#156 Add dataclasses for specifications

Author: astropenguin

xarray_dataclasses/specs.py

@@ -0,0 +1,80 @@
+# standard library
+from dataclasses import dataclass
+from typing import Any, Dict, Hashable, Optional, Type
+
+
+# dependencies
+from typing_extensions import Literal, TypeAlias
+
+
+# submodules
+from .typing import Dims, DataClass, AnyDType
+
+
+# type hints
+AnySpec: TypeAlias = "ArraySpec | ScalarSpec"
+
+
+# runtime classes
+@dataclass(frozen=True)
+class ArraySpec:
+    """Specification of an array."""
+
+    name: Hashable
+    """Name of the array."""
+
+    role: Literal["coord", "data"]
+    """Role of the array."""
+
+    default: Any
+    """Default value of the array."""
+
+    dims: Dims
+    """Dimensions of the array."""
+
+    type: Optional[AnyDType]
+    """Data type of the array."""
+
+    origin: Optional[Type[DataClass[Any]]] = None
+    """Dataclass of dims and type origins."""
+
+
+@dataclass(frozen=True)
+class ScalarSpec:
+    """Specification of a scalar."""
+
+    name: Hashable
+    """Name of the scalar."""
+
+    role: Literal["attr", "name"]
+    """Role of the scalar."""
+
+    default: Any
+    """Default value of the scalar."""
+
+    type: Any
+    """Data type of the scalar."""
+
+
+class Specs(Dict[str, AnySpec]):
+    """Dictionary of any specifications."""
+
+    @property
+    def of_attr(self) -> Dict[str, ScalarSpec]:
+        """Limit to attribute specifications."""
+        return {k: v for k, v in self.items() if v.role == "attr"}
+
+    @property
+    def of_coord(self) -> Dict[str, ArraySpec]:
+        """Limit to coordinate specifications."""
+        return {k: v for k, v in self.items() if v.role == "coord"}
+
+    @property
+    def of_data(self) -> Dict[str, ArraySpec]:
+        """Limit to data specifications."""
+        return {k: v for k, v in self.items() if v.role == "data"}
+
+    @property
+    def of_name(self) -> Dict[str, ScalarSpec]:
+        """Limit to name specifications."""
+        return {k: v for k, v in self.items() if v.role == "name"}