#!/usr/bin/env python3
# /// script
# requires-python = ">=3.10"
# dependencies = [
#     "vllm>=0.6.6",
#     "transformers",
#     "torch",
#     "datasets",
#     "huggingface-hub[hf_transfer]",
# ]
# ///

"""
Classify text columns in Hugging Face datasets using vLLM with structured outputs.

This script provides efficient GPU-based classification with guaranteed valid outputs,
optimized for running on HF Jobs.

Example:
    uv run classify-dataset.py \\
        --input-dataset imdb \\
        --column text \\
        --labels "positive,negative" \\
        --output-dataset user/imdb-classified

HF Jobs example:
    hfjobs run --flavor a10 uv run classify-dataset.py \\
        --input-dataset user/emails \\
        --column content \\
        --labels "spam,ham" \\
        --output-dataset user/emails-classified \\
        --prompt-style reasoning
"""

import argparse
import logging
import os
import sys
from typing import List, Dict, Any, Optional

import torch
from datasets import load_dataset, Dataset
from huggingface_hub import HfApi
from vllm import LLM, SamplingParams
from vllm.sampling_params import GuidedDecodingParams

# Default model - SmolLM3 for good balance of speed and quality
DEFAULT_MODEL = "HuggingFaceTB/SmolLM3-3B"

# Prompt styles for classification
PROMPT_STYLES = {
    "simple": """Classify this text as one of: {labels}

Text: {text}

Label:""",
    
    "detailed": """Task: Classify the following text into EXACTLY ONE of these categories.
Available categories: {labels}

Text to classify:
{text}

Category:""",
    
    "reasoning": """Analyze the following text and determine which category it belongs to.
Available categories: {labels}

Text to analyze:
{text}

Brief analysis: Let me examine the key aspects of this text.
Category:""",
}

# Minimum text length for valid classification
MIN_TEXT_LENGTH = 3

# Maximum text length (in characters) to avoid context overflow
MAX_TEXT_LENGTH = 4000

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


def parse_args():
    parser = argparse.ArgumentParser(
        description="Classify text in HuggingFace datasets using vLLM with structured outputs",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=__doc__
    )
    
    # Required arguments
    parser.add_argument(
        "--input-dataset",
        type=str,
        required=True,
        help="Input dataset ID on Hugging Face Hub"
    )
    parser.add_argument(
        "--column",
        type=str,
        required=True,
        help="Name of the text column to classify"
    )
    parser.add_argument(
        "--labels",
        type=str,
        required=True,
        help="Comma-separated list of classification labels (e.g., 'positive,negative')"
    )
    parser.add_argument(
        "--output-dataset",
        type=str,
        required=True,
        help="Output dataset ID on Hugging Face Hub"
    )
    
    # Optional arguments
    parser.add_argument(
        "--model",
        type=str,
        default=DEFAULT_MODEL,
        help=f"Model to use for classification (default: {DEFAULT_MODEL})"
    )
    # Removed --batch-size argument as vLLM handles batching internally
    parser.add_argument(
        "--prompt-style",
        type=str,
        choices=list(PROMPT_STYLES.keys()),
        default="simple",
        help="Prompt style to use (default: simple)"
    )
    parser.add_argument(
        "--max-samples",
        type=int,
        default=None,
        help="Maximum number of samples to process (for testing)"
    )
    parser.add_argument(
        "--hf-token",
        type=str,
        default=os.environ.get("HF_TOKEN"),
        help="Hugging Face API token (default: HF_TOKEN env var)"
    )
    parser.add_argument(
        "--split",
        type=str,
        default="train",
        help="Dataset split to process (default: train)"
    )
    parser.add_argument(
        "--temperature",
        type=float,
        default=0.1,
        help="Temperature for generation (default: 0.1)"
    )
    parser.add_argument(
        "--max-tokens",
        type=int,
        default=50,
        help="Maximum tokens to generate (default: 50)"
    )
    parser.add_argument(
        "--guided-backend",
        type=str,
        default="outlines",
        help="Guided decoding backend (default: outlines)"
    )
    
    return parser.parse_args()


def preprocess_text(text: str) -> str:
    """Preprocess text for classification."""
    if not text or not isinstance(text, str):
        return ""
    
    # Strip whitespace
    text = text.strip()
    
    # Truncate if too long
    if len(text) > MAX_TEXT_LENGTH:
        text = text[:MAX_TEXT_LENGTH] + "..."
        
    return text


def validate_text(text: str) -> bool:
    """Check if text is valid for classification."""
    if not text or len(text) < MIN_TEXT_LENGTH:
        return False
    return True


def prepare_prompts(
    texts: List[str],
    labels: List[str],
    prompt_template: str
) -> tuple[List[str], List[int]]:
    """Prepare prompts for classification, filtering invalid texts."""
    prompts = []
    valid_indices = []
    
    for i, text in enumerate(texts):
        processed_text = preprocess_text(text)
        if validate_text(processed_text):
            prompt = prompt_template.format(
                labels=", ".join(labels),
                text=processed_text
            )
            prompts.append(prompt)
            valid_indices.append(i)
    
    return prompts, valid_indices


def main():
    args = parse_args()
    
