Fix timestamp bug + return diff in nanoseconds

src/aa_remove_data/remove_data.py

@@ -105,17 +105,17 @@ def get_index_at_timestamp(
         nano (int, optional): Nanoseconds portion of timestamp. Defaults to 0.
 
     Returns:
-        tuple[int, float]: Index of closest sample, difference in seconds
+        tuple[int, float]: Index of closest sample, difference in nanoseconds
         between the target timestamp and sample.
     """
-    target = seconds + nano * 10**-9
-    last_diff = target + 1
+    target = seconds * 10**9 + nano
+    last_diff = target - samples[0].secondsintoyear * 10**9 + samples[0].nano
     for i, sample in enumerate(samples):
-        diff = target - (sample.secondsintoyear + sample.nano * 10**-9)
-        if abs(last_diff) <= abs(diff):
+        diff = target - (sample.secondsintoyear * 10**9 + sample.nano)
+        if abs(last_diff) < abs(diff):
             return i - 1, last_diff
         last_diff = diff
-    return -1, last_diff
+    return len(samples) - 1, last_diff
 
 
 def remove_before_ts(samples: list, seconds: int, nano: int = 0) -> list: