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#!/bin/sh
[ "$skip_libraries" ] && return
export now="$(date +%s.%N)"

# export state
state() { echo "$lap $running $time" ; }

# load original_state once per invocation of dppt
if [ -z "$original_state" ] ; then
	# import state
	mkdir -p "$POMODORO_STATE_PATH"
	if [ -e "$POMODORO_STATE_PATH/current" ] ; then
		read -r lap running time < "$POMODORO_STATE_PATH/current"
	fi

	# ensure state variables are always initialized
	lap=${lap:-0}
	running=${running:-0}
	time=${time:-0}

	# save original state (see save_state function)
	original_state="$(state)"
fi

# allow overriding this value manually
[ -z "$update_time" ] && update_time=0

# calculate remaining time on timer
if [ -z "$remaining" ] ; then
	remaining="$time"
	[ $running -eq 1 ] && remaining="$(echo "( $time - $now ) / 1" | bc)"
fi

# go to next lap if this timer expired
if [ $running -eq 1 ] && [ "${remaining#-}" != "${remaining}" ] ; then
	lap=$(( $lap + 1 ))
	state='paused'
	update_time=1
fi

if [ $update_time -eq 1 ] ; then
	# skip_libraries is used to prevent endless loop (see top of this file)
	time=$(skip_libraries=y "$prog" lap $lap)
	remaining=$time
fi

save_state() {
	new_state="$(state)"
	# do not save files if state didn't change
	[ "$original_state" = "$new_state" ] && return

	# The state update needs to be atomic since other instances may access the
	# state during an update. This is accomplished by replacing a single symlink,
	# which should be atomic on most POSIX-compatible platforms, and is less
	# complicated than a lockfile. $POMODORO_STATE_PATH contains three items:
	#
	# 1. current -- a symlink to `primary` or `secondary`
	# 2. primary -- file containing current state*
	# 3. secondary -- temporary file used write new state
	#
	# * `primary` will only contain stale state during an update (i.e. while
	# `current` is pointing to `secondary`)

	# save state and create replacement symlink for `current`
	echo "$new_state" > "$POMODORO_STATE_PATH/secondary"
	ln -sf "secondary" "$POMODORO_STATE_PATH/current~"

	# this is the atomic update that replaces the `current` symlink with the new
	# state
	mv "$POMODORO_STATE_PATH/current~" "$POMODORO_STATE_PATH/current"

	# next, replace the old `primary` state with the new state from `secondary`
	cp "$POMODORO_STATE_PATH/secondary" "$POMODORO_STATE_PATH/primary"
	# and update the symlink a second time to now point to `primary` again (this
	# does not change the state)
	ln -sf "primary" "$POMODORO_STATE_PATH/current~"
	mv "$POMODORO_STATE_PATH/current~" "$POMODORO_STATE_PATH/current"
}

# state variables
export lap running time
# calculated variables
export remaining