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/**
 * Copyright (c) 2009-2012, Netbout.com
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met: 1) Redistributions of source code must retain the above
 * copyright notice, this list of conditions and the following
 * disclaimer. 2) Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided
 * with the distribution. 3) Neither the name of the NetBout.com nor
 * the names of its contributors may be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.netbout.spi.cpa;

import com.jcabi.log.Logger;
import com.netbout.spi.Identity;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.reflections.Reflections;

/**
 * Discovers operations in classpath.
 *
 * @author Yegor Bugayenko ([email protected])
 * @version $Id: OpDiscoverer.java 3470 2012-10-16 18:46:28Z [email protected] $
 */
final class OpDiscoverer {

    /**
     * The identity of the helper.
     */
    private final transient Identity identity;

    /**
     * Public ctor.
     * @param idnt The identity of helper
     */
    public OpDiscoverer(final Identity idnt) {
        this.identity = idnt;
    }

    /**
     * Discover all targets in the JAR.
     * @param url The URL with sources
     * @return Associative array of discovered targets/operations
     */
    public ConcurrentMap discover(final URL url) {
        Reflections reflections;
        if ("file".equals(url.getProtocol())) {
            reflections = this.fromPackage(url.getPath());
        } else {
            throw new IllegalArgumentException(
                String.format(
                    "Unknown protocol '%s' in '%s' (has to be 'file')",
                    url.getProtocol(),
                    url
                )
            );
        }
        return this.retrieve(reflections);
    }

    /**
     * Discover all methods in the provided farm.
     * @param farm The object annotated with {@link Farm}
     * @return Associative array of discovered targets/operations
     */
    private ConcurrentMap inFarm(final Object farm) {
        final ConcurrentMap targets =
            new ConcurrentHashMap();
        for (Method method : farm.getClass().getDeclaredMethods()) {
            final Annotation atn = method.getAnnotation(Operation.class);
            if (atn == null) {
                continue;
            }
            final String mnemo = ((Operation) atn).value();
            targets.put(mnemo, HelpTarget.build(farm, method));
            Logger.debug(
                this,
                "#inFarm(%s): @Operation('%[type]s') found",
                farm,
                mnemo
            );
        }
        return targets;
    }

    /**
     * Load them from reflections.
     * @param ref The reflections
     * @return Associative array of discovered targets/operations
     */
    @SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops")
    private ConcurrentMap retrieve(final Reflections ref) {
        final ConcurrentMap targets =
            new ConcurrentHashMap();
        for (Class tfarm : ref.getTypesAnnotatedWith(Farm.class)) {
            Logger.debug(
                this,
                "#discover(..): @Farm found at '%s'",
                tfarm.getName()
            );
            Object farm;
            try {
                farm = tfarm.newInstance();
            } catch (InstantiationException ex) {
                throw new IllegalArgumentException(ex);
            } catch (IllegalAccessException ex) {
                throw new IllegalArgumentException(ex);
            }
            if (farm instanceof IdentityAware) {
                final Identity safe = new SafeIdentity(this.identity);
                ((IdentityAware) farm).init(safe);
                Logger.debug(
                    this,
                    // @checkstyle LineLength (1 line)
                    "#retrieve(..): %[type]s farm instantiated and initialized as '%s'",
                    farm,
                    safe
                );
            } else {
                Logger.debug(
                    this,
                    "#retrieve(..): %[type]s farm instantiated anonymously",
                    farm
                );
            }
            for (ConcurrentMap.Entry entry
                : this.inFarm(farm).entrySet()) {
                if (targets.containsKey(entry.getKey())) {
                    throw new IllegalStateException(
                        String.format(
                            // @checkstyle LineLength (1 line)
                            "duplicate operation '%s' in '%s' (already exists in '%s')",
                            entry.getKey(),
                            entry.getValue(),
                            targets.get(entry.getKey())
                        )
                    );
                }
                targets.put(entry.getKey(), entry.getValue());
            }
        }
        return targets;
    }

    /**
     * Creates reflections from package.
     * @param pkg The name of the package
     * @return Reflections
     */
    private Reflections fromPackage(final String pkg) {
        if (pkg.isEmpty()) {
            throw new IllegalArgumentException(
                "Package is empty, can't load classes"
            );
        }
        String name = pkg;
        if (name.charAt(0) == '/') {
            name = name.substring(1);
        }
        return new Reflections(name);
    }

}




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