import {
  BarcodeFormat,
  BrowserMultiFormatReader,
} from '@zxing/browser';
import { DecodeHintType } from '@zxing/library';

const KITCHEN_ITEM_PREFIX = 'kitchen:item::';
const UUID_B64_PATTERN = /^[A-Za-z0-9_-]{22}$/;
const UUID_B64_WITH_PADDING_PATTERN = /^[A-Za-z0-9_-]{22}={0,2}$/;

const SCANNER_FORMATS = [
  BarcodeFormat.DATA_MATRIX,
  BarcodeFormat.EAN_13,
  BarcodeFormat.EAN_8,
  BarcodeFormat.UPC_A,
  BarcodeFormat.UPC_E,
  BarcodeFormat.CODE_128,
  BarcodeFormat.CODE_39,
  BarcodeFormat.QR_CODE,
];

export function normalizeIdentifierCode(value) {
  return String(value || '').replace(/\s+/g, '').trim();
}

export function parseKitchenScanPayload(rawValue) {
  const value = normalizeIdentifierCode(rawValue);
  if (!value) {
    return { type: 'empty', raw: '' };
  }

  if (value.toLowerCase().startsWith(KITCHEN_ITEM_PREFIX)) {
    const uuidB64 = value.slice(KITCHEN_ITEM_PREFIX.length).trim();
    return uuidB64
      ? { type: 'item', uuidB64, raw: value }
      : { type: 'unknown', raw: value };
  }

  // Backward compatibility: some labels/scanners provide the raw base64 UUID only.
  if (UUID_B64_PATTERN.test(value) || UUID_B64_WITH_PADDING_PATTERN.test(value)) {
    return {
      type: 'item',
      uuidB64: value.replace(/=+$/g, ''),
      raw: value,
    };
  }

  return { type: 'identifier', identifierCode: value, raw: value };
}

export function canUseCameraScanner() {
  return Boolean(
    typeof navigator !== 'undefined'
    && navigator.mediaDevices
    && typeof navigator.mediaDevices.getUserMedia === 'function',
  );
}

export function createScannerReader() {
  const hints = new Map();
  hints.set(DecodeHintType.POSSIBLE_FORMATS, SCANNER_FORMATS);
  return new BrowserMultiFormatReader(hints);
}

export function normalizeScannerError(error) {
  const message = String(error?.message || '');
  const normalized = message.toLowerCase();

  if (error?.name === 'NotAllowedError' || normalized.includes('permission')) {
    return 'Camera access was denied. Allow access to scan, or enter the code manually.';
  }

  if (error?.name === 'NotFoundError' || normalized.includes('requested device not found')) {
    return 'No camera was found on this device. Enter the code manually.';
  }

  if (error?.name === 'NotReadableError' || normalized.includes('could not start video source')) {
    return 'Camera is busy in another app. Close it there and try scanning again.';
  }

  return 'Could not start scanning. Enter the code manually.';
}

export async function startCameraScanner({
  reader,
  videoElement,
  onDetected,
  onDecodeError,
}) {
  const activeReader = reader || createScannerReader();
  const shouldLogDecodeErrors = import.meta.env.DEV;
  let lastDecodeErrorName = '';
  let lastDecodeErrorAt = 0;

  const controls = await activeReader.decodeFromConstraints(
    {
      audio: false,
      video: {
        facingMode: { ideal: 'environment' },
      },
    },
    videoElement,
    (result, error) => {
      if (result) {
        onDetected?.(result.getText?.() || '');
        return;
      }

      if (!error) {
        return;
      }

      onDecodeError?.(error);
      if (!shouldLogDecodeErrors) {
        return;
      }

      const errorName = String(error?.name || 'UnknownError');
      const now = Date.now();
      if (errorName !== lastDecodeErrorName || now - lastDecodeErrorAt > 2000) {
        console.debug('[scanner] Ignoring frame decode error while scanning:', errorName, error?.message || '');
        lastDecodeErrorName = errorName;
        lastDecodeErrorAt = now;
      }
    },
  );

  return { reader: activeReader, controls };
}

export function stopCameraScanner({ reader, controls, videoElement }) {
  try {
    controls?.stop?.();
  } catch {
    // Ignore cleanup errors when scanner is already stopped.
  }

  try {
    reader?.reset?.();
  } catch {
    // Ignore cleanup errors from stale reader state.
  }

  const stream = videoElement?.srcObject;
  if (stream && typeof stream.getTracks === 'function') {
    stream.getTracks().forEach((track) => track.stop());
  }
  if (videoElement) {
    videoElement.srcObject = null;
  }
}