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+;;; my-uptime.el --- calculates uptime for SLOs
+
+;;; Commentary:
+
+;; Calculate how much downtime is allowed for different period of time
+;; based on a given SLO.
+
+;;; Code:
+
+(defconst my-uptime/buffer-name "*slo-calculator*")
+
+(defconst my-uptime/seconds-per-hour 3600
+  "Number of seconds in an hour.")
+(defconst my-uptime/seconds-per-day (* my-uptime/seconds-per-hour 24)
+  "Number of seconds in a day.")
+(defconst my-uptime/seconds-per-week (* my-uptime/seconds-per-day 7)
+  "Number of seconds in a week.")
+(defconst my-uptime/seconds-per-month (* my-uptime/seconds-per-day 30)
+  "Number of seconds in a month.")
+(defconst my-uptime/seconds-per-quarter (* my-uptime/seconds-per-month 3)
+  "Number of seconds in a quarter.")
+(defconst my-uptime/seconds-per-year (* my-uptime/seconds-per-month 12)
+  "Number of seconds in a year.")
+
+(defun my/uptime-is (slo)
+  "Return the amount of allowed downtime for a given SLO."
+  (interactive "nSLO:")
+  (let* ((slo (cond ((< slo 0) 0)
+                    ((> slo 100) 100)
+                    (t slo)))
+         (allowed (/ (- (* 100 100) (* slo 100.0)) (* 100 100))))
+    (my/uptime--message allowed slo)))
+
+(defun my/uptime--message (seconds slo)
+  "Insert buffer text with allowed downtime based on SECONDS (derived from SLO)."
+  (let ((inhibit-read-only t)
+	(buffer-undo-list t))
+    (pop-to-buffer my-uptime/buffer-name)
+    (erase-buffer)
+    (insert (format "calculated allowed downtime for %s%% availability.\n" slo))
+    (insert
+     (format "daily:     %s\n" (format-seconds "%H %M %S" (seconds-to-time (* my-uptime/seconds-per-day seconds)))))
+    (insert
+     (format "weekly:    %s\n" (format-seconds "%H %M %S" (seconds-to-time (* my-uptime/seconds-per-week seconds)))))
+    (insert
+     (format "monthly:   %s\n" (format-seconds "%D %H %M %S" (seconds-to-time (* my-uptime/seconds-per-month seconds)))))
+    (insert
+     (format "quarterly: %s\n" (format-seconds "%D %H %M %S" (seconds-to-time (* my-uptime/seconds-per-quarter seconds)))))
+    (insert
+     (format "yearly:    %s\n" (format-seconds "%D %H %M %S" (seconds-to-time (* my-uptime/seconds-per-year seconds))))))
+  (special-mode))
+
+(provide 'my-uptime)
+
+;;; my-uptime.el ends here