from netCDF4 import Dataset
import glob
import datetime

def copy_static(i,o):
    #copy dimensions
    for (dn, dim) in i.dimensions.items():
        o.createDimension(dn, len(dim) if not dim.isunlimited() else None)

    #copy variables
    for (vn, ivar) in i.variables.items():
        ovar = o.createVariable(vn, ivar.datatype, ivar.dimensions)

        #copy variable attributes
        ovar.setncatts({an: ivar.getncattr(an) for an in ivar.ncattrs()})
        ovar[:] = ivar[:]

def concat(i, o):
    for (name, ovar) in o.variables.items():
        if name == "time": #unit->hours
            otime = datetime.datetime(*list(int(j[-1]) if len(j) == 2 and j[0] == 0 else
            int(j) for j in ovar.units.split()[2].split("-")))

            #calculate time of input files
            for index, fin in enumerate(i):
                if index != 0:
                    ivar = fin.variables[name]
                    itime = datetime.datetime(*list(int(j[-1]) if len(j) == 2 and j[0] == 0 else
                        int(j) for j in ivar.units.split()[2].split("-")))
                    hour = (otime - itime).total_seconds() / 3600
                    ovar[index] = hour

        elif name == "Canint" or name == "SWE":
            for index, fin in enumerate(i):
                if index != 0:
                    ovar[index] = fin.variables[name][:]

if __name__ == "__main__":
    fin = raw_input("Enter input files( separated by spaces): ")
    fout = raw_input("Enter an output file: ")

    fin = fin.split()
    if len(fin) == 1:
        fin = glob.glob(fin[0])

    input_list = [ Dataset(i) for i in fin ]
    output_file = Dataset(fout, 'w', format="NETCDF4")

    copy_static(input_list[0], output_file)
    concat(input_list, output_file)