/**
 * scanner.ts — camera-based Aztec scanning for Codex restoration.
 *
 * Wraps `@zxing/library`'s `BrowserAztecCodeReader` with a tiny lifecycle:
 * one `startScanner` returns a `{ stop }` handle that releases the camera
 * via `reset()`. The decoder fires on every frame; `NotFoundException` is
 * the library's "no code in this frame" signal and must be swallowed
 * silently — otherwise the console fills up at ~30 errors/second.
 *
 * Deduplication and envelope parsing are NOT this module's job. Callers
 * feed every decoded string through `parseRawScan` + `ChunkBuffer` in
 * `./restore.ts`.
 *
 * Browser-only. Never imported by tests directly — vitest runs in `node`
 * environment per `vitest.config.ts` and `navigator.mediaDevices` is
 * undefined there.
 */

import { BrowserAztecCodeReader, NotFoundException } from "@zxing/library";

export interface ScannerOptions {
  videoEl: HTMLVideoElement;
  /** Called for every successful Aztec decode. The caller dedups via ChunkBuffer. */
  onScan: (text: string) => void;
  /** Reported on hard errors only — NotFoundException is filtered out. */
  onError?: (err: Error) => void;
}

export interface ScannerHandle {
  stop: () => void;
}

export async function startScanner(
  opts: ScannerOptions,
): Promise<ScannerHandle> {
  const reader = new BrowserAztecCodeReader();

  // Passing `null` for deviceId lets zxing pick the default camera (typically
  // the back camera on mobile, the only camera on a laptop). The library
  // attaches the MediaStream to the provided <video> element internally.
  await reader.decodeFromVideoDevice(null, opts.videoEl, (result, err) => {
    if (result) {
      opts.onScan(result.getText());
      return;
    }
    if (err && !(err instanceof NotFoundException)) {
      opts.onError?.(err);
    }
  });

  return {
    stop: () => {
      reader.reset();
    },
  };
}