main.py

from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse
import os

app = FastAPI()

# Path to the Svelte build output (mounted in Docker)
STATIC_DIR = "/app/static"

# 1. Mount the assets folder (CSS/JS) generated by Svelte
# SvelteKit puts assets in _app, so we look for that.
if os.path.isdir(os.path.join(STATIC_DIR, "_app")):
    app.mount("/_app", StaticFiles(directory=os.path.join(STATIC_DIR, "_app")), name="_app")

# 2. Catch-all route for SPA (Single Page Application)
# Any route not found above (like /about, /flow/123) returns index.html
@app.get("/{full_path:path}")
async def serve_spa(full_path: str):
    # Check if a specific file exists (like favicon.png), serve it
    file_path = os.path.join(STATIC_DIR, full_path)
    if os.path.exists(file_path) and os.path.isfile(file_path):
        return FileResponse(file_path)
    
    # Otherwise return the app entry point
    return FileResponse(os.path.join(STATIC_DIR, "index.html"))