#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p "python3.withPackages (ps: [  ])" -p iw -p wirelesstools
# vim: set filetype=python :

# common operations:
# enable-clean
# arp --dest-ip A.B.C.D
# tcp --source-port N

import argparse
import logging
import subprocess

logger = logging.getLogger(__name__)

def octet_to_hex(o: int) -> str:
    ''' format an octet as a two-character hex string (lowercase) '''
    return '%02X' % o

class Encodable:
    @staticmethod
    def get_octets(e: 'Encodable|None', len_: int) -> int|None:
        if e is None: return [None]*len_

        octets = e.octets()
        assert len(octets) == len_, octets
        return octets

    @staticmethod
    def get_octet(e: 'Encodable|None', idx: int) -> int|None:
        if e is None: return None
        return e.octets()[idx]

    def octects(self) -> list[int|None]:
        raise NotImplementedError()

    def __str__(self) -> str:
        return ':'.join(octet_to_hex(b) if b is not None else '-' for b in self.octets())

class Port(Encodable):
    def __init__(self, port: int|str):
        self.port = int(port) if isinstance(port, str) else port
    def octets(self) -> list[int]:
        return [self.port // 256, self.port % 256]

class IpAddr(Encodable):
    def __init__(self, addr: str):
        pieces = addr.split('.')
        self._octets = [int(p) if p else 0 for p in pieces]

    def octets(self) -> list[int]:
        return self._octets

class EtherType:
    # ethertype: <https://en.wikipedia.org/wiki/EtherType#Values>
    IPv4 = [ 0x08, 0x00 ]  # 0x0800
    ARP  = [ 0x08, 0x06 ]   # 0x0806

class EthernetFrame(Encodable):
    def __init__(self, ether_type: EtherType, payload: Encodable):
        self.ether_type = ether_type
        self.payload = payload

    def octets(self) -> list[int|None]:
        return [
            # ethernet frame: <https://en.wikipedia.org/wiki/Ethernet_frame#Structure>
            ## dest MAC address (this should be the device's MAC, but i think that's implied?)
            None, None, None, None, None, None,
            ## src MAC address
            None, None, None, None, None, None,
            ## ethertype: <https://en.wikipedia.org/wiki/EtherType#Values>
            self.ether_type[0], self.ether_type[1]
        ] + self.payload.octets()

class ArpFrame(Encodable):
    def __init__(self, dest_ip: IpAddr|None):
        self.dest_ip = dest_ip

    def octets(self) -> list[int|None]:
        return [
            # ARP frame: <https://en.wikipedia.org/wiki/Address_Resolution_Protocol#Packet_structure>
            ## hardware type
            None, None,
            ## protocol type. same coding as EtherType
            0x08, 0x00,  # 0x0800 = IPv4
            ## hardware address length (i.e. MAC)
            0x06,
            ## protocol address length (i.e. IP address)
            0x04,
            ## operation
            0x00, 0x01,  # 0x0001 = request
            ## sender hardware address
            None, None, None, None, None, None,
            ## sender protocol address
            None, None, None, None,
            ## target hardware address
            ## this is left as "Don't Care" because the packets we want to match
            ## are those mapping protocol addr -> hw addr.
            ## sometimes clients do include this field if they've seen the address before though
            None, None, None, None, None, None,
            ## target protocol address
        ] + Encodable.get_octets(self.dest_ip, 4)

class TcpFrame(Encodable):
    def __init__(self, source_port: Port|None=None, dest_port: Port|None=None):
        self.source_port = source_port
        self.dest_port = dest_port

    def octets(self) -> list[int|None]:
        return [
            # IP frame: <https://en.wikipedia.org/wiki/Internet_Protocol_version_4#Header>
            ## Version, Internet Header Length. 0x45 = 69 decimal
            None,  # should be 69 (0x45), but fails to wake if i include this
            ## Differentiated Services Code Point (DSCP), Explicit Congestion Notification (ECN)
            None,
            ## total length
            None, None,
            ## identification
            None, None,
            ## flags, fragment offset
            None, None,
            ## Time-to-live
            None,
            ## protocol: <https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers>
            0x06,  # 6 = TCP
            ## header checksum
            None, None,
            ## source IP addr
            None, None, None, None,
            ## dest IP addr
            None, None, None, None,

            # TCP frame: <https://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure>
            Encodable.get_octet(self.source_port, 0), Encodable.get_octet(self.source_port, 1),
            Encodable.get_octet(self.dest_port, 0), Encodable.get_octet(self.dest_port, 1),
            ## rest is Don't Care
        ]


def build_arp(dest_ip: str|None = None) -> EthernetFrame:
    dest_ip = IpAddr(dest_ip) if dest_ip is not None else None
    return EthernetFrame(EtherType.ARP, ArpFrame(dest_ip))

def build_tcp(source_port: int|None = None, dest_port: int|None = None) -> EthernetFrame:
    source_port = Port(source_port) if source_port is not None else None
    dest_port = Port(dest_port) if dest_port is not None else None
    return EthernetFrame(EtherType.IPv4, TcpFrame(source_port=source_port, dest_port=dest_port))

def exec_with(executor, args: list[str]):
    logger.debug("invoking: {}".format(' '.join(args)))
    executor(args)

def exec_real(args: list[str]):
    exec_with(subprocess.check_output, args)

def exec_dry(args: list[str]):
    exec_with(lambda _: None, args)

def main():
    logging.basicConfig()
    logging.getLogger().setLevel(logging.DEBUG)

    parser = argparse.ArgumentParser(description="configure the RTL8723cs WiFi chip to wake the CPU on specific incoming packets")
    parser.add_argument('--dry-run', action='store_true')
    subparsers = parser.add_subparsers(help="type of match")

    enable_clean_parser = subparsers.add_parser('enable-clean', help="enable WOWLAN and wipe existing patterns")
    enable_clean_parser.set_defaults(type_='enable_clean')

    arp_parser = subparsers.add_parser('arp', help="wake on ARP request")
    arp_parser.set_defaults(type_='arp')
    arp_parser.add_argument('--dest-ip')

    tcp_parser = subparsers.add_parser('tcp', help="wake on TCP packet")
    tcp_parser.set_defaults(type_='tcp')
    tcp_parser.add_argument('--source-port', type=int)
    tcp_parser.add_argument('--dest-port', type=int)

    args = parser.parse_args()

    if args.dry_run:
        exec_ = exec_dry
    else:
        exec_ = exec_real

    if args.type_ == 'enable_clean':
        exec_(['iw', 'phy0', 'wowlan', 'enable', 'any'])
        exec_(['iwpriv', 'wlan0', 'wow_set_pattern', 'clean'])

    frame = None
    if args.type_ == 'arp':
        frame = build_arp(dest_ip=args.dest_ip)
    if args.type_ == 'tcp':
        frame = build_tcp(source_port=args.source_port, dest_port=args.dest_port)

    if frame is not None:
        pattern = str(frame)
        exec_(['iwpriv', 'wlan0', 'wow_set_pattern', f'pattern={pattern}'])

if __name__ == '__main__':
    main()