2 files changed, 89 insertions, 0 deletions
diff --git a/tools/emacs-pkgs/dottime/default.nix b/tools/emacs-pkgs/dottime/default.nix
new file mode 100644
index 000000000000..b09756dea560
--- /dev/null
+++ b/tools/emacs-pkgs/dottime/default.nix
@@ -0,0 +1,7 @@
+{ pkgs, ... }:
+
+pkgs.third_party.emacsPackagesNg.trivialBuild rec {
+  pname = "dottime";
+  version = "1.0";
+  src = ./dottime.el;
+}
diff --git a/tools/emacs-pkgs/dottime/dottime.el b/tools/emacs-pkgs/dottime/dottime.el
new file mode 100644
index 000000000000..3500b1c9f489
--- /dev/null
+++ b/tools/emacs-pkgs/dottime/dottime.el
@@ -0,0 +1,82 @@
+;;; dottime.el --- use dottime in the modeline
+;;
+;; Copyright (C) 2019 Google Inc.
+;;
+;; Author: Vincent Ambo <tazjin@google.com>
+;; Version: 1.0
+;; Package-Requires: (cl-lib)
+;;
+;;; Commentary:
+;;
+;; This package changes the display of time in the modeline to use
+;; dottime (see https://dotti.me/) instead of the standard time
+;; display.
+;;
+;; Modeline dottime display is enabled by calling
+;; `dottime-display-mode' and dottime can be used in Lisp code via
+;; `dottime-format'.
+
+(require 'cl-lib)
+(require 'time)
+
+(defun dottime--format-string (&optional offset prefix)
+  "Creates the dottime format string for `format-time-string'
+  based on the local timezone."
+
+  (let* ((offset-sec (or offset (car (current-time-zone))))
+         (offset-hours (/ offset-sec 60 60))
+         (base (concat prefix "%m-%dT%H·%M")))
+    (if (/= offset-hours 0)
+        (concat base (format "%0+3d" offset-hours))
+      base)))
+
+(defun dottime--display-time-update-advice (orig)
+  "Function used as advice to `display-time-update' with a
+  rebound definition of `format-time-string' that renders all
+  timestamps as dottime."
+
+  (cl-letf* ((format-orig (symbol-function 'format-time-string))
+             ((symbol-function 'format-time-string)
+              (lambda (&rest _)
+                (funcall format-orig (dottime--format-string) nil t))))
+    (funcall orig)))
+
+(defun dottime-format (&optional time offset prefix)
+  "Format the given TIME in dottime at OFFSET. If TIME is nil,
+  the current time will be used. PREFIX is prefixed to the format
+  string verbatim.
+
+  OFFSET can be an integer representing an offset in seconds, or
+  the argument can be elided in which case the system time zone
+  is used."
+
+  (format-time-string (dottime--format-string offset prefix) time t))
+
+(defun dottime-display-mode (arg)
+  "Enable time display as dottime. Disables dottime if called
+  with prefix 0 or nil."
+
+  (interactive "p")
+  (if (or (eq arg 0) (eq arg nil))
+      (advice-remove 'display-time-update #'dottime--display-time-update-advice)
+    (advice-add 'display-time-update :around #'dottime--display-time-update-advice))
+  (display-time-update)
+
+  ;; Amend the time display in telega.el to use dottime.
+  ;;
+  ;; This will never display offsets in the chat window, as those are
+  ;; always visible in the modeline anyways.
+  (when (featurep 'telega)
+    (require 'telega)
+    (defun telega-ins--dottime-advice (orig timestamp)
+      (let* ((dtime (decode-time timestamp t))
+             (current-ts (time-to-seconds (current-time)))
+             (ctime (decode-time current-ts))
+             (today00 (telega--time-at00 current-ts ctime)))
+        (if (> timestamp today00)
+            (telega-ins-fmt "%02d·%02d" (nth 2 dtime) (nth 1 dtime))
+          (funcall orig timestamp))))
+
+    (advice-add 'telega-ins--date :around #'telega-ins--dottime-advice)))
+
+(provide 'dottime)