from __future__ import annotations

import base64
import hashlib
import hmac
import json
import logging
import os
from typing import Any
from urllib.parse import urlparse

import aiohttp

from yuxi.channels.exceptions import ChannelNotConnectedError

logger = logging.getLogger(__name__)


def _compute_bot_signature(body: bytes, random_hex: str, secret: str) -> str:
    payload = random_hex.encode() + body
    return base64.b64encode(hmac.digest(secret.encode(), payload, hashlib.sha256)).decode()


def verify_hmac_signature(body: bytes, random_header: str, signature_header: str, secret: str) -> bool:
    if not random_header or not signature_header or not secret:
        return False
    expected = _compute_bot_signature(body, random_header, secret)
    return hmac.compare_digest(expected, signature_header)


class NextcloudTalkClient:
    def __init__(
        self,
        server_url: str,
        bot_user: str,
        app_password: str,
        proxy: str | None = None,
        bot_secret: str | None = None,
    ):
        self.server_url = server_url.rstrip("/")
        self.bot_user = bot_user
        self.basic_auth = base64.b64encode(f"{bot_user}:{app_password}".encode()).decode()
        self.proxy = proxy
        self.bot_secret = bot_secret
        self._session: aiohttp.ClientSession | None = None

    async def start(self) -> None:
        if self._session is None:
            connector_kwargs: dict[str, Any] = {"limit": 10, "ttl_dns_cache": 300}
            timeout = aiohttp.ClientTimeout(total=60)
            session_kwargs: dict[str, Any] = {
                "connector": aiohttp.TCPConnector(**connector_kwargs),
                "timeout": timeout,
                "headers": {"User-Agent": "ForcePilot-NextcloudTalk-Adapter/1.0"},
            }
            if self.proxy:
                session_kwargs["proxy"] = self.proxy
            self._session = aiohttp.ClientSession(**session_kwargs)

    async def stop(self) -> None:
        if self._session:
            await self._session.close()
            self._session = None

    @property
    def session(self) -> aiohttp.ClientSession:
        if self._session is None:
            raise ChannelNotConnectedError()
        return self._session

    def auth_headers(self) -> dict[str, str]:
        return {"Authorization": f"Basic {self.basic_auth}"}

    def api_url(self, path: str) -> str:
        return f"{self.server_url}{path}"

    def _sign_body(self, body_bytes: bytes) -> dict[str, str]:
        if not self.bot_secret:
            return {}
        random_hex = os.urandom(32).hex()
        signature = _compute_bot_signature(body_bytes, random_hex, self.bot_secret)
        return {
            "X-Nextcloud-Talk-Bot-Random": random_hex,
            "X-Nextcloud-Talk-Bot-Signature": signature,
        }

    def _validate_url(self, url: str) -> None:
        parsed = urlparse(url)
        server_parsed = urlparse(self.server_url)
        if parsed.scheme not in ("https", "http"):
            raise ValueError(f"Invalid URL scheme: {parsed.scheme}")
        if parsed.hostname != server_parsed.hostname:
            raise ValueError(f"SSRF blocked: external host {parsed.hostname} != {server_parsed.hostname}")

    async def get(self, path: str, **kwargs) -> dict[str, Any]:
        url = self.api_url(path)
        self._validate_url(url)
        headers = {**self.auth_headers(), "OCS-APIRequest": "true", "Accept": "application/json"}
        headers.update(self._sign_body(b""))
        headers.update(kwargs.pop("headers", {}))
        async with self.session.get(url, headers=headers, **kwargs) as resp:
            resp.raise_for_status()
            return await resp.json()

    async def post(self, path: str, json_data: dict[str, Any] | None = None, **kwargs) -> dict[str, Any]:
        url = self.api_url(path)
        self._validate_url(url)
        headers = {**self.auth_headers(), "OCS-APIRequest": "true", "Accept": "application/json"}
        body_bytes = json.dumps(json_data).encode() if json_data else b""
        headers.update(self._sign_body(body_bytes))
        headers.update(kwargs.pop("headers", {}))
        async with self.session.post(url, headers=headers, json=json_data, **kwargs) as resp:
            resp.raise_for_status()
            return await resp.json()

    async def post_form(self, path: str, form: aiohttp.FormData, **kwargs) -> dict[str, Any]:
        url = self.api_url(path)
        self._validate_url(url)
        headers = {**self.auth_headers(), "OCS-APIRequest": "true", "Accept": "application/json"}
        headers.update(self._sign_body(b""))
        headers.update(kwargs.pop("headers", {}))
        async with self.session.post(url, headers=headers, data=form, **kwargs) as resp:
            resp.raise_for_status()
            return await resp.json()

    async def put(self, path: str, json_data: dict[str, Any] | None = None, **kwargs) -> dict[str, Any]:
        url = self.api_url(path)
        self._validate_url(url)
        headers = {**self.auth_headers(), "OCS-APIRequest": "true", "Accept": "application/json"}
        body_bytes = json.dumps(json_data).encode() if json_data else b""
        headers.update(self._sign_body(body_bytes))
        headers.update(kwargs.pop("headers", {}))
        async with self.session.put(url, headers=headers, json=json_data, **kwargs) as resp:
            resp.raise_for_status()
            return await resp.json()

    async def delete(self, path: str, **kwargs) -> dict[str, Any]:
        url = self.api_url(path)
        self._validate_url(url)
        headers = {**self.auth_headers(), "OCS-APIRequest": "true", "Accept": "application/json"}
        headers.update(self._sign_body(b""))
        headers.update(kwargs.pop("headers", {}))
        async with self.session.delete(url, headers=headers, **kwargs) as resp:
            resp.raise_for_status()
            return await resp.json()