# HandlerCommand.java

    /*
     * Licensed to the Apache Software Foundation (ASF) under one
     * or more contributor license agreements.  See the NOTICE file
     * distributed with this work for additional information
     * regarding copyright ownership.  The ASF licenses this file
     * to you 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.rest.client.api;

    import java.lang.reflect.ParameterizedType;
    import org.qi4j.api.util.Classes;
    import org.qi4j.library.rest.client.spi.ResponseHandler;
    import org.qi4j.library.rest.client.spi.ResultHandler;
    import org.qi4j.library.rest.common.link.Link;
    import org.restlet.Response;

    /**
     * TODO
     */
    public abstract class HandlerCommand
    {
        public static HandlerCommand refresh()
        {
            return new RefreshCommand();
        }

        public static HandlerCommand query(String relation)
        {
            return new QueryCommand( relation, null);
        }

        public static HandlerCommand query(String relation, Object requestObject)
        {
            return new QueryCommand( relation, requestObject);
        }

        public static HandlerCommand query(Link relation)
        {
            return new QueryLinkCommand( relation );
        }

        public static HandlerCommand command(String relation)
        {
            return new CommandRelationCommand( relation, null );
        }

        public static HandlerCommand command(String relation, Object requestObject)
        {
            return new CommandRelationCommand( relation, requestObject );
        }

        public static HandlerCommand command(Link link)
        {
            return new CommandLinkCommand( link, null );
        }

        public static HandlerCommand command(Link link, Object requestObject)
        {
            return new CommandLinkCommand( link, requestObject );
        }

        public static HandlerCommand delete()
        {
            return new DeleteCommand();
        }

        protected ResponseHandler responseHandler;
        protected ResponseHandler processingErrorHandler;

        public HandlerCommand onSuccess(ResponseHandler responseHandler)
        {
            this.responseHandler = responseHandler;
            return this;
        }

        public <T> HandlerCommand onSuccess(final ResultHandler<T> resultHandler)
        {
            final Class<T> resultType = (Class<T>) Classes.RAW_CLASS.map(( (ParameterizedType) resultHandler.getClass().getGenericInterfaces()[ 0 ] ).getActualTypeArguments()[0]);
            this.responseHandler = new ResponseHandler()
            {
                @Override
                public HandlerCommand handleResponse( Response response, ContextResourceClient client )
                {
                    T result = client.getContextResourceClientFactory().readResponse( response, resultType );
                    return resultHandler.handleResult( result, client );
                }
            };
            return this;
        }

        public HandlerCommand onProcessingError(ResponseHandler processingErrorHandler)
        {
            this.processingErrorHandler = processingErrorHandler;
            return this;
        }

        public <T> HandlerCommand onProcessingError(final ResultHandler<T> resultHandler)
        {
            final Class<T> resultType = (Class<T>) Classes.RAW_CLASS.map(( (ParameterizedType) resultHandler.getClass().getGenericInterfaces()[ 0 ] ).getActualTypeArguments()[0]);
            this.processingErrorHandler = new ResponseHandler()
            {
                @Override
                public HandlerCommand handleResponse( Response response, ContextResourceClient client )
                {
                    T result = client.getContextResourceClientFactory().readResponse( response, resultType );
                    return resultHandler.handleResult( result, client );
                }
            };
            return this;
        }

        abstract HandlerCommand execute( ContextResourceClient client);

        private static class RefreshCommand
            extends HandlerCommand
        {
            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.refresh();
            }
        }

        private static class QueryCommand
            extends HandlerCommand
        {
            private String relation;
            private Object requestObject;

            private QueryCommand( String relation, Object requestObject)
            {
                this.relation = relation;
                this.requestObject = requestObject;
            }

            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.query( client.getResource()
                                         .query( relation ), requestObject, responseHandler, processingErrorHandler );
            }
        }

        private static class QueryLinkCommand
            extends HandlerCommand
        {
            private Link link;

            private QueryLinkCommand( Link link)
            {
                this.link = link;
            }

            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.query( link, null, responseHandler, processingErrorHandler );
            }
        }

        private static class CommandRelationCommand
            extends HandlerCommand
        {
            private String relation;
            private Object requestObject;

            private CommandRelationCommand( String relation, Object requestObject )
            {
                this.relation = relation;
                this.requestObject = requestObject;
            }

            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.command( client.getResource()
                                           .command( relation ), requestObject, responseHandler, processingErrorHandler );
            }
        }

        private static class CommandLinkCommand
            extends HandlerCommand
        {
            private Link link;
            private Object requestObject;

            private CommandLinkCommand( Link link, Object requestObject )
            {
                this.link = link;
                this.requestObject = requestObject;
            }

            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.command( link, requestObject, responseHandler, processingErrorHandler );
            }
        }

        private static class DeleteCommand
            extends HandlerCommand
        {
            @Override
            HandlerCommand execute( ContextResourceClient client )
            {
                return client.delete(responseHandler, processingErrorHandler);
            }
        }

    }