import asyncio
import logging
import time
from datetime import timedelta
from ssl import SSLError

import aiohttp
from aiohttp import ClientTimeout
from aiohttp.client_exceptions import ClientConnectorError, ClientResponseError
from django.conf import settings
from django.utils import timezone

from .constants import MonitorCheckReason, MonitorType
from .models import MonitorCheck

logger = logging.getLogger(__name__)

DEFAULT_TIMEOUT = 20  # Seconds
PAYLOAD_LIMIT = 2_000_000  # 2mb
PAYLOAD_SAVE_LIMIT = 500_000  # pseudo 500kb


async def process_response(monitor, response):
    if response.status == monitor["expected_status"]:
        if monitor["expected_body"]:
            # Limit size to 2MB
            body = await response.content.read(PAYLOAD_LIMIT)
            try:
                encoding = response.get_encoding()
                payload = body.decode(encoding, errors="ignore")
            except RuntimeError:
                payload = body.decode(errors="ignore")
            if monitor["expected_body"] in payload:
                monitor["is_up"] = True
            else:
                monitor["reason"] = MonitorCheckReason.BODY
                if monitor["latest_is_up"] != monitor["is_up"]:
                    # Save only first 500k chars, to roughly reduce disk usage
                    # Note that a unicode char is not always one byte
                    # Only save on changes
                    monitor["data"] = {"payload": payload[:PAYLOAD_SAVE_LIMIT]}
        else:
            monitor["is_up"] = True
    else:
        monitor["reason"] = MonitorCheckReason.STATUS


async def fetch(session, monitor):
    monitor["is_up"] = False
    if monitor["monitor_type"] == MonitorType.HEARTBEAT:
        interval = timedelta(seconds=monitor["interval"])
        if await MonitorCheck.objects.filter(
            monitor_id=monitor["id"],
            start_check__gte=timezone.now() - interval,
        ).aexists():
            monitor["is_up"] = True
        return monitor

    url = monitor["url"]
    timeout = monitor["timeout"] or DEFAULT_TIMEOUT
    try:
        start = time.monotonic()
        if monitor["monitor_type"] == MonitorType.PORT:
            fut = asyncio.open_connection(*url.split(":"))
            await asyncio.wait_for(fut, timeout=timeout)
            monitor["is_up"] = True
        else:
            client_timeout = ClientTimeout(total=monitor["timeout"] or DEFAULT_TIMEOUT)
            if monitor["monitor_type"] == MonitorType.PING:
                async with session.head(url, timeout=client_timeout):
                    monitor["is_up"] = True
            elif monitor["monitor_type"] == MonitorType.GET:
                async with session.get(url, timeout=client_timeout) as response:
                    await process_response(monitor, response)
            elif monitor["monitor_type"] == MonitorType.POST:
                async with session.post(url, timeout=client_timeout) as response:
                    await process_response(monitor, response)
        monitor["response_time"] = (
            timedelta(seconds=time.monotonic() - start).total_seconds() * 1000
        )
    except SSLError:
        monitor["reason"] = MonitorCheckReason.SSL
    except asyncio.TimeoutError:
        monitor["reason"] = MonitorCheckReason.TIMEOUT
    except ClientConnectorError:
        monitor["reason"] = MonitorCheckReason.NETWORK
    except (OSError, ClientResponseError) as e:
        logger.warning(f"Monitor {monitor['id']} check failed", exc_info=e)
        monitor["reason"] = MonitorCheckReason.UNKNOWN
    except Exception as e:
        logger.error(f"Monitor {monitor['id']} check failed", exc_info=e)
        monitor["reason"] = MonitorCheckReason.UNKNOWN
    return monitor


async def fetch_all(monitors):
    async with aiohttp.ClientSession(**settings.AIOHTTP_CONFIG) as session:
        results = await asyncio.gather(
            *[fetch(session, monitor) for monitor in monitors], return_exceptions=True
        )
        return results