Adobe-Consulting-Services/acs-aem-commons

/*
 * ACS AEM Commons
 *
 * Copyright (C) 2013 - 2023 Adobe
 *
 * 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 com.adobe.acs.commons.ccvar.filter;

import javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;

/**
 * Response Wrapper used to allow for full output of the current response data so that it can be manipulated
 * and rewritten.
 */
public class CapturingResponseWrapper extends HttpServletResponseWrapper {

    private final ByteArrayOutputStream capture;
    private ServletOutputStream output;
    private PrintWriter writer;

    public CapturingResponseWrapper(HttpServletResponse response) {
        super(response);
        capture = new ByteArrayOutputStream(response.getBufferSize());
    }

    @Override
    public ServletOutputStream getOutputStream() {
        if (writer != null) {
            throw new IllegalStateException(
                    "getWriter() has already been called on this response.");
        }

        if (output == null) {
            output = new ServletOutputStream() {
                @Override
                public void write(int b) throws IOException {
                    capture.write(b);
                }

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

                @Override
                public void close() throws IOException {
                    capture.close();
                }

                @Override
                public boolean isReady() {
                    return true;
                }

                @Override
                public void setWriteListener(WriteListener writeListener) {
                    // do nothing
                }
            };
        }

        return output;
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        if (output != null) {
            throw new IllegalStateException(
                    "getOutputStream() has already been called on this response.");
        }

        if (writer == null) {
            writer = new PrintWriter(new OutputStreamWriter(capture,
                    getCharacterEncoding()));
        }

        return writer;
    }

    public byte[] getCaptureAsBytes() throws IOException {
        if (writer != null) {
            writer.close();
        } else if (output != null) {
            output.close();
        }

        return capture.toByteArray();
    }

    public String getCaptureAsString() throws IOException {
        return new String(getCaptureAsBytes(), getCharacterEncoding());
    }
}