#!/bin/sh
set +e

export PATH="/usr/bin:/bin"

error() {
	echo "$@" >&2
}

alt_ab() {
	if [ "$1" == "a" ]; then echo "b"; else echo "a"; fi
}

: ${S6_PATH:="${XDG_DATA_HOME:="/etc"}/s6"}
: ${S6_DIST_PATH:="${XDG_CONFIG_HOME:="/usr/share"}/nnd/s6/dist"}
: ${S6_LIVE_PATH:="${XDG_RUNTIME_DIR:="/run"}/s6-rc"}
: ${S6_SCANDIR_PATH:="${XDG_RUNTIME_DIR:="/run"}/service"}
: ${S6_RC_PATH:="$S6_PATH/rc"}
: ${S6_ENV_PATH:="$S6_PATH/env"}
: ${S6_SV_PATH:="$S6_PATH/sv"}

# A/B mode, always keep last copy
DB_FRESH_ACT() {
	readlink "$S6_SV_PATH/current" | cut -d. -f2 # if it fails (missing), it will be empty and 'a' will be used as inactive by default
}

DB_FRESH_NAC() {
	alt_ab "$(DB_FRESH_ACT)"
}

generate() {
	if ! mkdir -p "$S6_SV_PATH"; then
		error "Failed to create sv directory"
		return "$?"
	fi

	local NAC="$(DB_FRESH_NAC)"
	if [ -d "$S6_SV_PATH/current.$NAC" ]; then
		if ! rm -rf "$S6_SV_PATH/current.$NAC"; then
			error "Failed to remove inactive database path"
			return "$?"
		fi
	fi
	if ! s6-rc-compile "$S6_SV_PATH/current.$NAC" "$S6_RC_PATH"; then
		error "Failed to compile current s6 database"
		return "$?"
	fi
}

swap() {
	local new="current.$(DB_FRESH_NAC)"
	if ! [ -d "$S6_SV_PATH/$new" ]; then
		error "There's no database to switch to"
		return 1
	fi

	if ! s6-rc-db -c "$S6_SV_PATH/$new" check; then
		error "Database $new is invalid"
		return "$?"
	fi

	if ! ln -sfn "$new" "$S6_SV_PATH/current"; then
		error "Failed to update A/B current symlink"
		return "$?"
	fi
}

update() {
	if ! s6-rc-update -l "$S6_LIVE_PATH" "$S6_SV_PATH/current.$(DB_FRESH_ACT)"; then
		error "Failed to update live state of the database"
		return "$?"
	fi
}

dist() {
	#for src in "$S6_DIST_PATH/rc"/* "$S6_DIST_PATH/env"/*; do
	for src in "$S6_DIST_PATH/rc"/*; do
		local svc="${src#$S6_DIST_PATH/}"
		if [ ! -e "$S6_PATH/$svc" ]; then
			default "$svc" || return "$?"
		fi
	done
}

cleanup() {
	# Remove any dangling invalid symlinks
	for i in rc env; do
		removedangle /etc/s6/"$i" || return "$?"
	done
}

default() {
	for svc in $@; do
		local src="$S6_DIST_PATH/$svc"
		local target="$S6_PATH/$svc"

		if ! [ -e "$src" ]; then
			error "$svc doesn't exist"
			return "$?"
		fi

		if [ -h "$target" ]; then
			error "$svc is already a default instance"
			return "$?"
		fi

		defaultfunc || return "$?"
	done
}

custom() {
	for svc in $@; do
		local src="$S6_DIST_PATH/$svc"
		local target="$S6_PATH/$svc"

		if ! [ -e "$src" ]; then
			error "$svc doesn't exist"
			return "$?"
		fi

		if ! [ -h "$target" ]; then
			error "$svc is already a custom instance"
			return "$?"
		fi

		customfunc || return "$?"
	done
}

customfunc() {
	: ${src:?"Missing src in customfunc"}
	: ${target:?"Missing target in customfunc"}
	if ! rm "$target"; then
		error "Failed to remove distributed directory $target"
		return "$?"
	fi

	if ! cp -r "$src" "$target"; then
		error "Failed to initialise custom directory $target"
		return "$?"
	fi
}

defaultfunc() {
	: ${src:?"Missing src in defaultfunc"}
	: ${target:?"Missing target in defaultfunc"}
	if ! rm -rf "$target"; then
		error "Failed to remove custom directory $target"
		return "$?"
	fi

	if ! ln -sv "$src" "$target"; then
		error "Failed to create reference to $src"
		return "$?"
	fi
}

removedangle() {
	local dir="$1"
	find -L "$dir" -maxdepth 1 -type l -exec rm -v -- {} +
}

# TODO
# makeusertree() {
# 	USR="$1"
# 	UID="$(id -u "$USR")"
# 	RUNTIME_DIR="/run/user/$UID"
# 	: ${PARENT_RCDIR:+"/etc/s6/rc"}
# 	s6-usertree-maker \
# 		-d "$RUNTIME_DIR"/service \
# 		-r usertree."$UID"/logger.usertree."$UID" \
# 		-l "$USR" \
# 		"$USR" \
# 		"$RUNTIME_DIR"/uncaught-logs/ \
# 		"$PARENT_RCDIR"
# }

cmd="$1"
shift
if [ -z "$cmd" ]; then
	generate || return "$?"
	swap || return "$?"
	update || return "$?"
else
	case "$cmd" in
		generate|swap|update|dist|custom|default|cleanup) eval "$cmd" $@ || return "$?";;
		*) error "Invalid command $cmd"; return 1;;
	esac
fi