app/main_fastai.py

"""
FastAPI application for FastAI GAN Image Colorization
with Firebase Authentication and Gradio UI
"""
import os
# Set environment variables BEFORE any imports
os.environ["OMP_NUM_THREADS"] = "1"
os.environ["HF_HOME"] = "/tmp/hf_cache"
os.environ["TRANSFORMERS_CACHE"] = "/tmp/hf_cache"
os.environ["HF_HUB_CACHE"] = "/tmp/hf_cache"
os.environ["HUGGINGFACE_HUB_CACHE"] = "/tmp/hf_cache"
os.environ["XDG_CACHE_HOME"] = "/tmp/hf_cache"
os.environ["MPLCONFIGDIR"] = "/tmp/matplotlib_config"

import io
import uuid
import logging
from pathlib import Path
from typing import Optional

from fastapi import FastAPI, UploadFile, File, HTTPException, Depends, Request
from fastapi.responses import FileResponse, JSONResponse
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
import firebase_admin
from firebase_admin import credentials, app_check, auth as firebase_auth
from PIL import Image
import torch
import uvicorn
import gradio as gr

# FastAI imports
from fastai.vision.all import *
from huggingface_hub import from_pretrained_fastai

from app.config import settings

# Configure logging
logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
logger = logging.getLogger(__name__)

# Create writable directories
Path("/tmp/hf_cache").mkdir(parents=True, exist_ok=True)
Path("/tmp/matplotlib_config").mkdir(parents=True, exist_ok=True)
Path("/tmp/colorize_uploads").mkdir(parents=True, exist_ok=True)
Path("/tmp/colorize_results").mkdir(parents=True, exist_ok=True)

# Initialize FastAPI app
app = FastAPI(
    title="FastAI Image Colorizer API",
    description="Image colorization using FastAI GAN model with Firebase authentication",
    version="1.0.0"
)

# CORS middleware
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Initialize Firebase Admin SDK
firebase_cred_path = os.getenv("FIREBASE_CREDENTIALS_PATH", "/tmp/firebase-adminsdk.json")
if os.path.exists(firebase_cred_path):
    try:
        cred = credentials.Certificate(firebase_cred_path)
        firebase_admin.initialize_app(cred)
        logger.info("Firebase Admin SDK initialized")
    except Exception as e:
        logger.warning("Failed to initialize Firebase: %s", str(e))
        try:
            firebase_admin.initialize_app()
        except:
            pass
else:
    logger.warning("Firebase credentials file not found. App Check will be disabled.")
    try:
        firebase_admin.initialize_app()
    except:
        pass

# Storage directories
UPLOAD_DIR = Path("/tmp/colorize_uploads")
RESULT_DIR = Path("/tmp/colorize_results")

# Mount static files
app.mount("/results", StaticFiles(directory=str(RESULT_DIR)), name="results")
app.mount("/uploads", StaticFiles(directory=str(UPLOAD_DIR)), name="uploads")

# Initialize FastAI model
learn = None
model_load_error: Optional[str] = None

@app.on_event("startup")
async def startup_event():
    """Load FastAI model on startup"""
    global learn, model_load_error
    try:
        model_id = os.getenv("MODEL_ID", "Hammad712/GAN-Colorization-Model")
        logger.info("🔄 Loading FastAI GAN Colorization Model: %s", model_id)
        learn = from_pretrained_fastai(model_id)
        logger.info("✅ Model loaded successfully!")
        model_load_error = None
    except Exception as e:
        error_msg = str(e)
        logger.error("❌ Failed to load model: %s", error_msg)
        model_load_error = error_msg
        # Don't raise - allow health check to work

@app.on_event("shutdown")
async def shutdown_event():
    """Cleanup on shutdown"""
    global learn
    if learn:
        del learn
    logger.info("Application shutdown")

def _extract_bearer_token(authorization_header: str | None) -> str | None:
    if not authorization_header:
        return None
    parts = authorization_header.split(" ", 1)
    if len(parts) == 2 and parts[0].lower() == "bearer":
        return parts[1].strip()
    return None

async def verify_request(request: Request):
    """
    Verify Firebase authentication
    Accept either:
      - Firebase Auth id_token via Authorization: Bearer <id_token>
      - Firebase App Check token via X-Firebase-AppCheck (when ENABLE_APP_CHECK=true)
    """
    # If Firebase is not initialized or auth is explicitly disabled, allow
    if not firebase_admin._apps or os.getenv("DISABLE_AUTH", "false").lower() == "true":
        return True

    # Try Firebase Auth id_token first if present
    bearer = _extract_bearer_token(request.headers.get("Authorization"))
    if bearer:
        try:
            decoded = firebase_auth.verify_id_token(bearer)
            request.state.user = decoded
            logger.info("Firebase Auth id_token verified for uid: %s", decoded.get("uid"))
            return True
        except Exception as e:
            logger.warning("Auth token verification failed: %s", str(e))

