import argparse
import datetime
import pathlib
import re
import uuid

MIGRATION_FILE_PATT = re.compile(
    r"^(?P<year>\d{4})(?P<month>\d{2})(?P<day>\d{2})_(?P<from>\w+)_(?P<direction>(:?up)|(:?down))_(?P<to>\w+).(?P<format>(:?sql)|(:?py))$"
)


def parse_args():
    parser = argparse.ArgumentParser(
        description="Automatically generates a new migration file for asyncpg-trek."
    )
    parser.add_argument(
        "-f", "--folder", default="migrations", help="the migration folder to check"
    )
    parser.add_argument(
        "--dry-run",
        action="store_true",
        help="whether to perform a dry run of this script",
    )
    parser.add_argument(
        "-t",
        "--type",
        choices=["sql", "py"],
        default="sql",
        help="the type of file to produce. defaults to .sql",
    )
    parser.add_argument(
        "-d",
        "--direction",
        choices=["up", "down"],
        default=None,
        help="direction of migration to generate. defaults to up & down",
    )
    parser.add_argument(
        "--preserve-env",
        default=False,
        action="store_true",
        help="whether to not modify the .env with the new revision",
    )
    return parser.parse_args()


def main():
    args = parse_args()
    migration_folder = pathlib.Path(args.folder)

    revisions = {}
    possible_unlinked = []
    for file in migration_folder.iterdir():
        if not file.is_file():
            continue

        match = MIGRATION_FILE_PATT.match(file.name)
        if not match:
            continue

        if match.group("direction") != "up":
            continue

        from_rev = match.group("from")
        to_rev = match.group("to")

        revisions[from_rev] = to_rev
        if to_rev not in revisions:
            possible_unlinked.append(to_rev)
        if from_rev in possible_unlinked:
            possible_unlinked.remove(from_rev)

    from_: str
    to = uuid.uuid4().hex[0:6]
    if len(revisions) == 0:
        from_ = "initial"
    elif (
        len(possible_unlinked) == 1
    ):  # this most likely means the lone unlinked pair remains
        from_ = possible_unlinked[0]
    else:
        keys = list(revisions.keys())
        for revision in possible_unlinked:
            if revision not in keys:
                from_ = revision
                break
        else:
            raise RuntimeError("last node in linked list not found")

    today = datetime.datetime.now()
    month = f"0{today.month}" if today.month < 10 else str(today.month)
    day = f"0{today.day}" if today.day < 10 else str(today.day)
    filename = f"{today.year}{month}{day}_{from_}_{{direction}}_{to}.{args.type}"

    directions: tuple[str, ...] = (
        (args.direction,) if args.direction is not None else ("up", "down")
    )
    for direction in directions:
        file = migration_folder / filename.format(direction=direction)

        if args.dry_run:
            print("Made file", file)
        else:
            file.touch()

    print("Done! New revision is now", to)


if __name__ == "__main__":
    main()