/**
 * 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 org.apache.camel.component.file;

import java.io.File;
import java.io.InputStream;

import org.apache.camel.Exchange;
import org.apache.camel.Expression;
import org.apache.camel.impl.DefaultProducer;
import org.apache.camel.spi.Language;
import org.apache.camel.util.ExchangeHelper;
import org.apache.camel.util.FileUtil;
import org.apache.camel.util.ObjectHelper;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Generic file producer
 */
public class GenericFileProducer<T> extends DefaultProducer {
    protected final transient Log log = LogFactory.getLog(getClass());
    protected final GenericFileEndpoint<T> endpoint;
    protected final GenericFileOperations<T> operations;
    
    protected GenericFileProducer(GenericFileEndpoint<T> endpoint, GenericFileOperations<T> operations) {
        super(endpoint);
        this.endpoint = endpoint;
        this.operations = operations;
    }
    
    protected String getFileSeparator() {
        return File.separator;
    }

    protected String normalizePath(String name) {        
        return FileUtil.normalizePath(name);
    }

    public void process(Exchange exchange) throws Exception {
        Exchange fileExchange = endpoint.createExchange(exchange);
        processExchange(fileExchange);
        ExchangeHelper.copyResults(exchange, fileExchange);
    }

    /**
     * Perform the work to process the fileExchange
     *
     * @param exchange fileExchange
     * @throws Exception is thrown if some error
     */
    protected void processExchange(Exchange exchange) throws Exception {
        if (log.isTraceEnabled()) {
            log.trace("Processing " + exchange);
        }

        try {
            String target = createFileName(exchange);

            preWriteCheck();

            // should we write to a temporary name and then afterwards rename to real target
            boolean writeAsTempAndRename = ObjectHelper.isNotEmpty(endpoint.getTempFileName());
            String tempTarget = null;
            if (writeAsTempAndRename) {
                // compute temporary name with the temp prefix
                tempTarget = createTempFileName(exchange, target);

                if (log.isTraceEnabled()) {
                    log.trace("Writing using tempNameFile: " + tempTarget);
                }

                // cater for file exists option on the real target as
                // the file operations code will work on the temp file

                // if an existing file already exists what should we do?
                if (operations.existsFile(target)) {
                    if (endpoint.getFileExist() == GenericFileExist.Ignore) {
                        // ignore but indicate that the file was written
                        if (log.isTraceEnabled()) {
                            log.trace("An existing file already exists: " + target + ". Ignore and do not override it.");
                        }
                        return;
                    } else if (endpoint.getFileExist() == GenericFileExist.Fail) {
                        throw new GenericFileOperationFailedException("File already exist: " + target + ". Cannot write new file.");
                    } else if (endpoint.isEagerDeleteTargetFile() && endpoint.getFileExist() == GenericFileExist.Override) {
                        // we override the target so we do this by deleting it so the temp file can be renamed later
                        // with success as the existing target file have been deleted
                        if (log.isTraceEnabled()) {
                            log.trace("Eagerly deleting existing file: " + target);
                        }
                        if (!operations.deleteFile(target)) {
                            throw new GenericFileOperationFailedException("Cannot delete file: " + target);
                        }
                    }
                }

                // delete any pre existing temp file
                if (operations.existsFile(tempTarget)) {
                    if (log.isTraceEnabled()) {
                        log.trace("Deleting existing temp file: " + tempTarget);
                    }
                    if (!operations.deleteFile(tempTarget)) {
                        throw new GenericFileOperationFailedException("Cannot delete file: " + tempTarget);
                    }
                }
            }

            // write/upload the file
            writeFile(exchange, tempTarget != null ? tempTarget : target);

            // if we did write to a temporary name then rename it to the real
            // name after we have written the file
            if (tempTarget != null) {

                // if we should not eager delete the target file then do it now just before renaming
                if (!endpoint.isEagerDeleteTargetFile() && operations.existsFile(target)
                        && endpoint.getFileExist() == GenericFileExist.Override) {
                    // we override the target so we do this by deleting it so the temp file can be renamed later
                    // with success as the existing target file have been deleted
                    if (log.isTraceEnabled()) {
                        log.trace("Deleting existing file: " + target);
                    }
                    if (!operations.deleteFile(target)) {
                        throw new GenericFileOperationFailedException("Cannot delete file: " + target);
                    }
                }

                // now we are ready to rename the temp file to the target file
                if (log.isTraceEnabled()) {
                    log.trace("Renaming file: [" + tempTarget + "] to: [" + target + "]");
                }
                boolean renamed = operations.renameFile(tempTarget, target);
                if (!renamed) {
                    throw new GenericFileOperationFailedException("Cannot rename file from: " + tempTarget + " to: " + target);
                }
            }

