Implement version checking into the /version command

By: Thinkofdeath <thinkofdeath@spigotmc.org>

paper-api/src/main/java/org/bukkit/command/defaults/VersionCommand.java

@@ -1,5 +1,6 @@
 package org.bukkit.command.defaults;
 
+import com.google.common.base.Charsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -13,6 +14,19 @@ import org.bukkit.plugin.PluginDescriptionFile;
 import org.bukkit.util.StringUtil;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.io.Resources;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.net.URL;
+import java.net.URLEncoder;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import org.json.simple.JSONObject;
+import org.json.simple.parser.JSONParser;
+import org.json.simple.parser.ParseException;
 
 public class VersionCommand extends BukkitCommand {
     public VersionCommand(String name) {
@@ -30,6 +44,7 @@ public class VersionCommand extends BukkitCommand {
 
         if (args.length == 0) {
             sender.sendMessage("This server is running " + Bukkit.getName() + " version " + Bukkit.getVersion() + " (Implementing API version " + Bukkit.getBukkitVersion() + ")");
+            sendVersion(sender);
         } else {
             StringBuilder name = new StringBuilder();
 
@@ -126,4 +141,114 @@ public class VersionCommand extends BukkitCommand {
         }
         return ImmutableList.of();
     }
+
+    private final ReentrantLock versionLock = new ReentrantLock();
+    private boolean hasVersion = false;
+    private String versionMessage = null;
+    private final Set<CommandSender> versionWaiters = new HashSet<CommandSender>();
+    private boolean versionTaskStarted = false;
+    private long lastCheck = 0;
+
+    private void sendVersion(CommandSender sender) {
+        if (hasVersion) {
+            if (System.currentTimeMillis() - lastCheck > 21600000) {
+                lastCheck = System.currentTimeMillis();
+                hasVersion = false;
+            } else {
+                sender.sendMessage(versionMessage);
+                return;
+            }
+        }
+        versionLock.lock();
+        try {
+            if (hasVersion) {
+                sender.sendMessage(versionMessage);
+                return;
+            }
+            versionWaiters.add(sender);
+            sender.sendMessage("Checking version, please wait...");
+            if (!versionTaskStarted) {
+                versionTaskStarted = true;
+                new Thread(new Runnable() {
+
+                    @Override
+                    public void run() {
+                        obtainVersion();
+                    }
+                }).start();
+            }
+        } finally {
+            versionLock.unlock();
+        }
+    }
+
+    private void obtainVersion() {
+        String version = Bukkit.getVersion();
+        if (version == null) version = "Custom";
+        if (version.startsWith("git-Spigot-")) {
+            String[] parts = version.substring("git-Spigot-".length()).split("-");
+            int cbVersions = getDistance("craftbukkit", parts[0]);
+            int spigotVersions = getDistance("spigot", parts[1]);
+            if (cbVersions == -1 || spigotVersions == -1) {
+                setVersionMessage("Error obtaining version information");
+            } else {
+                if (cbVersions != 0 && spigotVersions != 0) {
+                    setVersionMessage("You are running the latest version");
+                } else {
+                    setVersionMessage("You are " + (cbVersions + spigotVersions) + " behind");
+                }
+            }
+
+        } else if (version.startsWith("git-Bukkit-")) {
+            int cbVersions = getDistance("craftbukkit", version.substring("git-Bukkit-".length()));
+            if (cbVersions == -1) {
+                setVersionMessage("Error obtaining version information");
+            } else {
+                if (cbVersions != 0) {
+                    setVersionMessage("You are running the latest version");
+                } else {
+                    setVersionMessage("You are " + cbVersions + " behind");
+                }
+            }
+        } else {
+            setVersionMessage("Unknown version, custom build?");
+        }
+    }
+
+    private void setVersionMessage(String msg) {
+        lastCheck = System.currentTimeMillis();
+        versionMessage = msg;
+        versionLock.lock();
+        try {
+            hasVersion = true;
+            versionTaskStarted = false;
+            for (CommandSender sender : versionWaiters) {
+                sender.sendMessage(versionMessage);
+            }
+            versionWaiters.clear();
+        } finally {
+            versionLock.unlock();
+        }
+    }
+
+    private static int getDistance(String repo, String hash) {
+        try {
+            BufferedReader reader = Resources.asCharSource(
+                    new URL("https://hub.spigotmc.org/stash/rest/api/1.0/projects/SPIGOT/repos/" + repo + "/commits?since=" + URLEncoder.encode(hash, "UTF-8") + "&withCounts=true"),
+                    Charsets.UTF_8
+            ).openBufferedStream();
+            try {
+                JSONObject obj = (JSONObject) new JSONParser().parse(reader);
+                return ((Number) obj.get("totalCount")).intValue();
+            } catch (ParseException ex) {
+                ex.printStackTrace();
+                return -1;
+            } finally {
+                reader.close();
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+            return -1;
+        }
+    }
 }