expo-barcode-scanner/src/ExpoBarCodeScannerModule.web.ts

import { PermissionResponse, PermissionStatus, UnavailabilityError } from 'expo-modules-core';

function getUserMedia(constraints: MediaStreamConstraints): Promise<MediaStream> {
  if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
    return navigator.mediaDevices.getUserMedia(constraints);
  }

  // Some browsers partially implement mediaDevices. We can't just assign an object
  // with getUserMedia as it would overwrite existing properties.
  // Here, we will just add the getUserMedia property if it's missing.

  // First get ahold of the legacy getUserMedia, if present
  const getUserMedia =
    // TODO: this method is deprecated, migrate to https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia
    navigator.getUserMedia ||
    navigator.webkitGetUserMedia ||
    navigator.mozGetUserMedia ||
    function () {
      const error: any = new Error('Permission unimplemented');
      error.code = 0;
      error.name = 'NotAllowedError';
      throw error;
    };

  return new Promise((resolve, reject) => {
    getUserMedia.call(navigator, constraints, resolve, reject);
  });
}

function handleGetUserMediaError({ message }: { message: string }): PermissionResponse {
  // name: NotAllowedError
  // code: 0
  if (message === 'Permission dismissed') {
    return {
      status: PermissionStatus.UNDETERMINED,
      expires: 'never',
      canAskAgain: true,
      granted: false,
    };
  } else {
    return {
      status: PermissionStatus.DENIED,
      expires: 'never',
      canAskAgain: true,
      granted: false,
    };
  }
}

async function handleRequestPermissionsAsync(): Promise<PermissionResponse> {
  try {
    await getUserMedia({
      video: true,
    });
    return {
      status: PermissionStatus.GRANTED,
      expires: 'never',
      canAskAgain: true,
      granted: true,
    };
  } catch ({ message }) {
    return handleGetUserMediaError({ message });
  }
}

async function handlePermissionsQueryAsync(): Promise<PermissionResponse> {
  if (!navigator?.permissions?.query) {
    throw new UnavailabilityError(
      'expo-barcode-scanner',
      'navigator.permissions API is not available'
    );
  }

  const { state } = await navigator.permissions.query({ name: 'camera' });
  switch (state) {
    case 'prompt':
      return {
        status: PermissionStatus.UNDETERMINED,
        expires: 'never',
        canAskAgain: true,
        granted: false,
      };
    case 'granted':
      return {
        status: PermissionStatus.GRANTED,
        expires: 'never',
        canAskAgain: true,
        granted: true,
      };
    case 'denied':
      return {
        status: PermissionStatus.DENIED,
        expires: 'never',
        canAskAgain: true,
        granted: false,
      };
  }
}

export default {
  get name(): string {
    return 'ExpoBarCodeScannerModule';
  },
  get BarCodeType() {
    return {
      code39mod43: 'code39mod43',
      code138: 'code138',
      interleaved2of5: 'interleaved2of5',
      aztec: 'aztec',
      ean13: 'ean13',
      ean8: 'ean8',
      qr: 'qr',
      pdf417: 'pdf417',
      upc_e: 'upc_e',
      datamatrix: 'datamatrix',
      code39: 'code39',
      code93: 'code93',
      itf14: 'itf14',
      codabar: 'codabar',
      code128: 'code128',
      upc_a: 'upc_a',
    };
  },
  get Type() {
    return { front: 'front', back: 'back' };
  },
  async requestPermissionsAsync(): Promise<PermissionResponse> {
    return handleRequestPermissionsAsync();
  },
  async getPermissionsAsync(): Promise<PermissionResponse> {
    return handlePermissionsQueryAsync();
  },
};