# ================================================================
# gateway/app/routes/user.py
# ================================================================
"""
Authentication routes for API Gateway
"""

import logging
import httpx
from fastapi import APIRouter, Request, Response, HTTPException, status
from fastapi.responses import JSONResponse
from typing import Dict, Any
import json

from app.core.config import settings
from app.core.service_discovery import ServiceDiscovery
from shared.monitoring.metrics import MetricsCollector

logger = logging.getLogger(__name__)
router = APIRouter()

# Initialize service discovery and metrics
service_discovery = ServiceDiscovery()
metrics = MetricsCollector("gateway")

# Auth service configuration
AUTH_SERVICE_URL = settings.AUTH_SERVICE_URL or "http://auth-service:8000"

class UserProxy:
    """Authentication service proxy with enhanced error handling"""
    
    def __init__(self):
        self.client = httpx.AsyncClient(
            timeout=httpx.Timeout(30.0),
            limits=httpx.Limits(max_connections=100, max_keepalive_connections=20)
        )
    
    async def forward_request(
        self, 
        method: str, 
        path: str, 
        request: Request
    ) -> Response:
        """Forward request to auth service with proper error handling"""
        
        # Handle OPTIONS requests directly for CORS
        if request.method == "OPTIONS":
            return Response(
                status_code=200,
                headers={
                    "Access-Control-Allow-Origin": settings.CORS_ORIGINS_LIST,
                    "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
                    "Access-Control-Allow-Headers": "Content-Type, Authorization, X-Tenant-ID",
                    "Access-Control-Allow-Credentials": "true",
                    "Access-Control-Max-Age": "86400"  # Cache preflight for 24 hours
                }
            )
            
        try:
            # Get auth service URL (with service discovery if available)
            auth_url = await self._get_auth_service_url()
            target_url = f"{auth_url}/api/v1/users/{path}"
            
            # Prepare headers (remove hop-by-hop headers)
            headers = self._prepare_headers(dict(request.headers))
            
            # Get request body
            body = await request.body()
            
            # Forward request
            logger.info(f"Forwarding {method} {path} to auth service")
            
            response = await self.client.request(
                method=method,
                url=target_url,
                headers=headers,
                content=body,
                params=dict(request.query_params)
            )
            
            # Record metrics
            metrics.increment_counter("gateway_auth_requests_total")
            metrics.increment_counter(
                "gateway_auth_responses_total", 
                labels={"status_code": str(response.status_code)}
            )
            
            # Prepare response headers
            response_headers = self._prepare_response_headers(dict(response.headers))
            
            return Response(
                content=response.content,
                status_code=response.status_code,
                headers=response_headers,
                media_type=response.headers.get("content-type")
            )
            
        except httpx.TimeoutException:
            logger.error(f"Timeout forwarding {method} {path} to auth service")
            metrics.increment_counter("gateway_auth_errors_total", labels={"error": "timeout"})
            raise HTTPException(
                status_code=status.HTTP_504_GATEWAY_TIMEOUT,
                detail="Authentication service timeout"
            )
            
        except httpx.ConnectError:
            logger.error(f"Connection error forwarding {method} {path} to auth service")
            metrics.increment_counter("gateway_auth_errors_total", labels={"error": "connection"})
            raise HTTPException(
                status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
                detail="Authentication service unavailable"
            )
            
        except Exception as e:
            logger.error(f"Error forwarding {method} {path} to auth service: {e}")
            metrics.increment_counter("gateway_auth_errors_total", labels={"error": "unknown"})
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail="Internal gateway error"
            )
    
    async def _get_auth_service_url(self) -> str:
        """Get auth service URL with service discovery"""
        try:
            # Try service discovery first
            service_url = await service_discovery.get_service_url("auth-service")
            if service_url:
                return service_url
        except Exception as e:
            logger.warning(f"Service discovery failed: {e}")
        
        # Fall back to configured URL
        return AUTH_SERVICE_URL
    
    def _prepare_headers(self, headers: Dict[str, str]) -> Dict[str, str]:
        """Prepare headers for forwarding (remove hop-by-hop headers)"""
        # Remove hop-by-hop headers
        hop_by_hop_headers = {
            'connection', 'keep-alive', 'proxy-authenticate',
            'proxy-authorization', 'te', 'trailers', 'upgrade'
        }
        
        filtered_headers = {
            k: v for k, v in headers.items()
            if k.lower() not in hop_by_hop_headers
        }
        
        # Add gateway identifier
        filtered_headers['X-Forwarded-By'] = 'bakery-gateway'
        filtered_headers['X-Gateway-Version'] = '1.0.0'
        
        return filtered_headers
    
    def _prepare_response_headers(self, headers: Dict[str, str]) -> Dict[str, str]:
        """Prepare response headers"""
        # Remove server-specific headers
        filtered_headers = {
            k: v for k, v in headers.items()
            if k.lower() not in {'server', 'date'}
        }
        
        # Add CORS headers if needed
        if settings.CORS_ORIGINS:
            filtered_headers['Access-Control-Allow-Origin'] = '*'
            filtered_headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, DELETE, OPTIONS'
            filtered_headers['Access-Control-Allow-Headers'] = 'Content-Type, Authorization'
        
        return filtered_headers

# Initialize proxy
user_proxy = UserProxy()

# ================================================================
# USER MANAGEMENT ENDPOINTS - Proxied to auth service
# ================================================================

@router.get("/me")
async def get_current_user(request: Request):
    """Proxy get current user to auth service"""
    return await user_proxy.forward_request("GET", "me", request)

@router.put("/me")
async def update_current_user(request: Request):
    """Proxy update current user to auth service"""
    return await user_proxy.forward_request("PUT", "me", request)

@router.get("/delete/{user_id}/deletion-preview")
async def preview_user_deletion(user_id: str, request: Request):
    """Proxy user deletion preview to auth service"""
    return await user_proxy.forward_request("GET", f"delete/{user_id}/deletion-preview", request)

@router.delete("/delete/{user_id}")
async def delete_user(user_id: str, request: Request):
    """Proxy admin user deletion to auth service"""
    return await user_proxy.forward_request("DELETE", f"delete/{user_id}", request)

# ================================================================
# CATCH-ALL ROUTE for any other user endpoints
# ================================================================

@router.api_route("/{path:path}", methods=["GET", "POST", "PUT", "DELETE", "PATCH"])
async def proxy_auth_requests(path: str, request: Request):
    """Catch-all proxy for auth requests"""
    return await user_proxy.forward_request(request.method, path, request)