#!/usr/bin/env python3
"""Explicit task-v2 schema migration. Default is read-only; --apply backs up first."""
import argparse
import datetime
import json
from pathlib import Path
import sqlite3


def migrate(database: Path, apply: bool = False) -> dict:
    if not database.is_file():
        raise ValueError("database must already exist")
    with sqlite3.connect(database.resolve().as_uri() + ("?mode=rw" if apply else "?mode=ro"), uri=True) as db:
        if not db.execute("pragma table_info(gallery)").fetchall():
            raise ValueError("required table missing: gallery")
        duplicates = db.execute("select count(*) from (select gid from gallery group by gid having count(*)>1)").fetchone()[0]
        if duplicates:
            raise ValueError("duplicate gallery gid; reconcile before migration")
        present = bool(db.execute("pragma table_info(task_operation)").fetchall())
        result = {"apply": apply, "create_operation_table": not present}
        if not apply:
            return result
        stamp = datetime.datetime.now(datetime.timezone.utc).strftime("%Y%m%dT%H%M%S%fZ")
        backup = database.with_name(database.name + ".before-task-v2." + stamp)
        with sqlite3.connect(backup) as copy:
            db.backup(copy)
        backup.chmod(0o600)
        sql = Path(__file__).with_name("migrate_task_operation_v2.sql").read_text()
        try:
            db.executescript("BEGIN IMMEDIATE;\n" + sql + "\nCOMMIT;")
        except BaseException:
            db.rollback()
            raise
        result["backup"] = str(backup)
        result["operation_rows"] = db.execute("select count(*) from task_operation").fetchone()[0]
        return result


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("database", type=Path)
    parser.add_argument("--apply", action="store_true")
    arguments = parser.parse_args()
    print(json.dumps(migrate(arguments.database, arguments.apply), ensure_ascii=False))