Synology FileStation Upload function (TypeScript, Angular, Capacitor, Filesystem, Ionic, FormData, HttpClient)

synology.filestation.upload.ts

import { HttpClient } from '@angular/common/http';

type Response<T> = {
  data: T;
  success: boolean;
  error: {code: number, errors: []};
}
type API = {
  name: string,
  version: number,
  path: string,
  supported: boolean
};

export enum ExistingFileAction {
  Overwrite,
  Skip,
  ErrorResponse
}


  
private fsUploadAPI: API = { name: 'SYNO.FileStation.Upload', version: 2, path: undefined, supported: false };

public async upload(fileContent: string, fileName: string, destinationFolder: string, createParents: boolean, existingFileAction: ExistingFileAction) {
  if (this.sessionId === undefined) {
    console.error('Can\'t upload files. Not logged in.');
    return;
  }

  let formData = new FormData();
  formData.append('api', this.fsUploadAPI.name);
  formData.append('version', this.fsUploadAPI.version.toString());
  formData.append('method', 'upload');

  formData.append('path', destinationFolder); // NOTE: destinationFolder has leading slash and no trailing slash.
  formData.append('create_parents', createParents.toString());

  let overwrite;
  switch (existingFileAction)
  {
    case ExistingFileAction.Overwrite:
      overwrite = true;
      break;
    case ExistingFileAction.Skip:
      overwrite = false;
      break;
    case ExistingFileAction.ErrorResponse:
      // Exclude 'overwrite' argument for error response.
      break;
  }
  if (overwrite !== undefined) {
    formData.append('overwrite', overwrite);
  }

  formData.append('_sid', this.sessionId);
  formData.append('file', new Blob([fileContent]), fileName);

  let url = `https://insert.your.synology.drive.ip.here:5001/webapi/${this.fsUploadAPI.path}`;
  console.log('POST ' + url);
  return this.http.post<Response<any>>(url, formData).toPromise();
}