import argparse
import os
import sqlite3

import lmdb


def get_map_size(lmdb_path):
    data_path = os.path.join(lmdb_path, "data.mdb")
    try:
        size = os.path.getsize(data_path)
    except OSError:
        return 1048576 * 2
    return max(size * 2, 1048576 * 2)


def open_sqlite(path):
    conn = sqlite3.connect(path)
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS pixif_cache (
            post_id TEXT PRIMARY KEY,
            url TEXT
        )
        """
    )
    conn.commit()
    return conn


def upsert_rows(conn, rows):
    if not rows:
        return
    conn.executemany(
        """
        INSERT INTO pixif_cache (post_id, url)
        VALUES (?, ?)
        ON CONFLICT(post_id) DO UPDATE SET url = excluded.url
        """,
        rows,
    )


def migrate(lmdb_path, sqlite_path, batch_size):
    map_size = get_map_size(lmdb_path)
    lmdb_env = lmdb.open(
        lmdb_path,
        subdir=True,
        readonly=True,
        lock=False,
        map_size=map_size,
    )
    conn = open_sqlite(sqlite_path)

    rows = []
    with lmdb_env.begin() as txn:
        cursor = txn.cursor()
        for key, value in cursor:
            post_id = key.decode("utf-8")
            url = value.decode("utf-8") if value else ""
            rows.append((post_id, url))

            if len(rows) >= batch_size:
                with conn:
                    upsert_rows(conn, rows)
                rows.clear()

    if rows:
        with conn:
            upsert_rows(conn, rows)

    conn.close()
    lmdb_env.close()


def main():
    parser = argparse.ArgumentParser(description="Migrate LMDB cache to SQLite.")
    parser.add_argument("--lmdb", default="db", help="Path to LMDB directory.")
    parser.add_argument("--sqlite", default="db.sqlite", help="Path to SQLite file.")
    parser.add_argument("--batch-size", type=int, default=1000, help="Rows per batch insert.")
    args = parser.parse_args()

    os.chdir(os.path.dirname(os.path.abspath(__file__)))
    migrate(args.lmdb, args.sqlite, args.batch_size)


if __name__ == "__main__":
    main()