#!/usr/bin/env python3

import sqlite3
import argparse


def main(main_db, merged_db):
    print(f"Merging {merged_db} into {main_db}")
    connection = sqlite3.connect(main_db)
    connection.row_factory = sqlite3.Row
    connection.text_factory = bytes

    cursor = connection.cursor()
    cursor.execute("ATTACH ? AS merged_db", (merged_db,))
    print("Gathering database statistics:")

    cursor.execute("SELECT count(*) from merged_db.torrents")
    total_merged = cursor.fetchone()[0]
    cursor.execute(
        "SELECT name FROM pragma_table_info('files') "
        "WHERE name not in ('id', 'torrent_id')"
    )
    remaining_file_colums = [row[0].decode() for row in cursor]
    cursor.execute(
        "SELECT name FROM pragma_table_info('torrents')"
        "WHERE name not in ('id')"
    )
    remaining_torrent_colums = [row[0].decode() for row in cursor]

    print(f"{total_merged} torrents to merge.")

    insert_files_statement = (
        f"INSERT INTO files (torrent_id, {','.join(remaining_file_colums)}) "
        f"SELECT ?, {','.join(remaining_file_colums)} "
        f"FROM merged_db.files WHERE torrent_id = ?"
    )
    insert_torrents_statement = (
        f"INSERT INTO torrents ({','.join(remaining_torrent_colums)})"
        f"VALUES ({','.join('?' * len(remaining_torrent_colums))})"
    )
    failed_count = 0

    cursor.execute("BEGIN")
    merged = cursor.execute("SELECT * FROM merged_db.torrents")
    for i, row in enumerate(merged):
        try:
            torrent_merge = connection.execute(
                insert_torrents_statement, (*row[1:],))
            # Now merge files
            connection.execute(
                insert_files_statement, (torrent_merge.lastrowid, row["id"]))
        except sqlite3.IntegrityError:
            failed_count += 1

    print("Comitting… ", end="")
    connection.commit()
    print("OK."
          f"{total_merged} torrents processed.",
          f"{total_merged - failed_count} new torrents added.",
          sep="\n")
    connection.close()


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Tool to merge magnetico DBs")
    parser.add_argument("main", type=str,
                        help="main dabatase")
    parser.add_argument("merge", type=str,
                        help="dabatase to merge into main")
    args = parser.parse_args()
    main(args.main, args.merge)