"""
Chart2CSV extraction using Granite Vision
Extracts tabular data from chart images as CSV format
"""

import spaces
from PIL import Image
from typing import Optional
import tempfile
import os


# Global model cache
_processor = None
_model = None


def load_model():
    """Lazy-load Chart2CSV model and processor."""
    global _processor, _model

    if _processor is not None and _model is not None:
        return _processor, _model

    try:
        from transformers import AutoProcessor, AutoModelForVision2Seq
        import torch

        model_id = "ibm-granite/granite-vision-3.3-2b-chart2csv-preview"

        _processor = AutoProcessor.from_pretrained(model_id, trust_remote_code=True)

        device = "cuda" if torch.cuda.is_available() else "cpu"
        _model = AutoModelForVision2Seq.from_pretrained(
            model_id,
            trust_remote_code=True,
            torch_dtype=torch.float16 if torch.cuda.is_available() else torch.float32,
        ).to(device)

        print(f"✅ Loaded {model_id} on {device}")
        return _processor, _model

    except ImportError:
        print("⚠️ Transformers not available, using stub")
        return None, None
    except Exception as e:
        print(f"⚠️ Model load error: {e}")
        import traceback
        traceback.print_exc()
        return None, None


def _save_image_to_temp(image: Image.Image) -> str:
    """Save PIL image to temporary file and return path."""
    temp_file = tempfile.NamedTemporaryFile(suffix=".png", delete=False)
    image.save(temp_file.name)
    return temp_file.name


@spaces.GPU
def extract_csv(image: Image.Image) -> str:
    """
    Extract CSV from a chart image using Granite Vision Chart2CSV model.

    Args:
        image: PIL Image of chart/table

    Returns:
        CSV text
    """
    processor, model = load_model()

    if processor is None or model is None:
        # Stub response
        return "col1,col2,col3\nvalue1,value2,value3\nvalue4,value5,value6"

    try:
        import torch

        # Save image to temp file
        image_path = _save_image_to_temp(image)

        try:
            # Prepare conversation with chart extraction prompt
            conversation = [
                {
                    "role": "user",
                    "content": [
                        {"type": "image", "url": image_path},  # Use file path
                        {"type": "text", "text": "Extract the data from this chart as CSV format. Return only the CSV data without explanation."},
                    ],
                }
            ]

            # Apply chat template and process
            inputs = processor.apply_chat_template(
                conversation,
                add_generation_prompt=True,
                tokenize=True,
                return_dict=True,
                return_tensors="pt"
            )

            # Determine device
            device = "cuda" if torch.cuda.is_available() else "cpu"
            inputs = {k: v.to(device) for k, v in inputs.items()}

            # Generate CSV
            with torch.inference_mode():
                outputs = model.generate(**inputs, max_new_tokens=1024)

            # Decode response
            full_response = processor.decode(outputs[0], skip_special_tokens=True)

            # Extract just the CSV data (remove chat template)
            if "<|assistant|>" in full_response:
                csv_text = full_response.split("<|assistant|>")[-1].strip()
            else:
                csv_text = full_response

            return csv_text

        finally:
            # Clean up temp file
            if os.path.exists(image_path):
                try:
                    os.unlink(image_path)
                except Exception:
                    pass

    except Exception as e:
        import traceback
        traceback.print_exc()
        return f"❌ Error: {str(e)}"