# /// script
# dependencies = [
#     "sentence-transformers",
#     "torch",
#     "scikit-learn",
#     "numpy<2",
#     "polars[pyarrow]",
#     "pyarrow",
#     "huggingface_hub",
# ]
# requires-python = ">=3.10"
# ///
"""
Classify all documents in duarteocarmo/fineweb2-bagaco into 9 categories
using intfloat/multilingual-e5-small embeddings + Logistic Regression.

Usage (from repo root):
    uv run scripts/classify_bagaco.py

Requires HF_TOKEN environment variable for upload.
Resumes automatically if interrupted (skips already-classified shards).
"""

import os
import time
from concurrent.futures import ThreadPoolExecutor, as_completed
from pathlib import Path
from types import SimpleNamespace

import numpy
import polars
import pyarrow.parquet as pq
from huggingface_hub import HfApi, hf_hub_download
from sklearn.linear_model import LogisticRegression
from sklearn.metrics import classification_report
from sklearn.model_selection import train_test_split

config = SimpleNamespace(
    repo_id="duarteocarmo/fineweb2-bagaco",
    sample_file="classification_sample.parquet",
    model_name="intfloat/multilingual-e5-small",
    output_dir="./classified_output",
    download_dir="./shard_cache",
    max_chars=800,
    encode_batch_size=2048,
    download_workers=8,
    row_group_size=1024,
    random_state=42,
)

CATEGORIES = [
    "Society",
    "Arts",
    "Business",
    "Science",
    "Sports",
    "Lifestyle",
    "Health",
    "Games",
    "News",
]


def get_device() -> str:
    import torch

    if torch.cuda.is_available():
        return "cuda"
    if torch.backends.mps.is_available():
        return "mps"
    return "cpu"


def load_model(device: str):
    from sentence_transformers import SentenceTransformer

    model_kwargs = {}
    if device in ("cuda", "mps"):
        model_kwargs["torch_dtype"] = "float16"

    model = SentenceTransformer(
        config.model_name, device=device, model_kwargs=model_kwargs
    )
    print(f"Loaded {config.model_name} on {device} (fp16={device in ('cuda', 'mps')})")
    return model


def encode(model, texts: list[str]) -> numpy.ndarray:
    truncated = [t[: config.max_chars].strip() for t in texts]
    return model.encode(
        truncated, batch_size=config.encode_batch_size, show_progress_bar=False
    )


# ─── Step 1: Download classification sample ───


def download_sample() -> polars.DataFrame:
    path = hf_hub_download(
        repo_id=config.repo_id, filename=config.sample_file, repo_type="dataset"
    )
    df = polars.read_parquet(path).select(["text", "category"]).drop_nulls()
    df = df.filter(polars.col("category").is_in(CATEGORIES))
    print(f"Downloaded classification sample: {len(df)} rows")
    print(df["category"].value_counts().sort("count", descending=True))
    return df


# ─── Step 2: Train classifier (with validation) ───


def train_classifier(model, df: polars.DataFrame) -> LogisticRegression:
    texts = df["text"].to_list()
    labels = df["category"].to_list()

    train_texts, test_texts, train_labels, test_labels = train_test_split(
        texts,
        labels,
        test_size=0.20,
        random_state=config.random_state,
        stratify=labels,
    )

    print(f"\n--- Validation (train={len(train_texts)}, test={len(test_texts)}) ---")
    train_emb = encode(model=model, texts=train_texts)
    val_classifier = LogisticRegression(
        max_iter=2000, C=1.0, class_weight="balanced", random_state=config.random_state
    )
    val_classifier.fit(X=train_emb, y=train_labels)

    test_emb = encode(model=model, texts=test_texts)
    predictions = val_classifier.predict(X=test_emb)
    print(
        classification_report(y_true=test_labels, y_pred=predictions, zero_division=0)
    )

    # Retrain on full sample for production
    print(f"--- Retraining on full sample ({len(texts)} rows) ---")
    all_emb = encode(model=model, texts=texts)
    classifier = LogisticRegression(
        max_iter=2000, C=1.0, class_weight="balanced", random_state=config.random_state
    )
    classifier.fit(X=all_emb, y=labels)
    print(f"Classifier trained on {len(texts)} samples")
    return classifier


