First attempt at ripping out agnostic code into ifcopenshell.api namespace. See #1399.

src/ifcopenshell-python/ifcopenshell/api/context/add_context.py

@@ -0,0 +1,45 @@
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {
+            "context": None,
+            "subcontext": None,
+            "target_view": None,
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        parent = [
+            c
+            for c in self.file.by_type("IfcGeometricRepresentationContext")
+            if c.ContextType == self.settings["context"]
+        ]
+        if not parent:
+            self.create_origin()
+            if self.settings["context"] == "Plan":
+                context = self.file.createIfcGeometricRepresentationContext(None, "Plan", 2, 1.0e-05, self.origin)
+            else:
+                context = self.file.createIfcGeometricRepresentationContext(None, "Model", 3, 1.0e-05, self.origin)
+            project = self.file.by_type("IfcProject")[0]
+            if project.RepresentationContexts:
+                contexts = list(project.RepresentationContexts)
+            else:
+                contexts = []
+            contexts.append(context)
+            project.RepresentationContexts = contexts
+            return context
+        parent = parent[0]
+        return self.file.create_entity("IfcGeometricRepresentationSubContext", **{
+            "ContextIdentifier": self.settings["subcontext"],
+            "ContextType": self.settings["context"],
+            "ParentContext": parent,
+            "TargetView": self.settings["target_view"],
+        })
+
+    def create_origin(self):
+        self.origin = self.file.createIfcAxis2Placement3D(
+            self.file.createIfcCartesianPoint((0.0, 0.0, 0.0)),
+            self.file.createIfcDirection((0.0, 0.0, 1.0)),
+            self.file.createIfcDirection((1.0, 0.0, 0.0)),
+        )

src/ifcopenshell-python/ifcopenshell/api/context/data.py

@@ -0,0 +1,27 @@
+class Data:
+    is_loaded = False
+    contexts = {}
+
+    @classmethod
+    def purge(cls):
+        cls.is_loaded = False
+        cls.contexts = {}
+
+    @classmethod
+    def load(cls, file):
+        if not file:
+            return
+        cls.contexts = {}
+        for context in file.by_type("IfcGeometricRepresentationContext", include_subtypes=False):
+            subcontexts = {}
+            for subcontext in context.HasSubContexts:
+                subcontexts[int(subcontext.id())] = {
+                    "ContextType": subcontext.ContextType,
+                    "ContextIdentifier": subcontext.ContextIdentifier,
+                    "TargetView": subcontext.TargetView,
+                }
+            cls.contexts[int(context.id())] = {
+                "ContextType": context.ContextType,
+                "HasSubContexts": subcontexts
+            }
+        cls.is_loaded = True

src/ifcopenshell-python/ifcopenshell/api/context/remove_context.py

@@ -0,0 +1,12 @@
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {"context": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        # TODO: this is a light remove only
+        for subcontext in self.settings["context"].HasSubContexts:
+            self.file.remove(subcontext)
+        self.file.remove(self.settings["context"])