# Author: Simon-Pierre Boucher — simon-pierre.boucher@uqo.ca
"""I/O helpers: read-only SQLite access, parquet layers, manifests."""
from __future__ import annotations

import hashlib
import json
import sqlite3
from datetime import datetime, timezone
from pathlib import Path

import polars as pl


def sha256_file(path: Path, chunk: int = 1 << 24) -> str:
    h = hashlib.sha256()
    with open(path, "rb") as f:
        while True:
            b = f.read(chunk)
            if not b:
                break
            h.update(b)
    return h.hexdigest()


def sqlite_ro(path: Path) -> sqlite3.Connection:
    """Open a SQLite file strictly read-only (URI mode)."""
    return sqlite3.connect(f"file:{path}?mode=ro", uri=True)


def query(con: sqlite3.Connection, sql: str) -> pl.DataFrame:
    return pl.read_database(sql, con, infer_schema_length=None)


def write_manifest(path: Path, payload: dict) -> None:
    payload = {"written_utc": datetime.now(timezone.utc).isoformat(timespec="seconds"), **payload}
    path.write_text(json.dumps(payload, indent=2, ensure_ascii=False, default=str))


def read_manifest(path: Path) -> dict:
    return json.loads(path.read_text())