format: Add a function for formatting search strings

This takes the input string, casefolds it, and then adds some extra glob
operators to it so we can do a case insensitive substring search by
default.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/format.py

@@ -0,0 +1,21 @@
+# Copyright 2022 (c) Anna Schumaker
+"""Helper functions for formatting strings."""
+
+
+def search(input: str) -> str | None:
+    """Translate the input string into a sqlite3 GLOB statement."""
+    input = input.strip().casefold()
+    if len(input) == 0:
+        return None
+
+    if input[0] == "^":
+        input = input[1:] if len(input) > 1 else "*"
+    elif input[0] != "*":
+        input = "*" + input
+
+    if input[-1] == "$":
+        input = input[:-1]
+    elif input[-1] != "*":
+        input += "*"
+
+    return input

tests/test_format.py

@@ -0,0 +1,20 @@
+# Copyright 2022 (c) Anna Schumaker
+"""Tests our string formatting functions."""
+import unittest
+from emmental import format
+
+
+class TestFormatter(unittest.TestCase):
+    """Tests our formatting functions."""
+
+    def test_search(self):
+        """Test formatting a case-insensitive search query."""
+        self.assertIsNone(format.search(""))
+        self.assertIsNone(format.search("    "))
+        self.assertEqual(format.search(" TeSt "), "*test*")
+        self.assertEqual(format.search("*Test*"), "*test*")
+        self.assertEqual(format.search("^Test*"), "test*")
+        self.assertEqual(format.search("^*Test*"), "*test*")
+        self.assertEqual(format.search("*Test$"), "*test")
+        self.assertEqual(format.search("^"), "*")
+        self.assertEqual(format.search("$"), "*")