add exchangeInfo symbol validation

app/src/integrations/exchange/rest_client.py

@@ -0,0 +1,62 @@
+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