Initial JobSize class

Added a dataclass to represent batch job sizes, including light
validation.

flepimop/gempyor_pkg/src/gempyor/batch.py

@@ -5,9 +5,10 @@
 metadata and job size calculations for example.
 """
 
-__all__ = ["write_manifest"]
+__all__ = ["JobSize", "write_manifest"]
 
 
+from dataclasses import dataclass
 import json
 from pathlib import Path
 from shlex import quote
@@ -19,6 +20,35 @@
 from .utils import _git_head, _shutil_which
 
 
+@dataclass(frozen=True, slots=True)
+class JobSize:
+    """
+    A batch submission job size.
+
+    Attributes:
+        jobs: The number of jobs to use.
+        simulations: The number of simulations to run per a block.
+        blocks: The number of sequential blocks to run per a job.
+
+    Raises:
+        ValueError: If any of the attributes are less than 1.
+    """
+
+    jobs: int
+    simulations: int
+    blocks: int
+
+    def __post_init__(self) -> None:
+        for p in self.__slots__:
+            if (val := getattr(self, p)) < 1:
+                raise ValueError(
+                    (
+                        f"The '{p}' attribute must be greater than 0, "
+                        f"but instead was given '{val}'."
+                    )
+                )
+
+
 def write_manifest(
     job_name: str,
     flepi_path: Path,

flepimop/gempyor_pkg/tests/batch/test_job_size_class.py

@@ -0,0 +1,31 @@
+from typing import Literal
+
+import pytest
+
+from gempyor.batch import JobSize
+
+
+@pytest.mark.parametrize(
+    "kwargs",
+    (
+        {"jobs": 0, "simulations": 1, "blocks": 1},
+        {"jobs": 1, "simulations": 0, "blocks": 1},
+        {"jobs": 1, "simulations": 1, "blocks": 0},
+        {"jobs": 0, "simulations": 0, "blocks": 1},
+        {"jobs": 1, "simulations": 0, "blocks": 0},
+        {"jobs": 0, "simulations": 1, "blocks": 0},
+        {"jobs": 0, "simulations": 0, "blocks": 0},
+    ),
+)
+def test_less_than_one_value_error(
+    kwargs: dict[Literal["jobs", "simulations", "blocks"], int]
+) -> None:
+    param = next(k for k, v in kwargs.items() if v < 1)
+    with pytest.raises(
+        ValueError,
+        match=(
+            f"^The '{param}' attribute must be greater than 0, "
+            f"but instead was given '{kwargs.get(param)}'.$"
+        ),
+    ):
+        JobSize(**kwargs)