from __future__ import annotations

import json
from urllib.error import HTTPError, URLError
from urllib.parse import urlencode
from urllib.request import Request, urlopen

from src.core.config import load_settings
from src.integrations.exchange.exceptions import (
    ExchangeConnectionError,
    ExchangeResponseError,
)


class ExchangeRestClient:
    def __init__(self) -> None:
        self.settings = load_settings()
        if not self.settings.exchange_base_url:
            raise ExchangeConnectionError("EXCHANGE_BASE_URL is empty.")
        self.base_url = self.settings.exchange_base_url.rstrip("/")
        self.timeout = self.settings.exchange_timeout_sec

    def get_json(self, path: str, params: dict[str, str] | None = None) -> dict:
        query = f"?{urlencode(params)}" if params else ""
        url = f"{self.base_url}{path}{query}"

        request = Request(
            url=url,
            method="GET",
            headers={
                "Accept": "application/json",
                "User-Agent": "dzentra-bot/2.0.0",
            },
        )

        try:
            with urlopen(request, timeout=self.timeout) as response:
                status = getattr(response, "status", 200)
                body = response.read().decode("utf-8")
        except HTTPError as exc:
            raise ExchangeResponseError(
                f"HTTP {exc.code} from exchange: {exc.reason}"
            ) from exc
        except URLError as exc:
            raise ExchangeConnectionError(
                f"Network error while calling exchange: {exc.reason}"
            ) from exc
        except TimeoutError as exc:
            raise ExchangeConnectionError("Timeout while calling exchange.") from exc

        if status != 200:
            raise ExchangeResponseError(f"Unexpected HTTP status: {status}")

        try:
            payload = json.loads(body)
        except json.JSONDecodeError as exc:
            raise ExchangeResponseError("Exchange returned non-JSON response.") from exc

        if not isinstance(payload, dict):
            raise ExchangeResponseError("Exchange response is not a JSON object.")

        return payload