Added optional alert system for low TPS and server start/stop messages

src/main/java/com/justinmtech/minebuddy/Minebuddy.java

@@ -1,6 +1,7 @@
 package com.justinmtech.minebuddy;
 
 import com.justinmtech.minebuddy.commands.*;
+import com.justinmtech.minebuddy.notifications.Notifier;
 import com.justinmtech.minebuddy.util.ActivityMessageUpdater;
 import com.justinmtech.minebuddy.util.ServerStatus;
 import org.bukkit.plugin.java.JavaPlugin;
@@ -13,6 +14,7 @@
 public final class Minebuddy extends JavaPlugin {
     private DiscordApi api;
     private ServerStatus status;
+    private Notifier notifier;
 
     @Override
     public void onEnable() {
@@ -30,11 +32,13 @@ public void onEnable() {
 
         setStatus(new ServerStatus(getConfig()));
         new ActivityMessageUpdater(this);
+
     }
 
     @Override
     public void onDisable() {
         if (getApi() != null) {
+            getNotifier().sendDiscordAlert(getStatus().getName() + " is now offline!");
             getApi().disconnect();
             setApi(null);
         }
@@ -55,6 +59,15 @@ private void onConnectToDiscord(DiscordApi api) {
         api.addListener(new StopServerCommand(getConfig()));
         api.addListener(new ServerStatusCommand(getConfig(), getStatus()));
 
+        activateAlertsIfEnabled();
+    }
+
+    private void activateAlertsIfEnabled() {
+        if (getConfig().getBoolean("alerts.enabled", false)) {
+            notifier = new Notifier(this);
+            getServer().getPluginManager().registerEvents(getNotifier(), this);
+            getNotifier().sendDiscordAlert(getStatus().getName() + " is now online!");
+        }
     }
 
     public String getToken() {
@@ -76,4 +89,8 @@ public void setApi(DiscordApi api) {
     public void setStatus(ServerStatus status) {
         this.status = status;
     }
+
+    public Notifier getNotifier() {
+        return notifier;
+    }
 }

src/main/java/com/justinmtech/minebuddy/notifications/Notifier.java

@@ -0,0 +1,95 @@
+package com.justinmtech.minebuddy.notifications;
+
+import com.justinmtech.minebuddy.Minebuddy;
+import com.justinmtech.minebuddy.util.ServerStatus;
+import org.bukkit.configuration.file.FileConfiguration;
+import org.bukkit.event.Listener;
+import org.bukkit.scheduler.BukkitRunnable;
+import org.javacord.api.entity.channel.TextChannel;
+import org.javacord.api.entity.message.MessageBuilder;
+
+import java.util.Optional;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class Notifier implements Listener {
+    private final Minebuddy plugin;
+    private final ServerStatus status;
+    private final FileConfiguration config;
+    private final Logger logger;
+    private double lastTpsCheck;
+
+    public Notifier(Minebuddy plugin) {
+        this.plugin = plugin;
+        this.status = plugin.getStatus();
+        this.config = plugin.getConfig();
+        this.logger = plugin.getLogger();
+        setLastTpsCheck(20.0);
+        run();
+    }
+
+    private void run() {
+        new BukkitRunnable() {
+            @Override
+            public void run() {
+                double tps = getStatus().getTpsFromPastMinuteAsDouble();
+                if (isTpsLow()) {
+                    setLastTpsCheck(tps);
+                    sendDiscordAlert(getStatus().getName() + " TPS is currently " + tps + "! :cry:");
+                } else if (!isTpsLow() && getLastTpsCheck() < getTpsThreshold()) {
+                    sendDiscordAlert(getStatus().getName() + " TPS has recovered! :cowboy:");
+                    setLastTpsCheck(tps);
+                }
+            }
+        }.runTaskTimerAsynchronously(getPlugin(), 1200L, 1200L);
+    }
+
+    private boolean isTpsLow() {
+        double tps = getStatus().getTpsFromPastMinuteAsDouble();
+        double threshold = getTpsThreshold();
+        return tps < threshold;
+    }
+
+    private double getTpsThreshold() {
+        return getConfig().getDouble("alerts.tps-threshold", 15.0);
+    }
+
+    public void sendDiscordAlert(String message) {
+        if (getAlertChannel().isPresent()) {
+            new MessageBuilder()
+                    .append(message)
+                    .send(getAlertChannel().get());
+        }
+    }
+
+    private Optional<TextChannel> getAlertChannel() {
+        String channelId = getConfig().getString("alerts.channel-id", "");
+        if (channelId == null) return Optional.empty();
+        if (channelId.equals("")) getLogger().log(Level.SEVERE, "Alerts are enabled but you have not set a channel ID!");
+        return getPlugin().getApi().getTextChannelById(channelId);
+    }
+
+    private Minebuddy getPlugin() {
+        return plugin;
+    }
+
+    public ServerStatus getStatus() {
+        return status;
+    }
+
+    public FileConfiguration getConfig() {
+        return config;
+    }
+
+    public Logger getLogger() {
+        return logger;
+    }
+
+    public double getLastTpsCheck() {
+        return lastTpsCheck;
+    }
+
+    public void setLastTpsCheck(double lastTpsCheck) {
+        this.lastTpsCheck = lastTpsCheck;
+    }
+}

src/main/java/com/justinmtech/minebuddy/util/ServerStatus.java

@@ -44,6 +44,19 @@ public String getTpsFromPastMinute() {
         return getPlaceholders("%server_tps_1%");
     }
 
+    public double getTpsFromPastMinuteAsDouble() {
+        String tpsString = getPlaceholders("%server_tps_1%");
+        if (tpsString.contains("*")) tpsString = tpsString.replace("*", "");
+        double tps;
+        try {
+            tps = Double.parseDouble(tpsString);
+        } catch (NumberFormatException e) {
+            return 5.0;
+        }
+        return tps;
+    }
+
+
     public int getStaffOnline() {
         String permission = getConfig().getString("staff-permission");
         if (permission == null) return 0;

src/main/resources/config.yml

@@ -4,21 +4,31 @@ server-name: "My Server"
 broadcast-prefix: "&c&l[Broadcast] &e"
 staff-permission: "staff.perm"
 invisible-on-list-permission: "staff.invisible"
+
 #Symbol used before command
 command-symbol: "!"
+
 #Optional prefix used after symbol and before command (leave empty for none)
 command-prefix: ""
+
 #Do not change the values on the left, only the right
 commands:
   HELP: "help"
   BROADCAST: "broadcast"
   PLAYERS: "players"
   STATUS: "status"
   STOP: "stop"
+
 messages:
   server-status: "Here is the server status:"
   stop-server: "The server is shutting down..."
   players-online: "There are %placeholder% players online."
   no-players-online: "There are no players online."
   player-list: "The following players are online:"
-  help: "The following commands can be prefixed with '%placeholder%' to be executed:"
+  help: "The following commands can be prefixed with '%placeholder%' to be executed:"
+
+#Enable TPS alerts and server start/stop messages if enabled. Channel ID cannot be blank.
+alerts:
+  enabled: false
+  channel-id: ""
+  tps-threshold: 15.0