platypush/platypush/backend/nfc.py

import base64
import json
import nfc
import ndef

from platypush.backend import Backend
from platypush.message.event.nfc import NFCTagDetectedEvent, NFCTagRemovedEvent, NFCDeviceConnectedEvent, \
    NFCDeviceDisconnectedEvent


class NfcBackend(Backend):
    """
    Backend to detect NFC card events from a compatible reader.

    Triggers:

        * :class:`platypush.message.event.nfc.NFCDeviceConnectedEvent` when an NFC reader/writer is connected
        * :class:`platypush.message.event.nfc.NFCDeviceDisconnectedEvent` when an NFC reader/writer is disconnected
        * :class:`platypush.message.event.nfc.NFCTagDetectedEvent` when an NFC tag is detected
        * :class:`platypush.message.event.nfc.NFCTagRemovedEvent` when an NFC tag is removed

    Requires:

        * **nfcpy** >= 1.0 (``pip install nfcpy``)
    """

    def __init__(self, device='usb', *args, **kwargs):
        """
        :param device: Address or ID of the device to be opened. Examples:

            * `'usb:003:009'` opens device 9 on bus 3
            * `'usb:003'` opens the first available device on bus 3
            * `'usb'` opens the first available USB device (default)
        """

        super().__init__(*args, **kwargs)

        self.device_id = device
        self._clf = None

    def _get_clf(self):
        if not self._clf:
            self._clf = nfc.ContactlessFrontend()
            self._clf.open(self.device_id)
            self.bus.post(NFCDeviceConnectedEvent(reader=self._get_device_str()))
            self.logger.info('Initialized NFC reader backend on device {}'.format(self._get_device_str()))

        return self._clf

    def _get_device_str(self):
        return str(self._clf.device)

    def close(self):
        if self._clf:
            self._clf.close()
            self._clf = None
            self.bus.post(NFCDeviceDisconnectedEvent(reader=self._get_device_str()))

    @staticmethod
    def _parse_records(tag):
        records = []

        for record in tag.ndef.records:
            r = {
                'record_type': record.type,
                'record_name': record.name,
            }

            if isinstance(record, ndef.TextRecord):
                try:
                    r = {
                        **r,
                        'type': 'json',
                        'value': json.loads(record.text),
                    }
                except ValueError:
                    r = {
                        **r,
                        'type': 'text',
                        'text': record.text,
                    }
            elif isinstance(record, ndef.UriRecord):
                r = {
                    **r,
                    'type': 'uri',
                    'uri': record.uri,
                    'iri': record.iri,
                }
            elif isinstance(record, ndef.SmartposterRecord):
                r = {
                    **r,
                    'type': 'smartposter',
                    **{attr: getattr(record, attr) for attr in ['resource', 'titles', 'title', 'action', 'icon',
                                                                'icons', 'resource_size', 'resource_type']},
                }
            elif isinstance(record, ndef.DeviceInformationRecord):
                r = {
                    **r,
                    'type': 'device_info',
                    **{attr: getattr(record, attr) for attr in ['vendor_name', 'model_name', 'unique_name',
                                                                'uuid_string', 'version_string']},
                }
            elif isinstance(record, ndef.WifiSimpleConfigRecord):
                r = {
                    **r,
                    'type': 'wifi_simple_config',
                    **{attr: record[attr] for attr in record.attribute_names()}
                }
            elif isinstance(record, ndef.WifiPeerToPeerRecord):
                r = {
                    **r,
                    'type': 'wifi_peer_to_peer',
                    **{attr: record[attr] for attr in record.attribute_names()}
                }
            elif isinstance(record, ndef.BluetoothEasyPairingRecord):
                r = {
                    **r,
                    'type': 'bluetooth_easy_pairing',
                    **{attr: getattr(record, attr) for attr in ['device_address', 'device_name', 'device_class']},
                }
            elif isinstance(record, ndef.BluetoothLowEnergyRecord):
                r = {
                    **r,
                    'type': 'bluetooth_low_energy',
                    **{attr: getattr(record, attr) for attr in ['device_address', 'device_name', 'role_capabilities',
                                                                'appearance', 'flags', 'security_manager_tk_value',
                                                                'secure_connections_confirmation_value',
                                                                'secure_connections_random_value']},
                }
            elif isinstance(record, ndef.SignatureRecord):
                r = {
                    **r,
                    'type': 'signature',
                    **{attr: getattr(record, attr) for attr in ['version', 'signature_type', 'hash_type', 'signature',
                                                                'signature_uri', 'certificate_format',
                                                                'certificate_store', 'certificate_uri',
                                                                'secure_connections_random_value']},
                }
            else:
                r = {
                    **r,
                    'type': 'binary',
                    'data': base64.encodebytes(record.data).decode(),
                }

            records.append(r)

        return records

    @staticmethod
    def _parse_id(tag):
        return ''.join([('%02X' % c) for c in tag.identifier])

    def _on_connect(self):
        def callback(tag):
            if not tag:
                return False

            tag_id = self._parse_id(tag)
            records = self._parse_records(tag)
            self.bus.post(NFCTagDetectedEvent(reader=self._get_device_str(), tag_id=tag_id, records=records))
            return True

        return callback

    def _on_release(self):
        def callback(tag):
            tag_id = self._parse_id(tag)
            self.bus.post(NFCTagRemovedEvent(reader=self._get_device_str(), tag_id=tag_id))

        return callback

    def run(self):
        super().run()

        while not self.should_stop():
            try:
                clf = self._get_clf()
                clf.connect(rdwr={
                    'on-connect': self._on_connect(),
                    'on-release': self._on_release(),
                })
            finally:
                self.close()


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