feat: implement backend API clients for multi-marketplace integration and frontend service layer

backend/mega_api/client.py

@@ -0,0 +1,79 @@
+import os
+import requests
+import time
+from typing import Dict, Any, Optional
+from .exceptions import MegaAPIError, MegaAuthError, MegaRateLimitError, MegaBadRequestError, MegaNotFoundError
+
+class MegaClient:
+    """Base client for interacting with MegaMarket API."""
+    
+    BASE_URL = "https://partner.goodsteam.tech/api/market/v1"
+    
+    def __init__(self, api_token: Optional[str] = None):
+        # Fetch from env if not provided
+        self.api_token = api_token or os.getenv('MEGA_API_TOKEN')
+        
+        if not self.api_token:
+            raise ValueError("MEGA_API_TOKEN must be provided")
+            
+        self.session = requests.Session()
+        # Мегамаркет может требовать токен как Bearer, либо внутри тела JSON в "meta".
+        # Будем использовать Bearer, как наиболее распространенный стандарт для V1.
+        self.session.headers.update({
+            "Authorization": f"Bearer {self.api_token}",
+            "Content-Type": "application/json"
+        })
+
+    def request(self, method: str, path: str, data: Optional[Dict[str, Any]] = None, params: Optional[Dict[str, Any]] = None, retries: int = 3) -> Dict[str, Any]:
+        """Perform HTTP request to MegaMarket API with automatic retries."""
+        url = f"{self.BASE_URL}{path}"
+        
+        for attempt in range(retries):
+            try:
+                response = self.session.request(method, url, json=data, params=params)
+                
+                # Check rate limiting
+                if response.status_code == 429:
+                    if attempt < retries - 1:
+                        time.sleep(2 ** attempt)  # Exponential backoff
+                        continue
+                    raise MegaRateLimitError("Rate limit exceeded")
+
+                if response.status_code in (401, 403):
+                    raise MegaAuthError(f"Authentication failed: {response.text}")
+                    
+                if response.status_code == 400:
+                    raise MegaBadRequestError(f"Bad Request: {response.text}")
+
+                if response.status_code == 404:
+                    raise MegaNotFoundError(f"Not Found: {response.text}")
+                    
+                response.raise_for_status()
+                
+                if response.content:
+                    return response.json()
+                return {}
+
+            except requests.exceptions.RequestException as e:
+                if attempt < retries - 1:
+                    time.sleep(2 ** attempt)
+                    continue
+                raise MegaAPIError(f"Request failed: {str(e)}")
+                
+        raise MegaAPIError("Request failed after max retries")
+
+    def post(self, path: str, data: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+        # Мегамаркет во многих методах требует структуру {"meta": {}, "data": {}}
+        # Если data не обернута, обернем ее
+        if data and "data" not in data and "meta" not in data:
+            payload = {
+                "meta": {},
+                "data": data
+            }
+        else:
+            payload = data
+            
+        return self.request("POST", path, data=payload)
+
+    def get(self, path: str, params: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+        return self.request("GET", path, params=params)