More things for #11 😄

api/src/main/java/net/jitse/npclib/hologram/Hologram.java

@@ -1,4 +1,17 @@
 package net.jitse.npclib.hologram;
 
+import org.bukkit.entity.Player;
+
+import java.util.List;
+import java.util.UUID;
+
 public interface Hologram {
+
+    void show(Player player);
+
+    void hide(Player player);
+
+    void silentHide(UUID uuid);
+
+    void updateText(List<String> text);
 }

api/src/main/java/net/jitse/npclib/hologram/HologramBase.java

@@ -1,5 +1,6 @@
 package net.jitse.npclib.hologram;
 
+import org.bukkit.Bukkit;
 import org.bukkit.Location;
 import org.bukkit.entity.Player;
 
@@ -18,17 +19,68 @@ public abstract class HologramBase implements Hologram, HologramPacketHandler {
 
     protected List<String> text;
 
-
     public HologramBase(Location start, List<String> text) {
         this.start = start;
         this.text = text;
+
+        // Generate the necessary show and hide packets.
+        createPackets();
     }
 
-    abstract public void show(Player player);
+    @Override
+    public void show(Player player) {
+        UUID uuid = player.getUniqueId();
+        if (shown.contains(uuid))
+            throw new IllegalArgumentException("Hologram is already shown to player");
 
-    abstract public void hide(Player player);
+        sendShowPackets(player);
 
-    abstract public void silentHide(UUID uuid);
+        this.shown.add(uuid);
+    }
 
-    abstract public void updateText(List<String> text);
+    @Override
+    public void hide(Player player) {
+        UUID uuid = player.getUniqueId();
+        if (!shown.contains(uuid))
+            throw new IllegalArgumentException("Hologram is not shown to player");
+
+        sendHidePackets(player);
+
+        this.shown.remove(uuid);
+    }
+
+    @Override
+    public void silentHide(UUID uuid) {
+        if (!shown.contains(uuid))
+            throw new IllegalArgumentException("Hologram is not shown to player");
+
+        this.shown.remove(uuid);
+    }
+
+    @Override
+    public void updateText(List<String> text) {
+        if (this.text.size() != text.size())
+            throw new IllegalArgumentException("When updating the text, the old and new text should have the same amount of lines");
+
+        for (int i = 0; i < text.size(); i++) {
+            String oldLine = this.text.get(i);
+            String newLine = text.get(i);
+
+            if (oldLine.equals(newLine))
+                continue; // No need to update.
+
+            // Perhaps this should return an object so we can send all immediately to the shown players.
+            createTextUpdatePacket(oldLine, newLine);
+        }
+
+        for (UUID uuid : shown) {
+            Player player = Bukkit.getPlayer(uuid);
+            if (player == null || !player.isOnline()) {
+                throw new IllegalStateException("Tried to update hologram for offline player");
+            }
+
+//            sendTextUpdatePackets(player, );
+        }
+        this.text = text;
+    }
 }

api/src/main/java/net/jitse/npclib/hologram/HologramPacketHandler.java

@@ -1,6 +1,16 @@
 package net.jitse.npclib.hologram;
 
+import org.bukkit.entity.Player;
+
 public interface HologramPacketHandler {
 
-    void sendTextUpdatePackets(int index, String newLine);
+    void createPackets();
+
+    void sendShowPackets(Player player);
+
+    void sendHidePackets(Player player);
+
+    void createTextUpdatePacket(String oldLine, String newLine);
+
+    void sendTextUpdatePackets(Player player);
 }