"""
Utility functions for URL detection and management.
Automatically detects frontend URL from cloud platform environment variables,
request headers, or falls back to environment variables.
"""
import os
from typing import Optional
from fastapi import Request


def get_frontend_url(request: Optional[Request] = None) -> str:
    """
    Automatically detect the frontend URL from various sources.
    
    Priority order:
    1. FRONTEND_URL environment variable (manual override)
    2. Cloud platform environment variables (AWS ECS, Azure Container Instances, etc.)
    3. Request headers (Origin, Referer, X-Forwarded-Host)
    4. Default fallback to localhost
    
    Args:
        request: Optional FastAPI Request object to extract headers
        
    Returns:
        Frontend URL string (without trailing slash)
    """
    # 1. Check manual override from .env file
    # We use get_setting to allow runtime updates
    from utils.config_loader import get_setting
    frontend_url = get_setting("FRONTEND_URL")
    if frontend_url:
        return frontend_url.rstrip('/')
    
    # 2. Check cloud platform environment variables
    # AWS ECS/Fargate
    aws_container_url = os.getenv("AWS_CONTAINER_URL") or os.getenv("ECS_CONTAINER_METADATA_URI_V4")
    if aws_container_url:
        # Extract base URL from container metadata or use directly
        # For ECS, you might need to construct from service discovery
        # This is a placeholder - adjust based on your AWS setup
        pass
    
    # Azure Container Instances / App Service
    azure_website_hostname = os.getenv("WEBSITE_HOSTNAME")  # Azure App Service
    azure_container_url = os.getenv("AZURE_CONTAINER_URL")
    if azure_website_hostname:
        # Azure App Service provides WEBSITE_HOSTNAME
        scheme = "https" if os.getenv("HTTPS") == "on" else "http"
        return f"{scheme}://{azure_website_hostname}".rstrip('/')
    if azure_container_url:
        return azure_container_url.rstrip('/')
    
    # Generic cloud platform variables
    # Check for common reverse proxy headers that indicate the public URL
    public_url = os.getenv("PUBLIC_URL") or os.getenv("BASE_URL") or os.getenv("APP_URL")
    if public_url:
        return public_url.rstrip('/')
    
    # 3. Try to extract from request headers if available
    if request:
        # Check Origin header (most reliable for CORS requests)
        origin = request.headers.get("origin")
        if origin:
            return origin.rstrip('/')
        
        # Check Referer header
        referer = request.headers.get("referer")
        if referer:
            # Extract base URL from referer
            from urllib.parse import urlparse
            parsed = urlparse(referer)
            if parsed.scheme and parsed.netloc:
                return f"{parsed.scheme}://{parsed.netloc}".rstrip('/')
        
        # Check X-Forwarded-Host (common in reverse proxy setups)
        forwarded_host = request.headers.get("x-forwarded-host")
        forwarded_proto = request.headers.get("x-forwarded-proto", "https")
        if forwarded_host:
            return f"{forwarded_proto}://{forwarded_host}".rstrip('/')
        
        # Check Host header and construct URL
        host = request.headers.get("host")
        if host:
            # Determine scheme from headers
            scheme = request.headers.get("x-forwarded-proto", "https" if request.url.scheme == "https" else "http")
            # For cloud deployments, typically use https
            if "localhost" not in host.lower() and "127.0.0.1" not in host:
                scheme = "https"
            return f"{scheme}://{host}".rstrip('/')
    
    # 4. Final fallback to localhost (development) or inferred production
    # If we are likely in production (e.g. on AWS), default to the Vercel app
    if os.getenv("AWS_EXECUTION_ENV") or os.getenv("NODE_ENV") == "production":
        return "https://medisync-ai1.vercel.app"
        
    return "http://localhost:3000"


def get_backend_url(request: Optional[Request] = None) -> str:
    """
    Automatically detect the backend URL (useful for internal redirects).
    
    Args:
        request: Optional FastAPI Request object
        
    Returns:
        Backend URL string (without trailing slash)
    """
    # Check manual override
    backend_url = os.getenv("BACKEND_URL")
    if backend_url:
        return backend_url.rstrip('/')
    
    # Try to construct from request
    if request:
        base_url = str(request.base_url).rstrip('/')
        return base_url
    
    # Fallback
    return "http://localhost:8000"