from __future__ import annotations

import datetime
from typing import Any, Dict, List

import aiohttp
import pytimeparse
from aiohttp import ClientError
from aiotools import AsyncContextManager
from diskcache import Cache

from matrix_alertbot.errors import (
    AlertmanagerError,
    AlertNotFoundError,
    SilenceNotFoundError,
)


class AlertmanagerClient(AsyncContextManager):
    def __init__(self, url: str, cache: Cache) -> None:
        self.api_url = f"{url}/api/v2"
        self.cache = cache
        self.session = aiohttp.ClientSession()

    async def __aenter__(self) -> AlertmanagerClient:
        return self

    async def __aexit__(self, *args: Any, **kwargs: Any) -> None:
        await super().__aexit__(*args, **kwargs)
        await self.close()

    async def close(self) -> None:
        await self.session.close()

    async def get_alerts(self) -> List[Dict]:
        try:
            async with self.session.get(f"{self.api_url}") as response:
                response.raise_for_status()
                return await response.json()
        except ClientError as e:
            raise AlertmanagerError(f"Cannot fetch alerts from Alertmanager") from e

    async def get_alert(self, fingerprint: str) -> Dict:
        alerts = await self.get_alerts()
        return self._find_alert(fingerprint, alerts)

    async def get_alert_labels(self, fingerprint: str) -> Dict[str, str]:
        alert = await self.get_alert(fingerprint)
        return alert["labels"]

    async def create_silence(self, fingerprint: str, duration: str, user: str) -> str:
        labels = await self.get_alert_labels(fingerprint)
        matchers = []
        for label_name, label_value in labels.items():
            matchers.append(
                {"name": label_name, "value": label_value, "isRegex": False}
            )

        start_time = datetime.datetime.now()
        duration_seconds = pytimeparse.parse(duration)
        duration_delta = datetime.timedelta(seconds=duration_seconds)
        end_time = start_time + duration_delta

        silence = {
            "matchers": matchers,
            "startsAt": start_time.isoformat(),
            "endsAt": end_time.isoformat(),
            "createdBy": user,
            "comment": "Acknowledge alert from Matrix",
        }

        try:
            async with self.session.post(
                f"{self.api_url}/silences", json=silence
            ) as response:
                response.raise_for_status()
                data = await response.json()
        except ClientError as e:
            raise AlertmanagerError(
                f"Cannot create silence for alert fingerprint {fingerprint}"
            ) from e

        return data["silenceID"]

    async def delete_silence(self, fingerprint: str) -> None:
        alert = await self.get_alert(fingerprint)

        alert_state = alert["status"]["state"]
        if alert_state != "suppressed":
            raise SilenceNotFoundError(
                f"Cannot find silences for alert fingerprint {fingerprint} in state {alert_state}"
            )

        silences = alert["status"]["silencedBy"]
        for silence in silences:
            await self._delete_silence_by_id(silence)

    async def _delete_silence_by_id(self, silence: str) -> None:
        try:
            async with self.session.delete(
                f"{self.api_url}/silence/{silence}"
            ) as response:
                response.raise_for_status()
        except ClientError as e:
            raise AlertmanagerError(f"Cannot delete silence with ID {silence}") from e

    @staticmethod
    def _find_alert(fingerprint: str, alerts: List[Dict]) -> Dict:
        for alert in alerts:
            if alert["fingerprint"] == fingerprint:
                return alert
        raise AlertNotFoundError(f"Cannot find alert with fingerprint {fingerprint}")