lib/strings: add extra string matching predicates

Centralize logic to avoid needing to rewrite it elsewhere.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

modules/lib/strings.nix

@@ -63,4 +63,29 @@ rec {
     Type: string -> string
   */
   toKebabCase = toCaseWithSeparator "-";
+
+  # A predicate that returns true only for camelCase.
+  isCamelCase =
+    str:
+    # This regex enforces the entire structure:
+    # - Must start with one or more lowercase letters.
+    # - Must be followed by one or more "humps" of an uppercase letter
+    #   and then subsequent lowercase letters/numbers.
+    builtins.match "^[a-z]+([A-Z][a-z0-9]*)+$" str != null;
+
+  # Returns true for strings like `PascalCase`, `Application`, `URLShortener`.
+  # Must start with an uppercase letter.
+  isPascalCase = str: builtins.match "^[A-Z][a-z0-9]*([A-Z][a-z0-9]*)*$" str != null;
+
+  # Returns true for strings like `snake_case`, `a_longer_variable`, `var1`.
+  # Must be all lowercase letters/numbers, with words separated by single underscores.
+  isSnakeCase = str: builtins.match "^[a-z0-9]+(_[a-z0-9]+)*$" str != null;
+
+  # Returns true for strings like `kebab-case`, `a-css-class-name`.
+  # Must be all lowercase letters/numbers, with words separated by single hyphens.
+  isKebabCase = str: builtins.match "^[a-z0-9]+(-[a-z0-9]+)*$" str != null;
+
+  # Returns true for strings like `SCREAMING_SNAKE_CASE`, `SOME_CONSTANT`.
+  # Must be all uppercase letters/numbers, with words separated by single underscores.
+  isScreamingSnakeCase = str: builtins.match "^[A-Z0-9]+(_[A-Z0-9]+)*$" str != null;
 }