app/backend/main.py

import sys, os

# ── Path fix: allow "python -m uvicorn" from project root ──────────────────
sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..")))

from fastapi import FastAPI, UploadFile, File, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from contextlib import asynccontextmanager
from typing import List

from backend.model import load_model, is_model_loaded, predict_image
from backend.schemas import (
    PredictResponse,
    PredictionResult,
    DiseaseListItem,
    DiseaseDetail,
    HealthResponse,
)

# Load disease info directly by path (avoids package import issues)
import importlib.util
_spec = importlib.util.spec_from_file_location(
    "disease_info",
    os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "data", "disease_info.py"))
)
_mod = importlib.util.module_from_spec(_spec)
_spec.loader.exec_module(_mod)
DISEASE_INFO = _mod.DISEASE_INFO

ALLOWED_TYPES = {"image/jpeg", "image/png", "image/webp", "image/bmp"}

MODEL_PATH = os.path.abspath(
    os.path.join(os.path.dirname(__file__), "..", "..", "skin_disease_classifier.pkl")
)


@asynccontextmanager
async def lifespan(app: FastAPI):
    result = load_model(MODEL_PATH)
    print(f"STARTUP: load_model returned {result}", flush=True)
    print(f"STARTUP: model_loaded={is_model_loaded()}", flush=True)
    yield


app = FastAPI(
    title="DermAI — Skin Disease Classifier API",
    description="FastAPI backend powering the DermAI skin disease diagnosis web app.",
    version="1.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)


# ── Health check ────────────────────────────────────────────────────────────
@app.get("/health", response_model=HealthResponse, tags=["Utility"])
async def health_check():
    return HealthResponse(status="ok", model_loaded=is_model_loaded())


# ── Prediction ──────────────────────────────────────────────────────────────
import asyncio
from concurrent.futures import ThreadPoolExecutor

_executor = ThreadPoolExecutor(max_workers=1)

@app.post("/predict", response_model=PredictResponse, tags=["Inference"])
async def predict(file: UploadFile = File(...)):
    if file.content_type not in ALLOWED_TYPES:
        raise HTTPException(status_code=415, detail=f"Unsupported format '{file.content_type}'.")
    
    raw = await file.read()
    if len(raw) > 15 * 1024 * 1024:
        raise HTTPException(status_code=413, detail="Image too large. Maximum 15 MB.")

    loop = asyncio.get_event_loop()
    try:
        top3 = await loop.run_in_executor(_executor, predict_image, raw)
    except Exception as exc:
        raise HTTPException(status_code=500, detail=f"Inference error: {str(exc)}")

    if top3 is None:
        raise HTTPException(status_code=500, detail="Prediction failed.")

    results = [
    PredictionResult(
        label=p["medical_name"],
        friendly_name=p["friendly_name"],
        confidence=p["confidence"],
    )
    for p in top3
    ]
    return PredictResponse(top3=results)


# ── Disease encyclopedia ────────────────────────────────────────────────────
@app.get("/diseases", response_model=List[DiseaseListItem], tags=["Encyclopedia"])
async def list_diseases():
    """Summary info for all 21 classifiable skin conditions."""
    return [
        DiseaseListItem(
            key=key,
            friendly_name=info["friendly_name"],
            category=info["category"],
            severity=info["severity"],
            emoji=info["emoji"],
        )
        for key, info in DISEASE_INFO.items()
    ]


@app.get("/disease/{disease_key}", response_model=DiseaseDetail, tags=["Encyclopedia"])
async def get_disease(disease_key: str):
    """Full detail for a single disease by its key name."""
    info = DISEASE_INFO.get(disease_key)
    if info is None:
        for k, v in DISEASE_INFO.items():
            if k.lower() == disease_key.lower():
                disease_key, info = k, v
                break
    if info is None:
        raise HTTPException(status_code=404, detail=f"Disease '{disease_key}' not found.")
    return DiseaseDetail(key=disease_key, **info)