import os
import xarray as xr
import glob

# Navigate to directory with .nc files
directory = '/Users/geel5095/Desktop/obs-le/seawifs/'
# Identify new directory to store .nc files with time stamp
output_directory = '/Users/geel5095/Desktop/obs-le/seawifs_post_processed/'
# This is an arbitrary order
filelist = glob.glob(os.path.join(directory, '*.nc'))

# enumerate also prints a counter (i) along
for i, file in enumerate(sorted(filelist)):
    print(f'{file}...')
    ds = xr.open_dataset(file)
    # Add time dimension
    ds = ds.expand_dims('time')
    # Make each time coordinate an interger that increases monotonically with each file
    ds['time'] = [i]
    # Save out with same file name to new folder
    # file.split() command puls file name and discards original directory
    filename = file.split('/')[-1]
    # `ncrcat` can only concatenate over unlimited, or "record" variables.
    # This means you expect this variable to expand, such as time.
    # The alternative is a "fixed" variable such as lat/lon.
    # This ensures that time is saved out as a record variable.
    ds.to_netcdf(path=f'{output_directory}/{filename}', unlimited_dims='time',
                 engine='scipy')