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;;; host-environment.el --- Host Environment Convenience Functions -*- lexical-binding: t; coding: utf-8; -*-
;; author Craig Jennings <c@cjennings.net>
;;; Commentary:
;;
;; Layer: 1 (Foundation).
;; Category: F/L.
;; Load shape: eager.
;; Eager reason: host predicates (laptop-p, battery presence) used by other
;; foundation/UI modules deciding behavior at startup.
;; Top-level side effects: none.
;; Runtime requires: none (battery loaded on demand; declared via
;; `declare-function').
;; Direct test load: yes (pure predicates; batch-safe).
;;
;; Convenience functions to report about the host environment
;;
;;; Code:
;; for the byte-compiler/linter
(declare-function battery-format "battery" (format data))
(defvar battery-status-function)
(defun env--battery-status-char-indicates-battery-p (status)
"Return non-nil if STATUS indicates a real battery is present.
STATUS is the value returned by `battery-format' with the \"%B\" spec.
A real battery reports \"!\" (critical), \"+\" (charging), or \"-\"
(discharging). Desktops report \"N/A\", \"unknown\", or empty, which
all mean no battery."
(and (stringp status)
(member status '("!" "+" "-"))
t))
(defun env--power-supply-has-battery-p (power-supply-dir)
"Return non-nil if POWER-SUPPLY-DIR contains a BAT* entry.
Canonical Linux check. A laptop exposes directories like
/sys/class/power_supply/BAT0; a desktop exposes only AC adapters
and USB-C power entries."
(and (file-directory-p power-supply-dir)
(file-expand-wildcards (expand-file-name "BAT*" power-supply-dir))
t))
(defun env-laptop-p ()
"Non-nil if the host has a battery.
On Linux, checks /sys/class/power_supply for BAT* entries, which is the
canonical signal. On other platforms, falls back to `battery-format'
\"%B\" and checks for a live battery status char."
(cond
((eq system-type 'gnu/linux)
(env--power-supply-has-battery-p "/sys/class/power_supply"))
((and (require 'battery nil 'noerror)
battery-status-function)
(env--battery-status-char-indicates-battery-p
(battery-format "%B" (funcall battery-status-function))))))
(defun env-desktop-p ()
"Return t if host is a desktop (no battery), nil if it has one."
(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 non-nil if running on macOS (Darwin)."
(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 the frame uses an X display, including XWayland.
Compare `env-x11-p', which is t only in a real X11 session and nil under
Wayland/XWayland. Uses symbol comparison to match `env-x11-p' style."
(eq (window-system) 'x))
(defun env-x11-p ()
"Return t in a real X11 session: an X display with no WAYLAND_DISPLAY.
Compare `env-x-p', which is also t under XWayland (X display, Wayland set)."
(and (eq (window-system) 'x)
(not (getenv "WAYLAND_DISPLAY"))))
(defun env-wayland-p ()
"Return t if running under Wayland.
Checks WAYLAND_DISPLAY env var, which is set by Wayland compositors.
This returns t even if Emacs is running through XWayland."
(and (getenv "WAYLAND_DISPLAY") t))
(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. File comparison of /etc/localtime with zoneinfo database
2. Environment variable TZ
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 if detection fails
nil))
(provide 'host-environment)
;;; host-environment.el ends here.
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