import argparse
from decimal import Decimal
import sys
from typing import Union

import simfile
from simfile.dir import SimfilePack


class ChangeSyncBiasArgs:
    """Stores the command-line arguments for this script."""

    pack: str
    itg_to_null: bool
    null_to_itg: bool


def argparser():
    """Get an ArgumentParser instance for this command-line script."""
    parser = argparse.ArgumentParser(prefix_chars="-+")
    parser.add_argument("pack", type=str, help="path to the pack to modify")
    group = parser.add_mutually_exclusive_group(required=True)
    group.add_argument(
        "-9", "--itg-to-null", action="store_true", help="subtract 9ms from offsets"
    )
    group.add_argument(
        "+9", "--null-to-itg", action="store_true", help="add 9ms to offsets"
    )
    return parser


def adjust_offset(
    obj: Union[simfile.types.Simfile, simfile.ssc.SSCChart],
    delta: Decimal,
):
    """Add the delta to the simfile or SSC chart's offset, if present."""
    if obj.offset is not None:
        obj.offset = str(Decimal(obj.offset) + delta)


def change_sync_bias(simfile_path: str, args: ChangeSyncBiasArgs):
    """
    Add or subtract 9 milliseconds to the simfile's offset,
    as well as any SSC charts with their own timing data.

    This saves the updated simfile to its original location
    and writes a backup copy with a ~ appended to the filename.
    """
    # Map the +9 or -9 arg to the actual offset delta.
    #
    # We don't have to check both itg_to_null and null_to_itg
    # because the mutually exclusive & required argument group
    # ensures that exactly one of them will be True.
    delta = Decimal("-0.009" if args.itg_to_null else "+0.009")

    # You could specify output_filename here to write the updated file elsewhere
    with simfile.mutate(
        input_filename=f"{simfile_path}",
        backup_filename=f"{simfile_path}~",
    ) as sf:
        # Always adjust the simfile's offset
        adjust_offset(sf, delta)

        # Additionally try to adjust SSC charts' offsets.
        # This won't do anything unless the chart has its own timing data.
        if isinstance(sf, simfile.ssc.SSCSimfile):
            for chart in sf.charts:
                adjust_offset(chart, delta)


def main(argv):
    # Parse command-line arguments
    args = argparser().parse_args(argv[1:], namespace=ChangeSyncBiasArgs())

    # Iterate over SimfileDirectory objects from the pack
    # so that we can easily get the .sm and/or .ssc paths
    for simfile_dir in SimfilePack(args.pack).simfile_dirs():

        # Try to update whichever formats exist
        for simfile_path in [simfile_dir.sm_path, simfile_dir.ssc_path]:
            if simfile_path:
                change_sync_bias(simfile_path, args)


if __name__ == "__main__":
    main(sys.argv)