"""
Component 2 verification script.

This script:
1) Trains tokenizer on a tiny sample file.
2) Saves tokenizer.
3) Loads tokenizer back.
4) Encodes and decodes a sample.
"""

from __future__ import annotations

import sys
from pathlib import Path

# This makes "src" imports work when script is run from project root.
PROJECT_ROOT = Path(__file__).resolve().parents[1]
if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

from src.tokenizer.code_tokenizer import CodeTokenizer


def main() -> None:
    sample_file = Path("data/external/component2_tokenizer_sample.jsonl")
    output_dir = Path("artifacts/tokenizer/code_tokenizer_v1")

    if not sample_file.exists():
        print("Verification failed.")
        print(f"Missing sample file: {sample_file}")
        print("Fix suggestion: ensure Component 2 sample file exists and run again.")
        raise SystemExit(1)

    # Train tokenizer from sample file via script-like path.
    from scripts.train_code_tokenizer import stream_jsonl_samples  # local import on purpose

    tokenizer = CodeTokenizer()
    tokenizer.train(stream_jsonl_samples(sample_file, tokenizer))
    tokenizer.save(str(output_dir))

    loaded = CodeTokenizer.load(str(output_dir))
    sample = loaded.format_training_sample(
        prompt="Write Python function that squares a number.",
        code="def square(x):\n    return x * x",
        language="python",
    )
    token_ids = loaded.encode(sample)
    decoded = loaded.decode(token_ids)

    print("=== Component 2 Verification ===")
    print(f"Tokenizer saved to: {output_dir}")
    print(f"Encoded token count: {len(token_ids)}")
    print("First 25 token IDs:", token_ids[:25])
    print("Decoded preview:")
    print(decoded[:300])
    print("")
    print("Component 2 tokenizer verification passed.")


if __name__ == "__main__":
    try:
        main()
    except Exception as exc:
        print("Verification failed.")
        print(f"What went wrong: {exc}")
        print("Fix suggestion: activate .venv and rerun this script.")
        raise SystemExit(1)