/**
 * Copyright (C) 2007 - 2016 52°North Initiative for Geospatial Open Source
 * Software GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * If the program is linked with libraries which are licensed under one of
 * the following licenses, the combination of the program with the linked
 * library is not considered a "derivative work" of the program:
 *
 *       • Apache License, version 2.0
 *       • Apache Software License, version 1.0
 *       • GNU Lesser General Public License, version 3
 *       • Mozilla Public License, versions 1.0, 1.1 and 2.0
 *       • Common Development and Distribution License (CDDL), version 1.0
 *
 * Therefore the distribution of the program linked with libraries licensed
 * under the aforementioned licenses, is permitted by the copyright holders
 * if the distribution is compliant with both the GNU General Public
 * License version 2 and the aforementioned licenses.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 */
package org.n52.wps.server;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.UUID;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.n52.wps.server.database.DatabaseFactory;
import org.n52.wps.server.database.IDatabase;
import org.n52.wps.commons.MIMEUtil;
import org.n52.wps.commons.XMLUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class RetrieveResultServlet extends HttpServlet {

    private final static Logger LOGGER = LoggerFactory.getLogger(RetrieveResultServlet.class);
    private static final long serialVersionUID = -268198171054599696L;
    // This is required for URL generation for response documents.
    public final static String SERVLET_PATH = "RetrieveResultServlet";
    // in future parameterize
    private final boolean indentXML = false;
    
    private final int uuid_length = 36;

    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// id of result to retrieve.
		String id = request.getParameter("id");

		// optional alternate name for filename (rename the file when retrieving
		// if requested)
		boolean altName = false;
		String alternateFilename = request.getParameter("filename");
		if (!StringUtils.isEmpty(alternateFilename)) {
			altName = true;
		}

        // return result as attachment (instructs browser to offer user "Save" dialog)
        String attachment = request.getParameter("attachment");

        if (StringUtils.isEmpty(id)) {
            errorResponse("id parameter missing", response);
        } else {

        	if(!isIDValid(id)){
        		errorResponse("id parameter not valid", response);
        	}
        	
            IDatabase db = DatabaseFactory.getDatabase();
            String mimeType = db.getMimeTypeForStoreResponse(id);
            long contentLength = db.getContentLengthForStoreResponse(id);
            
            InputStream inputStream = null;
            OutputStream outputStream = null;
            try {
                inputStream = db.lookupResponse(id);

                if (inputStream == null) {
                    errorResponse("id " + id + " is unknown to server", response);
                } else if (mimeType == null) {
                    errorResponse("Unable to determine mime-type for id " + id, response);
                } else {
                    String suffix = MIMEUtil.getSuffixFromMIMEType(mimeType).toLowerCase();

                    // if attachment parameter unset, default to false for mime-type of 'xml' and true for everything else.
					boolean useAttachment = (StringUtils.isEmpty(attachment) && !"xml".equals(suffix)) || Boolean.parseBoolean(attachment);
					if (useAttachment) {
						String attachmentName = (new StringBuilder(id)).append('.').append(suffix).toString();

						if (altName) {
							attachmentName = (new StringBuilder(alternateFilename)).append('.').append(suffix).toString();
						}
						response.addHeader("Content-Disposition", "attachment; filename=\"" + attachmentName + "\"");
					}

                    response.setContentType(mimeType);

                    if ("xml".equals(suffix)) {

                        // NOTE:  We don't set "Content-Length" header, xml may be modified

                        // need these to work around aggressive IE 8 caching.
                        response.addHeader("Cache-Control", "no-cache, no-store");
                        response.addHeader("Pragma", "no-cache");
                        response.addHeader("Expires", "-1");

                        try {
                            outputStream = response.getOutputStream();
                        } catch (IOException e) {
                            throw new IOException("Error obtaining output stream for response", e);
                        }
                        copyResponseAsXML(inputStream, outputStream, useAttachment || indentXML, id);
                    } else {

                        if (contentLength > -1) {
                            // Can't use response.setContentLength(...) as it accepts an int (max of 2^31 - 1) ?!
                            // response.setContentLength(contentLength);
                            response.setHeader("Content-Length", Long.toString(contentLength));
                        } else {
                            LOGGER.warn("Content-Length unknown for response to id {}", id);
                        }

                        try {
                            outputStream = response.getOutputStream();
                        } catch (IOException e) {
                            throw new IOException("Error obtaining output stream for response", e);
                        }
                        copyResponseStream(inputStream, outputStream, id, contentLength);
                    }
                }
            } catch (Exception e) {
                logException(e);
            } finally {
                IOUtils.closeQuietly(inputStream);
                IOUtils.closeQuietly(outputStream);
            }
        }
    }

    protected void errorResponse(String error, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
        PrintWriter writer = response.getWriter();
        writer.write("<html><title>Error</title><body>" + error + "</body></html>");
        writer.flush();
        LOGGER.warn("Error processing response: " + error);
    }

    protected void copyResponseStream(
            InputStream inputStream,
            OutputStream outputStream,
            String id,
            long contentLength) throws IOException {
        long contentWritten = 0;
        try {
            byte[] buffer = new byte[8192];
            int bufferRead;
            while ((bufferRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bufferRead);
                contentWritten += bufferRead;
            }
        } catch (IOException e) {
            String exceptionMessage = contentLength > -1
                    ? String.format("Error writing response to output stream for id %s, %d of %d bytes written", id, contentWritten, contentLength)
                    : String.format("Error writing response to output stream for id %s, %d bytes written", id, contentWritten);
            throw new IOException(exceptionMessage, e);
        }
        LOGGER.info("{} bytes written in response to id {}", contentWritten, id);
    }

    protected void copyResponseAsXML(
            InputStream inputStream,
            OutputStream outputStream,
            boolean indent,
            String id) throws IOException {
        try {
            XMLUtil.copyXML(inputStream, outputStream, indent);
        } catch (IOException e) {
            throw new IOException("Error writing XML response for id " + id, e);
        }
    }

    private void logException(Exception exception) {
        StringBuilder errorBuilder = new StringBuilder(exception.getMessage());
        Throwable cause = getRootCause(exception);
        if (cause != exception) {
            errorBuilder.append(", exception message: ").append(cause.getMessage());
        }
        LOGGER.error(errorBuilder.toString());
    }

    public static Throwable getRootCause(Throwable t) {
        return t.getCause() == null ? t : getRootCause(t.getCause());
    }
    
    public boolean isIDValid(String id){    
    	
    	if(id.length() <= uuid_length){
    		
            try {
                UUID checkUUID = UUID.fromString(id);
                
                if(checkUUID.toString().equals(id)){
                	return true;
                }else{
                	return false;
                }
			} catch (Exception e) {
            	return false;
			}
    		
    	}else {
    		
    		String uuidPartOne = id.substring(0, uuid_length);
    		String uuidPartTwo = id.substring(id.length() - uuid_length, id.length());
    		
    		return isUUIDValid(uuidPartOne) && isUUIDValid(uuidPartTwo);    		
    	}
    }
    
	public boolean isUUIDValid(String uuid) {

		// the following can be used to check whether the id is a valid UUID
		try {
			UUID checkUUID = UUID.fromString(uuid);

			if (checkUUID.toString().equals(uuid)) {
				return true;
			} else {
				return false;
			}
		} catch (Exception e) {
			return false;
		}
	}
}