bin/rc: New script

2 files changed, 202 insertions, 0 deletions

diff --git a/.gitignore.d/homerc b/.gitignore.d/homerc
index 89274fe..66206ac 100644
--- a/.gitignore.d/homerc
+++ b/.gitignore.d/homerc
@@ -4,6 +4,8 @@
 # Include relevant files
 !/.gitignore.d/
 !/.gitignore.d/homerc
+!/bin/
+!/bin/rc
 
 # Exclude swap and backup files
 *.s[a-w]?
diff --git a/bin/rc b/bin/rc
new file mode 100755
index 0000000..1b6c1cd
--- /dev/null
+++ b/bin/rc
@@ -0,0 +1,200 @@
+#!/bin/sh
+
+set -eu
+
+RC_MAGIC='~/rc'
+
+progname=
+rc_fifo=
+
+error()
+{
+	local fmt="${1}"
+	shift 1
+
+	printf "%s: ${fmt}\n" "${progname}" "${@}"
+
+	return 0
+}
+
+valid_session_type()
+{
+	local session_type="${1}"
+	shift 1
+
+	case "${session_type}" in *[!A-Za-z0-9:]* | '' | ':'* | *':')
+		return 1
+	esac
+	return 0
+}
+
+# Returns 0 if the session is the first of its type or was last of its type
+# TODO: Handle decrement from 0.
+inc_session()
+{
+	local s_type="${1}"
+	local dir=${2}
+	shift 2
+	local ret=
+
+	ret=1
+
+	s_type="$(printf '%s' "${s_type}" | tr ':' '_')"
+	eval "[ \${sessions_${s_type}:-0} -eq 0 ] && ret=0"
+	eval "sessions_${s_type}=\$((\${sessions_${s_type}:-0} + ${dir}))"
+	eval "[ \${sessions_${s_type}} -eq 0 ] && ret=0"
+
+	return ${ret}
+}
+
+chg_session()
+{
+	local session_type="${1}"
+	local inc_dir=${2}
+	local diff="${3}"
+	shift 3
+
+	while :; do
+		case "${session_type}" in *:*);; *) break;; esac
+		if inc_session "${session_type}" ${inc_dir}; then
+			diff="${diff}${session_type},"
+		fi
+		session_type="${session_type%:*}"
+	done
+
+	diff="${diff%,}"
+}
+
+beg_session()
+{
+	local session_type="${1}"
+	shift 1
+
+	chg_session "${session_type}" 1 '+'
+	return ${?}
+}
+
+end_session()
+{
+	local session_type="${1}"
+	shift 1
+
+	chg_session "${session_type}" -1 '-'
+	return ${?}
+}
+
+listen()
+{
+	local magic=
+	local cmd=
+	local arg=
+
+	while :; do
+		if read -r magic cmd arg; then
+			case "${magic}" in "${RC_MAGIC}");; *)
+				continue
+			esac
+		fi
+		case "${cmd}" in
+			'beg')
+				if valid_session_type "${arg}"; then
+					beg_session "${arg}"
+				fi
+				;;
+			'end')
+				if valid_session_type "${arg}"; then
+					end_session "${arg}"
+				fi
+				;;
+			'bye')
+				break
+				;;
+			*)
+				continue
+				;;
+		esac
+	done 0<"${rc_fifo}"
+}
+
+start()
+{
+	local session_type="${1}"
+	shift 1
+
+	if mkfifo "${rc_fifo}" 2>/dev/null; then
+		beg_session "${session_type}"
+		listen
+		rm "${rc_fifo}"
+	else
+		# Signal the running rc daemon.
+		printf "%s beg %s\n" "${RC_MAGIC}" "${session_type}" \
+			1>"${rc_fifo}"
+	fi
+
+	return 0
+}
+
+stop()
+{
+	local session_type="${1}"
+	shift 1
+
+	if mkfifo "${rc_fifo}" 2>/dev/null; then
+		# Assuming the daemon role just to end a non-existent session
+		# makes no sense.
+		error 'No running daemon found'
+		rm "${rc_fifo}"
+		return 1
+	else
+		# Signal the running rc daemon.
+		printf "%s end %s\n" "${RC_MAGIC}" "${session_type}" \
+			1>"${rc_fifo}"
+	fi
+
+	return 0
+}
+
+usage()
+{
+	printf 'Usage: %s {start|stop} <session-type>\n' "${0}"
+
+	return 0
+}
+
+main()
+{
+	local action=
+	local session_type=
+
+	if [ ${#} -ne 2 ]; then
+		usage 1>&2
+		return 1
+	fi
+	action="${1}"
+	session_type="${2}"
+
+	if ! valid_session_type; then
+		error 'Invalid session type'
+		return 1
+	fi
+
+	progname="${0##*/}"
+	rc_fifo="/tmp/homercrc-$(id -u)"
+
+	case "${action}" in
+		'start')
+			start "${session_type}"
+			;;
+		'stop')
+			stop "${session_type}"
+			;;
+		*)
+			usage 1>&2
+			return 1
+			;;
+	esac
+
+	return 0
+}
+
+main "${@}"