Develop Context class

src/bids_validator/context.py

@@ -298,3 +298,103 @@ def from_file(cls, file: FileTree, schema: Namespace) -> t.Self:
             suffix=suffix,
             extension=extension,
         )
+
+
+@attrs.define
+class Context:
+    """A context object that creates context for file on access."""
+
+    file: FileTree
+    dataset: Dataset
+    file_parts: FileParts = attrs.field(init=False)
+
+    def __attrs_post_init__(self):
+        self.file_parts = FileParts.from_file(self.file, self.schema)
+
+    @property
+    def schema(self) -> Namespace:
+        """The BIDS specification schema."""
+        return self.dataset.schema
+
+    @property
+    def path(self) -> str:
+        """Path of the current file."""
+        return self.file_parts.path
+
+    @property
+    def entities(self) -> dict[str, str] | None:
+        """Entities parsed from the current filename."""
+        return self.file_parts.entities
+
+    @property
+    def datatype(self) -> str | None:
+        """Datatype of current file, for examples, anat."""
+        return self.file_parts.datatype
+
+    @property
+    def suffix(self) -> str | None:
+        """Suffix of current file."""
+        return self.file_parts.suffix
+
+    @property
+    def extension(self) -> str | None:
+        """Extension of current file including initial dot."""
+        return self.file_parts.extension
+
+    @property
+    def modality(self) -> str | None:
+        """Modality of current file, for examples, MRI."""
+        modalities = self.schema.rules.modalities
+        for mod_name, mod_dtypes in modalities.items():
+            if self.datatype in mod_dtypes.datatypes:
+                return mod_name
+
+    @property
+    def size(self) -> int:
+        """Length of the current file in bytes."""
+        return self.file.direntry.stat().st_size
+
+    @property
+    def subject(self) -> ctx.Subject | None:
+        """Properties and contents of the current subject."""
+        return ctx.Subject()
+
+    @property
+    def associations(self) -> ctx.Associations:
+        """Associated files, indexed by suffix, selected according to the inheritance principle."""
+        return ctx.Associations()
+
+    @property
+    def columns(self) -> None:
+        """TSV columns, indexed by column header, values are arrays with column contents."""
+        pass
+
+    @property
+    def json(self) -> None:
+        """Contents of the current JSON file."""
+        pass
+
+    @property
+    def gzip(self) -> None:
+        """Parsed contents of gzip header."""
+        pass
+
+    @property
+    def nifti_header(self) -> None:
+        """Parsed contents of NIfTI header referenced elsewhere in schema."""
+        pass
+
+    @property
+    def ome(self) -> None:
+        """Parsed contents of OME-XML header, which may be found in OME-TIFF or OME-ZARR files."""
+        pass
+
+    @property
+    def tiff(self) -> None:
+        """TIFF file format metadata."""
+        pass
+
+    @property
+    def sidecar(self) -> None:
+        """Sidecar metadata constructed via the inheritance principle."""
+        pass

tests/test_context.py

@@ -41,3 +41,32 @@ def test_fileparts(examples, schema):
         suffix='T1w',
         extension='.nii',
     )
+
+def test_context(examples, schema):
+
+    tree = FileTree.read_from_filesystem(examples / 'synthetic')
+    ds = context.Dataset(tree, schema)
+    T1w = tree / 'sub-01' / 'ses-01' / 'anat' / 'sub-01_ses-01_T1w.nii'
+
+    file_context = context.Context(T1w, ds)
+
+    assert file_context.schema is schema
+    assert file_context.dataset is ds
+    assert file_context.entities == {'sub': '01', 'ses': '01'}
+    assert file_context.path == '/sub-01/ses-01/anat/sub-01_ses-01_T1w.nii'
+    assert file_context.datatype == 'anat'
+    assert file_context.suffix == 'T1w'
+    assert file_context.extension == '.nii'
+    assert file_context.modality == 'mri'
+    assert file_context.size == 352
+
+    ## Tests for:
+    #  subject
+    #  sidecar
+    #  associations
+    #  columns
+    #  json
+    #  gzip
+    #  nifti_header
+    #  ome
+    #  tiff