fix(calendar-sync): sanitize description text to prevent org heading corruption

Event descriptions containing lines starting with * were being interpreted
as org headings, breaking file structure. Replace leading asterisks with
dashes before writing descriptions.

3 files changed, 94 insertions, 5 deletions

diff --git a/modules/calendar-sync.el b/modules/calendar-sync.el
index 06248531..022aff80 100644
--- a/modules/calendar-sync.el
+++ b/modules/calendar-sync.el
@@ -275,6 +275,17 @@ Returns nil for nil input.  Returns empty string for whitespace-only input."
   (when text
     (string-trim (calendar-sync--strip-html (calendar-sync--unescape-ics-text text)))))
 
+(defun calendar-sync--sanitize-org-body (text)
+  "Sanitize TEXT for safe inclusion as org body content.
+Replaces leading asterisks with dashes to prevent lines from being
+parsed as org headings.  Handles multiple levels (e.g. ** becomes --)."
+  (when text
+    (replace-regexp-in-string
+     "^\\(\\*+\\) "
+     (lambda (match)
+       (concat (make-string (length (match-string 1 match)) ?-) " "))
+     text)))
+
 ;;; Date Utilities
 
 (defun calendar-sync--add-months (date months)
@@ -1175,9 +1186,9 @@ Description appears as body text after the drawer."
         (dolist (prop props)
           (push prop parts))
         (push ":END:" parts))
-      ;; Add description as body text
+      ;; Add description as body text (sanitized to prevent org heading conflicts)
       (when (and description (not (string-empty-p description)))
-        (push description parts))
+        (push (calendar-sync--sanitize-org-body description) parts))
       (string-join (nreverse parts) "\n"))))
 
 (defun calendar-sync--event-start-time (event)
diff --git a/tests/test-calendar-sync--event-to-org.el b/tests/test-calendar-sync--event-to-org.el
index 96ce49d5..a3dc0106 100644
--- a/tests/test-calendar-sync--event-to-org.el
+++ b/tests/test-calendar-sync--event-to-org.el
@@ -92,7 +92,7 @@
       (should (string-match-p ":END:" result)))))
 
 (ert-deftest test-calendar-sync--event-to-org-boundary-description-with-asterisks ()
-  "Test event description containing org-special asterisks."
+  "Test event description containing org-special asterisks are sanitized."
   (let* ((start (test-calendar-sync-time-days-from-now 5 14 0))
          (end (test-calendar-sync-time-days-from-now 5 15 0))
          (event (list :summary "Meeting"
@@ -100,8 +100,13 @@
                       :end end
                       :description "* agenda item 1\n** sub-item")))
     (let ((result (calendar-sync--event-to-org event)))
-      ;; Description should be present
-      (should (string-match-p "agenda item" result)))))
+      ;; Description content should be present
+      (should (string-match-p "agenda item" result))
+      ;; Leading asterisks replaced with dashes to prevent org heading conflicts
+      (should (string-match-p "^- agenda item 1" result))
+      (should (string-match-p "^-- sub-item" result))
+      ;; Only the event heading should use *
+      (should (= 1 (length (split-string result "^\\* " t)))))))
 
 (ert-deftest test-calendar-sync--event-to-org-boundary-organizer-email-only ()
   "Test organizer without CN shows email."
diff --git a/tests/test-calendar-sync--sanitize-org-body.el b/tests/test-calendar-sync--sanitize-org-body.el
new file mode 100644
index 00000000..c85e763c
--- /dev/null
+++ b/tests/test-calendar-sync--sanitize-org-body.el
@@ -0,0 +1,73 @@
+;;; test-calendar-sync--sanitize-org-body.el --- Tests for org body sanitization  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for calendar-sync--sanitize-org-body.
+;; Ensures description text with org-special syntax (leading asterisks)
+;; is escaped to prevent corruption of the org file structure.
+
+;;; Code:
+
+(require 'ert)
+(require 'calendar-sync)
+
+;;; Normal Cases
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-single-asterisk ()
+  "Single leading asterisk replaced with dash."
+  (should (equal "- item one" (calendar-sync--sanitize-org-body "* item one"))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-double-asterisk ()
+  "Double leading asterisks replaced with double dashes."
+  (should (equal "-- sub-item" (calendar-sync--sanitize-org-body "** sub-item"))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-triple-asterisk ()
+  "Triple leading asterisks replaced with triple dashes."
+  (should (equal "--- deep item" (calendar-sync--sanitize-org-body "*** deep item"))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-multiline ()
+  "Multiple lines with asterisks all get sanitized."
+  (let ((input "Format:\n* What did you do yesterday?\n* What are you doing today?\n* Is anything in your way?")
+        (expected "Format:\n- What did you do yesterday?\n- What are you doing today?\n- Is anything in your way?"))
+    (should (equal expected (calendar-sync--sanitize-org-body input)))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-mixed-lines ()
+  "Only lines starting with asterisks are changed."
+  (let ((input "Normal line\n* Bullet line\nAnother normal line"))
+        (should (equal "Normal line\n- Bullet line\nAnother normal line"
+                       (calendar-sync--sanitize-org-body input)))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-normal-mixed-levels ()
+  "Lines with different asterisk counts are each handled."
+  (let ((input "* Top\n** Middle\n*** Bottom"))
+    (should (equal "- Top\n-- Middle\n--- Bottom"
+                   (calendar-sync--sanitize-org-body input)))))
+
+;;; Boundary Cases
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-nil-input ()
+  "Nil input returns nil."
+  (should (null (calendar-sync--sanitize-org-body nil))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-empty-string ()
+  "Empty string returns empty string."
+  (should (equal "" (calendar-sync--sanitize-org-body ""))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-no-asterisks ()
+  "Text without leading asterisks is returned unchanged."
+  (let ((input "Just a normal description\nwith multiple lines"))
+    (should (equal input (calendar-sync--sanitize-org-body input)))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-asterisk-mid-line ()
+  "Asterisks not at line start are left alone."
+  (should (equal "Use * for emphasis" (calendar-sync--sanitize-org-body "Use * for emphasis"))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-asterisk-no-space ()
+  "Asterisk at line start without trailing space is not a heading — left alone."
+  (should (equal "*bold text*" (calendar-sync--sanitize-org-body "*bold text*"))))
+
+(ert-deftest test-calendar-sync--sanitize-org-body-boundary-asterisk-only ()
+  "Lone asterisk with space at start of line is sanitized."
+  (should (equal "- " (calendar-sync--sanitize-org-body "* "))))
+
+(provide 'test-calendar-sync--sanitize-org-body)
+;;; test-calendar-sync--sanitize-org-body.el ends here