from __future__ import annotations

import sqlite3
from pathlib import Path

THIS_FILE = Path(__file__).resolve()
PKG_DIR = THIS_FILE.parent
SCHEMA_DIR = PKG_DIR / "schema"


def _ensure_migrations_table(conn: sqlite3.Connection) -> None:
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS migrations (
          id INTEGER PRIMARY KEY,
          name TEXT NOT NULL UNIQUE,
          applied_at TEXT NOT NULL DEFAULT (datetime('now'))
        );
        """
    )


def _applied_migrations(conn: sqlite3.Connection) -> set[str]:
    _ensure_migrations_table(conn)
    rows = conn.execute("SELECT name FROM migrations;").fetchall()
    names: set[str] = set()
    for row in rows:
        try:
            names.add(row["name"])
        except Exception:
            names.add(row[0])
    return names


def _migration_files() -> list[Path]:
    if not SCHEMA_DIR.exists():
        return []
    files = [p for p in SCHEMA_DIR.iterdir() if p.is_file() and p.suffix == ".sql"]
    files.sort(key=lambda p: p.name)
    return files


def migrate(conn: sqlite3.Connection) -> None:
    applied = _applied_migrations(conn)
    for path in _migration_files():
        name = path.name
        if name in applied:
            continue

        sql = path.read_text(encoding="utf-8")
        conn.executescript(sql)
        conn.execute("INSERT INTO migrations (name) VALUES (?);", (name,))