src/train.py

# /// script
# requires-python = ">=3.9"
# dependencies = [
#     "python-crfsuite>=0.9.11",
#     "crfsuite>=0.3.0",
#     "datasets>=4.5.0",
#     "scikit-learn>=1.6.1",
#     "click>=8.0.0",
#     "psutil>=5.9.0",
#     "pyyaml>=6.0.0",
#     "underthesea>=6.8.0",
#     "underthesea-core @ file:///home/claude-user/projects/workspace_underthesea/underthesea-core-dev/extensions/underthesea_core/target/wheels/underthesea_core-1.0.7-cp312-cp312-manylinux_2_34_x86_64.whl",
# ]
# ///
"""
Training script for Vietnamese POS Tagger (TRE-1).

Supports 3 CRF trainers:
- python-crfsuite: Original Python bindings to CRFsuite
- crfsuite-rs: Rust bindings to CRFsuite (pip install crfsuite)
- underthesea-core: Underthesea's native Rust CRF implementation

Models are saved to: models/pos_tagger/{version}/model.crfsuite

Usage:
    uv run scripts/train.py
    uv run scripts/train.py --trainer crfsuite-rs
    uv run scripts/train.py --trainer underthesea-core
    uv run scripts/train.py --version v1.1.0
    uv run scripts/train.py --wandb
    uv run scripts/train.py --c1 0.5 --c2 0.01 --max-iterations 200
"""

import platform
import re
import time
from abc import ABC, abstractmethod
from datetime import datetime
from pathlib import Path

import click
import psutil
import yaml
from datasets import load_dataset
from sklearn.metrics import accuracy_score, classification_report


# Get project root directory
PROJECT_ROOT = Path(__file__).parent.parent

# Available trainers
TRAINERS = ["python-crfsuite", "crfsuite-rs", "underthesea-core"]


def get_hardware_info():
    """Collect hardware and system information."""
    info = {
        "platform": platform.system(),
        "platform_release": platform.release(),
        "architecture": platform.machine(),
        "python_version": platform.python_version(),
        "cpu_physical_cores": psutil.cpu_count(logical=False),
        "cpu_logical_cores": psutil.cpu_count(logical=True),
        "ram_total_gb": round(psutil.virtual_memory().total / (1024**3), 2),
    }

    try:
        if platform.system() == "Linux":
            with open("/proc/cpuinfo", "r") as f:
                for line in f:
                    if "model name" in line:
                        info["cpu_model"] = line.split(":")[1].strip()
                        break
    except Exception:
        info["cpu_model"] = "Unknown"

    return info


def format_duration(seconds):
    """Format duration in human-readable format."""
    if seconds < 60:
        return f"{seconds:.2f}s"
    elif seconds < 3600:
        minutes = int(seconds // 60)
        secs = seconds % 60
        return f"{minutes}m {secs:.2f}s"
    else:
        hours = int(seconds // 3600)
        minutes = int((seconds % 3600) // 60)
        secs = seconds % 60
        return f"{hours}h {minutes}m {secs:.2f}s"


FEATURE_TEMPLATES = [
    "T[0]", "T[0].lower", "T[0].istitle", "T[0].isupper",
    "T[0].isdigit", "T[0].isalpha", "T[0].prefix2", "T[0].prefix3",
    "T[0].suffix2", "T[0].suffix3", "T[-1]", "T[-1].lower",
    "T[-1].istitle", "T[-1].isupper", "T[-2]", "T[-2].lower",
    "T[1]", "T[1].lower", "T[1].istitle", "T[1].isupper",
    "T[2]", "T[2].lower", "T[-1,0]", "T[0,1]",
    "T[0].is_in_dict", "T[-1,0].is_in_dict", "T[0,1].is_in_dict",
]


def get_token_value(tokens, position, index):
    actual_pos = position + index
    if actual_pos < 0:
        return "__BOS__"
    elif actual_pos >= len(tokens):
        return "__EOS__"
    return tokens[actual_pos]


def apply_attribute(value, attribute, dictionary=None):
    if value in ("__BOS__", "__EOS__"):
        return value
    if attribute is None:
        return value
    elif attribute == "lower":
        return value.lower()
    elif attribute == "upper":
        return value.upper()
    elif attribute == "istitle":
        return str(value.istitle())
    elif attribute == "isupper":
        return str(value.isupper())
    elif attribute == "islower":
        return str(value.islower())
    elif attribute == "isdigit":
        return str(value.isdigit())
    elif attribute == "isalpha":
        return str(value.isalpha())
    elif attribute == "is_in_dict":
        return str(value in dictionary) if dictionary else "False"
    elif attribute.startswith("prefix"):
        n = int(attribute[6:]) if len(attribute) > 6 else 2
        return value[:n] if len(value) >= n else value
    elif attribute.startswith("suffix"):
        n = int(attribute[6:]) if len(attribute) > 6 else 2
        return value[-n:] if len(value) >= n else value
    return value


