maps.py

import abc
import json

from django.contrib.gis.gdal import SpatialReference, CoordTransform
from rest_framework.views import APIView

from core.models.assemblies import Assembly
from core.models.conference import ConferenceExportCache
from .mixins import ConferenceSlugMixin


class AssembliesExportView(ConferenceSlugMixin, APIView, metaclass=abc.ABCMeta):
    geometry_field = None
    _cts = {}  # cache of CoordTransforms (if needed)

    def get_queryset(self):
        exportable_states = Assembly.PLACED_STATES + [Assembly.State.HIDDEN]
        return Assembly.objects.filter(conference=self.conference, state_assembly__in=exportable_states)

    @staticmethod
    def get_field_geojson(value, srid: int, ct_cache: dict = None):
        if value.srid != srid:
            if ct_cache is None:
                ct_cache = {}
            if value.srid not in ct_cache:
                srs = SpatialReference(srid)
                ct_cache[value.srid] = CoordTransform(value.srs, srs)
            value.transform(ct_cache[value.srid])
        return json.loads(value.geojson)

    def get_geometry_field(self, obj):
        return getattr(obj, self.geometry_field)

    def get_geojson(self):
        srid = 4326  # RFC7946 mandates WGS84
        ct_cache = {}
        features = []
        result = {
            'type': 'FeatureCollection',
            # 'crs': {'type': 'name', 'properties': {'name': f'EPSG:{srid}'}},  # deprecated, not in RFC7946
            'features': features,
        }

        for assembly in self.get_queryset().prefetch_related('parent').all():
            geometry = self.get_geometry_field(assembly)
            if geometry is None:
                continue

            feature = {
                'type': 'Feature',
                'id': assembly.slug,
                'geometry': self.get_field_geojson(geometry, srid=srid, ct_cache=ct_cache),
                'properties': {
                    'name': assembly.name,
                    'official': assembly.is_official,
                    'cluster': assembly.is_cluster,
                    'parent': assembly.parent.slug if assembly.parent else None,
                },
            }
            features.append(feature)

        return result

    def get(self, request, *args, **kwargs):
        cache_id = 'geojson-' + self.geometry_field

        return ConferenceExportCache.handle_http_request(
            request=request,
            conference=self.conference,
            type=ConferenceExportCache.Type.MAP,
            ident=cache_id,
            content_type='application/geo+json',
            result_func=lambda: json.dumps(self.get_geojson()),
        )


class AssembliesPoiExportView(AssembliesExportView):
    geometry_field = 'location_point'


class AssembliesAreasExportView(AssembliesExportView):
    geometry_field = 'location_boundaries'