Move export logic to separate module

lib/export-to-csv.js

@@ -0,0 +1,45 @@
+import objectPath from 'object-path'
+import { Base64 } from 'js-base64'
+
+import { getColumnNamesForCsv, cycleDaysSortedByDate } from '../db'
+
+export default function makeDataURI() {
+  if (!cycleDaysSortedByDate.length) return null
+
+  const csv = transformToCsv(cycleDaysSortedByDate)
+  const encoded = Base64.encodeURI(csv)
+  return `data:text/csv;base64,${encoded}`
+}
+
+function transformToCsv(cycleDays) {
+  const columnNames = getColumnNamesForCsv()
+  const rows = cycleDays
+    .map(day => {
+      return columnNames.map(column => {
+        const val = objectPath.get(day, column)
+        return typeof val === 'string' ? csvify(val) : val
+      })
+    })
+    .map(row => row.join(','))
+
+  rows.unshift(columnNames.join(','))
+  return rows.join('\n')
+}
+
+function csvify (val) {
+  // we wrap fields with special characters in quotes,
+  // thus have to escape actual quotes
+  val = val.replace(/"/g, '""')
+
+  val = val.toLowerCase()
+  const hasSpecialChars = (
+    val.includes('\n') ||
+    val.includes('\t') ||
+    val.includes(',') ||
+    val.includes(';') ||
+    val.includes('.') ||
+    val.includes('\'')
+  )
+
+  return hasSpecialChars ? `"${val}"` : val
+}