def parse_template(template):
    match = re.match(r"T\[([^\]]+)\](?:\.(\w+))?", template)
    if not match:
        return None, None
    indices_str = match.group(1)
    attribute = match.group(2)
    indices = [int(i.strip()) for i in indices_str.split(",")]
    return indices, attribute


def extract_features(tokens, position, dictionary=None):
    features = {}
    for template in FEATURE_TEMPLATES:
        indices, attribute = parse_template(template)
        if indices is None:
            continue
        if len(indices) == 1:
            value = get_token_value(tokens, position, indices[0])
            value = apply_attribute(value, attribute, dictionary)
            features[template] = value
        else:
            values = [get_token_value(tokens, position, idx) for idx in indices]
            if attribute == "is_in_dict":
                combined = " ".join(values)
                features[template] = str(combined in dictionary) if dictionary else "False"
            else:
                combined = "|".join(values)
                features[template] = combined
    return features


def sentence_to_features(tokens):
    return [
        [f"{k}={v}" for k, v in extract_features(tokens, i).items()]
        for i in range(len(tokens))
    ]


# ============================================================================
# Trainer Abstraction
# ============================================================================

class CRFTrainerBase(ABC):
    """Abstract base class for CRF trainers."""

    name: str = "base"

    @abstractmethod
    def train(self, X_train, y_train, output_path, c1, c2, max_iterations, verbose=True):
        """Train the CRF model and save to output_path."""
        pass

    @abstractmethod
    def predict(self, model_path, X_test):
        """Load model and predict on test data."""
        pass


class PythonCRFSuiteTrainer(CRFTrainerBase):
    """Trainer using python-crfsuite (original Python bindings)."""

    name = "python-crfsuite"

    def train(self, X_train, y_train, output_path, c1, c2, max_iterations, verbose=True):
        import pycrfsuite

        trainer = pycrfsuite.Trainer(verbose=verbose)

        for xseq, yseq in zip(X_train, y_train):
            trainer.append(xseq, yseq)

        trainer.set_params({
            "c1": c1,
            "c2": c2,
            "max_iterations": max_iterations,
            "feature.possible_transitions": True,
        })

        trainer.train(str(output_path))

    def predict(self, model_path, X_test):
        import pycrfsuite

        tagger = pycrfsuite.Tagger()
        tagger.open(str(model_path))
        return [tagger.tag(xseq) for xseq in X_test]


class CRFSuiteRsTrainer(CRFTrainerBase):
    """Trainer using crfsuite-rs (Rust bindings via pip install crfsuite)."""

    name = "crfsuite-rs"

    def train(self, X_train, y_train, output_path, c1, c2, max_iterations, verbose=True):
        import crfsuite

        trainer = crfsuite.Trainer()

        # Set parameters
        trainer.set_params({
            "c1": c1,
            "c2": c2,
            "max_iterations": max_iterations,
            "feature.possible_transitions": True,
        })

        # Add training data
        for xseq, yseq in zip(X_train, y_train):
            trainer.append(xseq, yseq)

        # Train
        trainer.train(str(output_path))

    def predict(self, model_path, X_test):
        import crfsuite

        model = crfsuite.Model(str(model_path))
        return [model.tag(xseq) for xseq in X_test]


class UndertheseaCoreTrainer(CRFTrainerBase):
    """Trainer using underthesea-core native Rust CRF with LBFGS optimization.

    This trainer uses the native underthesea-core Rust CRF implementation
    with L-BFGS optimization, matching CRFsuite performance.

    Requires building underthesea-core from source:
        cd ~/projects/workspace_underthesea/underthesea-core-dev/extensions/underthesea_core
        uv venv && source .venv/bin/activate
        uv pip install maturin
        maturin develop --release
    """

    name = "underthesea-core"

    def _check_trainer_import(self):
        """Check if CRFTrainer is available."""
        try:
            from underthesea_core import CRFTrainer
            return CRFTrainer
        except ImportError:
            pass

        try:
            from underthesea_core.underthesea_core import CRFTrainer
            return CRFTrainer
        except ImportError:
            pass

        raise ImportError(
            "CRFTrainer not available in underthesea_core.\n"
            "Build from source with LBFGS support:\n"
            "  cd ~/projects/workspace_underthesea/underthesea-core-dev/extensions/underthesea_core\n"
            "  source .venv/bin/activate && maturin develop --release"
        )

    def _check_tagger_import(self):
        """Check if CRFModel and CRFTagger are available."""
        try:
            from underthesea_core import CRFModel, CRFTagger
            return CRFModel, CRFTagger
        except ImportError:
            pass

        try:
            from underthesea_core.underthesea_core import CRFModel, CRFTagger
            return CRFModel, CRFTagger
        except ImportError:
            pass

        raise ImportError("CRFModel/CRFTagger not available in underthesea_core")

    def train(self, X_train, y_train, output_path, c1, c2, max_iterations, verbose=True):
        CRFTrainer = self._check_trainer_import()

