fix: fix frequency_to_string outputing 108000s (#216)

## Description

Fixes #215


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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Ana Prieto Nemesio <[email protected]>

Author: 3 people

src/anemoi/utils/dates.py

@@ -260,39 +260,21 @@ def frequency_to_string(frequency: datetime.timedelta) -> str:
         A string representation of the frequency.
     """
 
-    frequency = frequency_to_timedelta(frequency)
+    total_seconds = int(frequency.total_seconds())
 
-    total_seconds = frequency.total_seconds()
     if total_seconds < 0:
         return f"-{frequency_to_string(-frequency)}"
-    assert int(total_seconds) == total_seconds, total_seconds
-    total_seconds = int(total_seconds)
 
-    seconds = total_seconds
+    if total_seconds % (24 * 3600) == 0:
+        return f"{total_seconds // (24 * 3600)}d"
 
-    days = seconds // (24 * 3600)
-    seconds %= 24 * 3600
-    hours = seconds // 3600
-    seconds %= 3600
-    minutes = seconds // 60
-    seconds %= 60
+    if total_seconds % 3600 == 0:
+        return f"{total_seconds // 3600}h"
 
-    if days > 0 and hours == 0 and minutes == 0 and seconds == 0:
-        return f"{days}d"
+    if total_seconds % 60 == 0:
+        return f"{total_seconds // 60}m"
 
-    if days == 0 and hours > 0 and minutes == 0 and seconds == 0:
-        return f"{hours}h"
-
-    if days == 0 and hours == 0 and minutes > 0 and seconds == 0:
-        return f"{minutes}m"
-
-    if days == 0 and hours == 0 and minutes == 0 and seconds > 0:
-        return f"{seconds}s"
-
-    if days > 0:
-        return f"{total_seconds}s"
-
-    return str(frequency)
+    return f"{total_seconds}s"
 
 
 def frequency_to_seconds(frequency: int | str | datetime.timedelta) -> int:

tests/test_frequency.py

@@ -17,10 +17,11 @@
 def test_frequency_to_string() -> None:
     """Test the frequency_to_string function for converting timedelta to string."""
     assert frequency_to_string(datetime.timedelta(hours=1)) == "1h"
-    assert frequency_to_string(datetime.timedelta(hours=1, minutes=30)) == "1:30:00"
+    assert frequency_to_string(datetime.timedelta(hours=1, minutes=30)) == "90m"
     assert frequency_to_string(datetime.timedelta(days=10)) == "10d"
+    assert frequency_to_string(datetime.timedelta(hours=30)) == "30h"
     assert frequency_to_string(datetime.timedelta(minutes=10)) == "10m"
-    assert frequency_to_string(datetime.timedelta(minutes=90)) == "1:30:00"
+    assert frequency_to_string(datetime.timedelta(minutes=90)) == "90m"
 
 
 def test_frequency_to_timedelta() -> None: