from __future__ import annotations

import hashlib
import sqlite3
from pathlib import Path

from .connection import DEFAULT_DATABASE_PATH, connect_database


MIGRATIONS_DIR = Path(__file__).resolve().parents[1] / "migrations"


def _migration_checksum(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as fh:
        for chunk in iter(lambda: fh.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def _ensure_migrations_table(conn: sqlite3.Connection) -> None:
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS cracklab_migrations (
            id TEXT PRIMARY KEY,
            checksum TEXT NOT NULL,
            applied_at TEXT NOT NULL
        )
        """
    )


def _load_applied_migrations(
    conn: sqlite3.Connection,
) -> dict[str, tuple[str, str]]:
    rows = conn.execute(
        """
        SELECT id, checksum, applied_at
        FROM cracklab_migrations
        """
    ).fetchall()

    return {
        migration_id: (checksum, applied_at)
        for migration_id, checksum, applied_at in rows
    }


def _migration_files(migrations_dir: Path) -> list[Path]:
    return sorted(
        path
        for path in migrations_dir.glob("*.sql")
        if path.is_file()
    )


def migrate_database(
    path: Path | None = None,
    migrations_dir: Path | None = None,
) -> list[str]:
    conn = connect_database(path)

    try:
        _ensure_migrations_table(conn)
        conn.commit()

        applied = _load_applied_migrations(conn)
        migration_directory = migrations_dir or MIGRATIONS_DIR
        migrations = _migration_files(migration_directory)
        newly_applied: list[str] = []

        for migration_path in migrations:
            migration_id = migration_path.name
            checksum = _migration_checksum(migration_path)

            if migration_id in applied:
                stored_checksum, _ = applied[migration_id]

                if stored_checksum != checksum:
                    raise RuntimeError(
                        f"Migration checksum mismatch: {migration_id}"
                    )

                continue

            sql = migration_path.read_text(encoding="utf-8")

            transaction_sql = f"""
BEGIN;
{sql}
INSERT INTO cracklab_migrations (
    id,
    checksum,
    applied_at
)
VALUES (
    '{migration_id.replace("'", "''")}',
    '{checksum}',
    strftime('%Y-%m-%dT%H:%M:%fZ', 'now')
);
COMMIT;
"""

            try:
                conn.executescript(transaction_sql)
            except Exception:
                conn.rollback()
                raise

            applied[migration_id] = (
                checksum,
                "",
            )
            newly_applied.append(migration_id)

        return newly_applied

    finally:
        conn.close()


def main() -> int:
    applied = migrate_database(DEFAULT_DATABASE_PATH)

    for migration_id in applied:
        print(migration_id)

    return 0


if __name__ == "__main__":
    raise SystemExit(main())