Adding chat history command

#82

src/main/java/buttondevteam/chat/commands/ucmds/HistoryCommand.java

@@ -0,0 +1,74 @@
+package buttondevteam.chat.commands.ucmds;
+
+import buttondevteam.lib.chat.Channel;
+import buttondevteam.lib.chat.ChatMessage;
+import buttondevteam.lib.chat.CommandClass;
+import lombok.RequiredArgsConstructor;
+import lombok.val;
+import org.bukkit.command.CommandSender;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+@CommandClass
+public class HistoryCommand extends UCommandBase {
+	private static HashMap<Channel, HistoryEntry[]> messages = new HashMap<>();
+
+	@Override
+	public String[] GetHelpText(String alias) {
+		return new String[]{ //
+				"§6--- Chat History ----", //
+				"Returns the last 10 messages the player can see." //
+		};
+	}
+
+	@Override
+	public boolean OnCommand(CommandSender sender, String alias, String[] args) {
+		Function<Map.Entry<Channel, HistoryEntry[]>, Map.Entry<Channel, HistoryEntry[]>> filterThem = e -> {
+			int score = e.getKey().getMCScore(sender);
+			HistoryEntry[] he = new HistoryEntry[10];
+			for (int i = 0, j = 0; i < 10; i++) {
+				val cm = e.getValue()[i].chatMessage;
+				if (cm == null)
+					break; //Don't have 10 messages yet
+				if (score == e.getKey().getMCScore(cm.getPermCheck()))
+					he[j++] = e.getValue()[i];
+			}
+			return new HashMap.SimpleEntry<>(e.getKey(), he);
+		};
+		sender.sendMessage("§6---- Chat History ----");
+		Stream<HistoryEntry> stream;
+		if (args.length == 0) {
+			stream = messages.entrySet().stream().map(filterThem).flatMap(e -> Arrays.stream(e.getValue()));
+		} else {
+			Channel ch = Channel.GlobalChat; //TODO: Channel param
+			val hes = messages.get(ch);
+			if (hes == null)
+				return true;
+			stream = Arrays.stream(hes);
+		}
+		AtomicBoolean sent = new AtomicBoolean();
+		stream.sorted(Comparator.comparingLong(he -> he.timestamp)).forEach(e -> {
+			val cm = e.chatMessage;
+			sender.sendMessage(cm.getSender().getName() + ": " + cm.getMessage());
+			sent.set(true);
+		});
+		if (!sent.get())
+			sender.sendMessage("No messages can be found.");
+		return true;
+	}
+
+	@RequiredArgsConstructor
+	public static class HistoryEntry {
+		/**
+		 * System.nanoTime()
+		 */
+		private final long timestamp;
+		private final ChatMessage chatMessage;
+	}
+}