feat: add filepicker package

packages/filepicker/src/Streaming/StreamingSaver.ts

@@ -0,0 +1,49 @@
+/**
+ * The File System Access API File Picker
+ * https://developer.mozilla.org/en-US/docs/Web/API/File_System_Access_API
+ */
+export class StreamingFileSaver {
+  public loggingEnabled = false
+  private writableStream!: FileSystemWritableFileStream
+
+  constructor(private name: string) {}
+
+  private log(...args: any[]): void {
+    if (!this.loggingEnabled) {
+      return
+    }
+    // eslint-disable-next-line no-console
+    console.log(args)
+  }
+
+  static available(): boolean {
+    return window.showSaveFilePicker != undefined
+  }
+
+  /** This function must be called in response to a user interaction, otherwise, it will be rejected by the browser. */
+  async selectFileToSaveTo(): Promise<void> {
+    this.log('Showing save file picker')
+
+    const downloadHandle = await window.showSaveFilePicker({
+      suggestedName: this.name,
+    })
+
+    this.writableStream = await downloadHandle.createWritable()
+  }
+
+  async pushBytes(bytes: Uint8Array): Promise<void> {
+    if (!this.writableStream) {
+      throw Error('Must call selectFileToSaveTo first')
+    }
+    this.log('Writing chunk to disk of size', bytes.length)
+    await this.writableStream.write(bytes)
+  }
+
+  async finish(): Promise<void> {
+    if (!this.writableStream) {
+      throw Error('Must call selectFileToSaveTo first')
+    }
+    this.log('Closing write stream')
+    await this.writableStream.close()
+  }
+}