/*******************************************************************************
 *
 * Copyright (c) 2004-2009 Oracle Corporation.
 *
 * 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
 *
 * Contributors:
 * 
 *    Kohsuke Kawaguchi, Luca Domenico Milanesio
 *
 *
 *******************************************************************************/ 

package hudson.tasks;

import hudson.Extension;
import hudson.ExtensionList;
import hudson.ExtensionListView;
import hudson.ExtensionPoint;
import hudson.model.Hudson;
import hudson.model.User;
import hudson.model.UserProperty;
import hudson.scm.SCM;

import java.util.List;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Infers e-mail addresses for the user when none is specified.
 *
 * <p> This is an extension point of Hudson. Plugins tha contribute new
 * implementation of this class should put {@link Extension} on your
 * implementation class, like this:
 *
 * <pre>
 * @Extension
 * class MyMailAddressResolver extends {@link MailAddressResolver} {
 *   ...
 * }
 * </pre>
 *
 * <h2>Techniques</h2> <p> User identity in Hudson is global, and not specific
 * to a particular job. As a result, mail address resolution only receives
 * {@link User}, which by itself doesn't really have that much information in
 * it.
 *
 * <p> So the common technique for a mail address resolution is to define your
 * own {@link UserProperty} types and add it to {@link User} objects where more
 * context is available. For example, an {@link SCM} implementation can have a
 * lot more information about a particular user during a check out, so that
 * would be a good place to capture information as {@link UserProperty}, which
 * then later used by a {@link MailAddressResolver}.
 *
 * @author Kohsuke Kawaguchi
 * @since 1.192
 */
public abstract class MailAddressResolver implements ExtensionPoint {

    /**
     * Infers e-mail address of the given user.
     *
     * <p> This method is called when a {@link User} without explicitly
     * configured e-mail address is used, as an attempt to infer e-mail address.
     *
     * <p> The normal strategy is to look at {@link User#getProjects() the projects that the user
     * is participating}, then use the repository information to infer the
     * e-mail address.
     *
     * <p> When multiple resolvers are installed, they are consulted in order
     * and the search will be over when an address is inferred by someone.
     *
     * <p> Since {@link MailAddressResolver} is singleton, this method can be
     * invoked concurrently from multiple threads.
     *
     * @return null if the inference failed.
     */
    public abstract String findMailAddressFor(User u);

    public static String resolve(User u) {
        LOGGER.fine("Resolving e-mail address for \"" + u + "\" ID=" + u.getId());

        for (MailAddressResolver r : all()) {
            String email = r.findMailAddressFor(u);
            if (email != null) {
                LOGGER.fine(r + " resolved " + u.getId() + " to " + email);
                return email;
            }
        }

        // fall back logic
        String extractedAddress = extractAddressFromId(u.getFullName());
        if (extractedAddress != null) {
            return extractedAddress;
        }

        if (u.getFullName().contains("@")) // this already looks like an e-mail ID
        {
            return u.getFullName();
        }

        String ds = Mailer.descriptor().getDefaultSuffix();
        if (ds != null) {
            // another common pattern is "DOMAIN\person" in Windows. Only
            // do this when this full name is not manually set. see HUDSON-5164
            Matcher m = WINDOWS_DOMAIN_REGEXP.matcher(u.getFullName());
            if (m.matches() && u.getFullName().replace('\\', '_').equals(u.getId())) {
                return m.group(1) + ds; // user+defaultSuffix
            }
            return u.getId() + ds;
        } else {
            return null;
        }
    }

    /**
     * Tries to extract an email address from the user id, or returns null
     */
    private static String extractAddressFromId(String id) {
        Matcher m = EMAIL_ADDRESS_REGEXP.matcher(id);
        if (m.matches()) {
            return m.group(1);
        }
        return null;
    }
    /**
     * Matches strings like "Kohsuke Kawaguchi <kohsuke.kawaguchi@sun.com>"
     * @see #extractAddressFromId(String)
     */
    private static final Pattern EMAIL_ADDRESS_REGEXP = Pattern.compile("^.*<([^>]+)>.*$");
    /**
     * Matches something like "DOMAIN\person"
     */
    private static final Pattern WINDOWS_DOMAIN_REGEXP = Pattern.compile("[^\\\\ ]+\\\\([^\\\\ ]+)");
    /**
     * All registered {@link MailAddressResolver} implementations.
     *
     * @deprecated as of 1.286 Use {@link #all()} for read access and
     * {@link Extension} for registration.
     */
    public static final List<MailAddressResolver> LIST = ExtensionListView.createList(MailAddressResolver.class);

    /**
     * Returns all the registered {@link MailAddressResolver} descriptors.
     */
    public static ExtensionList<MailAddressResolver> all() {
        return Hudson.getInstance().getExtensionList(MailAddressResolver.class);
    }
    private static final Logger LOGGER = Logger.getLogger(MailAddressResolver.class.getName());
}