reviewed changes and new case handling for error at start

Author: cgmaiorano

src/graphomotor/features/trails/time.py

@@ -7,44 +7,46 @@ def calculate_total_error_time(drawing: models.Drawing) -> dict[str, float]:
     """Calculate the total time spent making errors.
 
     A contiguous "error chunk" is any sequence of rows where df["error"] != "E0".
-    For each chunk, we find the midpoint time when the error started and the midpoint
-    time when the error ended. The total error time is the sum of the durations of all
-    error chunks.
+    The start of each chunk is defined as the midpoint between the last timestamp with
+    a "correct" entry and the first timestamp of an "error". The total error time is
+    the sum of the durations of all error chunks.
 
     Args:
         drawing: Drawing object containing drawing data.
 
     Returns:
-        Dictionary containing the total time spent in error states.
+        Dictionary containing the total time (s) spent in error states.
     """
     mask = drawing.data["error"] != "E0"
     if not mask.any():
         return {"total_error_time": 0.0}
 
-    chunk_start = (~mask.shift(fill_value=False) & mask).to_numpy().nonzero()[0]
-    chunk_end = (mask.shift(fill_value=False) & ~mask).to_numpy().nonzero()[0]
+    error_change = mask.astype(int).diff()
+    chunk_starts = error_change[error_change == 1].index.tolist()
+    chunk_ends = error_change[error_change == -1].index.tolist()
+
+    if mask.iloc[0]:
+        chunk_starts = [0] + chunk_starts
 
     if mask.iloc[-1]:
-        chunk_end = list(chunk_end) + [len(drawing.data) - 1]
+        chunk_ends = chunk_ends + [len(drawing.data)]
 
     seconds = drawing.data["seconds"].to_numpy()
     total_error_time = 0.0
 
-    for start_idx, end_idx in zip(chunk_start, chunk_end):
-        start_mid = (
+    for start_idx, end_idx in zip(chunk_starts, chunk_ends):
+        start_time = (
             (seconds[start_idx - 1] + seconds[start_idx]) / 2
             if start_idx > 0
             else seconds[0]
         )
 
-        if end_idx + 1 < len(drawing.data):
-            end_mid = (seconds[end_idx] + seconds[end_idx - 1]) / 2
-        else:
-            if mask.iloc[end_idx]:
-                end_mid = seconds[end_idx]
-            else:
-                end_mid = (seconds[end_idx] + seconds[end_idx - 1]) / 2
-        print(start_mid, end_mid)
-        total_error_time += end_mid - start_mid
+        end_time = (
+            (seconds[end_idx - 1] + seconds[end_idx]) / 2
+            if end_idx < len(seconds)
+            else seconds[-1]
+        )
+
+        total_error_time += end_time - start_time
 
     return {"total_error_time": float(total_error_time)}