# ─── Step 3: Pre-download all shards in parallel ───


def list_shards() -> list[str]:
    api = HfApi()
    files = api.list_repo_files(repo_id=config.repo_id, repo_type="dataset")
    shards = sorted(
        [f for f in files if f.startswith("shard_") and f.endswith(".parquet")]
    )
    print(f"Found {len(shards)} shards in {config.repo_id}")
    return shards


def download_shard(shard_filename: str) -> tuple[str, str]:
    local_path = hf_hub_download(
        repo_id=config.repo_id,
        filename=shard_filename,
        repo_type="dataset",
        cache_dir=config.download_dir,
    )
    return shard_filename, local_path


def download_all_shards(shard_filenames: list[str]) -> dict[str, str]:
    """Download all shards in parallel, returns {filename: local_path}."""
    print(
        f"\nPre-downloading {len(shard_filenames)} shards with {config.download_workers} workers..."
    )
    shard_paths = {}
    t0 = time.perf_counter()

    with ThreadPoolExecutor(max_workers=config.download_workers) as executor:
        futures = {executor.submit(download_shard, f): f for f in shard_filenames}
        for future in as_completed(futures):
            filename, local_path = future.result()
            shard_paths[filename] = local_path
            done = len(shard_paths)
            if done % 10 == 0 or done == len(shard_filenames):
                elapsed = time.perf_counter() - t0
                print(
                    f"  Downloaded {done}/{len(shard_filenames)} shards ({elapsed:.1f}s)"
                )

    total = time.perf_counter() - t0
    print(f"All shards downloaded in {total:.1f}s")
    return shard_paths


# ─── Step 4: Classify shard-by-shard (from local disk) ───


def classify_shard(
    model, classifier: LogisticRegression, local_path: str, output_path: Path
) -> int:
    df = polars.read_parquet(local_path)
    texts = df["text"].to_list()
    embeddings = encode(model=model, texts=texts)
    categories = classifier.predict(X=embeddings)
    df = df.with_columns(polars.Series(name="category", values=categories.tolist()))

    table = df.to_arrow()
    pq.write_table(
        table,
        str(output_path),
        row_group_size=config.row_group_size,
        use_dictionary=False,
        compression="zstd",
        compression_level=3,
        write_statistics=False,
    )
    return len(df)


def classify_all(model, classifier: LogisticRegression):
    shards = list_shards()
    os.makedirs(config.output_dir, exist_ok=True)

    # Figure out which shards still need classification
    to_classify = []
    skipped_rows = 0
    for shard_filename in shards:
        output_path = Path(config.output_dir) / shard_filename
        if output_path.exists() and output_path.stat().st_size > 0:
            existing = polars.read_parquet(str(output_path))
            if "category" in existing.columns:
                skipped_rows += len(existing)
                print(
                    f"  SKIP {shard_filename} (already classified, {len(existing):,} rows)"
                )
                continue
        to_classify.append(shard_filename)

    if skipped_rows > 0:
        print(
            f"Resuming: {skipped_rows:,} rows already classified, {len(to_classify)} shards remaining"
        )

    if not to_classify:
        print("All shards already classified!")
        return

    # Pre-download remaining shards
    shard_paths = download_all_shards(shard_filenames=to_classify)

    # Classify from local disk
    total_rows = skipped_rows
    total_time = 0.0

    for i, shard_filename in enumerate(to_classify):
        output_path = Path(config.output_dir) / shard_filename
        local_path = shard_paths[shard_filename]

        t0 = time.perf_counter()
        n_rows = classify_shard(
            model=model,
            classifier=classifier,
            local_path=local_path,
            output_path=output_path,
        )
        dt = time.perf_counter() - t0
        total_rows += n_rows
        total_time += dt
        throughput = n_rows / dt if dt > 0 else 0
        avg_throughput = (
            (total_rows - skipped_rows) / total_time if total_time > 0 else 0
        )

        print(
            f"[{i + 1}/{len(to_classify)}] {shard_filename}: {n_rows:,} rows in {dt:.1f}s "
            f"({throughput:,.0f} samp/s) | total: {total_rows:,} rows, avg {avg_throughput:,.0f} samp/s"
        )

    print(f"\nClassification complete: {total_rows:,} total rows in {total_time:.1f}s")


# ─── Step 5: Upload ───


def upload():
    token = os.getenv("HF_TOKEN")
    assert token is not None, "HF_TOKEN environment variable not set."
    api = HfApi(token=token)

    import shutil

    sample_path = hf_hub_download(
        repo_id=config.repo_id, filename=config.sample_file, repo_type="dataset"
    )
    shutil.copy2(sample_path, os.path.join(config.output_dir, config.sample_file))

    api.upload_large_folder(
        folder_path=config.output_dir,
        repo_id=config.repo_id,
        repo_type="dataset",
    )
    print(f"Uploaded to {config.repo_id}")


def main():
    device = get_device()
    print(f"Device: {device}")

    sample_df = download_sample()
    model = load_model(device=device)
    classifier = train_classifier(model=model, df=sample_df)
    classify_all(model=model, classifier=classifier)
    upload()


if __name__ == "__main__":
    main()
    os._exit(0)