from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse
from pathlib import Path

from backend.api.api import api_router

app = FastAPI(
    title="Perch API",
    description="Avian distribution intelligence API (eBird Status and Trends)",
    version="0.1.0",
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"], # Allow all for dev
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

app.include_router(api_router, prefix="/api/v1")

# Serve the built frontend, if present. Registered after the API router so that
# the catch-all below cannot shadow /api/v1 routes.
static_dir = Path(__file__).parent / "static"

if static_dir.exists():
    app.mount("/_next", StaticFiles(directory=static_dir / "_next"), name="next")

    @app.get("/{full_path:path}")
    async def serve_frontend(full_path: str):
        # An unknown API path is an error, not a page. Falling through to
        # index.html here would answer a bad API call with HTML and a 200,
        # and it makes this route shadow the API for non-GET methods.
        if full_path.startswith("api/"):
            raise HTTPException(status_code=404, detail=f"No such API route: /{full_path}")

        file_path = static_dir / full_path
        if file_path.exists() and file_path.is_file():
            return FileResponse(file_path)

        # Fall back to index.html so client-side routing works.
        index_path = static_dir / "index.html"
        if index_path.exists():
            return FileResponse(index_path)
        return {"error": "Frontend not found"}
else:
    @app.get("/")
    def read_root():
        return {"message": "Perch API is running (frontend not built)"}