import { Injectable } from '@angular/core';
import { Base64 } from '@yourcause/common';
import { I18nService } from '@yourcause/common/i18n';
import { LogService } from '@yourcause/common/logging';
import { NotifierService } from '@yourcause/common/notifier';


@Injectable({ providedIn: 'root' })
export class ImportExportService {

   constructor (
    private logger: LogService,
    private i18n: I18nService,
    private notifier: NotifierService
  ) { }

  decodeExportString<T> (exportString: string) {
    let fields: T[];
    try {
      fields = JSON.parse(Base64.decode(exportString));
    } catch (e) {
      this.logger.error(e);
      this.notifier.warning(this.i18n.translate(
        'FORMS:notificationInvalidFileType',
        {},
        'The provided file was invalid, please obtain a valid file and try again.'
      ));
    }

    return fields;
  }

  handleImportFileClick<T> () {
    return new Promise<T>((res, rej) => {
      const input = document.createElement('input');
      input.type = 'file';
      input.hidden = true;
      input.addEventListener('change', (event: any) => {
        const [file] = event.target.files;
        const fileReader = new FileReader();
        fileReader.addEventListener('loadend', async (loadEvent: any) => {
          const result = loadEvent.target.result;
          const decoded = this.decodeExportString(result);
          if (decoded) {
            res(decoded as any);
          } else {
            res(null);
          }
        });
        fileReader.readAsText(file);
      });
      input.addEventListener('cancel', () => {
        res(null);
      });
      document.body.appendChild(input);
      input.click();
    });
  }

}