import base64
import subprocess
from time import sleep
from struct import pack


class HCIBroadcaster:
    def __init__(self, b64key):
        self.key = base64.b64decode(b64key)

    def _advertisement_template():
        adv = ""
        adv += "1e"  # length (30)
        adv += "ff"  # manufacturer specific data
        adv += "4c00"  # company ID (Apple)
        adv += "1219"  # offline finding type and length
        adv += "00"  # state
        for _ in range(22):  # key[6:28]
            adv += "00"
        adv += "00"  # first two bits of key[0]
        adv += "00"  # hint
        return bytearray.fromhex(adv)

    def _bytes_to_strarray(self, bytes_, with_prefix=False):
        if with_prefix:
            return [hex(b) for b in bytes_]
        else:
            return [format(b, "x") for b in bytes_]

    def _run_hci_cmd(self, cmd, hci="hci0", wait=1):
        cmd_ = ["hcitool", "-i", hci, "cmd"]
        cmd_ += cmd
        print(cmd_)
        subprocess.run(cmd_)
        if wait > 0:
            sleep(wait)

    def start_advertising(self, interval_ms=2000):
        key = self.key
        addr = bytearray(key[:6])
        addr[0] |= 0b11000000

        adv = self._advertisement_template()
        adv[7:29] = key[6:28]
        adv[29] = key[0] >> 6

        print(f"key     ({len(key):2}) {key.hex()}")
        print(f"address ({len(addr):2}) {addr.hex()}")
        print(f"payload ({len(adv):2}) {adv.hex()}")

        # Set BLE address
        self._run_hci_cmd(
            ["0x3f", "0x001"] + self._bytes_to_strarray(addr, with_prefix=True)[::-1]
        )
        subprocess.run(["systemctl", "restart", "bluetooth"])
        sleep(1)

        # Set BLE advertisement payload
        self._run_hci_cmd(
            ["0x08", "0x0008"] + [format(len(adv), "x")] + self._bytes_to_strarray(adv)
        )

        # Set BLE advertising mode
        interval_enc = pack("<h", interval_ms)
        hci_set_adv_params = ["0x08", "0x0006"]
        hci_set_adv_params += self._bytes_to_strarray(interval_enc)
        hci_set_adv_params += self._bytes_to_strarray(interval_enc)
        hci_set_adv_params += ["03", "00", "00", "00", "00", "00", "00", "00", "00"]
        hci_set_adv_params += ["07", "00"]
        self._run_hci_cmd(hci_set_adv_params)

        # Start BLE advertising
        self._run_hci_cmd(["0x08", "0x000a"] + ["01"], wait=0)