feat(api): add some basic api interfaces

src/main/java/dev/protocollib/api/BinaryPacket.java

@@ -0,0 +1,8 @@
+package dev.protocollib.api;
+
+public interface BinaryPacket {
+
+    int id();
+
+    byte[] payload();
+}

src/main/java/dev/protocollib/api/Connection.java

@@ -0,0 +1,30 @@
+package dev.protocollib.api;
+
+import java.net.InetSocketAddress;
+
+import javax.annotation.Nullable;
+
+import org.bukkit.entity.Player;
+
+public interface Connection {
+
+    @Nullable
+    Player player();
+
+    InetSocketAddress address();
+
+    int protocolVersion();
+
+    ProtocolPhase protocolPhase(PacketDirection packetDirection);
+
+    boolean isConnected();
+
+    void sendPacket(BinaryPacket packet);
+
+    void sendPacket(PacketContainer packet);
+
+    void receivePacket(PacketContainer packet);
+
+    void disconnect(String reason);
+
+}

src/main/java/dev/protocollib/api/PacketContainer.java

@@ -0,0 +1,9 @@
+package dev.protocollib.api;
+
+public interface PacketContainer {
+
+    PacketType packetType();
+
+    Object packet();
+
+}

src/main/java/dev/protocollib/api/PacketDirection.java

@@ -0,0 +1,7 @@
+package dev.protocollib.api;
+
+public enum PacketDirection {
+
+    SERVERBOUND, CLIENTBOUND;
+
+}

src/main/java/dev/protocollib/api/PacketEvent.java

@@ -0,0 +1,11 @@
+package dev.protocollib.api;
+
+import org.bukkit.event.Cancellable;
+
+public interface PacketEvent extends Cancellable {
+
+    Connection connection();
+
+    PacketContainer packet();
+
+}

src/main/java/dev/protocollib/api/PacketListener.java

@@ -0,0 +1,8 @@
+package dev.protocollib.api;
+
+@FunctionalInterface
+public interface PacketListener {
+
+    void handlePacket(PacketEvent event);
+
+}

src/main/java/dev/protocollib/api/PacketListenerBuilder.java

@@ -0,0 +1,16 @@
+package dev.protocollib.api;
+
+import java.util.Collection;
+
+public interface PacketListenerBuilder {
+
+    PacketListenerBuilder types(PacketType...packetTypes);
+
+    PacketListenerBuilder types(Collection<PacketType> packetTypes);
+
+    PacketListenerBuilder priority(PacketListenerPriority priority);
+
+    PacketListenerBuilder listener(PacketListener listener);
+
+    PacketListenerRegistration register();
+}

src/main/java/dev/protocollib/api/PacketListenerPriority.java

@@ -0,0 +1,7 @@
+package dev.protocollib.api;
+
+public enum PacketListenerPriority {
+
+    LOWEST, LOW, NORMAL, HIGH, HIGHEST, MONITOR;
+
+}

src/main/java/dev/protocollib/api/PacketListenerRegistration.java

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+package dev.protocollib.api;
+
+public interface PacketListenerRegistration {
+
+    void unregister();
+}

src/main/java/dev/protocollib/api/PacketType.java

@@ -0,0 +1,13 @@
+package dev.protocollib.api;
+
+public interface PacketType {
+
+    PacketDirection packetDirection();
+
+    Class<?> packetClass();
+
+    boolean isSupported();
+
+    boolean isDeprecated();
+
+}

src/main/java/dev/protocollib/api/PacketTypes.java

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+package dev.protocollib.api;
+
+public class PacketTypes {
+
+    // TODO should contain all packet types as public static final fields
+
+}

src/main/java/dev/protocollib/api/ProtocolLib.java

@@ -0,0 +1,12 @@
+package dev.protocollib.api;
+
+import org.bukkit.entity.Player;
+import org.bukkit.plugin.Plugin;
+
+public interface ProtocolLib {
+
+    PacketListenerBuilder createListener(Plugin plugin);
+
+    Connection connection(Player player);
+
+}

src/main/java/dev/protocollib/api/ProtocolPhase.java

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+package dev.protocollib.api;
+
+public enum ProtocolPhase {
+
+    HANDSHAKE, PLAY, STATUS, LOGIN, CONFIGURATION, UNKNOWN;
+
+}