added edit score (#6)

* add edit score

* change metrics name

belar/metrics/simple.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from Levenshtein import distance, ratio
 import typing as t
 from dataclasses import dataclass
 
@@ -38,6 +39,28 @@ def score(self, ground_truth: str, generated_text: str):
         return score.fmeasure
 
 
+class EditScore(Metric):
+    measure: t.Literal["distance", "ratio"] = "ratio"
+
+    @property
+    def name(self) -> str:
+        return f"edit_{self.measure}"
+
+    @property
+    def is_batchable(self):
+        return True
+
+    def score(self, ground_truth: t.List[str], generated_text: t.List[str]):
+        if self.measure == "distance":
+            score = [distance(s1, s2) for s1, s2 in zip(ground_truth, generated_text)]
+        elif self.measure == "ratio":
+            score = [ratio(s1, s2) for s1, s2 in zip(ground_truth, generated_text)]
+        else:
+            raise ValueError(f"Unkown measure {self.measure}")
+
+        return score
+
+
 Rouge1 = ROUGE("rouge1")
 Rouge2 = ROUGE("rouge2")
 RougeL = ROUGE("rougeL")