#!/bin/sh
#
# clock - record how long you work
#
# SPDX-FileCopyrightText: 2023 Daniel Kalak
# SPDX-License-Identifier: GPL-3.0-or-later
#
# Inspired by my j script. The program logs clock-ins, clock-outs, and
# comments to the file specified in the environment variable CLOCKLOG.
# Every line in the log is preceded by the current time in the ISO 8601
# format as well as the UNIX time format, separated by spaces. Clock-ins
# and clock-outs can also be logged under a specified time instead of
# the current time; the line is then marked as "adjusted" and the action
# is logged separately. Clock-ins and clock-outs under the current time
# are only accepted if the log file isn't already in a clocked-in or
# clocked-out state; this check is skipped for adjusted clock-ins and
# clock-outs.
#
# The program returns 1 on bad usage, 0 otherwise.
#
# The program depends on GNU awk and the GNU coreutils.

function usage_quit() {
	cat <<- EOF >&2
	Usage:
	    $(basename "$0") in|out
	    $(basename "$0") note COMMENT [...]
	    $(basename "$0") adjust in|out TIME
	    $(basename "$0") tail
	    $(basename "$0") status
	Environment variables:
	    CLOCKLOG (needs to be a file, currently "$CLOCKLOG")
	Returns:
	    1 on bad usage
	    0 otherwise
	EOF
	exit 1
}

function msg_quit() {
	printf '%s\n' "$1" >&2
	exit 1
}

function append() {
	local iso unix line
	iso="$(date -Iseconds -d "$1")"
	unix="$(date +%s -d "$1")"
	line="$2"
	printf '%s %s %s\n' "$iso" "$unix" "$line" >> "$CLOCKLOG"
}

function inouts() {
	LC_ALL=C sort "$CLOCKLOG" |
	awk '$3 == "in" || $3 == "out" { print $3 }'
}

function clockedin() {
	[ "$(inouts | tail -n1)" = 'in' ]
}

function outofbalance() {
	[ "$(inouts | head -n1)" = 'out' ] ||
	[ "$(inouts | uniq -d)" ]
}

function hours() {
	awk -v "curr=$(date +%s)" '
		$3 == "in"  { s -= $2 }
		$3 == "out" { s += $2 }
		END {
			if (s < 0)
				print (s + curr) / 3600, "and counting";
			else
				print s / 3600;
		}' < "$CLOCKLOG"
}

[ -f "$CLOCKLOG" ] || usage_quit
curr="$(date -Iseconds)"

case "$1" in
'in')
	[ "$#" -eq 1 ] || usage_quit
	clockedin      && msg_quit 'Already clocked in'
	append "$curr" "$*"
	;;
'out')
	[ "$#" -eq 1 ] || usage_quit
	clockedin      || msg_quit 'Not clocked in'
	append "$curr" "$*"
	;;
'note')
	[ "$#" -gt 1 ] || usage_quit
	append "$curr" "$*"
	;;
'adjust')
	[ "$#" -eq 3 ]                      || usage_quit
	[ "$2" = 'in' ] || [ "$2" = 'out' ] || usage_quit
	adj="$(date -Iseconds -d "$3")"     || exit 1
	append "$curr" "$* ($adj)"
	append "$adj"  "$2 adjusted"
	;;
'tail')
	[ "$#" -eq 1 ] || usage_quit
	tail "$CLOCKLOG"
	;;
'status')
	[ "$#" -eq 1 ] || usage_quit
	if clockedin
	then printf 'Currently clocked in\n'
	else printf 'Currently not clocked in\n'
	fi
	outofbalance && printf 'Log is out of balance! Might miscount hours\n'
	printf 'Hours clocked in: %s\n' "$(hours)"
	;;
*)
	usage_quit
	;;
esac