"""Telnet server for the MUD."""

import asyncio
import logging
import time
from typing import cast

import telnetlib3
from telnetlib3.server_shell import readline2

import mudlib.commands
import mudlib.commands.look
import mudlib.commands.movement
import mudlib.commands.quit
from mudlib.player import Player, players
from mudlib.world.terrain import World

log = logging.getLogger(__name__)

PORT = 6789

# Module-level world instance, generated once at startup
_world: World | None = None


def find_passable_start(world: World, start_x: int, start_y: int) -> tuple[int, int]:
    """Find a passable tile starting from (start_x, start_y) and searching outward.

    Args:
        world: The world to search in
        start_x: Starting X coordinate
        start_y: Starting Y coordinate

    Returns:
        Tuple of (x, y) for the first passable tile found
    """
    # Try the starting position first
    if world.is_passable(start_x, start_y):
        return start_x, start_y

    # Spiral outward from the starting position (wrapping)
    for radius in range(1, 100):
        for dx in range(-radius, radius + 1):
            for dy in range(-radius, radius + 1):
                # Only check the perimeter of the current radius
                if abs(dx) != radius and abs(dy) != radius:
                    continue

                x, y = world.wrap(start_x + dx, start_y + dy)

                if world.is_passable(x, y):
                    return x, y

    # Fallback to starting position if nothing found
    return start_x, start_y


async def shell(
    reader: telnetlib3.TelnetReader | telnetlib3.TelnetReaderUnicode,
    writer: telnetlib3.TelnetWriter | telnetlib3.TelnetWriterUnicode,
) -> None:
    """Shell callback that handles player connection and command loop."""
    _reader = cast(telnetlib3.TelnetReaderUnicode, reader)
    _writer = cast(telnetlib3.TelnetWriterUnicode, writer)

    assert _world is not None, "World must be initialized before accepting connections"

    log.debug("new connection from %s", _writer.get_extra_info("peername"))

    _writer.write("Welcome to the MUD!\r\n")
    _writer.write("What is your name? ")
    await _writer.drain()

    name_input = await readline2(_reader, _writer)
    if name_input is None or not name_input.strip():
        _writer.close()
        return

    player_name = name_input.strip()

    # Find a passable starting position (start at world center)
    center_x = _world.width // 2
    center_y = _world.height // 2
    start_x, start_y = find_passable_start(_world, center_x, center_y)

    # Create player
    player = Player(
        name=player_name,
        x=start_x,
        y=start_y,
        writer=_writer,
        reader=_reader,
    )

    # Register player
    players[player_name] = player
    log.info("%s connected at (%d, %d)", player_name, start_x, start_y)

    _writer.write(f"\r\nWelcome, {player_name}!\r\n")
    _writer.write("Type 'help' for commands or 'quit' to disconnect.\r\n\r\n")
    await _writer.drain()

    # Show initial map
    await mudlib.commands.look.cmd_look(player, "")

    # Command loop
    while not _writer.is_closing():
        _writer.write("mud> ")
        await _writer.drain()

        inp = await readline2(_reader, _writer)
        if inp is None:
            break

        command = inp.strip()
        if not command:
            continue

        # Dispatch command
        await mudlib.commands.dispatch(player, command)

        # Check if writer was closed by quit command
        if _writer.is_closing():
            break

    # Clean up: remove from registry if still present
    if player_name in players:
        del players[player_name]
        log.info("%s disconnected", player_name)

    _writer.close()


async def run_server() -> None:
    """Start the MUD telnet server."""
    global _world

    # Generate world once at startup
    log.info("generating world (seed=42, 1000x1000)...")
    t0 = time.monotonic()
    _world = World(seed=42, width=1000, height=1000)
    elapsed = time.monotonic() - t0
    log.info("world generated in %.2fs", elapsed)

    # Inject world into command modules
    mudlib.commands.look.world = _world
    mudlib.commands.movement.world = _world

    # connect_maxwait: how long to wait for telnet option negotiation (CHARSET
    # etc) before starting the shell. default is 4.0s which is painful.
    # MUD clients like tintin++ reject CHARSET immediately via MTTS, but
    # telnetlib3 still waits for the full timeout. 0.5s is plenty.
    server = await telnetlib3.create_server(
        host="127.0.0.1", port=PORT, shell=shell, connect_maxwait=0.5
    )
    log.info("listening on 127.0.0.1:%d", PORT)

    try:
        while True:
            await asyncio.sleep(3600)
    except KeyboardInterrupt:
        log.info("shutting down...")
        server.close()
        await server.wait_closed()