"""Checksum-verified exact name/alias lookup; standard library only.

Usage: python3 example.py taxonomy.json PostgreSQL
"""
import hashlib
import json
import sys
from pathlib import Path


def lookup(path, query):
    raw = path.read_bytes()
    expected = Path(str(path) + ".sha256").read_text().split()[0]
    if hashlib.sha256(raw).hexdigest() != expected:
        raise ValueError("Dataset checksum mismatch")
    release = json.loads(raw)
    categories = {row["id"]: row["name"] for row in release["categories"]}
    matches = []
    for row in release["technologies"]:
        candidates = [row["name"], *row.get("aliases", [])]
        if any(query.casefold() == name.casefold() for name in candidates):
            matches.append({
                "canonical_id": row["canonical_id"],
                "name": row["name"],
                "requires_context": row["requires_context"],
                "categories": [categories[k] for k in row.get("category_ids", [])],
            })
    return {"release_version": release["taxonomy_version"], "query": query, "candidates": matches}


if __name__ == "__main__":
    if len(sys.argv) != 3:
        raise SystemExit("Usage: python3 example.py taxonomy.json 'technology name'")
    print(json.dumps(lookup(Path(sys.argv[1]), sys.argv[2]), ensure_ascii=False, indent=2))