import sys
import os
import cv2
import numpy as np
import tempfile
import logging
import argparse

from fastapi import FastAPI, File, UploadFile, HTTPException
from fastapi.middleware.cors import CORSMiddleware

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

# Add the cloned MiVOLO repo to Python path
sys.path.insert(0, '/app/mivolo_repo')

app = FastAPI(title="MiVOLO Age & Gender Detection API")

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

# Global predictor — loaded lazily on first request to avoid OOM during build
predictor = None


def get_predictor():
    """
    Lazy-loads the MiVOLO predictor on the first request.
    Downloads model weights from Hugging Face Hub automatically.
    """
    global predictor
    if predictor is not None:
        return predictor

    logger.info("Loading MiVOLO predictor for the first time...")

    from huggingface_hub import hf_hub_download
    from mivolo.predictor import Predictor

    # Download the YOLOv8 person+face detector weights from the public working repo
    detector_weights = hf_hub_download(
        repo_id="iitolstykh/demo_yolov8_detector",
        filename="yolov8x_person_face.pt"
    )

    # The age/gender checkpoint is no longer publicly hosted on HF.
    # We auto-detect any .pth.tar file uploaded to the Space.
    import glob
    checkpoint_files = glob.glob("*.pth.tar")
    if not checkpoint_files:
        raise FileNotFoundError("No checkpoint file ending in .pth.tar found in Space root! Please upload it.")
    checkpoint_path = checkpoint_files[0]

    # Build MiVOLO config
    config = argparse.Namespace(
        detector_weights=detector_weights,
        checkpoint=checkpoint_path,
        device="cpu",
        with_persons=True,     # Use full-body context for better accuracy
        disable_faces=False,   # Also use face features
        draw=False
    )

    predictor = Predictor(config, verbose=False)
    logger.info("MiVOLO predictor loaded successfully.")
    return predictor


@app.get("/")
def health_check():
    return {
        "status": "MiVOLO API is running!",
        "model": "MiVOLO D1 — State-of-the-Art Age & Gender Estimation"
    }


@app.post("/predict")
async def predict_age_gender(file: UploadFile = File(...)):
    try:
        # Read and decode image
        contents = await file.read()
        nparr = np.frombuffer(contents, np.uint8)
        img = cv2.imdecode(nparr, cv2.IMREAD_COLOR)

        if img is None:
            raise HTTPException(status_code=400, detail="Invalid or unreadable image file.")

        # Apply CLAHE (Contrast Limited Adaptive Histogram Equalization)
        # This dramatically improves face visibility in bad webcam lighting
        lab = cv2.cvtColor(img, cv2.COLOR_BGR2LAB)
        l_channel, a_channel, b_channel = cv2.split(lab)
        clahe = cv2.createCLAHE(clipLimit=2.0, tileGridSize=(8,8))
        cl = clahe.apply(l_channel)
        limg = cv2.merge((cl, a_channel, b_channel))
        img = cv2.cvtColor(limg, cv2.COLOR_LAB2BGR)

        # Convert BGR (OpenCV default) to RGB (MiVOLO expectation)
        img_rgb = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

        # Run MiVOLO prediction directly on the numpy image array
        pred = get_predictor()
        detected_objects, _ = pred.recognize(img_rgb)

        if detected_objects is None or not detected_objects.ages:
            raise HTTPException(
                status_code=422,
                detail="No face detected. Please use a clear, well-lit photo."
            )

        # Take the primary (highest-confidence) detection
        age = round(float(detected_objects.ages[0]))
        gender_raw = detected_objects.genders[0]        # "male" or "female"
        gender_score = float(detected_objects.gender_scores[0])

        # Format gender to match dashboard expectations
        gender = "Man" if gender_raw == "male" else "Woman"

        logger.info(f"MiVOLO Result — Age: {age}, Gender: {gender} ({gender_score:.2f})")

        return {
            "success": True,
            "age": age,
            "gender": gender,
            "confidence": round(gender_score, 2),
            "model_used": "MiVOLO D1"
        }

    except HTTPException:
        raise
    except Exception as e:
        logger.error(f"Prediction error: {str(e)}")
        raise HTTPException(status_code=500, detail=str(e))