    # Check CUDA availability
    if not torch.cuda.is_available():
        logger.error("CUDA is not available. This script requires a GPU.")
        logger.error("Please run on a machine with GPU support or use HF Jobs.")
        sys.exit(1)
    
    logger.info(f"CUDA available. Using device: {torch.cuda.get_device_name(0)}")
    
    # Parse and validate labels
    labels = [label.strip() for label in args.labels.split(",")]
    if len(labels) < 2:
        logger.error("At least two labels are required for classification.")
        sys.exit(1)
    logger.info(f"Classification labels: {labels}")
    
    # Load dataset
    logger.info(f"Loading dataset: {args.input_dataset}")
    try:
        dataset = load_dataset(args.input_dataset, split=args.split)
        
        # Limit samples if specified
        if args.max_samples:
            dataset = dataset.select(range(min(args.max_samples, len(dataset))))
            logger.info(f"Limited dataset to {len(dataset)} samples")
        
        logger.info(f"Loaded {len(dataset)} samples from split '{args.split}'")
    except Exception as e:
        logger.error(f"Failed to load dataset: {e}")
        sys.exit(1)
    
    # Verify column exists
    if args.column not in dataset.column_names:
        logger.error(f"Column '{args.column}' not found in dataset.")
        logger.error(f"Available columns: {dataset.column_names}")
        sys.exit(1)
    
    # Extract texts
    texts = dataset[args.column]
    
    # Initialize vLLM
    logger.info(f"Initializing vLLM with model: {args.model}")
    logger.info(f"Using guided decoding backend: {args.guided_backend}")
    try:
        llm = LLM(
            model=args.model,
            trust_remote_code=True,
            dtype="auto",
            gpu_memory_utilization=0.95,
            guided_decoding_backend=args.guided_backend,
        )
    except Exception as e:
        logger.error(f"Failed to initialize vLLM: {e}")
        sys.exit(1)
    
    # Set up guided decoding parameters
    guided_params = GuidedDecodingParams(choice=labels)
    
    # Set up sampling parameters with structured output
    sampling_params = SamplingParams(
        guided_decoding=guided_params,
        temperature=args.temperature,
        max_tokens=args.max_tokens,
    )
    
    # Get prompt template
    prompt_template = PROMPT_STYLES[args.prompt_style]
    logger.info(f"Using prompt style '{args.prompt_style}'")
    logger.info("Using structured output with guided_choice - outputs guaranteed to be valid labels")
    
    # Prepare all prompts
    logger.info("Preparing prompts for classification...")
    all_prompts, valid_indices = prepare_prompts(texts, labels, prompt_template)
    
    if not all_prompts:
        logger.error("No valid texts found for classification.")
        sys.exit(1)
    
    logger.info(f"Prepared {len(all_prompts)} valid prompts out of {len(texts)} texts")
    
    # Let vLLM handle batching internally
    logger.info("Starting classification (vLLM will handle batching internally)...")
    
    try:
        # Generate all classifications at once - vLLM handles batching
        outputs = llm.generate(all_prompts, sampling_params)
        
        # Map results back to original indices
        all_classifications = [None] * len(texts)
        for idx, output in enumerate(outputs):
            original_idx = valid_indices[idx]
            generated_text = output.outputs[0].text.strip()
            all_classifications[original_idx] = generated_text
        
        # Count statistics
        valid_texts = len(valid_indices)
        total_texts = len(texts)
        
    except Exception as e:
        logger.error(f"Classification failed: {e}")
        sys.exit(1)
    
    # Add classifications to dataset
    dataset = dataset.add_column("classification", all_classifications)
    
    # Calculate statistics
    none_count = total_texts - valid_texts
    if none_count > 0:
        logger.warning(f"{none_count} texts were too short or invalid for classification")
    
    # Show classification distribution
    label_counts = {label: all_classifications.count(label) for label in labels}
    logger.info("Classification distribution:")
    for label, count in label_counts.items():
        percentage = count / total_texts * 100 if total_texts > 0 else 0
        logger.info(f"  {label}: {count} ({percentage:.1f}%)")
    if none_count > 0:
        none_percentage = none_count / total_texts * 100
        logger.info(f"  Invalid/Skipped: {none_count} ({none_percentage:.1f}%)")
    
    # Log success rate
    success_rate = (valid_texts / total_texts * 100) if total_texts > 0 else 0
    logger.info(f"Classification success rate: {success_rate:.1f}%")
    
    # Save to Hub
    logger.info(f"Pushing dataset to Hub: {args.output_dataset}")
    try:
        dataset.push_to_hub(
            args.output_dataset,
            token=args.hf_token,
            commit_message=f"Add classifications using {args.model} with structured outputs"
        )
        logger.info(f"Successfully pushed to: https://huggingface.co/datasets/{args.output_dataset}")
    except Exception as e:
        logger.error(f"Failed to push to Hub: {e}")
        sys.exit(1)


if __name__ == "__main__":
    if len(sys.argv) == 1:
        print("Example HF Jobs command:")
        print("hf jobs uv run \\")
        print("  --flavor l4x1 \\")
        print("  --image vllm/vllm-openai:latest \\")
        print("  classify-dataset.py \\")
        print("  --input-dataset stanfordnlp/imdb \\")
        print("  --column text \\")
        print("  --labels 'positive,negative' \\")
        print("  --output-dataset user/imdb-classified")
        sys.exit(0)
    
    main()