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+;;; calendar-sync-org.el --- Org rendering and atomic file output -*- coding: utf-8; lexical-binding: t; -*-
+
+;; Author: Craig Jennings <c@cjennings.net>
+;; Created: 2025-11-16
+
+;;; Commentary:
+;;
+;; Layer: 3 (Domain Workflow).
+;; Category: D.
+;; Load shape: library.
+;; Top-level side effects: none (defuns only).
+;; Runtime requires: subr-x, cj-org-text-lib, calendar-sync-ics.
+;; Direct test load: yes (requires calendar-sync-ics explicitly).
+;;
+;; Output layer of the calendar-sync parser: render a parsed event plist
+;; into an Org entry (heading, property drawer, body) and write generated
+;; content to disk atomically via a same-directory temp file plus rename,
+;; so a reader never sees a half-written calendar.
+
+;;; Code:
+
+(require 'subr-x)
+(require 'cj-org-text-lib)
+(require 'calendar-sync-ics)
+
+;;; Org Rendering
+
+(defun calendar-sync--event-to-org (event)
+  "Convert parsed EVENT plist to org entry string.
+Produces property drawer with LOCATION, ORGANIZER, STATUS, URL when present.
+Description appears as body text after the drawer."
+  (let* ((summary (cj/org-sanitize-heading
+                   (or (plist-get event :summary) "(No Title)")))
+         (description (plist-get event :description))
+         (location (plist-get event :location))
+         (start (plist-get event :start))
+         (end (plist-get event :end))
+         (organizer (plist-get event :organizer))
+         (status (plist-get event :status))
+         (url (plist-get event :url))
+         (timestamp (calendar-sync--format-timestamp start end))
+         ;; Build property drawer entries
+         (props '()))
+    ;; Collect non-nil properties
+    (when (and location (not (string-empty-p location)))
+      (push (format ":LOCATION: %s"
+                    (cj/org-sanitize-property-value location))
+            props))
+    (when organizer
+      (let ((org-name (or (plist-get organizer :cn)
+                          (plist-get organizer :email))))
+        (when org-name
+          (push (format ":ORGANIZER: %s"
+                        (cj/org-sanitize-property-value org-name))
+                props))))
+    (when (and status (not (string-empty-p status)))
+      (push (format ":STATUS: %s"
+                    (cj/org-sanitize-property-value status))
+            props))
+    (when (and url (not (string-empty-p url)))
+      (push (format ":URL: %s"
+                    (cj/org-sanitize-property-value url))
+            props))
+    (setq props (nreverse props))
+    ;; Build output
+    (let ((parts (list timestamp (format "* %s" summary))))
+      ;; Add property drawer if any properties exist
+      (when props
+        (push ":PROPERTIES:" parts)
+        (dolist (prop props)
+          (push prop parts))
+        (push ":END:" parts))
+      ;; Add description as body text (sanitized to prevent org heading conflicts)
+      (when (and description (not (string-empty-p description)))
+        (push (cj/org-sanitize-body-text description) parts))
+      (string-join (nreverse parts) "\n"))))
+
+;;; Atomic File Output
+
+(defun calendar-sync--write-file (content file)
+  "Write CONTENT to FILE atomically.
+Creates parent directories if needed, then writes a temp file in the same
+directory and renames it into place, so org-agenda or chime reading mid-write
+never sees a half-written calendar."
+  (let ((dir (file-name-directory file)))
+    (unless (file-directory-p dir)
+      (make-directory dir t))
+    (let ((tmp (make-temp-file (expand-file-name ".calendar-sync-" dir))))
+      (with-temp-file tmp
+        (insert content))
+      (rename-file tmp file t))))
+
+(provide 'calendar-sync-org)
+;;; calendar-sync-org.el ends here