metadata parsing post n5 attribute cache about n5-ij HOT 3 CLOSED

Some of the issues with the current implementation should be solved by the attribute caching. For Paintera, I think we'll additionally want:

• access to attributes.json of a group/non-dataset
• move getAttributes() into a N5DatasetMetadata interface which inherits from N5Metadata
  • If we do this, maybe could get rid of isDataset in favor of a type check for implementing N5DatasetMetadata, unless we expect it could still be null
• If we want Paintera to depend on the existing metadata parsers here (for COSEM, for example) they would need to not implement ImagePlus directly, but maybe have an ImagePlus compliant subclass specific to n5-ij?

The last point brings up the question of where the metadata API will reside, or if we just duplicate it in Paintera

from n5-ij.

Working in the cache-attrs branch:

move getAttributes() into a N5DatasetMetadata interface which inherits from N5Metadata

I agree that this is sensible and have done it. Have not yet made N5DatasetMetadata, but I'm open to it. Let's discuss more.
Also have not yet split parsing and metadata storage objects, but think that's likely worth doing. But will put that off for now.

Main progress so far is separation of discovery and parsing as shown here. So (for n5-ij) the code looks like this:

// find a set of paths
String[] datasetPaths = n5.deepList( base, executor );

// build a tree from the paths
N5TreeNode root = N5TreeNode.fromFlatList( base, datasetPaths, groupSeparator );

// parse metadata and groups
parseMetadataRecursive( root );
parseGroupsRecursive( root );

where in this example the set of metadata and group parsers are stored in local fields. There are also some static methods in N5DatasetDiscoverer (which need some cleaning up, but may still be useful).

Metadata parsers can be applied on any group (not just datasets) as shown in this test using paintera-sytle metadata

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This issue is no longer relevant because caching is implemented and new version released.

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