mc-server-manager/agent/source/server_actions.d

module server_actions;

import std.stdio;
import std.process;
import std.format;
import std.algorithm;
import std.array;
import std.string;
import std.file;
import std.datetime;
import mcrcd;

import shared_utils.discord;
import shared_utils.server_status;

import server_metadata;
import config;

ServerStatus determineStatus(in ServerMetaData server) {
	const bool online = isServiceActive(server.serviceName);
	int playersOnline = 0;
	string[] playerNames;
	if (online) {
		MCRconResponse response = executeRconCommand(server, "list");
		string playersList;
		int tmp;
		response.text.formattedRead!"There are %d of a max of %d players online: %s"(
			playersOnline,
			tmp,
			playersList
		);
		playerNames = playersList.strip.split(",")
			.filter!(s => s !is null && s.strip.length > 0)
			.map!(s => s.strip)
			.array;
	}
	return ServerStatus(
		server.name,
		server.displayName,
        server.description,
		online,
		playersOnline,
		server.maxPlayers,
		playerNames.idup
	);
}

void startServer(in ServerMetaData server, in AgentConfig config) {
    writeln("Starting server " ~ server.name);
    Pid pid = spawnProcess(["sudo", "systemctl", "start", server.serviceName]);
    int result = wait(pid);
    if (result != 0) {
        string msg = format!"Starting server %s failed with code %d."(server.name, result);
        stderr.writeln(msg);
        throw new Exception(msg);
    }
    sendDiscordMessage(
        config.discordWebhookUrl,
        format!"Started server %s as a result of a user request."(server.name)
    );
}

void stopServer(in ServerMetaData server, in AgentConfig config) {
    writeln("Shutting down server " ~ server.name ~ " after a period of inactivity.");
    Pid pid = spawnProcess(["sudo", "systemctl", "stop", server.serviceName]);
    int result = wait(pid);
    if (result == 0) {
        removeIdleTrackerFileIfPresent(server);
        sendDiscordMessage(
            config.discordWebhookUrl,
            format!"Shut down server %s after inactivity for more than %d minutes."(
                server.name,
                config.serverInactivityTimeoutMinutes
            )
        );
    } else {
        stderr.writefln!"Failed to stop server %s. systemctl stop exited with code %d."(server.name, result);
    }
}

Duration getOrCreateIdleTrackerFileAndGetAge(in ServerMetaData server) {
    string filename = getIdleTrackerFilename(server);
    if (exists(filename)) {
        SysTime timestamp = std.file.timeLastModified(filename);
        return Clock.currTime - timestamp;
    } else {
        File f = File(filename, "w");
        f.close();
        writeln("Created idle tracker for server " ~ server.name ~ ".");
        return seconds(0);
    }
}

void removeIdleTrackerFileIfPresent(in ServerMetaData server) {
    string trackerFile = getIdleTrackerFilename(server);
    if (exists(trackerFile)) {
        std.file.remove(trackerFile);
        writeln("Removed idle tracker for server " ~ server.name);
    }
}

private MCRconResponse executeRconCommand(in ServerMetaData server, string command) {
	MCRcon rcon = new MCRcon();
	rcon.connect("127.0.0.1", server.rconPort);
	scope(exit) {
		rcon.disconnect();
	}
	rcon.login(server.rconPassword);
	return rcon.command(command);
}

private bool isServiceActive(string serviceName) {
	import std.process;
	Pid pid = spawnProcess(["systemctl", "is-active", "--quiet", serviceName]);
	int result = wait(pid);
	return result == 0;
}

private string getIdleTrackerFilename(in ServerMetaData server) {
    return "agent-idle-tracker__" ~ server.name ~ ".txt";
}