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package org.jruby.runtime.profile;

import org.jruby.Ruby;
import org.jruby.RubyInstanceConfig;
import org.jruby.runtime.profile.builtin.BuiltinProfilingService;

/**
 * This helper is used to get the configured {@link org.jruby.runtime.profile.ProfilingService} for the current {@link Ruby} instance.
 * Each {@link Ruby} instance has a {@link org.jruby.runtime.profile.ProfilingServiceLookup} property.
 *
 * @author Andre Kullmann
 */
public class ProfilingServiceLookup {

    private final Ruby runtime;

    /**
     * The service which is configured. Will be lazy loaded, and never changed.
     */
    private ProfilingService service;

    /**
     *
     * @param runtime the ruby instance this instance belongs to
     * @throws java.lang.IllegalArgumentException if given runtime is null
     */
    public ProfilingServiceLookup(final Ruby runtime) {

        if( runtime == null )
            throw new IllegalArgumentException( "Given runtime must not be null." );

        this.runtime = runtime;
    }

    /**
     * Returns {@link #runtime}. At first invocation {@link #newProfiler()} is called to create a new instance
     * of the configured {@link org.jruby.runtime.profile.ProfilingService} instance.
     *
     * @return the configured {@link org.jruby.runtime.profile.ProfilingService} for the {@link #runtime}.
     */
    public ProfilingService getService() {
        return service == null ? newProfiler() : service;
    }

    /**
     * Getter to avoid direct property access.
     */
    private Ruby getRuntime() {
        return runtime;
    }

    /**
     * Getter to avoid direct property access.
     */
    private RubyInstanceConfig getConfig() {
        return getRuntime().getInstanceConfig();
    }

    /**
     * Getter to avoid direct property access.
     */
    private RubyInstanceConfig.ProfilingMode getProfilingMode() {
        return getConfig().getProfilingMode();
    }

    /**
     * Getter to avoid direct property access.
     */
    private String getServiceClassName() {
        return getConfig().getProfilingService();
    }

    /**
     * Creates a new instance of the configured {@link org.jruby.runtime.profile.ProfilingService} instance.
     * @return The service instance which should be used.
     */
    private synchronized ProfilingService newProfiler(  ) {
        if( service == null ) {
            switch( getProfilingMode() ) {
                case SERVICE:
                    if( getServiceClassName() == null || getServiceClassName().trim().isEmpty() ) {
                        throw new RuntimeException( "No profiling service property found.");
                    }

                    service = newServiceInstance();
                    break;

                default:
                    service = new BuiltinProfilingService();
                    break;
            }
        }

        return service;
    }

    /**
     * @return new instance created by reflection
     */
    private ProfilingService newServiceInstance() {

        Class<? extends ProfilingService> clazz = loadServiceClass();

        try {
            return clazz.newInstance();
        } catch (InstantiationException e) {
            throw new RuntimeException( "Can't create service service. " + e.getClass().getSimpleName() + ": " + e.getMessage() );
        } catch (IllegalAccessException e) {
            throw new RuntimeException( "Can't create service service. " + e.getClass().getSimpleName() + ": " + e.getMessage() );
        }
    }

    /**
     * @return the configured {@link org.jruby.runtime.profile.ProfilingService} class.
     */
    @SuppressWarnings( "unchecked" )
    private Class<? extends ProfilingService> loadServiceClass() {

        ClassLoader cl = getRuntime().getJRubyClassLoader();

        try {
            return (Class<? extends ProfilingService>) cl.loadClass( getServiceClassName() );
        } catch (ClassNotFoundException e) {
            throw new RuntimeException( "Can't load service service class. " + e.getClass().getSimpleName() + ": " + e.getMessage() );
        }

    }

}
