import { InjectionToken } from '@angular/core';

/**
 * A shared seam for handing a generated `Blob` to the browser, WITHOUT the calling
 * command inlining `URL.createObjectURL`/`window.open`/`document.createElement('a')`
 * as its own last statement (TE-006) — those calls are unassertable in jsdom because
 * they are the end of the command, not a value the spec can intercept. A recording
 * fake satisfies this shape in specs; `realBlobPresenter` is the production default.
 */
export interface BlobPresenter {
  /** Open a blob in a new tab (e.g. a rendered letter preview). Never revokes the
      object URL — the tab outlives this call, and the POC treats the leak as cheap
      (see `BriefStore.previewLetter`'s original comment). */
  open(blob: Blob): void;
  /** Trigger a browser download of a blob under the given file name, then revoke the
      object URL once the click has been dispatched. */
  download(blob: Blob, filename: string): void;
}

const realBlobPresenter: BlobPresenter = {
  open(blob: Blob) {
    window.open(URL.createObjectURL(blob), '_blank');
  },
  download(blob: Blob, filename: string) {
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = filename;
    a.click();
    URL.revokeObjectURL(url);
  },
};

export const BLOB_PRESENTER = new InjectionToken<BlobPresenter>('BLOB_PRESENTER', {
  providedIn: 'root',
  factory: () => realBlobPresenter,
});