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

# load current state
mkdir -p "$POMODORO_STATE_PATH"
load_or_init() {
	property="$1"
	default_value="$2"
	property_path="$POMODORO_STATE_PATH/current/$property"
	if [ -f "$property_path" ] ; then
		eval $property='"$(cat "$property_path")"'
	else
		eval $property='$default_value'
	fi
}
[ -z "$lap" ] && load_or_init lap 0
[ -z "$state" ] && load_or_init state 'reset'
[ -z "$time" ] && load_or_init time 0.0

# save state (for diff)
diff_state() { printf '%s:' "$lap" "$state" "$time" ; }
original_state="$(diff_state)"

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

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

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

# update remaining time if in reset
[ "$state" = 'reset' ] && update_time=1
[ "$time" = "0.0" ] && update_time=1

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() {
	# do not save files if state didn't change
	[ "$original_state" = "$(diff_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 -- folder containing current state*
	# 3. secondary -- temporary folder used write new state
	#
	# * `primary` will only contain stale state during an update (i.e. while
	# `current` is pointing to `secondary`)

	mkdir -p "$POMODORO_STATE_PATH/primary" "$POMODORO_STATE_PATH/secondary"

	echo "$lap" > "$POMODORO_STATE_PATH/secondary/lap"
	echo "$state" > "$POMODORO_STATE_PATH/secondary/state"
	echo "$time" > "$POMODORO_STATE_PATH/secondary/time"

	ln -sf "secondary" "$POMODORO_STATE_PATH/secondary/current"

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

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

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