"""IPEchoAPI - returns real IP address of the host (behind NAT)"""
import asyncio
import functools
import logging
import time
import urllib
from pathlib import Path
from typing import Optional

from async_lru import alru_cache

from defence360agent.api.server import API, APIError
from defence360agent.utils import atomic_rewrite
from defence360agent.utils.validate import IP, IPVersion

logger = logging.getLogger(__name__)

TIMEOUT_FOR_IPECHO_REQUEST = 5  # in seconds
CACHE_TTL_SECONDS = 3 * 60 * 60
CACHE_FILE_PATH = Path("/var/imunify360") / "ipecho_cache"


class IPEchoAPI(API):
    """Make requests to the API for obtain own IP address"""

    URL = "/api/ip"

    @classmethod
    @alru_cache(maxsize=3)
    async def get_ip(cls, ip_version: IPVersion = None) -> Optional[str]:
        """Return cached result for resolved IP from echo ip API"""

        return await cls.ip_for_version(ip_version)

    @classmethod
    @functools.lru_cache(maxsize=1)
    def server_ip(cls):
        """Return cached result for resolved IP from echo ip API"""
        try:
            return cls._get_ip()
        except Exception as e:
            raise APIError from e

    @classmethod
    async def ip_for_version(
        cls, ip_version: IPVersion = None
    ) -> Optional[str]:
        """Return resolved IP from echo ip API"""

        loop = asyncio.get_event_loop()
        try:
            ip = await asyncio.wait_for(
                loop.run_in_executor(None, cls._get_ip),
                timeout=TIMEOUT_FOR_IPECHO_REQUEST,
            )
            if IP.type_of(ip) != ip_version:
                raise ValueError("Wrong ip type")
            return ip
        except (asyncio.TimeoutError, ValueError) as e:
            raise APIError from e

    @classmethod
    def _load_cache(cls) -> Optional[str]:
        try:
            if not CACHE_FILE_PATH.exists():
                return None

            mtime = CACHE_FILE_PATH.stat().st_mtime
            cache_age = time.time() - mtime

            if cache_age < 0:
                return None

            if cache_age < CACHE_TTL_SECONDS:
                ip = CACHE_FILE_PATH.read_text().strip()
                return ip
            else:
                return None
        except Exception as e:
            logger.error("IPEchoAPI cache read error: %s", e)
            return None

    @classmethod
    def _save_cache(cls, ip: str) -> None:
        try:
            atomic_rewrite(
                CACHE_FILE_PATH,
                ip,
                backup=False,
                permissions=0o644,
            )
        except Exception as e:
            logger.error("IPEchoAPI cache write error: %s", e)

    @classmethod
    def _get_ip(cls):
        """Get IP from file-based cache or send request to API and process response."""
        cached_ip = cls._load_cache()
        if cached_ip is not None:
            return cached_ip

        request = urllib.request.Request(cls._BASE_URL + cls.URL)
        response = cls.request(request)
        if response.get("status") != "ok":
            # time inside sync executor
            raise APIError("Unexpected API error")
        ip = response.get("ip")
        if ip:
            cls._save_cache(ip)

        return ip