# This example demonstrates a peripheral implementing the Nordic UART Service (NUS).

# This example demonstrates the low-level bluetooth module. For most
# applications, we recommend using the higher-level aioble library which takes
# care of all IRQ handling and connection management. See
# https://github.com/micropython/micropython-lib/tree/master/micropython/bluetooth/aioble

import bluetooth
from hw.esp32.ble_advertising import advertising_payload

from micropython import const
from log import log

_IRQ_CENTRAL_CONNECT = const(1)
_IRQ_CENTRAL_DISCONNECT = const(2)
_IRQ_GATTS_WRITE = const(3)

_FLAG_WRITE = const(0x0008)
_FLAG_NOTIFY = const(0x0010)

_UART_UUID = bluetooth.UUID("6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
_UART_TX = (
    bluetooth.UUID("6E400003-B5A3-F393-E0A9-E50E24DCCA9E"),
    _FLAG_NOTIFY,
)
_UART_RX = (
    bluetooth.UUID("6E400002-B5A3-F393-E0A9-E50E24DCCA9E"),
    _FLAG_WRITE,
)
_UART_SERVICE = (
    _UART_UUID,
    (_UART_TX, _UART_RX),
)

# org.bluetooth.characteristic.gap.appearance.xml
_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)


class BLEUART(log):
    def __init__(self, name="AR-UART", rxbuf=128):
        super().__init__(f'BLE-{name}')
        self.name = name
        self.rxbuf = rxbuf
        self._ble = None

    def __enter__(self):
        self.open()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()

    def open(self):
        self._ble = bluetooth.BLE()
        self._ble.active(True)
        self._ble.irq(self._irq)
        ((self._tx_handle, self._rx_handle),) = self._ble.gatts_register_services((_UART_SERVICE,))
        # Increase the size of the rx buffer and enable append mode.
        self._ble.gatts_set_buffer(self._rx_handle, self.rxbuf, True)
        self._connections = set()
        self._rx_buffer = bytearray()
        # Optionally add services=[_UART_UUID], but this is likely to make the payload too large.
        self._payload = advertising_payload(name=self.name, appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)
        self._advertise()
        self.info("BLE Opened, and ready")

    def irq(self, handler):
        if callable(handler):
            self._handler = handler

    def _irq(self, event, data):
        if self._ble is None:
            return

        # Track connections so we can send notifications.
        if event == _IRQ_CENTRAL_CONNECT:
            conn_handle, _, _ = data
            self._connections.add(conn_handle)
        elif event == _IRQ_CENTRAL_DISCONNECT:
            conn_handle, _, _ = data
            if conn_handle in self._connections:
                self._connections.remove(conn_handle)
            # Start advertising again to allow a new connection.
            self._advertise()
        elif event == _IRQ_GATTS_WRITE:
            conn_handle, value_handle = data
            if conn_handle in self._connections and value_handle == self._rx_handle:
                self._rx_buffer += self._ble.gatts_read(self._rx_handle)
                if self._handler:
                    rx = self.read()
                    self.dbg(f'RX: {rx}')
                    self._handler(rx)

    def any(self):
        return len(self._rx_buffer)

    def read(self, sz=None):
        if not sz:
            sz = len(self._rx_buffer)
        result = self._rx_buffer[0:sz]
        self._rx_buffer = self._rx_buffer[sz:]
        return result

    def write(self, data):
        if self._ble is None:
            return

        self.dbg(f'TX: {data}')
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle, self._tx_handle, data)

    def close(self):
        if self._ble is None:
            return

        self.info('BLE Closed')
        for conn_handle in self._connections:
            self._ble.gap_disconnect(conn_handle)
        self._connections.clear()
        self._ble.active(False)
        self._ble = None

    def _advertise(self, interval_us=500000):
        self._ble.gap_advertise(interval_us, adv_data=self._payload)
