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de804805ac
I did consider whether to store this explicitly in the SQLite DB, but this is less effort for now and we can always switch to that more robust approach in future if we need to.
66 lines
1.7 KiB
Python
66 lines
1.7 KiB
Python
from collections import defaultdict
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from app.broadcast_areas.models import CustomBroadcastArea
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def aggregate_areas(areas):
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areas = _convert_custom_areas_to_wards(areas)
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areas = _aggregate_wards_by_local_authority(areas)
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areas = _aggregate_lower_tier_authorities(areas)
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return areas
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def _convert_custom_areas_to_wards(areas):
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results = set()
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for area in areas:
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if type(area) == CustomBroadcastArea:
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results |= set(area.overlapping_electoral_wards)
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else:
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results |= {area}
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return results
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def _aggregate_wards_by_local_authority(areas):
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return {
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area.parent if area.is_electoral_ward
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else area for area in areas
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}
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def _aggregate_lower_tier_authorities(areas):
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results = set()
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clusters = _cluster_lower_tier_authorities(areas)
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for cluster in clusters:
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# always keep lone area as itself
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if len(cluster) == 1:
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results |= set(cluster)
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# aggregate multi-area cluster
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elif len(cluster) > 3:
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results |= {cluster[0].parent}
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# aggregate many small clusters
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elif len(clusters) > 1:
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area = cluster[0]
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results |= {area.parent or area}
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# keep one small cluster in full
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else:
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results |= set(cluster)
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return results
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def _cluster_lower_tier_authorities(areas):
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result = defaultdict(lambda: [])
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for area in areas:
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# group lower tier authorities by "county"
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if area.is_lower_tier_local_authority:
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result[area.parent] += [area]
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# leave countries, unitary authorities as-is
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else:
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result[area] = [area]
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return result.values()
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