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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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import glob
import os
from subprocess import call

from netCDF4 import Dataset, num2date

from sdap.processors import Processor


class CallNcra(Processor):
    def __init__(self, output_filename_pattern, time_var_name, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.output_filename_pattern = output_filename_pattern
        self.time_var_name = time_var_name

        self.glob_pattern = self.environ.get("FILEMATCH_PATTERN", '*.nc')

    def process(self, in_path):
        target_datetime = self.get_datetime_from_dataset(in_path)
        target_yearmonth = target_datetime.strftime('%Y%m')

        output_filename = target_datetime.strftime(self.output_filename_pattern)
        output_path = os.path.join(os.path.dirname(in_path), output_filename)

        datasets = glob.glob(os.path.join(os.path.dirname(in_path), self.glob_pattern))

        datasets_to_average = [dataset_path for dataset_path in datasets if
                               self.get_datetime_from_dataset(dataset_path).strftime('%Y%m') == target_yearmonth]

        command = ['ncra', '-O']
        command.extend(datasets_to_average)
        command.append(output_path)
        call(command)

        yield output_path

    def get_datetime_from_dataset(self, dataset_path):
        with Dataset(dataset_path) as dataset_in:
            time_units = getattr(dataset_in[self.time_var_name], 'units', None)
            calendar = getattr(dataset_in[self.time_var_name], 'calendar', 'standard')
            thedatetime = num2date(dataset_in[self.time_var_name][:].item(), units=time_units, calendar=calendar)
        return thedatetime