Implement `partition_all` function

Issue:
https://github.com/genenetwork/gn-gemtext-threads/blob/main/topics/gn1-migration-to-gn2/partial-correlations.gmi

* gn3/data_helpers.py: new function (partition_all)
* tests/unit/test_data_helpers.py: tests for function
  `gn3.data_helpers.partition_all`

  As part of migrating some functions that access the database, this commit
  extracts generic processes that can be accomplished on data, and implements
  the `partition_all` function, that is equivalent to Clojure's
  `partition-all` function.

2 files changed, 62 insertions, 0 deletions

diff --git a/gn3/data_helpers.py b/gn3/data_helpers.py
new file mode 100644
index 0000000..f0d971e
--- /dev/null
+++ b/gn3/data_helpers.py
@@ -0,0 +1,25 @@
+"""
+This module will hold generic functions that can operate on a wide-array of
+data structures.
+"""
+
+from math import ceil
+from functools import reduce
+from typing import Any, Tuple, Sequence
+
+def partition_all(num: int, items: Sequence[Any]) -> Tuple[Tuple[Any, ...], ...]:
+    """
+    Given a sequence `items`, return a new sequence of the same type as `items`
+    with the data partitioned into sections of `n` items per partition.
+
+    This is an approximation of clojure's `partition-all` function.
+    """
+    def __compute_start_stop__(acc, iteration):
+        start = iteration * num
+        return acc + ((start, start + num),)
+
+    iterations = range(ceil(len(items) / num))
+    return tuple([# type: ignore[misc]
+        tuple(items[start:stop]) for start, stop # type: ignore[has-type]
+        in reduce(
+            __compute_start_stop__, iterations, tuple())])
diff --git a/tests/unit/test_data_helpers.py b/tests/unit/test_data_helpers.py
new file mode 100644
index 0000000..1eec3cc
--- /dev/null
+++ b/tests/unit/test_data_helpers.py
@@ -0,0 +1,37 @@
+"""
+Test functions in gn3.data_helpers
+"""
+
+from unittest import TestCase
+
+from gn3.data_helpers import partition_all
+
+class TestDataHelpers(TestCase):
+    """
+    Test functions in gn3.data_helpers
+    """
+
+    def test_partition_all(self):
+        """
+        Test that `gn3.data_helpers.partition_all` partitions sequences as expected.
+
+        Given:
+            - `num`: The number of items per partition
+            - `items`: A sequence of items
+        When:
+            - The arguments above are passed to the `gn3.data_helpers.partition_all`
+        Then:
+            - Return a new sequence with partitions, each of which has `num`
+              items in the same order as those in `items`, save for the last
+              partition which might have fewer items than `num`.
+        """
+        for count, items, expected in (
+                (1, [0, 1, 2, 3], ((0,), (1,), (2,), (3,))),
+                (3, (0, 1, 2, 3, 4, 5, 6, 7, 8, 9),
+                 ((0, 1, 2), (3, 4, 5), (6, 7, 8), (9, ))),
+                (4, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+                 ((0, 1, 2, 3), (4, 5, 6, 7), (8, 9))),
+                (13, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
+                 ((0, 1, 2, 3, 4, 5, 6, 7, 8, 9), ))):
+            with self.subTest(n=count, items=items):
+                self.assertEqual(partition_all(count, items), expected)