/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.yangtools.yang.common;

import com.google.common.base.MoreObjects;
import com.google.common.collect.Interner;
import com.google.common.collect.Interners;
import java.io.Serializable;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Date;
import java.util.Objects;
import org.opendaylight.yangtools.concepts.Immutable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public final class QNameModule implements Immutable, Serializable {
    private static final Interner<QNameModule> INTERNER = Interners.newWeakInterner();
    private static final Logger LOG = LoggerFactory.getLogger(QNameModule.class);
    private static final QNameModule NULL_INSTANCE = new QNameModule(null, null);
    private static final long serialVersionUID = 2L;

    //Nullable
    private final URI namespace;

    //Nullable
    private final Date revision;

    //Nullable
    private transient volatile String formattedRevision;

    private transient int hash;

    private QNameModule(final URI namespace, final Date revision) {
        // FIXME: 2.0.0: Preconditions.checkNotNull(namespace)
        this.namespace = namespace;
        this.revision = revision;
    }

    /**
     * Return an interned reference to a equivalent QNameModule.
     *
     * @return Interned reference, or this object if it was interned.
     */
    public QNameModule intern() {
        return INTERNER.intern(this);
    }

    /**
     * Create a new QName module instance with specified namespace/revision.
     *
     * @param namespace Module namespace
     * @param revision Module revision
     * @return A new, potentially shared, QNameModule instance
     */
    public static QNameModule create(final URI namespace, final Date revision) {
        if (namespace == null && revision == null) {
            return NULL_INSTANCE;
        }

        return new QNameModule(namespace, revision);
    }

    public String getFormattedRevision() {
        if (revision == null) {
            return null;
        }

        String ret = formattedRevision;
        if (ret == null) {
            ret = SimpleDateFormatUtil.getRevisionFormat().format(revision);
            formattedRevision = ret;
        }

        return ret;
    }

    /**
     * Returns the namespace of the module which is specified as argument of
     * YANG Module <b><font color="#00FF00">namespace</font></b> keyword.
     *
     * @return URI format of the namespace of the module
     */
    public URI getNamespace() {
        return namespace;
    }

    /**
     * Returns the revision date for the module.
     *
     * @return date of the module revision which is specified as argument of
     *         YANG Module <b><font color="#339900">revison</font></b> keyword
     */
    // FIXME: BUG-4688: should return Optional<Revision>
    public Date getRevision() {
        return revision;
    }

    @Override
    public int hashCode() {
        if (hash == 0) {
            hash = Objects.hash(namespace, revision);
        }
        return hash;
    }

    @Override
    public boolean equals(final Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof QNameModule)) {
            return false;
        }
        final QNameModule other = (QNameModule) obj;
        return Objects.equals(revision, other.revision) && Objects.equals(namespace, other.namespace);
    }

    /**
     * Returns a namespace in form defined by section 5.6.4. of {@link https
     * ://tools.ietf.org/html/rfc6020}, if namespace is not correctly defined,
     * the method will return <code>null</code> <br>
     * example "http://example.acme.com/system?revision=2008-04-01"
     *
     * @return namespace in form defined by section 5.6.4. of {@link https
     *         ://tools.ietf.org/html/rfc6020}, if namespace is not correctly
     *         defined, the method will return <code>null</code>
     *
     */
    URI getRevisionNamespace() {
        if (namespace == null) {
            return null;
        }

        final String query = revision == null ? "" : "revision=" + getFormattedRevision();
        try {
            return new URI(namespace.getScheme(), namespace.getUserInfo(), namespace.getHost(),
                    namespace.getPort(), namespace.getPath(), query, namespace.getFragment());
        } catch (final URISyntaxException e) {
            LOG.error("Failed to construct URI for {}", this, e);
            return null;
        }
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(QNameModule.class).omitNullValues().add("ns", getNamespace()).add("rev", getFormattedRevision()).toString();
    }
}