Merge pull request #223 from stac-utils/feature/rde/extent-from-items

Add 'from_items' to Extent

pystac/collection.py

@@ -180,32 +180,7 @@ def update_extent_from_items(self):
         """
         Update datetime and bbox based on all items to a single bbox and time window.
         """
-        def extract_extent_props(item):
-            return item.bbox + [
-                item.datetime, item.common_metadata.start_datetime,
-                item.common_metadata.end_datetime
-            ]
-
-        xmins, ymins, xmaxs, ymaxs, datetimes, starts, ends = zip(
-            *map(extract_extent_props, self.get_all_items()))
-
-        if not any(datetimes + starts):
-            start_timestamp = None
-        else:
-            start_timestamp = min([
-                dt if dt.tzinfo else dt.replace(tzinfo=tz.UTC)
-                for dt in filter(None, datetimes + starts)
-            ])
-        if not any(datetimes + ends):
-            end_timestamp = None
-        else:
-            end_timestamp = max([
-                dt if dt.tzinfo else dt.replace(tzinfo=tz.UTC)
-                for dt in filter(None, datetimes + ends)
-            ])
-
-        self.extent.spatial.bboxes = [[min(xmins), min(ymins), max(xmaxs), max(ymaxs)]]
-        self.extent.temporal.intervals = [[start_timestamp, end_timestamp]]
+        self.extent = Extent.from_items(self.get_all_items())
 
 
 class Extent:
@@ -262,6 +237,45 @@ def from_dict(d):
         return Extent(SpatialExtent.from_dict(spatial_extent_dict),
                       TemporalExtent.from_dict(temporal_extent_dict))
 
+    @staticmethod
+    def from_items(items):
+        """Create an Extent based on the datetimes and bboxes of a list of items.
+
+        Args:
+            items (List[Item]): A list of items to derive the extent from.
+
+        Returns:
+            Extent: An Extent that spatially and temporally covers all of the
+                given items.
+        """
+        def extract_extent_props(item):
+            return item.bbox + [
+                item.datetime, item.common_metadata.start_datetime,
+                item.common_metadata.end_datetime
+            ]
+
+        xmins, ymins, xmaxs, ymaxs, datetimes, starts, ends = zip(*map(extract_extent_props, items))
+
+        if not any(datetimes + starts):
+            start_timestamp = None
+        else:
+            start_timestamp = min([
+                dt if dt.tzinfo else dt.replace(tzinfo=tz.UTC)
+                for dt in filter(None, datetimes + starts)
+            ])
+        if not any(datetimes + ends):
+            end_timestamp = None
+        else:
+            end_timestamp = max([
+                dt if dt.tzinfo else dt.replace(tzinfo=tz.UTC)
+                for dt in filter(None, datetimes + ends)
+            ])
+
+        spatial = SpatialExtent([[min(xmins), min(ymins), max(xmaxs), max(ymaxs)]])
+        temporal = TemporalExtent([[start_timestamp, end_timestamp]])
+
+        return Extent(spatial, temporal)
+
 
 class SpatialExtent:
     """Describes the spatial extent of a Collection.

tests/test_collection.py

@@ -3,6 +3,7 @@
 import json
 from tempfile import TemporaryDirectory
 from datetime import datetime
+from dateutil import tz
 
 import pystac
 from pystac.validation import validate_dict
@@ -223,17 +224,42 @@ def test_spatial_allows_single_bbox(self):
 
         collection.validate()
 
-    def test_temporal_allows_single_interval(self):
-        spatial_extent = SpatialExtent(bboxes=[RANDOM_BBOX])
+    def test_from_items(self):
+        item1 = Item(id='test-item-1',
+                     geometry=RANDOM_GEOM,
+                     bbox=[-10, -20, 0, -10],
+                     datetime=datetime(2000, 2, 1, 12, 0, 0, 0, tzinfo=tz.UTC),
+                     properties={})
 
-        # Pass in a single interval
-        temporal_extent = TemporalExtent(intervals=[TEST_DATETIME, None])
+        item2 = Item(id='test-item-2',
+                     geometry=RANDOM_GEOM,
+                     bbox=[0, -9, 10, 1],
+                     datetime=None,
+                     properties={
+                         'start_datetime':
+                         datetime_to_str(datetime(2000, 1, 1, 12, 0, 0, 0, tzinfo=tz.UTC)),
+                         'end_datetime':
+                         datetime_to_str(datetime(2000, 7, 1, 12, 0, 0, 0, tzinfo=tz.UTC))
+                     })
 
-        collection_extent = Extent(spatial=spatial_extent, temporal=temporal_extent)
+        item3 = Item(id='test-item-2',
+                     geometry=RANDOM_GEOM,
+                     bbox=[-5, -20, 5, 0],
+                     datetime=None,
+                     properties={
+                         'start_datetime':
+                         datetime_to_str(datetime(2000, 12, 1, 12, 0, 0, 0, tzinfo=tz.UTC)),
+                         'end_datetime':
+                         datetime_to_str(datetime(2001, 1, 1, 12, 0, 0, 0, tzinfo=tz.UTC), )
+                     })
 
-        collection = Collection(id='test', description='test desc', extent=collection_extent)
+        extent = Extent.from_items([item1, item2, item3])
 
-        # HREF required by validation
-        collection.set_self_href('https://example.com/collection.json')
+        self.assertEqual(len(extent.spatial.bboxes), 1)
+        self.assertEqual(extent.spatial.bboxes[0], [-10, -20, 10, 1])
 
-        collection.validate()
+        self.assertEqual(len(extent.temporal.intervals), 1)
+        interval = extent.temporal.intervals[0]
+
+        self.assertEqual(interval[0], datetime(2000, 1, 1, 12, 0, 0, 0, tzinfo=tz.UTC))
+        self.assertEqual(interval[1], datetime(2001, 1, 1, 12, 0, 0, 0, tzinfo=tz.UTC))