db2excel_exporter.js

'use strict';

var _ = require('underscore'),
  Excel = require('exceljs'),
  Promise = require('bluebird');

exports.getColumns = function (fieldMap, fields) {
  var data = _.pick.apply(null, [fieldMap].concat(fields));
  return _.map(data, function (v, k) {
    return {
      key: k,
      header: v,
    };
  });
};

exports.buildSheetFromMongoStream = function (sheet, stream, converter) {
  return new Promise(function (resolve, reject) {
    stream.on('data', function (data) {
      sheet.addRow(converter(data)).commit();
    });

    stream.on('end', function () {
      sheet.commit();
      resolve();
    });
    stream.on('error', reject);
  });
};

exports.buildSheet = function () {
  return exports.buildSheetFromMongoStream.apply(this, arguments);
};

/**
 *
 * @param params
 * @param params.filename
 * @param params.fieldMap
 * @param params.fields
 * @param params.dateFormat
 * @param params.stream
 * @param params.converter
 */
exports.exportExcel = function (params) {
  var columns = exports.getColumns(params.fieldMap, params.fields);

  var workbook = new Excel.stream.xlsx.WorkbookWriter({
    filename: params.filename,
  });
  workbook.creator = '__SYSTEM__';
  workbook.created = new Date();
  var sheet = workbook.addWorksheet('Sheet1');
  sheet.columns = columns;

  return exports
    .buildSheet(sheet, params.stream, params.converter)
    .then(function () {
      return workbook.commit();
    })
    .then(function () {
      return params.filename;
    });
};