change code structure

src/lib/utils/fileIo.js

@@ -0,0 +1,71 @@
+export default {
+  exportToFile (str, fileName, type = 'octet/stream') {
+    // Create downloader
+    const downloader = document.createElement('a')
+    const blob = new Blob([str], { type })
+    const url = URL.createObjectURL(blob)
+    downloader.href = url
+    downloader.download = fileName
+
+    // Trigger click
+    downloader.click()
+
+    // Clean up
+    URL.revokeObjectURL(url)
+  },
+
+  /**
+   * Note: if user press Cancel in file choosing dialog
+   * it will be an unsettled promise. But it's grabbed by
+   * the garbage collector (tested with FinalizationRegistry).
+   */
+  getFileFromUser (type) {
+    return new Promise(resolve => {
+      const uploader = document.createElement('input')
+
+      uploader.type = 'file'
+      uploader.accept = type
+
+      uploader.addEventListener('change', () => {
+        const file = uploader.files[0]
+        resolve(file)
+      })
+
+      uploader.click()
+    })
+  },
+
+  importFile () {
+    const reader = new FileReader()
+
+    return this.getFileFromUser('.json')
+      .then(file => {
+        return new Promise((resolve, reject) => {
+          reader.onload = e => {
+            resolve(e.target.result)
+          }
+          reader.readAsText(file)
+        })
+      })
+  },
+
+  readFile (path) {
+    return fetch(path)
+  },
+
+  readAsArrayBuffer (file) {
+    const fileReader = new FileReader()
+
+    return new Promise((resolve, reject) => {
+      fileReader.onerror = () => {
+        fileReader.abort()
+        reject(new Error('Problem parsing input file.'))
+      }
+
+      fileReader.onload = () => {
+        resolve(fileReader.result)
+      }
+      fileReader.readAsArrayBuffer(file)
+    })
+  }
+}