get ability estimation from source

app/models/ability_estimation.py

@@ -0,0 +1,23 @@
+from pydantic import BaseModel
+from typing import ClassVar, List
+
+from models.item import Item
+from lib.irt.models.three_parameter_logistic import ThreeParameterLogistic
+from lib.irt.models.rasch import Rasch
+
+class AbilityEstimation(BaseModel):
+  exam_id: int
+  items: List[Item] = []
+  irt_model: str
+  min_theta: float = -3.0
+  max_theta: float = 3.0
+
+  IRT_MODELS: ClassVar[dict] = {
+    'rasch': Rasch,
+    # not supported
+    # '3pl': ThreeParameterLogistic
+  }
+
+  def calculate(self) -> float:
+    model = self.IRT_MODELS[self.irt_model]
+    return model.ability_estimate(self.items)