/**
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* Module dependencies.
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*/
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var os = require('os');
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var lodashGet = require('lodash.get');
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/**
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* Main function that converts json to csv
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*
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* @param {Object} params Function parameters containing data, fields,
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* delimiter (default is ','), hasCSVColumnTitle (default is true)
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* and default value (default is '')
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* @param {Function} callback(err, csv) - Callback function
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* if error, returning error in call back.
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* if csv is created successfully, returning csv output to callback.
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*/
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module.exports = function (params, callback) {
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if (!callback || typeof callback !== 'function') {
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throw new Error('Callback is required');
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}
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checkParams(params, function (err) {
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if (err) {
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return callback(err);
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}
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var titles = createColumnTitles(params);
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var csv = createColumnContent(params, titles);
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callback(null, csv);
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});
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};
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/**
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* Check passing params
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*
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* @param {Object} params Function parameters containing data, fields,
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* delimiter, default value, mark quotes and hasCSVColumnTitle
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* @param {Function} callback Callback function returning error when invalid field is found
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*/
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function checkParams(params, callback) {
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params.data = params.data || [];
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// if data is an Object, not in array [{}], then just create 1 item array.
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// So from now all data in array of object format.
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if (!Array.isArray(params.data)) {
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params.data = [params.data];
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}
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// Set params.fields default to first data element's keys
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if (!params.fields && (params.data.length === 0 || typeof params.data[0] !== 'object')) {
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return callback(new Error('params should include "fields" and/or non-empty "data" array of objects'));
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}
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params.fields = params.fields || Object.keys(params.data[0]);
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//#check fieldNames
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if (params.fieldNames && params.fieldNames.length !== params.fields.length) {
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return callback(new Error('fieldNames and fields should be of the same length, if fieldNames is provided.'));
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}
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// Get fieldNames from fields
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params.fieldNames = params.fields.map(function (field, i) {
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if (params.fieldNames && typeof field === 'string') {
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return params.fieldNames[i];
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}
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return (typeof field === 'string') ? field : (field.label || field.value);
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});
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//#check delimiter
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params.del = params.del || ',';
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//#check end of line character
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params.eol = params.eol || '';
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//#check quotation mark
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params.quotes = typeof params.quotes === 'string' ? params.quotes : '"';
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//#check default value
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params.defaultValue = params.defaultValue;
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//#check hasCSVColumnTitle, if it is not explicitly set to false then true.
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params.hasCSVColumnTitle = params.hasCSVColumnTitle !== false;
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callback(null);
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}
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/**
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* Create the title row with all the provided fields as column headings
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*
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* @param {Object} params Function parameters containing data, fields and delimiter
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* @returns {String} titles as a string
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*/
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function createColumnTitles(params) {
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var str = '';
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//if CSV has column title, then create it
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if (params.hasCSVColumnTitle) {
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params.fieldNames.forEach(function (element) {
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if (str !== '') {
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str += params.del;
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}
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str += JSON.stringify(element).replace(/\"/g, params.quotes);
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});
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}
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return str;
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}
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/**
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* Replace the quotation marks of the field element if needed (can be a not string-like item)
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*
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* @param {string} stringifiedElement The field element after JSON.stringify()
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* @param {string} quotes The params.quotes value. At this point we know that is not equal to double (")
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*/
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function replaceQuotationMarks(stringifiedElement, quotes) {
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var lastCharIndex = stringifiedElement.length - 1;
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//check if it's an string-like element
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if (stringifiedElement[0] === '"' && stringifiedElement[lastCharIndex] === '"') {
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//split the stringified field element because Strings are immutable
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var splitElement = stringifiedElement.split('');
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//replace the quotation marks
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splitElement[0] = quotes;
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splitElement[lastCharIndex] = quotes;
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//join again
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stringifiedElement = splitElement.join('');
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}
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return stringifiedElement;
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}
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/**
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* Create the content column by column and row by row below the title
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*
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* @param {Object} params Function parameters containing data, fields and delimiter
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* @param {String} str Title row as a string
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* @returns {String} csv string
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*/
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function createColumnContent(params, str) {
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params.data.forEach(function (dataElement) {
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//if null or empty object do nothing
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if (dataElement && Object.getOwnPropertyNames(dataElement).length > 0) {
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var line = '';
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var eol = params.newLine || os.EOL || '\n';
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params.fields.forEach(function (fieldElement) {
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var val;
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if (fieldElement && (typeof fieldElement === 'string' || typeof fieldElement.value === 'string')) {
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var path = (typeof fieldElement === 'string') ? fieldElement : fieldElement.value;
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var defaultValue = fieldElement.default || params.defaultValue;
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val = lodashGet(dataElement, path, defaultValue);
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if (val === null && defaultValue !== undefined){
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val = defaultValue;
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}
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} else if (fieldElement && typeof fieldElement.value === 'function') {
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val = fieldElement.value(dataElement) || fieldElement.default;
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}
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if (val !== undefined) {
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var stringifiedElement = JSON.stringify(val);
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if (typeof val === 'object') stringifiedElement = JSON.stringify(stringifiedElement);
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if (params.quotes !== '"') {
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stringifiedElement = replaceQuotationMarks(stringifiedElement, params.quotes);
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}
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//JSON.stringify('\\') results in a string with two backslash
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//characters in it. I.e. '\\\\'.
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stringifiedElement = stringifiedElement.replace(/\\\\/g, '\\');
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line += stringifiedElement;
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}
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line += params.del;
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});
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//remove last delimeter
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line = line.substring(0, line.length - 1);
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//Replace single quotes with double quotes. Single quotes are preceeded by
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//a backslash. Be careful not to remove backslash content from the string.
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line = line.split('\\\\').map(function (portion) {
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return portion.replace(/\\"/g, Array(3).join(params.quotes));
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}).join('\\\\');
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//Remove the final excess backslashes from the stringified value.
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line = line.replace(/\\\\/g, '\\');
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//If header exists, add it, otherwise, print only content
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if (str !== '') {
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str += eol + line + params.eol;
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} else {
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str = line + params.eol;
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}
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}
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});
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return str;
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}
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