#
# blueart.py
#    BLE NUS UART routines
#
# Neil Gershenfeld 11/13/23
#
# based on:
#    https://github.com/micropython/micropython/blob/master/examples/bluetooth/ble_uart_peripheral.py
#    https://github.com/micropython/micropython/blob/master/examples/bluetooth/ble_advertising.py
#

from micropython import const
import struct
import bluetooth

_ADV_TYPE_FLAGS = const(0x01)
_ADV_TYPE_NAME = const(0x09)
_ADV_TYPE_UUID16_COMPLETE = const(0x3)
_ADV_TYPE_UUID32_COMPLETE = const(0x5)
_ADV_TYPE_UUID128_COMPLETE = const(0x7)
_ADV_TYPE_UUID16_MORE = const(0x2)
_ADV_TYPE_UUID32_MORE = const(0x4)
_ADV_TYPE_UUID128_MORE = const(0x6)
_ADV_TYPE_APPEARANCE = const(0x19)
_ADV_MAX_PAYLOAD = const(32)

def advertising_payload(limited_disc=False,br_edr=False,name=None, services=None,appearance=0):
    payload = bytearray()
    def _append(adv_type, value):
        nonlocal payload
        payload += struct.pack("BB",len(value)+1,adv_type)+value
    _append(_ADV_TYPE_FLAGS,struct.pack("B",(0x01 if limited_disc else 0x02)+(0x18 if br_edr else 0x04)),)
    if name:
        _append(_ADV_TYPE_NAME,name)
    if services:
        for uuid in services:
            b = bytes(uuid)
            if len(b) == 2:
                _append(_ADV_TYPE_UUID16_COMPLETE,b)
            elif len(b) == 4:
                _append(_ADV_TYPE_UUID32_COMPLETE,b)
            elif len(b) == 16:
                _append(_ADV_TYPE_UUID128_COMPLETE,b)
    if appearance:
        _append(_ADV_TYPE_APPEARANCE,struct.pack("<h",appearance))
    if len(payload) > _ADV_MAX_PAYLOAD:
        raise ValueError("advertising payload too large")
    return payload

def decode_field(payload,adv_type):
    i = 0
    result = []
    while (i+1 < len(payload)):
        if payload[i+1] == adv_type:
            result.append(payload[i+2:i+payload[i]+1])
        i += 1+payload[i]
    return result

def decode_name(payload):
    n = decode_field(payload,_ADV_TYPE_NAME)
    return str(n[0],"utf-8") if n else ""

def decode_services(payload):
    services = []
    for u in decode_field(payload,_ADV_TYPE_UUID16_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack("<h",u)[0]))
    for u in decode_field(payload,_ADV_TYPE_UUID32_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack("<d",u)[0]))
    for u in decode_field(payload,_ADV_TYPE_UUID128_COMPLETE):
        services.append(bluetooth.UUID(u))
    return services

_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),)
_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)

class uart:
    def __init__(self, name="BLE UART",rxbuf=100):
        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,))
        self._ble.gatts_set_buffer(self._rx_handle,rxbuf, True)
        self._connections = set()
        self._rx_buffer = bytearray()
        self._handler = None
        self._payload = advertising_payload(name=name,appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)
        self._advertise()
    def irq(self,handler):
        self._handler = handler
    def _irq(self,event,data):
        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)
            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:
                    self._handler()
    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):
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle,self._tx_handle,data)
    def close(self):
        for conn_handle in self._connections:
            self._ble.gap_disconnect(conn_handle)
        self._connections.clear()
    def _advertise(self, interval_us=500000):
        self._ble.gap_advertise(interval_us,adv_data=self._payload)