From 6366d8d3cb8928ffd06502122dc690e158df0b7f Mon Sep 17 00:00:00 2001
From: Ricardo Wurmus <rekado@elephly.net>
Date: Tue, 12 May 2020 13:20:52 +0200
Subject: view/utils: Add time->string.

---
 mumi/web/view/utils.scm | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/mumi/web/view/utils.scm b/mumi/web/view/utils.scm
index 0f037c3..3695045 100644
--- a/mumi/web/view/utils.scm
+++ b/mumi/web/view/utils.scm
@@ -1,6 +1,7 @@
 ;;; mumi -- Mediocre, uh, mail interface
 ;;; Copyright © 2017, 2018, 2019, 2020 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2018, 2019 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This program is free software: you can redistribute it and/or
 ;;; modify it under the terms of the GNU Affero General Public License
@@ -23,6 +24,7 @@
   #:use-module (ice-9 iconv)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-19)
   #:use-module (srfi srfi-26)
   #:use-module (syntax-highlight)
   #:use-module (syntax-highlight scheme)
@@ -31,7 +33,8 @@
   #:use-module (rnrs bytevectors)
   #:export (prettify
             avatar-color
-            display-message-body))
+            display-message-body
+            time->string))
 
 (define-record-type <block>
   (make-block type lines)
@@ -268,3 +271,43 @@ BUG-NUM), even when it is a multipart message."
      (make-mime-entity (email-headers message)
                        (email-body message))))))
 
+(define (time->string time)
+  "Return a string representing TIME in a concise, human-readable way."
+  (define seconds
+    (time-second
+     (if (date? time)
+         (date->time-utc time)
+         time)))
+
+  (define now*
+    (current-time time-utc))
+
+  (define now
+    (time-second now*))
+
+  (define elapsed
+    (- now seconds))
+
+  (cond ((< elapsed 120)
+         "seconds ago")
+        ((< elapsed 7200)
+         (let ((minutes (inexact->exact
+                         (round (/ elapsed 60)))))
+           (format #f "~a minutes ago" minutes)))
+        ((< elapsed (* 48 3600))
+         (let ((hours (inexact->exact
+                       (round (/ elapsed 3600)))))
+           (format #f "~a hours ago" hours)))
+        ((< elapsed (* 3600 24 7))
+         (let ((days (inexact->exact
+                      (round (/ elapsed 3600 24)))))
+           (format #f "~a days ago" days)))
+        (else
+         (let* ((time    (make-time time-utc 0 seconds))
+                (date    (time-utc->date time))
+                (year    (date-year date))
+                (current (date-year (time-utc->date now*)))
+                (format  (if (= year current)
+                             "~e ~b ~H:~M ~z"
+                             "~e ~b ~Y ~H:~M")))
+           (string-append "on " (date->string date format))))))
-- 
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