Attribute.java

/*
 * Copyright (C) 2010, Marc Strapetz <marc.strapetz@syntevo.com>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
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 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
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 *   with the distribution.
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package org.eclipse.jgit.attributes;

/**
 * Represents an attribute.
 * <p>
 * According to the man page, an attribute can have the following states:
 * <ul>
 * <li>Set - represented by
 * {@link org.eclipse.jgit.attributes.Attribute.State#SET}</li>
 * <li>Unset - represented by
 * {@link org.eclipse.jgit.attributes.Attribute.State#UNSET}</li>
 * <li>Set to a value - represented by
 * {@link org.eclipse.jgit.attributes.Attribute.State#CUSTOM}</li>
 * <li>Unspecified - used to revert an attribute . This is crucial in order to
 * mark an attribute as unspecified in the attributes map and thus preventing
 * following (with lower priority) nodes from setting the attribute to a value
 * at all</li>
 * </ul>
 *
 * @since 3.7
 */
public final class Attribute {

    /**
     * The attribute value state
     * see also https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
     */
    public static enum State {
        /** the attribute is set */
        SET,

        /** the attribute is unset */
        UNSET,

        /**
         * the attribute appears as if it would not be defined at all
         *
         * @since 4.2
         */
        UNSPECIFIED,

        /** the attribute is set to a custom value */
        CUSTOM
    }

    private final String key;
    private final State state;
    private final String value;

    /**
     * Creates a new instance
     *
     * @param key
     *            the attribute key. Should not be <code>null</code>.
     * @param state
     *            the attribute state. It should be either
     *            {@link org.eclipse.jgit.attributes.Attribute.State#SET} or
     *            {@link org.eclipse.jgit.attributes.Attribute.State#UNSET}. In
     *            order to create a custom value attribute prefer the use of
     *            {@link #Attribute(String, String)} constructor.
     */
    public Attribute(String key, State state) {
        this(key, state, null);
    }

    private Attribute(String key, State state, String value) {
        if (key == null)
            throw new NullPointerException(
                    "The key of an attribute should not be null"); //$NON-NLS-1$
        if (state == null)
            throw new NullPointerException(
                    "The state of an attribute should not be null"); //$NON-NLS-1$

        this.key = key;
        this.state = state;
        this.value = value;
    }

    /**
     * Creates a new instance.
     *
     * @param key
     *            the attribute key. Should not be <code>null</code>.
     * @param value
     *            the custom attribute value
     */
    public Attribute(String key, String value) {
        this(key, State.CUSTOM, value);
    }

    /** {@inheritDoc} */
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (!(obj instanceof Attribute))
            return false;
        Attribute other = (Attribute) obj;
        if (!key.equals(other.key))
            return false;
        if (state != other.state)
            return false;
        if (value == null) {
            if (other.value != null)
                return false;
        } else if (!value.equals(other.value))
            return false;
        return true;
    }

    /**
     * Get key
     *
     * @return the attribute key (never returns <code>null</code>)
     */
    public String getKey() {
        return key;
    }

    /**
     * Return the state.
     *
     * @return the state (never returns <code>null</code>)
     */
    public State getState() {
        return state;
    }

    /**
     * Get value
     *
     * @return the attribute value (may be <code>null</code>)
     */
    public String getValue() {
        return value;
    }

    /** {@inheritDoc} */
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + key.hashCode();
        result = prime * result + state.hashCode();
        result = prime * result + ((value == null) ? 0 : value.hashCode());
        return result;
    }

    /** {@inheritDoc} */
    @Override
    public String toString() {
        switch (state) {
        case SET:
            return key;
        case UNSET:
            return "-" + key; //$NON-NLS-1$
        case UNSPECIFIED:
            return "!" + key; //$NON-NLS-1$
        case CUSTOM:
        default:
            return key + "=" + value; //$NON-NLS-1$
        }
    }
}