.
     * 
     * @return the attribute value
     */
    @Override
    public String getValue() {
        return value;
    }

    /**
     * Set the attribute value.
     * 
     * @param value
     *            the new attribute value; must not be null
     */
    @Override
    public String setValue(String value) {
        Validate.notNull(value);
        String old = this.value;
        this.value = value;
        return old;
    }

    /**
     * Get the HTML representation of this attribute; e.g.
     * {@code href="index.html"}.
     * 
     * @return HTML
     */
    public String html() {
        return key + "=\""
                + Entities.escape(value, (new Document("")).outputSettings())
                + "\"";
    }

    protected void html(StringBuilder accum, Document.OutputSettings out) {
        accum.append(key).append("=\"").append(Entities.escape(value, out))
                .append("\"");
    }

    /**
     * Get the string representation of this attribute, implemented as
     * {@link #html()}.
     * 
     * @return string
     */
    @Override
    public String toString() {
        return html();
    }

    /**
     * Create a new Attribute from an unencoded key and a HTML attribute encoded
     * value.
     * 
     * @param unencodedKey
     *            assumes the key is not encoded, as can be only run of simple
     *            \w chars.
     * @param encodedValue
     *            HTML attribute encoded value
     * @return attribute
     */
    public static Attribute createFromEncoded(String unencodedKey,
            String encodedValue) {
        String value = Entities.unescape(encodedValue, true);
        return new Attribute(unencodedKey, value);
    }

    protected boolean isDataAttribute() {
        return key.startsWith(Attributes.dataPrefix)
                && key.length() > Attributes.dataPrefix.length();
    }

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

        Attribute attribute = (Attribute) o;

        if (key != null ? !key.equals(attribute.key) : attribute.key != null) {
            return false;
        }
        if (value != null ? !value.equals(attribute.value)
                : attribute.value != null) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int result = key != null ? key.hashCode() : 0;
        result = 31 * result + (value != null ? value.hashCode() : 0);
        return result;
    }

    @Override
    public Attribute clone() {
        try {
            return (Attribute) super.clone(); // only fields are immutable
                                              // strings key and value, so no
                                              // more deep copy required
        } catch (CloneNotSupportedException e) {
            throw new RuntimeException(e);
        }
    }
}