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+;;; host-environment.el --- Host Environment Convenience Functions -*- lexical-binding: t; coding: utf-8; -*-
+;; author Craig Jennings <c@cjennings.net>
+
+;;; Commentary:
+;; Convenience functions to report about the host environment
+
+;;; Code:
+
+(require 'battery)
+
+(defun env-laptop-p ()
+  "Return t if host is a laptop (i.e., has a battery), nil if not."
+  (when (and battery-status-function
+			 (not (string-match-p "N/A"
+								  (battery-format "%B"
+												  (funcall battery-status-function)))))
+	t))
+
+(defun env-desktop-p ()
+  "Return t if host is a laptop (has a battery), nil if not."
+  (when (not (env-laptop-p))
+	t))
+
+(defun env-linux-p ()
+  "Return t if host system is GNU/Linux."
+  (eq system-type "gnu/linux"))
+
+(defun env-bsd-p ()
+  "Return t if host system is FreeBSD."
+  (eq system-type 'berkeley-unix))
+
+(defun env-macos-p ()
+  "Return t if host system is Mac OS (darwin-based)."
+  (eq system-type "darwin"))
+
+(defun env-windows-p ()
+  "Return t if host system is Windows."
+  (memq system-type '(cygwin windows-nt ms-dos)))
+
+(defun env-x-p ()
+  "Return t if host system is running the X Window System."
+  (string= (window-system) "x"))
+
+(defun env-terminal-p ()
+  "Return t if running in a terminal."
+  (not (display-graphic-p)))
+
+(defun env-gui-p ()
+  "Return t if running in graphical environment."
+  (display-graphic-p))
+
+;; ------------------------------- Timezone Info -------------------------------
+
+(defun cj/match-localtime-to-zoneinfo ()
+  "Detect system timezone by comparing /etc/localtime with zoneinfo files.
+This replicates the shell command:
+find /usr/share/zoneinfo -type f ! -name 'posixrules' \\
+  -exec cmp -s {} /etc/localtime \\; -print | sed -e 's@.*/zoneinfo/@@' | head -n1"
+  (when (and (file-exists-p "/etc/localtime")
+			 (file-directory-p "/usr/share/zoneinfo"))
+	(let ((localtime-content
+		   (with-temp-buffer
+			 (insert-file-contents-literally "/etc/localtime")
+			 (buffer-string)))
+		  (result nil))
+	  (catch 'found
+		(dolist (file (directory-files-recursively
+					   "/usr/share/zoneinfo"
+					   ".*"
+					   nil
+					   (lambda (name)
+						 (not (string-match-p "posixrules" name)))))
+		  (when (and (file-regular-p file)
+					 (not (string-match-p "/posixrules$" file)))
+			(let ((file-content
+				   (with-temp-buffer
+					 (insert-file-contents-literally file)
+					 (buffer-string))))
+			  (when (string= localtime-content file-content)
+				(setq result (replace-regexp-in-string
+							  "^.*/zoneinfo/" "" file))
+				(throw 'found result)))))
+		result))))
+
+(defun cj/detect-system-timezone ()
+  "Detect the system timezone in IANA format (e.g., 'America/Los_Angeles').
+Tries multiple methods in order of reliability:
+1. Environment variable TZ
+2. File comparison of /etc/localtime with zoneinfo database
+3. /etc/timezone file contents
+4. /etc/localtime symlink target"
+  (or
+   ;; Compare file contents (reliable on Arch/modern systems)
+   (cj/match-localtime-to-zoneinfo)
+
+   ;; Environment variable (most explicit if set)
+   (getenv "TZ")
+
+   ;; Read /etc/timezone (Debian/Ubuntu)
+   (when (file-exists-p "/etc/timezone")
+	 (with-temp-buffer
+	   (insert-file-contents "/etc/timezone")
+	   (string-trim (buffer-string))))
+
+   ;; Method 4: Parse symlink (fallback for older systems)
+   (when (file-symlink-p "/etc/localtime")
+	 (let ((target (file-truename "/etc/localtime")))
+	   (when (string-match ".*/zoneinfo/\\(.+\\)" target)
+		 (match-string 1 target))))
+
+   ;; Default to nil - let org-gcal use its default
+   nil))
+
+
+(provide 'host-environment)
+;;; host-environment.el ends here.