    # If App Check is enabled, require valid App Check token
    if settings.ENABLE_APP_CHECK:
        app_check_token = request.headers.get("X-Firebase-AppCheck")
        if not app_check_token:
            raise HTTPException(status_code=401, detail="Missing App Check token")
        try:
            app_check_claims = app_check.verify_token(app_check_token)
            logger.info("App Check token verified for: %s", app_check_claims.get("app_id"))
            return True
        except Exception as e:
            logger.warning("App Check token verification failed: %s", str(e))
            raise HTTPException(status_code=401, detail="Invalid App Check token")

    # Neither token required nor provided → allow (App Check disabled)
    return True

@app.get("/api")
async def api_info():
    """API info endpoint"""
    return {
        "app": "FastAI Image Colorizer API",
        "version": "1.0.0",
        "health": "/health",
        "colorize": "/colorize",
        "gradio": "/"
    }

@app.get("/health")
async def health_check():
    """Health check endpoint"""
    response = {
        "status": "healthy",
        "model_loaded": learn is not None,
        "model_id": os.getenv("MODEL_ID", "Hammad712/GAN-Colorization-Model")
    }
    if model_load_error:
        response["model_error"] = model_load_error
    return response

def colorize_pil(image: Image.Image) -> Image.Image:
    """Run model prediction and return colorized image"""
    if learn is None:
        raise RuntimeError("Model not loaded")
    if image.mode != "RGB":
        image = image.convert("RGB")
    pred = learn.predict(image)
    # Handle different return types from FastAI
    if isinstance(pred, (list, tuple)):
        colorized = pred[0] if len(pred) > 0 else image
    else:
        colorized = pred
    
    # Ensure we have a PIL Image
    if not isinstance(colorized, Image.Image):
        if isinstance(colorized, torch.Tensor):
            # Convert tensor to PIL
            if colorized.dim() == 4:
                colorized = colorized[0]
            if colorized.dim() == 3:
                colorized = colorized.permute(1, 2, 0).cpu()
                if colorized.dtype in (torch.float32, torch.float16):
                    colorized = torch.clamp(colorized, 0, 1)
                    colorized = (colorized * 255).byte()
                colorized = Image.fromarray(colorized.numpy(), 'RGB')
            else:
                raise ValueError(f"Unexpected tensor shape: {colorized.shape}")
        else:
            raise ValueError(f"Unexpected prediction type: {type(colorized)}")
    
    if colorized.mode != "RGB":
        colorized = colorized.convert("RGB")
    
    return colorized

@app.post("/colorize")
async def colorize_api(
    file: UploadFile = File(...),
    verified: bool = Depends(verify_request)
):
    """
    Upload a black & white image -> returns colorized image.
    Requires Firebase authentication unless DISABLE_AUTH=true
    """
    if learn is None:
        raise HTTPException(status_code=503, detail="Colorization model not loaded")
    
    if not file.content_type or not file.content_type.startswith("image/"):
        raise HTTPException(status_code=400, detail="File must be an image")
    
    try:
        img_bytes = await file.read()
        image = Image.open(io.BytesIO(img_bytes)).convert("RGB")
        
        logger.info("Colorizing image...")
        colorized = colorize_pil(image)
        
        output_filename = f"{uuid.uuid4()}.png"
        output_path = RESULT_DIR / output_filename
        colorized.save(output_path, "PNG")
        
        logger.info("Colorized image saved: %s", output_filename)
        
        # Return the image file
        return FileResponse(
            output_path,
            media_type="image/png",
            filename=f"colorized_{output_filename}"
        )
    except Exception as e:
        logger.error("Error colorizing image: %s", str(e))
        raise HTTPException(status_code=500, detail=f"Error colorizing image: {str(e)}")

# ==========================================================
# Gradio Interface (for Space UI)
# ==========================================================
def gradio_colorize(image):
    """Gradio colorization function"""
    if image is None:
        return None
    try:
        if learn is None:
            return None
        return colorize_pil(image)
    except Exception as e:
        logger.error("Gradio colorization error: %s", str(e))
        return None

title = "🎨 FastAI GAN Image Colorizer"
description = "Upload a black & white photo to generate a colorized version using the FastAI GAN model."

iface = gr.Interface(
    fn=gradio_colorize,
    inputs=gr.Image(type="pil", label="Upload B&W Image"),
    outputs=gr.Image(type="pil", label="Colorized Image"),
    title=title,
    description=description,
)

# Mount Gradio app at root (this will be the Space UI)
# Note: This will override the root endpoint, so use /api for API info
app = gr.mount_gradio_app(app, iface, path="/")

# ==========================================================
# Run Server
# ==========================================================
if __name__ == "__main__":
    port = int(os.getenv("PORT", "7860"))
    uvicorn.run(app, host="0.0.0.0", port=port)