        # Use LBFGS (default, fast)
        trainer = CRFTrainer(
            loss_function="lbfgs",
            l1_penalty=c1,
            l2_penalty=c2,
            max_iterations=max_iterations,
            verbose=1 if verbose else 0,
        )

        # Train
        model = trainer.train(X_train, y_train)

        # Save model
        output_path_str = str(output_path)
        if output_path_str.endswith('.crfsuite'):
            output_path_str = output_path_str.replace('.crfsuite', '.crf')
        model.save(output_path_str)

        # Store the actual path for prediction
        self._model_path = output_path_str

    def predict(self, model_path, X_test):
        CRFModel, CRFTagger = self._check_tagger_import()

        # Use the actual saved path if available
        model_path_str = str(model_path)
        if hasattr(self, '_model_path'):
            model_path_str = self._model_path
        elif model_path_str.endswith('.crfsuite'):
            model_path_str = model_path_str.replace('.crfsuite', '.crf')

        model = CRFModel.load(model_path_str)
        tagger = CRFTagger.from_model(model)
        return [tagger.tag(xseq) for xseq in X_test]


def get_trainer(trainer_name: str) -> CRFTrainerBase:
    """Get trainer instance by name."""
    trainers = {
        "python-crfsuite": PythonCRFSuiteTrainer,
        "crfsuite-rs": CRFSuiteRsTrainer,
        "underthesea-core": UndertheseaCoreTrainer,
    }
    if trainer_name not in trainers:
        raise ValueError(f"Unknown trainer: {trainer_name}. Available: {list(trainers.keys())}")
    return trainers[trainer_name]()


# ============================================================================
# Data Loading
# ============================================================================

def load_data():
    click.echo("Loading UDD-1 dataset...")
    dataset = load_dataset("undertheseanlp/UDD-1")

    def extract_sentences(split):
        sentences = []
        for item in split:
            tokens = item["tokens"]
            tags = item["upos"]
            if tokens and tags:
                sentences.append((tokens, tags))
        return sentences

    train_data = extract_sentences(dataset["train"])
    val_data = extract_sentences(dataset["validation"])
    test_data = extract_sentences(dataset["test"])

    click.echo(f"Loaded {len(train_data)} train, {len(val_data)} val, {len(test_data)} test sentences")
    return train_data, val_data, test_data


def save_metadata(output_dir, version, trainer_name, train_data, val_data, test_data, c1, c2, max_iterations, accuracy, hw_info, training_time):
    """Save model metadata to YAML file."""
    metadata = {
        "model": {
            "name": "Vietnamese POS Tagger",
            "version": version,
            "type": "CRF (Conditional Random Field)",
            "framework": trainer_name,
        },
        "training": {
            "dataset": "undertheseanlp/UDD-1",
            "train_sentences": len(train_data),
            "val_sentences": len(val_data),
            "test_sentences": len(test_data),
            "hyperparameters": {
                "c1": c1,
                "c2": c2,
                "max_iterations": max_iterations,
            },
            "duration_seconds": round(training_time, 2),
        },
        "performance": {
            "test_accuracy": round(accuracy, 4),
        },
        "environment": {
            "platform": hw_info["platform"],
            "cpu_model": hw_info.get("cpu_model", "Unknown"),
            "python_version": hw_info["python_version"],
        },
        "files": {
            "model": "model.crfsuite",
            "config": "../../../configs/pos_tagger.yaml",
        },
        "created_at": datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
        "author": "undertheseanlp",
    }

    metadata_path = output_dir / "metadata.yaml"
    with open(metadata_path, "w") as f:
        yaml.dump(metadata, f, default_flow_style=False, allow_unicode=True, sort_keys=False)
    click.echo(f"Metadata saved to {metadata_path}")


def get_default_version():
    """Generate timestamp-based version."""
    return datetime.now().strftime("%Y%m%d_%H%M%S")


