# plugins/homeassistant/client.py
"""Talking to Home Assistant. Every request but the webhook carries the token,
because Home Assistant bans an address after a few refused requests, token-less
ones included. Every failure comes back as one sentence a page can show."""
from __future__ import annotations

import json

import httpx

TIMEOUT_SECONDS = 15.0
MAX_BYTES = 16 * 1024 * 1024


class Unreachable(Exception):
    """Home Assistant didn't answer usefully; it may be restarting."""


class Refused(Exception):
    """Home Assistant refused the token, or has banned this address."""


async def _get(url: str, path: str, token: str, verify_tls: bool, transport) -> list | dict | None:
    """The parsed JSON of a GET, or None for a 404."""
    headers = {"Authorization": f"Bearer {token}"}
    try:
        async with httpx.AsyncClient(timeout=TIMEOUT_SECONDS, verify=verify_tls, transport=transport,
                                     follow_redirects=False) as client:
            async with client.stream("GET", url.rstrip("/") + path, headers=headers) as response:
                if response.status_code == 401:
                    raise Refused("Home Assistant refused the token. Check it, or make a new one.")
                if response.status_code == 403:
                    raise Refused("Home Assistant answered 403: it may have banned Steward's address "
                                  "after refused requests. Look in its ip_bans.yaml.")
                if response.status_code == 404:
                    return None
                if response.status_code != 200:
                    raise Unreachable(f"Home Assistant answered {response.status_code}.")
                body = bytearray()
                async for chunk in response.aiter_bytes():
                    body.extend(chunk)
                    if len(body) > MAX_BYTES:
                        raise Unreachable("Home Assistant's answer was too large to read.")
                return json.loads(body)
    except httpx.TimeoutException:
        raise Unreachable(f"Home Assistant didn't answer within {TIMEOUT_SECONDS:.0f} s.") from None
    except httpx.HTTPError as exc:
        raise Unreachable(f"Couldn't reach Home Assistant: {exc}") from None
    except ValueError:
        raise Unreachable("Home Assistant's answer wasn't JSON.") from None


async def read_states(url: str, token: str, verify_tls: bool, transport=None) -> list[dict]:
    states = await _get(url, "/api/states", token, verify_tls, transport)
    if not isinstance(states, list):
        raise Unreachable("Home Assistant's answer wasn't a list of entities.")
    return states


async def read_state(url: str, entity_id: str, token: str, verify_tls: bool, transport=None) -> dict | None:
    return await _get(url, f"/api/states/{entity_id}", token, verify_tls, transport)


async def send_webhook(url: str, webhook_id: str, body: dict, verify_tls: bool, transport=None) -> None:
    """Hand the maintenance automation a request. Home Assistant answers 200
    whether or not the id is known, so what the request did is read afterwards."""
    try:
        async with httpx.AsyncClient(timeout=TIMEOUT_SECONDS, verify=verify_tls, transport=transport,
                                     follow_redirects=False) as client:
            response = await client.post(f"{url.rstrip('/')}/api/webhook/{webhook_id}", json=body)
    except httpx.TimeoutException:
        raise Unreachable(f"Home Assistant didn't answer within {TIMEOUT_SECONDS:.0f} s.") from None
    except httpx.HTTPError as exc:
        raise Unreachable(f"Couldn't reach Home Assistant: {exc}") from None
    if response.status_code != 200:
        raise Unreachable(f"Home Assistant answered {response.status_code} to the webhook.")