feat:count-characters: Add character counting functionality

Introduce functions to count characters in a buffer or region. Bind
new character counting function to "C-; C" in custom keymap.

1 files changed, 171 insertions, 0 deletions

diff --git a/tests/test-custom-misc-cj--count-characters.el b/tests/test-custom-misc-cj--count-characters.el
new file mode 100644
index 00000000..1834b5c4
--- /dev/null
+++ b/tests/test-custom-misc-cj--count-characters.el
@@ -0,0 +1,171 @@
+;;; test-custom-misc-cj--count-characters.el --- Tests for cj/--count-characters -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/--count-characters internal implementation function from custom-misc.el
+;;
+;; This internal function counts characters between START and END positions.
+;; It validates that START is not greater than END and returns the character count.
+
+;;; Code:
+
+(require 'ert)
+
+;; Add modules directory to load path
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+;; Stub dependencies before loading the module
+(defvar cj/custom-keymap (make-sparse-keymap)
+  "Stub keymap for testing.")
+
+;; Now load the actual production module
+(require 'custom-misc)
+
+;;; Setup and Teardown
+
+(defun test-count-characters-setup ()
+  "Set up test environment."
+  ;; No setup needed for this function
+  nil)
+
+(defun test-count-characters-teardown ()
+  "Clean up test environment."
+  ;; No teardown needed for this function
+  nil)
+
+;;; Normal Cases
+
+(ert-deftest test-custom-misc-cj--count-characters-normal-simple-text-returns-count ()
+  "Should count characters in simple text region."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello, world!")
+        (let ((result (cj/--count-characters 1 14)))
+          (should (= result 13))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-normal-partial-region-returns-count ()
+  "Should count characters in partial region."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello, world!")
+        (let ((result (cj/--count-characters 1 6)))
+          (should (= result 5))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-normal-multiline-returns-count ()
+  "Should count characters including newlines."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Line 1\nLine 2\nLine 3")
+        ;; 6 + 1 + 6 + 1 + 6 = 20 characters
+        (let ((result (cj/--count-characters (point-min) (point-max))))
+          (should (= result 20))))
+    (test-count-characters-teardown)))
+
+;;; Boundary Cases
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-empty-region-returns-zero ()
+  "Should return 0 for empty region (start equals end)."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello")
+        (let ((result (cj/--count-characters 3 3)))
+          (should (= result 0))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-single-character-returns-one ()
+  "Should return 1 for single character region."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello")
+        (let ((result (cj/--count-characters 1 2)))
+          (should (= result 1))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-large-region-returns-count ()
+  "Should handle very large region."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (let ((large-content (make-string 100000 ?x)))
+          (insert large-content)
+          (let ((result (cj/--count-characters (point-min) (point-max))))
+            (should (= result 100000)))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-unicode-returns-count ()
+  "Should count unicode characters (emoji, RTL text, combining characters)."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        ;; "Hello 👋 مرحبا" contains emoji and Arabic text
+        (insert "Hello 👋 مرحبا")
+        (let ((result (cj/--count-characters (point-min) (point-max))))
+          ;; Count the actual characters in the buffer
+          (should (= result (- (point-max) (point-min))))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-whitespace-only-returns-count ()
+  "Should count whitespace characters."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "   \t\n  ")
+        ;; 3 spaces + 1 tab + 1 newline + 2 spaces = 7 characters
+        (let ((result (cj/--count-characters (point-min) (point-max))))
+          (should (= result 7))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-newlines-at-boundaries-returns-count ()
+  "Should count newlines at start and end."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "\n\nHello\n\n")
+        ;; 2 newlines + 5 chars + 2 newlines = 9 characters
+        (let ((result (cj/--count-characters (point-min) (point-max))))
+          (should (= result 9))))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-boundary-binary-content-returns-count ()
+  "Should handle binary content."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert (string 0 1 2 255))
+        (let ((result (cj/--count-characters (point-min) (point-max))))
+          (should (= result 4))))
+    (test-count-characters-teardown)))
+
+;;; Error Cases
+
+(ert-deftest test-custom-misc-cj--count-characters-error-start-greater-than-end-signals-error ()
+  "Should signal error when start is greater than end."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello, world!")
+        (should-error (cj/--count-characters 10 5)
+                      :type 'error))
+    (test-count-characters-teardown)))
+
+(ert-deftest test-custom-misc-cj--count-characters-error-positions-out-of-bounds-handled ()
+  "Should handle positions beyond buffer bounds (Emacs handles this)."
+  (test-count-characters-setup)
+  (unwind-protect
+      (with-temp-buffer
+        (insert "Hello")
+        ;; Emacs will error if positions are truly out of bounds,
+        ;; but this tests that our function doesn't add additional errors
+        ;; Buffer has 6 positions (1-6), testing valid bounds
+        (let ((result (cj/--count-characters 1 6)))
+          (should (= result 5))))
+    (test-count-characters-teardown)))
+
+(provide 'test-custom-misc-cj--count-characters)
+;;; test-custom-misc-cj--count-characters.el ends here