@click.command()
@click.option(
    "--trainer", "-t",
    type=click.Choice(TRAINERS),
    default="python-crfsuite",
    help="CRF trainer to use",
    show_default=True,
)
@click.option(
    "--version", "-v",
    default=None,
    help="Model version (default: timestamp, e.g., 20260131_154530)",
)
@click.option(
    "--output", "-o",
    default=None,
    help="Custom output path (overrides version-based path)",
)
@click.option(
    "--c1",
    default=1.0,
    type=float,
    help="L1 regularization coefficient",
    show_default=True,
)
@click.option(
    "--c2",
    default=0.001,
    type=float,
    help="L2 regularization coefficient",
    show_default=True,
)
@click.option(
    "--max-iterations",
    default=100,
    type=int,
    help="Maximum training iterations",
    show_default=True,
)
@click.option(
    "--wandb/--no-wandb",
    default=False,
    help="Enable Weights & Biases logging",
)
def train(trainer, version, output, c1, c2, max_iterations, wandb):
    """Train Vietnamese POS Tagger using CRF on UDD-1 dataset."""
    total_start_time = time.time()
    start_datetime = datetime.now()

    # Get trainer
    crf_trainer = get_trainer(trainer)

    # Use timestamp version if not specified
    if version is None:
        version = get_default_version()

    # Determine output directory
    if output:
        output_path = Path(output)
        output_dir = output_path.parent
    else:
        output_dir = PROJECT_ROOT / "models" / "pos_tagger" / version
        output_dir.mkdir(parents=True, exist_ok=True)
        output_path = output_dir / "model.crfsuite"

    # Collect hardware info
    hw_info = get_hardware_info()

    click.echo("=" * 60)
    click.echo(f"POS Tagger Training - {version}")
    click.echo("=" * 60)
    click.echo(f"Trainer: {trainer}")
    click.echo(f"Platform: {hw_info['platform']}")
    click.echo(f"CPU: {hw_info.get('cpu_model', 'Unknown')}")
    click.echo(f"Output: {output_path}")
    click.echo(f"Started: {start_datetime.strftime('%Y-%m-%d %H:%M:%S')}")
    click.echo("=" * 60)

    train_data, val_data, test_data = load_data()

    click.echo(f"\nTrain: {len(train_data)} sentences")
    click.echo(f"Validation: {len(val_data)} sentences")
    click.echo(f"Test: {len(test_data)} sentences")

    # Prepare training data
    click.echo("\nExtracting features...")
    feature_start = time.time()
    X_train = [sentence_to_features(tokens) for tokens, _ in train_data]
    y_train = [tags for _, tags in train_data]
    click.echo(f"Feature extraction: {format_duration(time.time() - feature_start)}")

    # Train CRF
    click.echo(f"\nTraining CRF model with {trainer}...")

    use_wandb = wandb
    if use_wandb:
        try:
            import wandb as wb
            wb.init(project="pos-tagger-vietnamese", name=f"crf-{trainer}-{version}")
            wb.config.update({
                "trainer": trainer,
                "c1": c1,
                "c2": c2,
                "max_iterations": max_iterations,
                "num_features": len(FEATURE_TEMPLATES),
                "train_sentences": len(train_data),
                "val_sentences": len(val_data),
                "test_sentences": len(test_data),
                "version": version,
            })
        except ImportError:
            click.echo("wandb not installed, skipping logging", err=True)
            use_wandb = False

    crf_start = time.time()
    crf_trainer.train(X_train, y_train, output_path, c1, c2, max_iterations, verbose=True)
    crf_time = time.time() - crf_start
    click.echo(f"\nModel saved to {output_path}")
    click.echo(f"CRF training: {format_duration(crf_time)}")

    # Evaluation
    click.echo("\nEvaluating on test set...")
    X_test = [sentence_to_features(tokens) for tokens, _ in test_data]
    y_test = [tags for _, tags in test_data]

    y_pred = crf_trainer.predict(output_path, X_test)

    # Flatten for metrics
    y_test_flat = [tag for tags in y_test for tag in tags]
    y_pred_flat = [tag for tags in y_pred for tag in tags]

    accuracy = accuracy_score(y_test_flat, y_pred_flat)

    total_time = time.time() - total_start_time

    click.echo(f"\nAccuracy: {accuracy:.4f}")
    click.echo("\nClassification Report:")
    click.echo(classification_report(y_test_flat, y_pred_flat))

    # Save metadata
    if not output:
        save_metadata(output_dir, version, trainer, train_data, val_data, test_data,
                      c1, c2, max_iterations, accuracy, hw_info, total_time)

    click.echo("\n" + "=" * 60)
    click.echo("Training Summary")
    click.echo("=" * 60)
    click.echo(f"Trainer: {trainer}")
    click.echo(f"Version: {version}")
    click.echo(f"Model: {output_path}")
    click.echo(f"Accuracy: {accuracy:.4f}")
    click.echo(f"Total time: {format_duration(total_time)}")
    click.echo("=" * 60)

    if use_wandb:
        wb.log({"accuracy": accuracy})
        wb.finish()


if __name__ == "__main__":
    train()