DSL POC

Ref #1

Pipfile

@@ -12,3 +12,4 @@ pytest-cov = "==3.0.0"
 freezegun = "==1.2.2"
 pyyaml = "==5.4"
 pre-commit = "~=2.21.0"
+black = "*"

fhirpathpy/__init__.py

@@ -3,6 +3,7 @@
 from fhirpathpy.engine import do_eval
 from fhirpathpy.engine.util import arraify, get_data, set_paths
 from fhirpathpy.engine.nodes import FP_Type
+from fhirpathpy.dsl_impl import DSL
 
 __title__ = "fhirpathpy"
 __version__ = "0.1.2"
@@ -82,3 +83,6 @@ def compile(path, model=None):
     For example, you could pass in the result of require("fhirpath/fhir-context/r4")
     """
     return set_paths(apply_parsed_path, parsedPath=parse(path), model=model)
+
+
+dsl = DSL()

fhirpathpy/dsl_impl.py

@@ -0,0 +1,43 @@
+class DSL:
+    path: str
+
+    def __init__(self, prefix=None):
+        self.path = prefix
+
+    def __getattr__(self, attr):
+        if self.path is None and attr == "empty":
+            return DSL("{}")
+        if self.path is None and attr == "env":
+            return DSL("%")
+        elif self.path == "%":
+            return DSL(f"{self.path}{attr}")
+        elif self.path is not None:
+            return DSL(f"{self.path}.{attr}")
+        else:
+            return DSL(attr)
+
+    def __getitem__(self, attr):
+        return DSL(f"{self.path}[{attr}]")
+
+    def __eq__(self, other):
+        return DSL(f"{self.path} ~ {format_value(other)}")
+
+    def __ne__(self, other):
+        return DSL(f"{self.path} !~ {format_value(other)}")
+
+    def __call__(self, **kwargs):
+        args = build_args(kwargs)
+        return DSL(f"{self.path}({args})")
+
+    def __str__(self):
+        return self.path
+
+
+def format_value(value):
+    if isinstance(value, str):
+        return f"'{value}'"
+    return str(value)
+
+
+def build_args(args):
+    return ",".join(f"{k}={format_value(v)}" for k, v in args.items())

tests/test_dsl.py

@@ -0,0 +1,16 @@
+from fhirpathpy import dsl
+
+
+def dsl_test():
+    assert str(dsl.Patient.id) == "Patient.id"
+    assert (
+        str(dsl.Patient.name.where(use="usual").given.first())
+        == "Patient.name.where(use='usual').given.first()"
+    )
+    assert (
+        str(
+            dsl.env.Source.entry[0].resource.expansion.contains.where(code=dsl.env.Coding.code)
+            != dsl.empty
+        )
+        == "%Source.entry[0].resource.expansion.contains.where(code=%Coding.code) !~ {}"
+    )