Option to get date from filename (works with diag files)

[mefrediani]

My diag files didn't have xtime and there was no way to get the plot date from attributes.

import re

Replace the if block in line 436 with:
logger.debug(f"Plotting time step {i}") times.append( resolve_timestring(uxds, config_d["dataset"]["files"], i) )

And add these functions:

def parse_time_from_filename(filepath: str) -> str:
    """
    Parse a timestamp from filename patterns like:
      diag.2025-06-06_21.00.00.nc
    and return a string in YYYY-MM-DD_HH:MM:SS format.
    """
    basename = os.path.basename(filepath)
    match = re.search(r"(\d{4}-\d{2}-\d{2})_(\d{2}\.\d{2}\.\d{2})", basename)
    if not match:
        raise ValueError(
            f"Could not parse timestamp from filename '{basename}'. "
            "Expected pattern like 'diag.YYYY-MM-DD_HH.MM.SS.nc'."
        )

    date_part, time_part = match.groups()
    timestring = f"{date_part}_{time_part.replace('.', ':')}"
    try:
        datetime.strptime(timestring, "%Y-%m-%d_%H:%M:%S")
    except ValueError as e:
        raise ValueError(
            f"Parsed timestamp '{timestring}' from '{basename}' is invalid."
        ) from e
    return timestring

def resolve_timestring(
    uxds: ux.UxDataset,
    datafiles: list[str],
    time_index: int,
) -> str:
    """
    Resolve plot timestamp from xtime when present, otherwise from input filename.
    time_index == -1 is used for variables without a Time dimension.
    """
    if "xtime" in uxds:
        idx = 0 if time_index == -1 else time_index
        return "".join(uxds["xtime"].isel(Time=idx).values.astype(str))

    if not datafiles:
        raise ValueError("No input files available to derive timestamp")

    if time_index == -1:
        filepath = datafiles[0]
    else:
        n_time = uxds.sizes.get("Time", 0)
        if n_time != len(datafiles):
            raise ValueError(
                "'xtime' is missing and timestamp mapping is ambiguous: "
                f"dataset Time dimension has {n_time} steps, but only "
                f"{len(datafiles)} input file(s). Use one file per timestep "
                "or provide xtime in input data."
            )
        if time_index >= len(datafiles):
            raise ValueError(
                f"Time index {time_index} is out of range for {len(datafiles)} input files"
            )
        filepath = datafiles[time_index]

    timestring = parse_time_from_filename(filepath)
    logger.warning(
        f"'xtime' variable not found in input data; using timestamp parsed from "
        f"filename '{os.path.basename(filepath)}' -> {timestring}"
    )
    return timestring

[mkavulich]

@mefrediani Thanks for this (and other) issues with solutions! You mention that your diag file that does not have the xtime variable does have that information in the attributes, can you provide an example of that? I think reading the attributes would be a cleaner solution than parsing the filename if possible.