# Servlets.java

    /*
     * Copyright (c) 2008, Richard Wallace. All Rights Reserved.
     * Copyright (c) 2011, Paul Merlin. All Rights Reserved.
     *
     * Licensed  under the  Apache License,  Version 2.0  (the "License");
     * you may not use  this file  except in  compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed  under the  License is distributed on an "AS IS" BASIS,
     * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
     * implied.
     *
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.qi4j.library.http;

    import java.util.Collections;
    import java.util.EnumSet;
    import java.util.Map;
    import java.util.UUID;
    import javax.servlet.DispatcherType;
    import javax.servlet.Filter;
    import javax.servlet.Servlet;
    import javax.servlet.ServletContextListener;
    import org.qi4j.api.service.ServiceComposite;
    import org.qi4j.bootstrap.AssemblyException;
    import org.qi4j.bootstrap.ModuleAssembly;
    import org.qi4j.library.http.ConstraintInfo.Constraint;
    import org.qi4j.library.http.ConstraintInfo.HttpMethod;
    import org.qi4j.library.http.Dispatchers.Dispatcher;

    import static org.qi4j.api.common.Visibility.layer;

    public final class Servlets
    {

        private Servlets()
        {
        }

        public static ContextListenerDeclaration listen()
        {
            return new ContextListenerDeclaration();
        }

        public static ContextListenerAssembler addContextListeners( ContextListenerDeclaration... contextListenerDeclarations )
        {
            return new ContextListenerAssembler( contextListenerDeclarations );
        }

        public static class ContextListenerAssembler
        {

            final ContextListenerDeclaration[] contextListenerDeclarations;

            ContextListenerAssembler( ContextListenerDeclaration... eventListenerDeclarations )
            {
                this.contextListenerDeclarations = eventListenerDeclarations;
            }

            public void to( ModuleAssembly module )
                    throws AssemblyException
            {
                for ( ContextListenerDeclaration contextListenerDeclaration : contextListenerDeclarations ) {
                    module.services( contextListenerDeclaration.contextListener() ).
                            setMetaInfo( contextListenerDeclaration.contextListenerInfo() ).
                            instantiateOnStartup().visibleIn( layer );
                }
            }

        }

        public static class ContextListenerDeclaration
        {

            Class<? extends ServiceComposite> contextListener;

            Map<String, String> initParams = Collections.emptyMap();

            public <T extends ServletContextListener & ServiceComposite> ContextListenerDeclaration with( Class<T> contextListener )
            {
                this.contextListener = contextListener;
                return this;
            }

            public Class<? extends ServiceComposite> contextListener()
            {
                return contextListener;
            }

            public ContextListenerDeclaration withInitParams( Map<String, String> initParams )
            {
                this.initParams = initParams;
                return this;
            }

            private ContextListenerInfo contextListenerInfo()
            {
                return new ContextListenerInfo( initParams );
            }

        }

        public static ServletDeclaration serve( String path )
        {
            return new ServletDeclaration( path );
        }

        public static ServletAssembler addServlets( ServletDeclaration... servletDeclarations )
        {
            return new ServletAssembler( servletDeclarations );
        }

        public static class ServletAssembler
        {

            final ServletDeclaration[] servletDeclarations;

            ServletAssembler( ServletDeclaration... servletDeclarations )
            {
                this.servletDeclarations = servletDeclarations;
            }

            public void to( ModuleAssembly module )
                    throws AssemblyException
            {
                for ( ServletDeclaration servletDeclaration : servletDeclarations ) {
                    module.services( servletDeclaration.servlet() ).
                            setMetaInfo( servletDeclaration.servletInfo() ).
                            instantiateOnStartup().visibleIn( layer );
                }
            }

        }

        public static class ServletDeclaration
        {

            String path;

            Class<? extends ServiceComposite> servlet;

            Map<String, String> initParams = Collections.emptyMap();

            ServletDeclaration( String path )
            {
                this.path = path;
            }

            public <T extends Servlet & ServiceComposite> ServletDeclaration with( Class<T> servlet )
            {
                this.servlet = servlet;
                return this;
            }

            public ServletDeclaration withInitParams( Map<String, String> initParams )
            {
                this.initParams = initParams;
                return this;
            }

            Class<? extends ServiceComposite> servlet()
            {
                return servlet;
            }

