support merging into DiskWorkspace

CHANGELOG.md

@@ -20,6 +20,7 @@ and start a new "In Progress" section above it.
 <!-- start-of-changelog -->
 
 ## In progress
+- `export_workspace`: support STAC merge ([Open-EO/openeo-geopyspark-driver#677](https://github.com/Open-EO/openeo-geopyspark-driver/issues/677))
 
 - NDVI process: correctly handle band dimension as part of dry run
 

openeo_driver/workspace.py

@@ -2,10 +2,15 @@
 import logging
 import os.path
 import shutil
-from pathlib import Path
-from typing import Union
+from pathlib import Path, PurePath
+from typing import Optional, Union
+from urllib.parse import urlparse
 
 from openeo_driver.utils import remove_slash_prefix
+import pystac
+from pystac import Collection, STACObject, SpatialExtent, TemporalExtent
+from pystac.catalog import CatalogType
+from pystac.layout import HrefLayoutStrategy, CustomLayoutStrategy
 
 _log = logging.getLogger(__name__)
 
@@ -19,6 +24,12 @@ def import_file(self, common_path: str, file: Path, merge: str, remove_original:
     def import_object(self, common_path: str, s3_uri: str, merge: str, remove_original: bool = False) -> str:
         raise NotImplementedError
 
+    @abc.abstractmethod
+    def merge(self, stac_resource: STACObject, target: PurePath, remove_original: bool = False) -> STACObject:
+        # FIXME: replicate subdirectory behavior (#877)
+        # TODO: is a PurePath object fine as an abstraction?
+        raise NotImplementedError
+
 
 class DiskWorkspace(Workspace):
 
@@ -42,3 +53,144 @@ def import_file(self, common_path: Union[str, Path], file: Path, merge: str, rem
 
