// Copyright 2006, 2007, 2008, 2009 The Apache Software Foundation

 //

 // 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.apache.tapestry5.internal.transform;

 import org.apache.tapestry5.EventContext;

 import org.apache.tapestry5.annotations.OnEvent;

 import org.apache.tapestry5.ioc.util.BodyBuilder;

 import org.apache.tapestry5.model.MutableComponentModel;

 import org.apache.tapestry5.services.*;

 import java.util.Arrays;

 import java.util.List;

 /**

  * Provides implementations of the {@link org.apache.tapestry5.runtime.Component#dispatchComponentEvent(org.apache.tapestry5.runtime.ComponentEvent)}

  * method, based on {@link org.apache.tapestry5.annotations.OnEvent} annotations.

  */

 public class OnEventWorker implements ComponentClassTransformWorker

 {

     static final String OBJECT_ARRAY_TYPE = "java.lang.Object[]";

     static final String EVENT_CONTEXT_TYPE = EventContext.class.getName();

     static final String LIST_TYPE = List.class.getName();

     private final static int ANY_NUMBER_OF_PARAMETERS = -1;

     public void transform(final ClassTransformation transformation, MutableComponentModel model)

     {

         MethodFilter filter = new MethodFilter()

         {

             public boolean accept(TransformMethodSignature signature)

             {

                 return (hasCorrectPrefix(signature) || hasAnnotation(signature)) &&

                         !transformation.isMethodOverride(signature);

             }

             private boolean hasCorrectPrefix(TransformMethodSignature signature)

             {

                 return signature.getMethodName().startsWith("on");

             }

             private boolean hasAnnotation(TransformMethodSignature signature)

             {

                 return transformation.getMethodAnnotation(signature, OnEvent.class) != null;

             }

         };

         List<TransformMethodSignature> methods = transformation.findMethods(filter);

         // No methods, no work.

         if (methods.isEmpty()) return;

         BodyBuilder builder = new BodyBuilder();

         builder.begin();

         builder.addln("if ($1.isAborted()) return $_;");

         builder.addln("try");

         builder.begin();

         for (TransformMethodSignature method : methods)

             addCodeForMethod(builder, method, transformation, model);

         builder.end(); // try

         // Runtime exceptions pass right through.

         builder.addln("catch (RuntimeException ex) { throw ex; }");

         // Wrap others in a RuntimeException to communicate them up.

         builder.addln("catch (Exception ex) { throw new RuntimeException(ex); } ");

         builder.end();

         transformation.extendMethod(TransformConstants.DISPATCH_COMPONENT_EVENT, builder.toString());

     }

     private void addCodeForMethod(BodyBuilder builder, TransformMethodSignature method,

                                   ClassTransformation transformation, MutableComponentModel model)

     {

         // $1 is the event

         int parameterCount = getParameterCount(method);

         OnEvent annotation = transformation.getMethodAnnotation(method, OnEvent.class);

         String eventType = extractEventType(method, annotation);

         String componentId = extractComponentId(method, annotation);

         builder.addln("if ($1.matches(\"%s\", \"%s\", %d))", eventType, componentId, parameterCount);

         builder.begin();

         // Ensure that we return true, because *some* event handler method was invoked,

         // even if it chose not to abort the event.

         builder.addln("$_ = true;");

         builder.addln("$1.setMethodDescription(\"%s\");", transformation.getMethodIdentifier(method));

         boolean isNonVoid = !method.getReturnType().equals("void");

         // Store the result, converting primitives to wrappers automatically.

         if (isNonVoid) builder.add("if ($1.storeResult(($w) ");

         builder.add("%s(", method.getMethodName());

         buildMethodParameters(builder, method);

         if (isNonVoid) builder.addln("))) return true;");

         else builder.addln(");");

         builder.end();

         // Indicate that the eventType is handled.

         model.addEventHandler(eventType);

     }

     private String extractComponentId(TransformMethodSignature method, OnEvent annotation)

     {

         if (annotation != null) return annotation.component();

         // Method name started with "on". Extract the component id, if present.

         String name = method.getMethodName();

         int fromx = name.indexOf("From");

         if (fromx < 0) return "";

         return name.substring(fromx + 4);

     }

     private String extractEventType(TransformMethodSignature method, OnEvent annotation)

     {

         if (annotation != null) return annotation.value();

         // Method name started with "on". Extract the event type.

         String name = method.getMethodName();

         int fromx = name.indexOf("From");

         return fromx == -1 ? name.substring(2) : name.substring(2, fromx);

     }

     private int getParameterCount(TransformMethodSignature method)

     {

         String[] types = method.getParameterTypes();

         if (types.length == 0) return 0;

         if (types.length == 1)

         {

             String soloType = types[0];

             if (soloType.equals(OBJECT_ARRAY_TYPE) || soloType.equals(EVENT_CONTEXT_TYPE) || soloType.equals(LIST_TYPE))

                 return ANY_NUMBER_OF_PARAMETERS;

         }

         return types.length;

     }

     private void buildMethodParameters(BodyBuilder builder, TransformMethodSignature method)

     {

         int contextIndex = 0;

         for (int i = 0; i < method.getParameterTypes().length; i++)

         {

             if (i > 0) builder.add(", ");

             String type = method.getParameterTypes()[i];

             // Type Object[] is a special case, it gets all of the context parameters in one go.

             if (type.equals(OBJECT_ARRAY_TYPE))

             {

                 builder.add("$1.getContext()");

                 continue;

             }

             // Added for TAPESTRY-2177

             if (type.equals(EVENT_CONTEXT_TYPE))

             {

                 builder.add("$1.getEventContext()");

                 continue;

             }

             // Added for TAPESTRY-1999

             if (type.equals(LIST_TYPE))

             {

                 builder.add("%s.asList($1.getContext())", Arrays.class.getName());

                 continue;

             }

             boolean isPrimitive = TransformUtils.isPrimitive(type);

             String wrapperType = TransformUtils.getWrapperTypeName(type);

             // Add a cast to the wrapper type up front

             if (isPrimitive) builder.add("(");

             // A cast is always needed (i.e. from java.lang.Object to, say, java.lang.String, etc.).

             // The wrapper type will be the actual type unless its a primitive, in which case it

             // really will be the wrapper type.

             builder.add("(%s)", wrapperType);

             // The strings for desired type name will likely repeat a bit; it may be

             // worth it to inject them as final fields. Could increase the number

             // of constructor parameters pretty dramatically, however, and will reduce

             // the readability of the output method bodies.

             builder.add("$1.coerceContext(%d, \"%s\")", contextIndex++, wrapperType);

             // and invoke a method on the cast value to get back to primitive

             if (isPrimitive) builder.add(").%s()", TransformUtils.getUnwrapperMethodName(type));

         }

     }

 }