            ServletInfo servletInfo()
            {
                return new ServletInfo( path, initParams );
            }

        }

        public static FilterAssembler filter( String path )
        {
            return new FilterAssembler( path );
        }

        public static FilterDeclaration addFilters( FilterAssembler... filterAssemblers )
        {
            return new FilterDeclaration( filterAssemblers );
        }

        public static class FilterDeclaration
        {

            final FilterAssembler[] filterAssemblers;

            FilterDeclaration( FilterAssembler... filterAssemblers )
            {
                this.filterAssemblers = filterAssemblers;
            }

            @SuppressWarnings( "unchecked" )
            public void to( ModuleAssembly module )
                    throws AssemblyException
            {
                for ( FilterAssembler filterAssembler : filterAssemblers ) {
                    module.services( filterAssembler.filter() ).
                            setMetaInfo( filterAssembler.filterInfo() ).
                            instantiateOnStartup().visibleIn( layer );
                }
            }

        }

        public static class FilterAssembler
        {

            String path;

            Class<? extends ServiceComposite> filter;

            EnumSet<DispatcherType> dispatchers;

            Map<String, String> initParams = Collections.emptyMap();

            FilterAssembler( String path )
            {
                this.path = path;
            }

            public <T extends Filter & ServiceComposite> FilterAssembler through(
                    Class<T> filter )
            {
                this.filter = filter;
                return this;
            }

            public FilterAssembler on( DispatcherType first, DispatcherType... rest )
            {
                dispatchers = EnumSet.of( first, rest );
                return this;
            }

            @Deprecated
            public FilterAssembler on( Dispatcher first, Dispatcher... rest )
            {
                EnumSet<DispatcherType> dispatch = EnumSet.noneOf( DispatcherType.class );
                for ( Dispatcher each : Dispatchers.dispatchers( first, rest ) ) {
                    switch ( each ) {
                        case FORWARD:
                            dispatch.add( DispatcherType.FORWARD );
                            break;
                        case REQUEST:
                            dispatch.add( DispatcherType.REQUEST );
                            break;
                    }
                }
                dispatchers = dispatch;
                return this;
            }

            public FilterAssembler withInitParams( Map<String, String> initParams )
            {
                this.initParams = initParams;
                return this;
            }

            Class<? extends ServiceComposite> filter()
            {
                return filter;
            }

            FilterInfo filterInfo()
            {
                return new FilterInfo( path, initParams, dispatchers );
            }

        }

        public static ConstraintAssembler constrain( String path )
        {
            return new ConstraintAssembler( path );
        }

        public static ConstraintDeclaration addConstraints( ConstraintAssembler... constraintAssemblers )
        {
            return new ConstraintDeclaration( constraintAssemblers );
        }

        public static class ConstraintDeclaration
        {

            private final ConstraintAssembler[] constraintAssemblers;

            private ConstraintDeclaration( ConstraintAssembler[] constraintAssemblers )
            {
                this.constraintAssemblers = constraintAssemblers;
            }

            public void to( ModuleAssembly module )
                    throws AssemblyException
            {
                // TODO Refactor adding Map<ServiceAssembly,T> ServiceDeclaration.getMetaInfos( Class<T> type ); in bootstrap & runtime
                // This would allow removing the ConstraintServices instances and this horrible hack with random UUIDs
                for ( ConstraintAssembler eachAssembler : constraintAssemblers ) {
                    module.addServices( ConstraintService.class ).identifiedBy( UUID.randomUUID().toString() ).setMetaInfo( eachAssembler.constraintInfo() );
                }
            }

        }

        public static class ConstraintAssembler
        {

            private final String path;

            private Constraint constraint;

            private HttpMethod[] omittedHttpMethods = new HttpMethod[]{};

            private ConstraintAssembler( String path )
            {
                this.path = path;
            }

            public ConstraintAssembler by( Constraint constraint )
            {
                this.constraint = constraint;
                return this;
            }

            public ConstraintAssembler butNotOn( HttpMethod... omittedHttpMethods )
            {
                this.omittedHttpMethods = omittedHttpMethods;
                return this;
            }

            ConstraintInfo constraintInfo()
            {
                return new ConstraintInfo( path, constraint, omittedHttpMethods );
            }

        }

    }