     def import_object(self, common_path: str, s3_uri: str, merge: str, remove_original: bool = False):
         raise NotImplementedError(f"importing objects is not supported yet")
+
+    def merge(self, stac_resource: STACObject, target: PurePath, remove_original: bool = False) -> STACObject:
+        stac_resource = stac_resource.full_copy()
+
+        target = os.path.normpath(target)
+        target = Path(target[1:] if target.startswith("/") else target)
+        target = self.root_directory / target
+        target.relative_to(self.root_directory)  # assert target_directory is in root_directory
+
+        file_operation = shutil.move if remove_original else shutil.copy
+
+        if isinstance(stac_resource, Collection):
+            new_collection = stac_resource
+
+            existing_collection = None
+            try:
+                existing_collection = pystac.Collection.from_file(str(target))
+            except FileNotFoundError:
+                pass  # nothing to merge into
+
+            def href_layout_strategy() -> HrefLayoutStrategy:
+                def collection_func(_: Collection, parent_dir: str, is_root: bool) -> str:
+                    if not is_root:
+                        raise NotImplementedError("nested collections")
+                    # make the collection file end up at $target, not at $target/collection.json
+                    return str(Path(parent_dir) / target.name)
+
+                return CustomLayoutStrategy(collection_func=collection_func)
+
+            def replace_asset_href(asset_key: str, asset: pystac.Asset) -> pystac.Asset:
+                if urlparse(asset.href).scheme not in ["", "file"]:  # TODO: convenient place; move elsewhere?
+                    raise NotImplementedError(f"importing objects is not supported yet")
+
+                # TODO: crummy way to export assets after STAC Collection has been written to disk with new asset hrefs;
+                #  it ends up in the asset metadata on disk
+                asset.extra_fields["_original_absolute_href"] = asset.get_absolute_href()
+                asset.href = asset_key  # asset key matches the asset filename, becomes the relative path
+                return asset
+
+            if not existing_collection:
+                # TODO: write to a tempdir, then copy/move everything to $merge?
+                new_collection.normalize_hrefs(root_href=str(target.parent), strategy=href_layout_strategy())
+                new_collection = new_collection.map_assets(replace_asset_href)
+                new_collection.save(CatalogType.SELF_CONTAINED)
+
+                for new_item in new_collection.get_items():
+                    for asset in new_item.get_assets().values():
+                        file_operation(
+                            asset.extra_fields["_original_absolute_href"], str(Path(new_item.get_self_href()).parent)
+                        )
+
+                merged_collection = new_collection
+            else:
+                merged_collection = _merge_collection_metadata(existing_collection, new_collection)
+                new_collection = new_collection.map_assets(replace_asset_href)
+
+                for new_item in new_collection.get_items():
+                    new_item.clear_links()  # sever ties with previous collection
+                    merged_collection.add_item(new_item)
+
+                merged_collection.normalize_hrefs(root_href=str(target.parent), strategy=href_layout_strategy())
+                merged_collection.save(CatalogType.SELF_CONTAINED)
+
+                for new_item in new_collection.get_items():
+                    for asset in new_item.get_assets().values():
+                        file_operation(
+                            asset.extra_fields["_original_absolute_href"], Path(new_item.get_self_href()).parent
+                        )
+
+            for item in merged_collection.get_items():
+                for asset in item.assets.values():
+                    workspace_uri = f"file:{Path(item.get_self_href()).parent / Path(asset.href).name}"
+                    asset.extra_fields["alternate"] = {"file": workspace_uri}
+
+            return merged_collection
+        else:
+            raise NotImplementedError(stac_resource)
+
+
+def _merge_collection_metadata(existing_collection: Collection, new_collection: Collection) -> Collection:
+    existing_collection.extent.spatial = _merge_spatial_extents(
+        existing_collection.extent.spatial, new_collection.extent.spatial
+    )
+
+    existing_collection.extent.temporal = _merge_temporal_extents(
+        existing_collection.extent.temporal, new_collection.extent.temporal
+    )
+
+    # TODO: merge additional metadata?
+
+    return existing_collection
+
+
+def _merge_spatial_extents(a: SpatialExtent, b: SpatialExtent) -> SpatialExtent:
+    overall_bbox_a, *sub_bboxes_a = a.bboxes
+    overall_bbox_b, *sub_bboxes_b = b.bboxes
+
+    merged_overall_bbox = [
+        min(overall_bbox_a[0], overall_bbox_b[0]),
+        min(overall_bbox_a[1], overall_bbox_b[1]),
+        max(overall_bbox_a[2], overall_bbox_b[2]),
+        max(overall_bbox_a[3], overall_bbox_b[3])
+    ]
+
+    merged_sub_bboxes = sub_bboxes_a + sub_bboxes_b
+
+    merged_spatial_extent = SpatialExtent([merged_overall_bbox])
+    if merged_sub_bboxes:
+        merged_spatial_extent.bboxes.append(merged_sub_bboxes)
+
+    return merged_spatial_extent
+
+
+def _merge_temporal_extents(a: TemporalExtent, b: TemporalExtent) -> TemporalExtent:
+    overall_interval_a, *sub_intervals_a = a.intervals
+    overall_interval_b, *sub_intervals_b = b.intervals
+
+    def min_time(t1: Optional[str], t2: Optional[str]) -> Optional[str]:
+        if t1 is None or t2 is None:
+            return None
+
+        return min(t1, t2)
+
+    def max_time(t1: Optional[str], t2: Optional[str]) -> Optional[str]:
+        if t1 is None or t2 is None:
+            return None
+
+        return max(t1, t2)
+
+    merged_overall_interval = [
+        min_time(overall_interval_a[0], overall_interval_b[0]),
+        max_time(overall_interval_a[1], overall_interval_b[1])
+    ]
+
+    merged_sub_intervals = sub_intervals_a + sub_intervals_b
+
+    merged_temporal_extent = TemporalExtent([merged_overall_interval])
+    if merged_sub_intervals:
+        merged_temporal_extent.intervals.append(merged_sub_intervals)
+
+    return merged_temporal_extent

setup.py

@@ -73,6 +73,7 @@
         "reretry~=0.11.8",
         "markdown>3.4",
         "traceback-with-variables==2.0.4",
+        "pystac~=1.8.0",
     ],
     extras_require={
         "dev": tests_require,