Initial

map_location/fields.py

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+from typing import NamedTuple
+from django.db import models
+from django.forms import Widget
+
+
+class Position(NamedTuple):
+    lat: float
+    long: float
+
+    def __str__(self):
+        return f'{self.lat:.6f},{self.long:.6f}'
+
+
+class MapLocationWidget(Widget):
+    template_name = 'forms/map-location.html'
+
+    class Media:
+        # @see https://github.com/Leaflet/Leaflet
+        # @see https://github.com/domoritz/leaflet-locatecontrol
+        css = {'all': [
+            'leaflet/leaflet.css',
+            'leaflet/locate/L.Control.Locate.css']}
+        js = ['leaflet/leaflet.js',
+              'leaflet/locate/L.Control.Locate.min.js',
+              'map-location.js']
+
+    # def get_context(self, name, value, attrs):
+    #     context = super().get_context(name, value, attrs)
+    #     context['id'] = attrs.get('id')
+    #     return context
+
+
+class LocationField(models.Field):
+    description = 'Choose location on map'
+
+    def __init__(self, *args, options={}, **kwargs):
+        self.options = options
+        kwargs['max_length'] = 22  # e.g. "-180.123456,-90.123456"
+        super().__init__(*args, **kwargs)
+
+    def deconstruct(self):
+        name, path, args, kwargs = super().deconstruct()
+        del kwargs['max_length']
+        return name, path, args, kwargs
+
+    @property
+    def non_db_attrs(self):
+        return super().non_db_attrs + ('options',)  # type: ignore
+
+    def formfield(self, **kwargs):
+        return super().formfield(**{
+            'widget': MapLocationWidget({'options': self.options}),
+            **kwargs
+        })
+
+    def from_db_value(self, value: str, expression, connection) \
+            -> 'Position|None':
+        if not value:
+            return None
+        lat, lon = value.split(',')
+        return Position(float(lat), float(lon))
+
+    def to_python(self, value) -> 'Position|None':
+        # throw django.core.exceptions.ValidationError
+        if isinstance(value, Position):
+            return value
+        if not value:
+            return None
+        lat, lon = value.split(',')
+        return Position(float(lat), float(lon))
+
+    def get_prep_value(self, value) -> str:
+        if isinstance(value, Position):
+            return f'{value.lat},{value.long}'
+        return value
+
+    def db_type(self, connection):
+        return 'char(22)'