"""Join source-frame lane and direction fields by original frame and vehicle keys."""
from _common import lane_direction, numeric, parser, read_csv, require, save_csv, unique


def attach(metric, annotations):
    metric, annotations = metric.copy(), annotations.copy()
    keys, fields = ["Frame", "Vehicle_ID"], ["Lane number", "Direction"]
    if set(fields) & set(metric.columns):
        raise ValueError("Metric input already has lane/direction fields; explicitly resolve them first")
    for table in (metric, annotations):
        numeric(table, keys, integer=True)
        unique(table, keys)
    require(annotations, fields)
    lane_direction(annotations)
    if not annotations.Direction.isin(["Left", "Right"]).all() or annotations["Lane number"].isna().any():
        raise ValueError("Annotations require valid lane numbers and Left/Right directions")
    if "Source_ID" in metric:
        if metric.Source_ID.isna().any() or metric.Source_ID.nunique() != 1:
            raise ValueError("Attach lanes for one source at a time")
        if "Source_ID" in annotations and not annotations.Source_ID.eq(metric.Source_ID.iloc[0]).all():
            raise ValueError("Annotation source differs from metric source")
    result = metric.merge(annotations[keys + fields], on=keys, how="left", validate="one_to_one", indicator=True)
    if result._merge.ne("both").any():
        raise ValueError("Some metric observations lack verified lane/direction annotations")
    return result.drop(columns="_merge")


def main():
    p = parser(__doc__)
    p.add_argument("--input", required=True, help="One-source metric CSV with original Frame and Vehicle_ID")
    p.add_argument("--annotations", required=True, help="Verified source-frame CSV: Frame,Vehicle_ID,Lane number,Direction")
    p.add_argument("--output", required=True, help="New metric trajectory CSV with lane/direction fields")
    a = p.parse_args()
    save_csv(attach(read_csv(a.input), read_csv(a.annotations)), a.output)


if __name__ == "__main__":
    main()