from __future__ import annotations

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

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

from matrix_alertbot.errors import (
    AlertmanagerServerError,
    AlertMismatchError,
    AlertNotFoundError,
    SilenceNotFoundError,
)
from matrix_alertbot.matcher import AlertMatcher


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 create_silence(
        self,
        fingerprint: str,
        seconds: int,
        user: str,
        matchers: List[AlertMatcher],
    ) -> str:
        alert = await self.get_alert(fingerprint)

        self._match_alert(alert, matchers)

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

        start_time = datetime.now()

        duration_delta = timedelta(seconds=seconds)
        end_time = start_time + duration_delta

        silence = {
            "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_silences(
        self, fingerprint: str, matchers: List[AlertMatcher]
    ) -> List[str]:
        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}"
            )

        self._match_alert(alert, matchers)

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

    async def _delete_silence(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 AlertmanagerServerError(
                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}")

    @staticmethod
    def _match_alert(alert: Dict, matchers: List[AlertMatcher]) -> None:
        labels = alert["labels"]
        for matcher in matchers:
            if matcher.label not in labels:
                labels_text = ", ".join(labels)
                raise AlertMismatchError(
                    f"Cannot find label {matcher.label} in alert labels: {labels_text}"
                )

            if not matcher.match(labels):
                raise AlertMismatchError(
                    f"Alert with label {matcher.label}={labels[matcher.label]} does not match {matcher}"
                )