/*
 * 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.template.utility;

import java.io.IOException;
import java.io.Writer;
import java.util.Map;

import freemarker.core.Environment;
import freemarker.template.SimpleScalar;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateScalarModel;
import freemarker.template.TemplateTransformModel;

A transform that captures the output of a block of FTL code and stores that in a variable.
As this transform is initially present in the shared variable set, you can always
access it from the templates:
<@capture_output var="captured">
  ...
</@capture_output>

And later in the template you can use the captured output:
${captured}
This transform requires one of three parameters: var, local, or global.
Each of them specifies the name of the variable that stores the captured output, but the first creates a
variable in a name-space (as <#assign>), the second creates a macro-local variable (as <#local>),
and the last creates a global variable (as <#global>).

In the case of an assignment within a namespace, there is an optional parameter
namespace that indicates in which namespace to do the assignment.
if this is omitted, the current namespace is used, and this will be, by far, the most
common usage pattern.
Deprecated:
Use block-assignments instead, like <assign x>...</assign>./**
 * A transform that captures the output of a block of FTL code and stores that in a variable.
 *
 * <p>As this transform is initially present in the shared variable set, you can always
 * access it from the templates:</p>
 *
 * <pre>
 * &lt;@capture_output var="captured"&gt;
 *   ...
 * &lt;/@capture_output&gt;
 * </pre>
 *
 * <p>And later in the template you can use the captured output:</p>
 *
 * ${captured}
 *
 * <p>This transform requires one of three parameters: <code>var</code>, <code>local</code>, or <code>global</code>.
 * Each of them specifies the name of the variable that stores the captured output, but the first creates a
 * variable in a name-space (as &lt;#assign&gt;), the second creates a macro-local variable (as &lt;#local&gt;),
 * and the last creates a global variable (as &lt;#global&gt;).
 * </p>
 * <p>In the case of an assignment within a namespace, there is an optional parameter
 * <code>namespace</code> that indicates in which namespace to do the assignment.
 * if this is omitted, the current namespace is used, and this will be, by far, the most
 * common usage pattern.</p>
 *
 * @deprecated Use block-assignments instead, like <code>&lt;assign x&gt;...&lt;/assign&gt;</code>.
 */
@Deprecated
public class CaptureOutput implements TemplateTransformModel {

    public Writer getWriter(final Writer out, final Map args) throws TemplateModelException {
        String errmsg = "Must specify the name of the variable in "
                + "which to capture the output with the 'var' or 'local' or 'global' parameter.";
        if (args == null) throw new TemplateModelException(errmsg);

        boolean local = false, global = false;
        final TemplateModel nsModel = (TemplateModel) args.get("namespace");
        Object varNameModel = args.get("var");
        if (varNameModel == null) {
            varNameModel = args.get("local");
            if (varNameModel == null) {
                varNameModel = args.get("global");
                global = true;
            } else {
                local = true;
            }
            if (varNameModel == null) {
                throw new TemplateModelException(errmsg);
            }
        }
        if (args.size() == 2) {
            if (nsModel == null) {
                throw new TemplateModelException("Second parameter can only be namespace");
            }
            if (local) {
                throw new TemplateModelException("Cannot specify namespace for a local assignment");
            }
            if (global) {
                throw new TemplateModelException("Cannot specify namespace for a global assignment");
            }
            if (!(nsModel instanceof Environment.Namespace)) {
                throw new TemplateModelException("namespace parameter does not specify a namespace. It is a " + nsModel.getClass().getName());
            }
        } else if (args.size() != 1) throw new TemplateModelException(
                "Bad parameters. Use only one of 'var' or 'local' or 'global' parameters.");

        if (!(varNameModel instanceof TemplateScalarModel)) {
            throw new TemplateModelException("'var' or 'local' or 'global' parameter doesn't evaluate to a string");
        }
        final String varName = ((TemplateScalarModel) varNameModel).getAsString();
        if (varName == null) {
            throw new TemplateModelException("'var' or 'local' or 'global' parameter evaluates to null string");
        }

        final StringBuilder buf = new StringBuilder();
        final Environment env = Environment.getCurrentEnvironment();
        final boolean localVar = local;
        final boolean globalVar = global;

        return new Writer() {

            @Override
            public void write(char cbuf[], int off, int len) {
                buf.append(cbuf, off, len);
            }

            @Override
            public void flush() throws IOException {
                out.flush();
            }

            @Override
            public void close() throws IOException {
                SimpleScalar result = new SimpleScalar(buf.toString());
                try {
                    if (localVar) {
                        env.setLocalVariable(varName, result);
                    } else if (globalVar) {
                        env.setGlobalVariable(varName, result);
                    } else {
                        if (nsModel == null) {
                            env.setVariable(varName, result);
                        } else {
                            ((Environment.Namespace) nsModel).put(varName, result);
                        }
                    }
                } catch (java.lang.IllegalStateException ise) { // if somebody uses 'local' outside a macro
                    throw new IOException("Could not set variable " + varName + ": " + ise.getMessage());
                }
            }
        };
    }
}