#!/bin/bash
set -euo pipefail

opdir="${1?Output dir missing}"

: "${HOME?HOME is not set}"

check_file_exists() {
	if [[ -f "$1" ]]; then
		return 0
	fi
	echo "Warning: File does not exist- $1"
	return 1
}

script_path="$0"
script_dir=$(dirname "$(realpath "$0")")
common_ssh_cfg_path="${DIYVPN_SSH_CFG:-$script_dir/common_sshconfig}"
diyvpn_cfg="${DIYVPN_CFG:-$HOME/.config/diyvpn/servers}"

check_file_exists "$common_ssh_cfg_path"

generate() {
	local cfgpath name server_ssh_cfg idle_timeout listen_address
	cfgpath="$1"
	name=$(basename "$cfgpath" | tr -d '[:space:]')

	server_ssh_cfg="$cfgpath"/ssh_config
	server_config_rc="$cfgpath"/config.rc

	check_file_exists "$server_ssh_cfg" || return 0
	check_file_exists "$server_config_rc" || return 0

	# shellcheck disable=SC1090
	source "$server_config_rc"

	idle_timeout="${IDLE_TIMEOUT:-10min}"
	listen_address="${LISTEN_ADDRESS:?LISTEN_ADDRESS should be set}"
	header="# Automatically generated by $script_path"

	cat >"$opdir/diyvpnssh-$name.service" <<-EOF
		$header
		[Unit]
		Description=ssh to $name
		SourcePath=$server_config_rc
		StopWhenUnneeded=yes

		[Service]
		Type=notify
		NotifyAccess=all

		RuntimeDirectory=diyvpn-$name
		Environment=SSH_CFG_PATH=$server_ssh_cfg
		ExecStart=ssh -F "$common_ssh_cfg_path" default
	EOF

	cat >"$opdir/diyvpnact-$name.service" <<-EOF
		$header
		[Unit]
		Description=Socket activator for diyvpn to server $name
		SourcePath=$server_config_rc
		Requires=diyvpnssh-$name.service
		After=diyvpnssh-$name.service
		BindsTo=diyvpnssh-$name.service

		[Service]
		ExecStart=/usr/lib/systemd/systemd-socket-proxyd --exit-idle-time=$idle_timeout %t/diyvpn-$name/sock
	EOF

	cat >"$opdir/diyvpnact-$name.socket" <<-EOF
		$header
		[Unit]
		Description=Socket for diyvpn to server $name
		SourcePath=$server_config_rc

		[Socket]
		ListenStream=$listen_address

		[Install]
		WantedBy=sockets.target
	EOF

	mkdir -p "$opdir/sockets.target.wants"
	ln -snf "../diyvpnact-$name.socket" "$opdir/sockets.target.wants"
}

for server in "$diyvpn_cfg"/*; do
	if [[ -d "$server" ]]; then
		(generate "$server")
	else
		echo "Ignoring $server. Not a directory."
	fi
done