75 lines
2.2 KiB
EmacsLisp
75 lines
2.2 KiB
EmacsLisp
;;; dawn.el --- Do things at dawn (and dusk) -*- lexical-binding: t; -*-
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;;; Commentary:
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;; There is also circadian.el, but it doesn't quite work for me.
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;; This code comes mostly from https://gnu.xyz/auto_theme.html, but also
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;; somewhere else (which I've forgotten) and my own brain :)
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;;; Code:
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(require 'calendar)
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(require 'cl-lib)
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(require 'solar)
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(defvar dawn--dawn-timer nil
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"Timer for dawn-command.")
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(defvar dawn--dusk-timer nil
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"Timer for dusk-command.")
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(defvar dawn--reset-timer nil
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"Timer to reset dawn at midnight.")
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(defun dawn-encode-time (f)
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"Encode fractional time F."
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(let ((hhmm (cl-floor f))
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(date (cdddr (decode-time))))
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(encode-time
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(append (list 0
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(round (* 60 (cadr hhmm)))
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(car hhmm)
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)
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date))))
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(defun dawn-midnight ()
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"Return the time of the /next/ midnight."
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(let ((date (cdddr (decode-time))))
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(encode-time
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(append (list 0 0 0 (1+ (car date))) (cdr date)))))
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(defun dawn-sunrise ()
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"Return the time of today's sunrise."
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(dawn-encode-time (caar (solar-sunrise-sunset (calendar-current-date)))))
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(defun dawn-sunset ()
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"Return the time of today's sunset."
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(dawn-encode-time (caadr (solar-sunrise-sunset (calendar-current-date)))))
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(defun dawn-schedule (dawn-command dusk-command)
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"Run DAWN-COMMAND at sunrise, and DUSK-COMMAND at dusk.
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RESET is an argument for internal use."
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(let ((dawn (dawn-sunrise))
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(dusk (dawn-sunset)))
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(cond
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((time-less-p nil dawn)
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;; If it isn't dawn yet, it's still dark. Run DUSK-COMMAND and schedule
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;; DAWN-COMMAND and DUSK-COMMAND for later.
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(funcall dusk-command)
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(run-at-time dawn nil dawn-command)
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(run-at-time dusk nil dusk-command))
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((time-less-p nil dusk)
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;; If it isn't dusk yet, it's still light. Run DAWN-COMMAND and schedule
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;; DUSK-COMMAND.
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(funcall dawn-command)
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(run-at-time dusk nil dusk-command))
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(t ;; Otherwise, it's past dusk, so run DUSK-COMMAND.
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(funcall dusk-command)))
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;; Schedule a reset at midnight, to re-calculate dawn/dusk times.
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;(unless reset)
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(run-at-time (dawn-midnight) nil
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#'dawn-schedule dawn-command dusk-command)))
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(provide 'dawn)
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;;; dawn.el ends here
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