/*
 * 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 freemarker.core;

import java.io.IOException;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;

An instruction that processes the nested block within a macro instruction.
/**
 * An instruction that processes the nested block within a macro instruction.
 */
final class BodyInstruction extends TemplateElement {
    
    
    private List bodyParameters;
    
    
    BodyInstruction(List bodyParameters) {
        this.bodyParameters = bodyParameters;
    }
    
    List getBodyParameters() {
        return bodyParameters;
    }

    
There is actually a subtle but essential point in the code below.
A macro operates in the context in which it's defined. However, 
a nested block within a macro instruction is defined in the 
context in which the macro was invoked. So, we actually need to
temporarily switch the namespace and macro context back to
what it was before macro invocation to implement this properly.
I (JR) realized this thanks to some incisive comments from Daniel Dekany.
/**
     * There is actually a subtle but essential point in the code below.
     * A macro operates in the context in which it's defined. However, 
     * a nested block within a macro instruction is defined in the 
     * context in which the macro was invoked. So, we actually need to
     * temporarily switch the namespace and macro context back to
     * what it was before macro invocation to implement this properly.
     * I (JR) realized this thanks to some incisive comments from Daniel Dekany.
     */
    @Override
    TemplateElement[] accept(Environment env) throws IOException, TemplateException {
        Context bodyContext = new Context(env);
        env.invokeNestedContent(bodyContext);
        return null;
    }

    @Override
    protected String dump(boolean canonical) {
        StringBuilder sb = new StringBuilder();
        if (canonical) sb.append('<');
        sb.append(getNodeTypeSymbol());
        if (bodyParameters != null) {
            for (int i = 0; i < bodyParameters.size(); i++) {
                sb.append(' ');
                sb.append(((Expression) bodyParameters.get(i)).getCanonicalForm());
            }
        }
        if (canonical) sb.append('>');
        return sb.toString();
    }
    
    @Override
    String getNodeTypeSymbol() {
        return "#nested";
    }
    
    @Override
    int getParameterCount() {
        return bodyParameters != null ? bodyParameters.size() : 0;
    }

    @Override
    Object getParameterValue(int idx) {
        checkIndex(idx);
        return bodyParameters.get(idx);
    }

    @Override
    ParameterRole getParameterRole(int idx) {
        checkIndex(idx);
        return ParameterRole.PASSED_VALUE;
    }

    private void checkIndex(int idx) {
        if (bodyParameters == null || idx >= bodyParameters.size()) {
            throw new IndexOutOfBoundsException();
        }
    }
    
    /*
    boolean heedsOpeningWhitespace() {
        return true;
    }

    boolean heedsTrailingWhitespace() {
        return true;
    }
    */
    
    @Override
    boolean isShownInStackTrace() {
        return true;
    }

    class Context implements LocalContext {
        Macro.Context invokingMacroContext;
        Environment.Namespace bodyVars;
        
        Context(Environment env) throws TemplateException {
            invokingMacroContext = env.getCurrentMacroContext();
            List bodyParameterNames = invokingMacroContext.nestedContentParameterNames;
            if (bodyParameters != null) {
                for (int i = 0; i < bodyParameters.size(); i++) {
                    Expression exp = (Expression) bodyParameters.get(i);
                    TemplateModel tm = exp.eval(env);
                    if (bodyParameterNames != null && i < bodyParameterNames.size()) {
                        String bodyParameterName = (String) bodyParameterNames.get(i);
                        if (bodyVars == null) {
                            bodyVars = env.new Namespace();
                        }
                        bodyVars.put(bodyParameterName, tm);
                    }
                }
            }
        }
        
        public TemplateModel getLocalVariable(String name) throws TemplateModelException {
            return bodyVars == null ? null : bodyVars.get(name);
        }
        
        public Collection getLocalVariableNames() {
            List bodyParameterNames = invokingMacroContext.nestedContentParameterNames;
            return bodyParameterNames == null ? Collections.EMPTY_LIST : bodyParameterNames;
        }
    }

    @Override
    boolean isNestedBlockRepeater() {
        return false;
    }
}