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

import logging
import socket
import subprocess

from enum import Enum

logger = logging.getLogger(__name__)

# map from known devices -> required flags
DEVICE_MAP = {
  "Theater TV": [],
  "Cuddlevision": [ "-usewav" ],
}

def get_ranked_ip_addrs():
    """
    return the IP addresses most likely to be LAN addresses
    based on: <https://stackoverflow.com/a/1267524>
    """
    _name, _aliases, static_addrs = socket.gethostbyname_ex(socket.gethostname())
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.connect(("1", 53))
    con_addr, _port = s.getsockname()
    return sorted(set(static_addrs + [ con_addr ]), key=lambda a: (a.startswith("127"), a))


class ParserState(Enum):
    Break = "break"
    Receiver = "receiver"
    Ips = "ip"

class Status(Enum):
    Continue = "continue"
    Error = "error"
    RedoWithFlags = "redo_with_flags"
    Launched = "launched"

class BlastDriver:
    parsing: ParserState | None = None
    last_write: str | None = None
    def __init__(self, blast_flags: list[str] = []):
        self.ranked_ips = get_ranked_ip_addrs()
        self.blast = subprocess.Popen(
            ["blast", "-source", "blast.monitor"] + blast_flags,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        self.blast_flags = list(blast_flags)
        self.receiver_names = []
        self.ips = []

    def writeline(self, line: str) -> None:
        logger.debug("[send] %s", line)
        self.blast.stdin.write(f"{line}\n".encode())
        self.blast.stdin.flush()
        self.last_write = line

    def readline(self) -> str:
        line = self.blast.stdout.readline().decode('utf-8').strip()
        line = line.replace('\x1b[1A\x1b[K', '')  #< escape codes
        logger.debug("[recv] %r", line)
        return line

    def set_state(self, state: ParserState):
        logger.debug("[pars] %s", state)
        self.parsing = state

    def feedline(self, line: str) -> (Status, str|None):
        """
        apply a line from blast's stdout to modify parser state.
        returns a status code (e.g. Status.Continue), and optionally a reply to send back to blast.
        """
        if line == "Loading...":
            return Status.Continue, None
        elif line == "----------":
            self.set_state(ParserState.Break)
            return Status.Continue, None
        elif line == "DLNA receivers":
            self.set_state(ParserState.Receiver)
            return Status.Continue, None
        elif line == "Your LAN ip addresses":
            self.set_state(ParserState.Ips)
            return Status.Continue, None
        elif line == "Select the DLNA device:":
            assert len(self.receiver_names) == 1, self.receiver_names
            name = self.receiver_names[0]
            if name in DEVICE_MAP and DEVICE_MAP[name] != self.blast_flags:
                return Status.RedoWithFlags, None
            return Status.Continue, "0"
        elif line == "Select the lan IP address for the stream:":
            for r in self.ranked_ips:
                if r in self.ips:
                    return Status.Launched, str(self.ips.index(r))
            # fallback: just guess the best IP
            return Status.Launched, "0"
        elif self.parsing == ParserState.Receiver:
            id_, name = line.split(": ")
            assert id_ == str(len(self.receiver_names)), (id_, self.receiver_names)
            self.receiver_names.append(name)
            return Status.Continue, None
        elif self.parsing == ParserState.Ips:
            id_, ip = line.split(": ")
            assert id_ == str(len(self.ips)), (id_, self.ips)
            self.ips.append(ip)
            return Status.Continue, None
        elif line == f"[{self.last_write}]":
            # it's echoing to us what we wrote
            return Status.Continue, None
        # elif line == "":
        #     return Status.Continue, None
        else:
            logger.info("unrecognized output (state=%s): %r", self.parsing, line)
            return Status.Error, None

    def step(self) -> Status:
        """
        advance the interaction between us and blast.
        reads a line from blast, modifies internal state, maybe sends a reply.
        could block indefinitely.
        """
        line = self.readline()
        status, reply = self.feedline(line)
        if reply is not None:
            self.writeline(reply)
        return status

def try_blast(*args, **kwargs) -> BlastDriver | None:
    blast = BlastDriver(*args, **kwargs)
    status = Status.Continue
    while status == Status.Continue:
        status = blast.step()

    if status == Status.RedoWithFlags:
        dev = blast.receiver_names[0]
        blast_flags = DEVICE_MAP[dev]
        logger.info("re-exec blast for %s with flags: %r", dev, blast_flags)
        blast.blast.terminate()
        return try_blast(blast_flags=blast_flags)
    elif status == Status.Error:
        logger.info("blast error => terminating")
        blast.blast.terminate()
    else:
        # successfully launched
        return blast


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

    blast = try_blast()

    if blast is not None:
        logger.info("waiting until blast exits")
        blast.blast.wait()

if __name__ == "__main__":
    main()