Allow LibreOffice to be used when exporting a pad

This commit adds support for LibreOffice when exporting a pad to doc, pdf, ..

This commit also cleans up some export logic when exporting to txt

src/node/utils/LibreOffice.js

@@ -0,0 +1,93 @@
+/**
+ * Controls the communication with LibreOffice
+ */
+
+/*
+ * 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.
+ */
+
+var async = require("async");
+var fs = require("fs");
+var os = require("os");
+var path = require("path");
+var settings = require("./Settings");
+var spawn = require("child_process").spawn;
+
+// Conversion tasks will be queued up, so we don't overload the system
+var queue = async.queue(doConvertTask, 1);
+
+/**
+ * Convert a file from one type to another
+ *
+ * @param  {String}     srcFile     The path on disk to convert
+ * @param  {String}     destFile    The path on disk where the converted file should be stored
+ * @param  {String}     type        The type to convert into
+ * @param  {Function}   callback    Standard callback function
+ */
+exports.convertFile = function(srcFile, destFile, type, callback) {
+  queue.push({"srcFile": srcFile, "destFile": destFile, "type": type, "callback": callback});
+};
+
+function doConvertTask(task, callback) {
+  var tmpDir = os.tmpdir();
+
+  async.series([
+    // Generate a PDF file with LibreOffice
+    function(callback) {
+      var soffice = spawn(settings.soffice, [
+        '--headless',
+        '--invisible',
+        '--nologo',
+        '--nolockcheck',
+        '--convert-to', task.type,
+        task.srcFile,
+        '--outdir', tmpDir
+      ]);
+
+      var stdoutBuffer = '';
+
+      // Delegate the processing of stdout to another function
+      soffice.stdout.on('data', function(data) {
+        stdoutBuffer += data.toString();
+      });
+
+      // Append error messages to the buffer
+      soffice.stderr.on('data', function(data) {
+        stdoutBuffer += data.toString();
+      });
+
+      // Throw an exception if libreoffice failed
+      soffice.on('exit', function(code) {
+        if (code != 0) {
+          return callback("LibreOffice died with exit code " + code + " and message: " + stdoutBuffer);
+        }
+
+        callback();
+      })
+    },
+
+    // Move the PDF file to the correct place
+    function(callback) {
+      var filename = path.basename(task.srcFile);
+      var pdfFilename = filename.substr(0, filename.lastIndexOf('.')) + '.' + task.type;
+      var pdfPath = path.join(tmpDir, pdfFilename);
+      fs.rename(pdfPath, task.destFile, callback);
+    }
+  ], function(err) {
+    // Invoke the callback for the local queue
+    callback();
+
+    // Invoke the callback for the task
+    task.callback(err);
+  });
+}