/**
 * 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.
 */

const async = require('async');
const fs = require('fs');
const log4js = require('log4js');
const os = require('os');
const path = require('path');
const settings = require('./Settings');
const spawn = require('child_process').spawn;

// Conversion tasks will be queued up, so we don't overload the system
const queue = async.queue(doConvertTask, 1);

const libreOfficeLogger = log4js.getLogger('LibreOffice');

/**
 * 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) {
  // Used for the moving of the file, not the conversion
  const fileExtension = type;

  if (type === 'html') {
    // "html:XHTML Writer File:UTF8" does a better job than normal html exports
    if (path.extname(srcFile).toLowerCase() === '.doc') {
      type = 'html';
    }
    // PDF files need to be converted with LO Draw ref https://github.com/ether/etherpad-lite/issues/4151
    if (path.extname(srcFile).toLowerCase() === '.pdf') {
      type = 'html:XHTML Draw File';
    }
  }

  // soffice can't convert from html to doc directly (verified with LO 5 and 6)
  // we need to convert to odt first, then to doc
  // to avoid `Error: no export filter for /tmp/xxxx.doc` error
  if (type === 'doc') {
    queue.push({
      srcFile,
      destFile: destFile.replace(/\.doc$/, '.odt'),
      type: 'odt',
      callback() {
        queue.push({srcFile: srcFile.replace(/\.html$/, '.odt'), destFile, type, callback, fileExtension});
      },
    });
  } else {
    queue.push({srcFile, destFile, type, callback, fileExtension});
  }
};

function doConvertTask(task, callback) {
  const tmpDir = os.tmpdir();

  async.series([
    /*
     * use LibreOffice to convert task.srcFile to another format, given in
     * task.type
     */
    function (callback) {
      libreOfficeLogger.debug(`Converting ${task.srcFile} to format ${task.type}. The result will be put in ${tmpDir}`);
      const soffice = spawn(settings.soffice, [
        '--headless',
        '--invisible',
        '--nologo',
        '--nolockcheck',
        '--writer',
        '--convert-to',
        task.type,
        task.srcFile,
        '--outdir',
        tmpDir,
      ]);
      // Soffice/libreoffice is buggy and often hangs.
      // To remedy this we kill the spawned process after a while.
      const hangTimeout = setTimeout(() => {
        soffice.stdin.pause(); // required to kill hanging threads
        soffice.kill();
      }, 120000);

      let stdoutBuffer = '';

      // Delegate the processing of stdout to another function
      soffice.stdout.on('data', (data) => {
        stdoutBuffer += data.toString();
      });

      // Append error messages to the buffer
      soffice.stderr.on('data', (data) => {
        stdoutBuffer += data.toString();
      });

      soffice.on('exit', (code) => {
        clearTimeout(hangTimeout);
        if (code != 0) {
          // Throw an exception if libreoffice failed
          return callback(`LibreOffice died with exit code ${code} and message: ${stdoutBuffer}`);
        }

        // if LibreOffice exited succesfully, go on with processing
        callback();
      });
    },

    // Move the converted file to the correct place
    function (callback) {
      const filename = path.basename(task.srcFile);
      const sourceFilename = `${filename.substr(0, filename.lastIndexOf('.'))}.${task.fileExtension}`;
      const sourcePath = path.join(tmpDir, sourceFilename);
      libreOfficeLogger.debug(`Renaming ${sourcePath} to ${task.destFile}`);
      fs.rename(sourcePath, task.destFile, callback);
    },
  ], (err) => {
    // Invoke the callback for the local queue
    callback();

    // Invoke the callback for the task
    task.callback(err);
  });
}