"""
Base API client with common functionality.

Provides:
- Connection pooling
- Automatic retry with exponential backoff
- Timeout control
- Request/response logging
- OpenTelemetry tracing integration
- Error handling
"""

import asyncio
from typing import Any, Optional, Callable
from abc import ABC, abstractmethod
import httpx
from opentelemetry import trace
from opentelemetry.trace import Status, StatusCode
from observability.logging import get_logger

logger = get_logger(__name__)
tracer = trace.get_tracer(__name__)


class BaseAPIClient(ABC):
    """
    Abstract base class for all API clients.
    
    Provides common functionality like retry logic, timeout handling,
    logging, and tracing integration.
    """
    
    def __init__(
        self,
        base_url: str,
        timeout: float = 30.0,
        max_retries: int = 3,
        retry_delay: float = 1.0,
        retry_backoff: float = 2.0,
        trace_enabled: bool = True,
    ) -> None:
        """
        Initialize base API client.
        
        Args:
            base_url: Base URL for the API
            timeout: Request timeout in seconds
            max_retries: Maximum number of retry attempts
            retry_delay: Initial retry delay in seconds
            retry_backoff: Exponential backoff multiplier
            trace_enabled: Enable OpenTelemetry tracing
        """
        self.base_url = base_url.rstrip("/")
        self.timeout = timeout
        self.max_retries = max_retries
        self.retry_delay = retry_delay
        self.retry_backoff = retry_backoff
        self.trace_enabled = trace_enabled
        self._client: Optional[httpx.AsyncClient] = None
    
    @abstractmethod
    async def _get_client(self) -> httpx.AsyncClient:
        """
        Get or create HTTP client instance.
        
        Subclasses must implement this to provide their own client configuration.
        
        Returns:
            httpx.AsyncClient: Configured async HTTP client
        """
        pass
    
    async def close(self) -> None:
        """Close the HTTP client and cleanup resources."""
        if self._client is not None:
            await self._client.aclose()
            self._client = None
            logger.info(f"{self.__class__.__name__} client closed")
    
    async def __aenter__(self) -> "BaseAPIClient":
        """Async context manager entry."""
        return self
    
    async def __aexit__(self, exc_type: Any, exc_val: Any, exc_tb: Any) -> None:
        """Async context manager exit."""
        await self.close()
    
    async def _retry_with_backoff(
        self,
        func: Callable,
        *args: Any,
        **kwargs: Any
    ) -> Any:
        """
        Execute function with retry and exponential backoff.
        
        Args:
            func: Async function to execute
            *args: Positional arguments for the function
            **kwargs: Keyword arguments for the function
        
        Returns:
            Result from the function
        
        Raises:
            Exception: Last exception if all retries fail
        """
        last_exception = None
        delay = self.retry_delay
        
        for attempt in range(self.max_retries):
            try:
                return await func(*args, **kwargs)
            except (httpx.TimeoutException, httpx.NetworkError, httpx.RemoteProtocolError) as e:
                last_exception = e
                
                if attempt < self.max_retries - 1:
                    logger.warning(
                        f"Request failed (attempt {attempt + 1}/{self.max_retries}): {str(e)}. "
                        f"Retrying in {delay}s..."
                    )
                    await asyncio.sleep(delay)
                    delay *= self.retry_backoff
                else:
                    logger.error(
                        f"Request failed after {self.max_retries} attempts: {str(e)}"
                    )
            except Exception as e:
                # For non-retryable errors, raise immediately
                logger.error(f"Non-retryable error: {str(e)}")
                raise
        
        if last_exception:
            raise last_exception
    
    def _create_span_attributes(
        self,
        method: str,
        url: str,
        **kwargs: Any
    ) -> dict[str, Any]:
        """
        Create OpenTelemetry span attributes.
        
        Args:
            method: HTTP method
            url: Request URL
            **kwargs: Additional attributes
        
        Returns:
            Dictionary of span attributes
        """
        attributes = {
            "http.method": method,
            "http.url": url,
            "http.client": self.__class__.__name__,
        }
        attributes.update(kwargs)
        return attributes
    
    def _log_request(
        self,
        method: str,
        url: str,
        headers: Optional[dict[str, str]] = None,
        **kwargs: Any
    ) -> None:
        """
        Log outgoing request.
        
        Args:
            method: HTTP method
            url: Request URL
            headers: Request headers
            **kwargs: Additional log context
        """
        logger.debug(
            f"API Request: {method} {url}",
            extra={
                "method": method,
                "url": url,
                "headers": self._sanitize_headers(headers),
                **kwargs
            }
        )
    
    def _log_response(
        self,
        method: str,
        url: str,
        status_code: int,
        elapsed: float,
        **kwargs: Any
    ) -> None:
        """
        Log API response.
        
        Args:
            method: HTTP method
            url: Request URL
            status_code: Response status code
            elapsed: Request duration in seconds
            **kwargs: Additional log context
        """
        log_level = "info" if 200 <= status_code < 400 else "warning"
        log_func = getattr(logger, log_level)
        
        log_func(
            f"API Response: {method} {url} - {status_code} ({elapsed:.3f}s)",
            extra={
                "method": method,
                "url": url,
                "status_code": status_code,
                "elapsed_seconds": elapsed,
                **kwargs
            }
        )
    
    @staticmethod
    def _sanitize_headers(headers: Optional[dict[str, str]]) -> dict[str, str]:
        """
        Sanitize headers for logging (remove sensitive data).
        
        Args:
            headers: Request headers
        
        Returns:
            Sanitized headers
        """
        if not headers:
            return {}
        
        sensitive_keys = {"authorization", "api-key", "x-api-key", "cookie", "set-cookie"}
        return {
            k: "***REDACTED***" if k.lower() in sensitive_keys else v
            for k, v in headers.items()
        }
    
    async def health_check(self) -> bool:
        """
        Check if the API client can connect to the service.
        
        Returns:
            bool: True if healthy, False otherwise
        """
        try:
            client = await self._get_client()
            response = await client.get(f"{self.base_url}/health", timeout=5.0)
            return response.status_code == 200
        except Exception as e:
            logger.error(f"{self.__class__.__name__} health check failed: {str(e)}")
            return False