#!/bin/sh
set -eu

usage() {
	printf 'Usage:	%s -p PROFILE -c "COMMAND"\n' "$0"
}

help() {
	cat <<EOF
Options:
  -p, PROFILE    profile to be used for gathering and storing data
  -c, COMMAND    command to be run, reading from STDIN, writing to STDOUT
  -h, --help     show this help
  -V, --version  print the version number

See manpages for more information.
EOF
}

version() {
	printf 'remembering-@VERSION@ @DATE@\n'
}

missing() {
	printf 'Missing option: %s\n' "$1"
}

# shellcheck disable=2068
for flag in $@; do
	if [ "$flag" = '--help' ]; then
		usage
		help
		exit
	elif [ "$flag" = '--version' ]; then
		version
		exit
	fi
done

COMMANDFLAG=
PROFILEFLAG=
while getopts 'hc:p:V' name; do
	case "$name" in
		c)
			COMMANDFLAG="$OPTARG"
			;;
		p)
			PROFILEFLAG="$OPTARG"
			;;
		h)
			usage
			help
			exit
			;;
		V)
			version
			exit
			;;
		*)
			printf 'Ignoring unrecognized flag "%s"' "$name" >&2
			;;
	esac
done

if [ -z "$COMMANDFLAG" ]; then
	missing '-c "COMMAND"' >&2
	usage >&2
	exit 2
fi

if [ -z "$PROFILEFLAG" ]; then
	missing '-p PROFILE' >&2
	usage >&2
	exit 2
fi

COMMAND="$COMMANDFLAG"
PROFILE="${XDG_DATA_HOME:-$HOME/.local/share/remembering}/$PROFILEFLAG"

if [ ! -e "$PROFILE" ]; then
	mkdir -p "$(dirname "$PROFILE")"
	touch "$PROFILE"
fi

MERGED="$(mktemp)"
FILTERED="$(mktemp)"
SORTED_STDIN="$(mktemp)"
cat - > "$SORTED_STDIN"

# sed line to reverse lines, replacing GNU/Linux's tac
# Taken from:
# https://unix.stackexchange.com/questions/280685/reverse-sequence-of-a-file-with-posix-tools/280686#comment601716_280686
xargs -I{} printf '0:%s\n' "{}" < "$SORTED_STDIN" | \
	sort -t: -k2,2 -m - "$PROFILE" | \
	sed '1!x;H;1h;$!d;g' | \
	sort -t: -k2,2 -u > "$MERGED"

xargs -I{} printf 'filter_marker:%s\n' "{}" < "$SORTED_STDIN" | \
	cat - "$PROFILE" | \
	sort -t: -k2,2 | \
	awk '{
		split($0, l, ":")
		rank = l[1]
		entry = substr($0, length(rank) + 2)
		if (rank != "filter_marker") {
			prev_rank = rank
			prev_entry = entry
		} else {
			if (prev_entry == entry) {
				print prev_rank ":" entry
			} else {
				print "0:" entry
			}
		}
	}' > "$FILTERED"

CHOICE="$(sort -t: -k1nr,1 -k2,2 < "$FILTERED" | \
	cut -d: -f2- | \
	sh -c "$COMMAND")"

if [ -n "$CHOICE" ]; then
	NEW_PROFILE="$(mktemp)"
	awk -v choice="$CHOICE" '{
		split($0, l, ":")
		rank = l[1]
		entry = substr($0, length(rank) + 2)
		if (entry == choice) {
			# Naively increment ranking by one
			print rank + 1 ":" entry
		} else {
			print rank ":" entry
		}
	}' "$MERGED" > "$NEW_PROFILE"
	mv "$NEW_PROFILE" "$PROFILE"
	printf '%s\n' "$CHOICE"
fi