            // lets store the name we really used in the header, so end-users
            // can retrieve it
            exchange.getIn().setHeader(Exchange.FILE_NAME_PRODUCED, target);
        } catch (Exception e) {
            handleFailedWrite(exchange, e);
        }

        postWriteCheck();
    }

    /**
     * If we fail writing out a file, we will call this method. This hook is
     * provided to disconnect from servers or clean up files we created (if needed).
     */
    protected void handleFailedWrite(Exchange exchange, Exception exception) throws Exception {
        throw exception;
    }

    /**
     * Perform any actions that need to occur before we write such as connecting to an FTP server etc.
     */
    protected void preWriteCheck() throws Exception {
        // nothing needed to check
    }

    /**
     * Perform any actions that need to occur after we are done such as disconnecting.
     */
    protected void postWriteCheck() {
        // nothing needed to check
    }

    protected void writeFile(Exchange exchange, String fileName) throws GenericFileOperationFailedException {
        InputStream payload = exchange.getIn().getBody(InputStream.class);
        try {
            // build directory if auto create is enabled
            if (endpoint.isAutoCreate()) {
                // use java.io.File to compute the file path
                File file = new File(fileName);
                String directory = file.getParent();
                boolean absolute = FileUtil.isAbsolute(file);
                if (directory != null) {
                    if (!operations.buildDirectory(directory, absolute)) {
                        if (log.isDebugEnabled()) {
                            log.debug("Cannot build directory [" + directory + "] (could be because of denied permissions)");
                        }
                    }
                }
            }

            // upload
            if (log.isTraceEnabled()) {
                log.trace("About to write [" + fileName + "] to [" + getEndpoint() + "] from exchange [" + exchange + "]");
            }

            boolean success = operations.storeFile(fileName, exchange);
            if (!success) {
                throw new GenericFileOperationFailedException("Error writing file [" + fileName + "]");
            }
            if (log.isDebugEnabled()) {
                log.debug("Wrote [" + fileName + "] to [" + getEndpoint() + "]");
            }

        } finally {
            ObjectHelper.close(payload, "Closing payload", log);
        }

    }

    protected String createFileName(Exchange exchange) {
        String answer;

        String name = exchange.getIn().getHeader(Exchange.FILE_NAME, String.class);

        // expression support
        Expression expression = endpoint.getFileName();
        if (name != null) {
            // the header name can be an expression too, that should override
            // whatever configured on the endpoint
            if (name.indexOf("${") > -1) {
                if (log.isDebugEnabled()) {
                    log.debug(Exchange.FILE_NAME + " contains a FileLanguage expression: " + name);
                }
                Language language = getEndpoint().getCamelContext().resolveLanguage("file");
                expression = language.createExpression(name);
            }
        }
        if (expression != null) {
            if (log.isDebugEnabled()) {
                log.debug("Filename evaluated as expression: " + expression);
            }
            name = expression.evaluate(exchange, String.class);
        }

        // flatten name
        if (name != null && endpoint.isFlatten()) {
            int pos = name.lastIndexOf(getFileSeparator());
            if (pos == -1) {
                pos = name.lastIndexOf('/');
            }
            if (pos != -1) {
                name = name.substring(pos + 1);
            }
        }

        // compute path by adding endpoint starting directory
        String endpointPath = endpoint.getConfiguration().getDirectory();
        // Its a directory so we should use it as a base path for the filename
        // If the path isn't empty, we need to add a trailing / if it isn't already there
        String baseDir = "";
        if (endpointPath.length() > 0) {
            baseDir = endpointPath + (endpointPath.endsWith(getFileSeparator()) ? "" : getFileSeparator());
        }
        if (name != null) {
            answer = baseDir + name;
        } else {
            // use a generated filename if no name provided
            answer = baseDir + endpoint.getGeneratedFileName(exchange.getIn());
        }

        // must normalize path to cater for Windows and other OS
        answer = normalizePath(answer);

        return answer;
    }

    protected String createTempFileName(Exchange exchange, String fileName) {
        // must normalize path to cater for Windows and other OS
        fileName = normalizePath(fileName);

        String tempName;
        if (exchange.getIn().getHeader(Exchange.FILE_NAME) == null) {
            // its a generated filename then add it to header so we can evaluate the expression
            exchange.getIn().setHeader(Exchange.FILE_NAME, FileUtil.stripPath(fileName));
            tempName = endpoint.getTempFileName().evaluate(exchange, String.class);
            // and remove it again after evaluation
            exchange.getIn().removeHeader(Exchange.FILE_NAME);
        } else {
            tempName = endpoint.getTempFileName().evaluate(exchange, String.class);
        }

        int path = fileName.lastIndexOf(getFileSeparator());
        if (path == -1) {
            // no path
            return tempName;
        } else {
            StringBuilder sb = new StringBuilder(fileName.substring(0, path + 1));
            sb.append(tempName);
            return sb.toString();
        }
    }

}