"""
SPA Static Files Handler for FastAPI
Serves Vue.js SPA while preserving API routes
"""
from fastapi.staticfiles import StaticFiles
from starlette.responses import FileResponse
from starlette.types import Scope
import os


class SPAStaticFiles(StaticFiles):
    """
    Custom StaticFiles that serves index.html for non-API routes (SPA fallback)
    while allowing API routes to pass through
    """
    
    async def get_response(self, path: str, scope: Scope):
        """
        Handle requests:
        - API routes (/api/*) → 404 (let FastAPI handle)
        - Static files (exist) → serve file  
        - Everything else → index.html (SPA routing)
        """
        # Let API routes pass through to FastAPI
        if path.startswith("api/") or path.startswith("docs") or path.startswith("redoc") or path.startswith("openapi.json"):
            # Return 404 to let FastAPI handle it
            raise RuntimeError("Not found")
        
        try:
            # Try to serve the file
            return await super().get_response(path, scope)
        except Exception:
            # File not found → serve index.html for SPA routing
            return FileResponse(os.path.join(self.directory, "index.html"))