"""
CalorieCLIP API for FitGenie backend.

  POST /predict  { "image": "<base64>" }  ->  { "calories": 342 }
  GET  /health                              ->  { "status": "ok" }
"""

from __future__ import annotations

import os
from contextlib import asynccontextmanager

from fastapi import FastAPI, Header, HTTPException
from pydantic import BaseModel, Field

from model_core import decode_base64_image, load_models, predict_calories

API_KEY = os.getenv("CALORIE_CLIP_API_KEY", "").strip()


def _require_api_key(x_api_key: str | None) -> None:
    if not API_KEY:
        return
    if x_api_key != API_KEY:
        raise HTTPException(status_code=401, detail="Invalid API key")


@asynccontextmanager
async def lifespan(_: FastAPI):
    load_models()
    yield


app = FastAPI(title="FitGenie CalorieCLIP", version="1.1.0", lifespan=lifespan)


class PredictRequest(BaseModel):
    image: str = Field(..., description="Base64-encoded food photo")


@app.get("/")
def root() -> dict[str, str]:
    return {"service": "FitGenie CalorieCLIP", "endpoints": "/health, /predict"}


@app.get("/health")
def health() -> dict[str, str]:
    return {"status": "ok", "model": "CalorieCLIP"}


@app.post("/predict")
def predict(
    req: PredictRequest,
    x_api_key: str | None = Header(default=None, alias="X-API-Key"),
) -> dict[str, int]:
    _require_api_key(x_api_key)
    try:
        image = decode_base64_image(req.image)
    except ValueError as exc:
        raise HTTPException(status_code=400, detail=str(exc)) from exc
    return {"calories": predict_calories(image)}