"""UX-15: setup-only mode. A new install serves the setup wizard and commands
nothing. The rule and the argument are in DECISIONS/UX-15-setup-only-mode.md.

`applies()` says when: the startup gate's only refusal is that no inverter is
named. `serve()` then runs the ingress page on a `SetupOnly` stand-in for the
controller. Nothing that can command is built: no Controller, no inverter, no
MQTT, no meter task. Its HomeAssistant is read-only, so a service call refuses
before anything is sent (hass.py), and `/action` refuses too (web.py).
"""

import asyncio
import contextlib
import logging
import signal
from datetime import datetime, timezone

from . import messages, web
from .inverter import roster_entries
from .validate import actuator_writers, no_power_request_problem

_LOG = logging.getLogger("goodwe.setup")


def applies(opts: dict, problems) -> bool:
    """True when the options name no inverter at all and that is the gate's
    only refusal. Anything else refused keeps the exit 78 (CFG-01)."""
    return (not actuator_writers(opts) and not roster_entries(opts)
            and list(problems) == [no_power_request_problem()])


class SetupOnly:
    """What web.build_app() needs from a controller, and nothing that writes.

    It holds no inverter and no publisher. `hass` must be read-only."""

    setup_only = True
    auto = False            # control is never started here
    grid = None             # no meter is read here
    inverters = ()

    def __init__(self, opts: dict, hass, store):
        if getattr(hass, "read_only", False) is not True:
            raise ValueError("setup-only mode needs a read-only HomeAssistant")
        self.o, self.hass, self.store = opts, hass, store
        self.events: list[str] = []
        self.hint = ""

    def log_event(self, msg: str, hint: str | None = None) -> None:
        stamp = datetime.now(timezone.utc).strftime("%H:%M:%S")
        self.events.insert(0, f"{stamp} {msg}")
        del self.events[40:]
        if hint is not None:
            self.hint = f"{datetime.now().astimezone():%H:%M} {hint}"

    def status_payload(self) -> dict:
        return {"setup_only": True, "mode": "setup_only",
                "banner": messages.banner_setup_only(), "level": "warn",
                "rows": [["Control", "not started, in setup"]],
                "checks": [{"ok": False, "warn": True,
                            "text": messages.row_setup_only()}],
                "hint": self.hint, "events": list(self.events)}

    async def handle_action(self, what):
        # web.py answers 409 before it gets here. Nothing is done either way.
        _LOG.warning("The page asked for an action in setup, so nothing "
                     "was done.")
        return None

    async def shutdown(self) -> None:
        """Nothing to wind down: nothing was ever commanded."""


async def serve(opts: dict, hass, store, *, port: int) -> None:
    """Serve the page in setup-only mode until the Supervisor stops us."""
    controller = SetupOnly(opts, hass, store)
    _LOG.warning("No inverter is named yet, so the add-on is in setup and "
                 "controls nothing. Open its page to finish setup.")
    controller.log_event("setup-only mode: no inverter named, nothing is "
                         "commanded", hint=messages.hint("setup_only"))
    runner = await web.start(controller, port=port)
    stop = asyncio.Event()
    loop = asyncio.get_running_loop()
    for sig in (signal.SIGTERM, signal.SIGINT):
        with contextlib.suppress(NotImplementedError):
            loop.add_signal_handler(sig, stop.set)
    try:
        await stop.wait()
    finally:
        await runner.cleanup()
        _LOG.info("stopped")