from __future__ import annotations

from datetime import datetime, timedelta
from typing import Dict, List, Optional

import aiohttp
from aiohttp import ClientError
from aiohttp_prometheus_exporter.trace import PrometheusTraceConfig
from diskcache import Cache

from matrix_alertbot.errors import (
    AlertmanagerServerError,
    AlertNotFoundError,
    InvalidDurationError,
    SilenceExpiredError,
    SilenceNotFoundError,
)


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

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

    async def get_silence(self, silence_id: str) -> Dict:
        silences = await self.get_silences()
        return self._find_silence(silence_id, silences)

    async def create_silence(
        self,
        fingerprint: str,
        user: str,
        duration_seconds: Optional[int] = None,
        silence_id: Optional[str] = None,
    ) -> str:
        alert = await self.get_alert(fingerprint)

        silence_matchers = [
            {"name": label, "value": value, "isRegex": False, "isEqual": True}
            for label, value in alert["labels"].items()
        ]

        start_time = datetime.now()
        if duration_seconds is None:
            end_time = datetime.max
        elif duration_seconds > 0:
            try:
                duration_delta = timedelta(seconds=duration_seconds)
                end_time = start_time + duration_delta
            except OverflowError:
                end_time = datetime.max
        else:
            raise InvalidDurationError(f"Duration must be positive: {duration_seconds}")

        silence = {
            "id": silence_id,
            "matchers": silence_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 AlertmanagerServerError(
                f"Cannot create silence for alert fingerprint {fingerprint}"
            ) from e

        return data["silenceID"]

    async def delete_silence(self, silence_id: str) -> None:
        silence = await self.get_silence(silence_id)

        silence_state = silence["state"]
        if silence_state == "expired":
            raise SilenceExpiredError(
                f"Cannot delete already expired silence with ID {silence_id}"
            )

        try:
            async with self.session.delete(
                f"{self.api_url}/silence/{silence_id}"
            ) as response:
                response.raise_for_status()
        except ClientError as e:
            raise AlertmanagerServerError(
                f"Cannot delete silence with ID {silence_id}"
            ) 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}")

    @staticmethod
    def _find_silence(silence_id: str, silences: List[Dict]) -> Dict:
        for silence in silences:
            if silence["id"] == silence_id:
                return silence
        raise SilenceNotFoundError(f"Cannot find silence with ID {silence_id}")