feat: add filepicker package

packages/filepicker/example/src/classic_file_api.ts

@@ -0,0 +1,56 @@
+import { SNApplication, ContentType, FileItem, ClientDisplayableError } from '../../../snjs'
+import { ClassicFileReader, ClassicFileSaver } from '../../../filepicker'
+
+export class ClassicFileApi {
+  constructor(private application: SNApplication) {
+    this.configureFilePicker()
+  }
+
+  configureFilePicker(): void {
+    const input = document.getElementById('filePicker') as HTMLInputElement
+    input.onclick = () => {
+      void this.openFilePicker()
+    }
+    console.log('Classic file picker ready.')
+  }
+
+  async openFilePicker(): Promise<void> {
+    const files = await ClassicFileReader.selectFiles()
+    for (const file of files) {
+      const operation = await this.application.files.beginNewFileUpload()
+      if (operation instanceof ClientDisplayableError) {
+        continue
+      }
+      const fileResult = await ClassicFileReader.readFile(file, 2_000_000, async (chunk, index, isLast) => {
+        await this.application.files.pushBytesForUpload(operation, chunk, index, isLast)
+      })
+      const snFile = await this.application.files.finishUpload(operation, fileResult)
+
+      if (snFile instanceof ClientDisplayableError) {
+        return
+      }
+
+      const bytes = await this.downloadFileBytes(snFile.remoteIdentifier)
+
+      new ClassicFileSaver().saveFile(`${snFile.name}.${snFile.ext}`, bytes)
+    }
+  }
+
+  downloadFileBytes = async (remoteIdentifier: string): Promise<Uint8Array> => {
+    console.log('Downloading file', remoteIdentifier)
+    const file = this.application['itemManager']
+      .getItems(ContentType.File)
+      .find((file: FileItem) => file.remoteIdentifier === remoteIdentifier)
+
+    let receivedBytes = new Uint8Array()
+
+    await this.application.files.downloadFile(file, async (decryptedBytes: Uint8Array) => {
+      console.log(`Downloaded ${decryptedBytes.length} bytes`)
+      receivedBytes = new Uint8Array([...receivedBytes, ...decryptedBytes])
+    })
+
+    console.log('Successfully downloaded and decrypted file!')
+
+    return receivedBytes
+  }
+}