From bcddeb1d28584a3b174557f3da72d4bbb2ddeb2c Mon Sep 17 00:00:00 2001
From: Chris Markiewicz <effigies@gmail.com>
Date: Tue, 2 May 2023 08:40:19 -0400
Subject: [PATCH] ENH: Start concrete implementations

---
 bids_ng/dataset.py | 119 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 bids_ng/dataset.py

diff --git a/bids_ng/dataset.py b/bids_ng/dataset.py
new file mode 100644
index 00000000..1188af0a
--- /dev/null
+++ b/bids_ng/dataset.py
@@ -0,0 +1,119 @@
+import os
+import re
+import typing as ty
+from functools import cached_property
+from pathlib import Path
+
+import bidsschematools as bst  # type: ignore[import]
+import bidsschematools.schema  # type: ignore[import]
+import bidsschematools.types  # type: ignore[import]
+
+from . import types as bt
+
+
+class BIDSValidationError(ValueError):
+    """Error arising from invalid files or values in a BIDS dataset"""
+
+
+class Schema:
+    schema: bst.types.Namespace
+
+    def __init__(
+        self,
+        schema: ty.Union[bst.types.Namespace, None] = None,
+    ):
+        if schema is None:
+            # Bundled
+            schema = bst.schema.load_schema()
+        self.schema = schema
+
+    @classmethod
+    def from_spec(cls, schema_spec: str) -> "Schema":
+        return cls(bst.schema.load_schema(schema_spec))
+
+    # Conveniences to avoid `schema.schema` pattern
+    @property
+    def objects(self) -> bst.types.Namespace:
+        return self.schema.objects
+
+    @property
+    def rules(self) -> bst.types.Namespace:
+        return self.schema.rules
+
+    @property
+    def meta(self) -> bst.types.Namespace:
+        return self.schema.meta
+
+
+default_schema = Schema()
+
+
+class File(bt.File[Schema]):
+    """Generic file holder
+
+    This serves as a base class for :class:`BIDSFile` and can represent
+    non-BIDS files.
+    """
+
+    def __init__(
+        self,
+        path: ty.Union[os.PathLike, str],
+        dataset: ty.Optional["BIDSDataset"] = None,
+    ):
+        self.path = Path(path)
+        self.dataset = dataset
+
+
+class BIDSFile(File, bt.BIDSFile[Schema]):
+    """BIDS file"""
+
+    pattern = re.compile(
+        r"""
+        (?:(?P<entities>(?:[a-z]+-[a-zA-Z0-9]+(?:_[a-z]+-[a-zA-Z0-9]+)*))_)?
+        (?P<suffix>[a-zA-Z0-9]+)
+        (?P<extension>\.[^/\\]+)$
+        """,
+        re.VERBOSE,
+    )
+
+    def __init__(
+        self,
+        path: ty.Union[os.PathLike, str],
+        dataset: ty.Optional["BIDSDataset"] = None,
+    ):
+        super().__init__(path, dataset)
+        self.entities = {}
+        self.datatype = None
+        self.suffix = None
+        self.extension = None
+
+        schema = default_schema if dataset is None else dataset.schema
+
+        if self.path.parent.name in schema.objects.datatypes:
+            self.datatype = self.path.parent.name
+
+        matches = self.pattern.match(self.path.name)
+        if matches is None:
+            return
+
+        entities, self.suffix, self.extension = matches.groups()
+
+        if entities:
+            found_entities = dict(ent.split("-") for ent in entities.split("_"))
+            self.entities = {
+                key: bt.Index(value) if entity.format == "index" else value
+                for key, entity in schema.rules.entities.items()
+                if (value := found_entities.get(entity.name)) is not None
+            }
+
+    @cached_property
+    def metadata(self) -> dict[str, ty.Any]:
+        """Sidecar metadata aggregated according to inheritance principle"""
+        if not self.dataset:
+            raise ValueError
+        # TODO
+        return {}
+
+
+class BIDSDataset(bt.BIDSDataset[Schema]):
+    ...