#!/usr/bin/env sh

# POSIX shell implementation of Gitrect.
# Clean up folders not present in the git-list
# For all directories found in $WORKDIR

# Operate on tempfile
TEMPFILE="/tmp/gitrect.temp.$(od -t x1 -An -N6 /dev/urandom | tr -d '\n ')"
touch "$TEMPFILE"
PREFIX="/tmp/gitrect.prefix.$(od -t x1 -An -N6 /dev/urandom | tr -d '\n ')"
touch "$PREFIX"

# Reset all variables that might be set
DEFAULT_STATE="$HOME/.local/share/git/repolist"
WORKDIR="$HOME/.code"
verbose=0 # Variables to be evaluated as shell arithmetic
# should be initialized to a default or validated beforehand.

usage="$(basename "$0") [-h] [-v -w WORKDIR -f FILE]

Scan directories in the state file and delete those not referenced:
    -w  set the working directory (default: ${WORKDIR})
    -f  set the git list file (default: ${DEFAULT_STATE})

    -h  show this help text
    -v  increase output verbosity
"

while :; do
	case $1 in
	-h | -\? | --help) # Call a "show_help" function to display a synopsis, then exit.
		echo "$usage"
		exit
		;;
	-f) # Takes an option argument, ensuring it has been specified.
		if [ -n "$2" ]; then
			DEFAULT_STATE="$2"
			shift
		fi
		;;
	-f=?*)
		DEFAULT_STATE=${1#*=} # Delete everything up to "=" and assign the remainder.
		;;
	-f=) # Handle the case of an empty --file=
		printf 'ERROR: "-f" requires a non-empty option argument.\n' >&2
		exit 1
		;;
	-w) # Takes an option argument, ensuring it has been specified.
		if [ -n "$2" ]; then
			WORKDIR="$2"
			shift
		fi
		;;
	-w=?*)
		WORKDIR=${1#*=} # Delete everything up to "=" and assign the remainder.
		;;
	-w=) # Handle the case of an empty --file=
		printf 'ERROR: "-w" requires a non-empty option argument.\n' >&2
		exit 1
		;;
	-v)
		verbose=$((verbose + 1)) # Each -v argument adds 1 to verbosity.
		;;
	--) # End of all options.
		shift
		break
		;;
	-?*)
		printf 'WARN: Unknown option (ignored): %s\n' "$1" >&2
		;;
	*) # Default case: If no more options then break out of the loop.
		break ;;
	esac
	shift
done

# If there are input files (for example) that follow the options, they
# will remain in the "$@" positional parameters.

# No posix-compliant way of getting processor count, so leverage OS-specifics
FS_SEPARATOR="/"
if [ "$(uname -s)" = "Darwin" ]; then
	NPROC=$(eval "sysctl -n hw.ncpu")
elif [ "$(uname -s)" = "Linux" ]; then
	NPROC=$(eval "nproc")
else
	# Windows uses backslash
	FS_SEPARATOR="\\"
	if [ $verbose -gt 0 ]; then
		echo "cannot detect CPU total"
	fi
fi

# This double loop is super inefficient, but, it works (?)
while read -r line; do
	dir=$(echo "$line" | cut -d, -f1 | rev | cut -d/ -f2- | rev) #top directories
	echo "${dir}"\$ >>"$PREFIX"
done <"$DEFAULT_STATE"

uniq "$PREFIX" "$TEMPFILE"
rm "$PREFIX"

while read -r line; do
	dir=$(echo "$line" | cut -d, -f 1)
	echo "$dir" >>"$TEMPFILE"
done <"$DEFAULT_STATE"

if [ $verbose -gt 0 ]; then
	find "${WORKDIR}"/* -depth |
		sed -e "s,${WORKDIR}/,," |
		grep -E -v -f "${TEMPFILE}" |
		xargs -P "$NPROC" -t -r -I {} rm -rf "${WORKDIR}""${FS_SEPARATOR}"{}
else
	find "${WORKDIR}"/* -depth |
		sed -e "s,${WORKDIR}/,," |
		grep -E -v -f "${TEMPFILE}" |
		xargs -P "$NPROC" -r -I {} rm -rf "${WORKDIR}""${FS_SEPARATOR}"{}
fi

rm "$TEMPFILE"