#!/bin/sh
NORM="\033[0m"
CYN="\033[0;36m"
GRN="\033[0;32m"
RED="\033[0;31m"

me="$(basename "$0")"

concat="pv -EE -F'%r [%b] [%t] [%e] %p'"

printhelp() {
cat << HELPDOC
Usage: $me [options] [file/directory]...

OPTIONS:
  -o, --stdout             Output checksum to STDOUT
  -S, --supress            Supress all warnings and progress notes (default with -o)
  -n, --no-progress        Don't output progress bar (default with -o & -S)
  -m, --md5                Create/verify md5 checksum
  -s[mode], --sha[mode]    Create/verify sha[mode] checksum
  -x[mode], --xxh[mode]    Create/verify xxh[mode] checksum (default)
  -c [alg], --crypt [alg]  Create/verify [alg] checksum (uses [alg]sum program; e.g. '-c sha256' uses sha256sum)
  -v, --verify             Verify files with existing checksums
  -h, --help               Print help
HELPDOC
}

crypt=xxh
while true; do
	case "$1" in
		-o|--stdout)	stdout=1; nowarn=1; concat="cat" ;;
		-S|--supress)	nowarn=1; concat="cat" ;;
		-n|--no-progressbar)	concat="cat" ;;
		-m|--md5)	crypt=md5 ;;
		-s*|--sha*)	crypt=sha$(echo "$1" | tr -cd [:digit:]) ;;
		-x*|--xxh*)	crypt=xxh$(echo "$1" | tr -cd [:digit:]) ;;
		-c|--crypt)	crypt=$2 && shift ;; # Shift twice
		-v|--verify)	verify=1 ;;
		-h|--help)	printhelp; exit 0 ;;
		-*)		printhelp; exit 2 ;;
		*)		break ;;
	esac
	shift
done
hashalg=${crypt}sum
command -v $hashalg >/dev/null || (echo "Hashing algorithm '$hashalg' does not exist!" && exit 2)

# Warn user
if [ ! "$nowarn" ]; then
	for file in "$@"; do
		[ -d "$file" ] && echo "${RED}NOTE:${NORM} getting a checksum from an entire directory is NOT a standard feature in any other checksum-checking program! They can only be checked with this script!" && break
	done
fi

while [ -n "$1" ]; do
	file="$1"
	[ ! "`echo "$file" | sed "s/.$crypt$//"`" = "$file" ] && shift && continue # Skip hash files
	[ ! -e "$file" ] && echo "file '$file' does not exist!" && exit 1
	[ -d "$file" ] && type=directory || type=file
	hashfile="$file.$crypt"
	[ -n "$verify" ] && [ ! -e "$hashfile" ] && shift && continue # Skip files without a hash in verify mode

	[ ! "$nowarn" ] && echo "Getting $crypt checksum of $type '$file'..."
	hash=`find "$file" -type f -print0 | sort -z | xargs -r0 $concat | $hashalg | cut -d' ' -f1`

	if [ "$stdout" ]; then
		echo "$hash  ($crypt)  $file"
	else
		if [ -e "$hashfile" ]; then
			phash=`cat "$hashfile"`
			[ $phash = $hash ] \
				&& echo "${GRN}Success: $type matches saved checksum!" \
				|| (echo "${RED}Error: $type does not match saved checksum!\nExpected checksum: $phash\nActual checksum: $hash" && ec=1)
		else
			echo $hash > "$hashfile" \
				&& echo "${CYN}$crypt checksum file saved at '$hashfile'!" \
				|| (echo "${RED}'$hashfile' could not be created!\n$crypt checksum of $type '$file' is $hash" && ec=1)
		fi
		printf "$NORM"; [ -n "$2" ] && echo
	fi
	shift
done
exit $ec