Add MC packets

src/main/java/me/braydon/mc/common/EnumUtils.java

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+package me.braydon.mc.common;
+
+import lombok.NonNull;
+import lombok.experimental.UtilityClass;
+
+/**
+ * @author Braydon
+ */
+@UtilityClass
+public final class EnumUtils {
+    /**
+     * Get the enum constant of the specified enum type with the specified name.
+     *
+     * @param enumType the enum type
+     * @param name     the name of the constant to return
+     * @param <T>      the type of the enum
+     * @return the enum constant of the specified enum type with the specified name
+     */
+    public <T extends Enum<T>> T getEnumConstant(@NonNull Class<T> enumType, @NonNull String name) {
+        try {
+            return Enum.valueOf(enumType, name);
+        } catch (IllegalArgumentException ex) {
+            return null;
+        }
+    }
+}

src/main/java/me/braydon/mc/common/packet/MinecraftPacket.java

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+package me.braydon.mc.common.packet;
+
+import lombok.NonNull;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+/**
+ * Represents a packet in
+ * the Minecraft protocol.
+ *
+ * @author Braydon
+ */
+public abstract class MinecraftPacket {
+    /**
+     * Process this packet.
+     *
+     * @param inputStream the input stream to read from
+     * @param outputStream the output stream to write to
+     * @throws IOException if an I/O error occurs
+     */
+    public abstract void process(@NonNull DataInputStream inputStream, @NonNull DataOutputStream outputStream) throws IOException;
+
+    /**
+     * Write a variable integer to the output stream.
+     *
+     * @param outputStream the output stream to write to
+     * @param paramInt the integer to write
+     * @throws IOException if an I/O error occurs
+     */
+    protected final void writeVarInt(DataOutputStream outputStream, int paramInt) throws IOException {
+        while (true) {
+            if ((paramInt & 0xFFFFFF80) == 0) {
+                outputStream.writeByte(paramInt);
+                return;
+            }
+            outputStream.writeByte(paramInt & 0x7F | 0x80);
+            paramInt >>>= 7;
+        }
+    }
+
+    /**
+     * Read a variable integer from the input stream.
+     *
+     * @param inputStream the input stream to read from
+     * @return the integer that was read
+     * @throws IOException if an I/O error occurs
+     */
+    protected final int readVarInt(@NonNull DataInputStream inputStream) throws IOException {
+        int i = 0;
+        int j = 0;
+        while (true) {
+            int k = inputStream.readByte();
+            i |= (k & 0x7F) << j++ * 7;
+            if (j > 5) {
+                throw new RuntimeException("VarInt too big");
+            }
+            if ((k & 0x80) != 128) {
+                break;
+            }
+        }
+        return i;
+    }
+}

src/main/java/me/braydon/mc/common/packet/impl/PacketHandshakingInSetProtocol.java

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+package me.braydon.mc.common.packet.impl;
+
+import lombok.AllArgsConstructor;
+import lombok.NonNull;
+import lombok.ToString;
+import me.braydon.mc.common.packet.MinecraftPacket;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+/**
+ * This packet is sent by the client to the server to set
+ * the hostname, port, and protocol version of the client.
+ *
+ * @author Braydon
+ * @see <a href="https://wiki.vg/Protocol#Handshake">Protocol Docs</a>
+ */
+@AllArgsConstructor @ToString
+public final class PacketHandshakingInSetProtocol extends MinecraftPacket {
+    private static final byte ID = 0x00; // The ID of the packet
+    private static final int STATUS_HANDSHAKE = 1; // The status handshake ID
+
+    /**
+     * The hostname of the server.
+     */
+    @NonNull private final String hostname;
+
+    /**
+     * The port of the server.
+     */
+    private final int port;
+
+    /**
+     * The protocol version of the server.
+     */
+    private final int protocolVersion;
+
+    /**
+     * Process this packet.
+     *
+     * @param inputStream  the input stream to read from
+     * @param outputStream the output stream to write to
+     * @throws IOException if an I/O error occurs
+     */
+    @Override
+    public void process(@NonNull DataInputStream inputStream, @NonNull DataOutputStream outputStream) throws IOException {
+        try (ByteArrayOutputStream handshakeBytes = new ByteArrayOutputStream();
+             DataOutputStream handshake = new DataOutputStream(handshakeBytes)
+        ) {
+            handshake.writeByte(ID); // Write the ID of the packet
+            writeVarInt(handshake, protocolVersion); // Write the protocol version
+            writeVarInt(handshake, hostname.length()); // Write the length of the hostname
+            handshake.writeBytes(hostname); // Write the hostname
+            handshake.writeShort(port); // Write the port
+            writeVarInt(handshake, STATUS_HANDSHAKE); // Write the status handshake ID
+
+            // Write the handshake bytes to the output stream
+            writeVarInt(outputStream, handshakeBytes.size());
+            outputStream.write(handshakeBytes.toByteArray());
+        }
+    }
+}

src/main/java/me/braydon/mc/common/packet/impl/PacketStatusInStart.java

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+package me.braydon.mc.common.packet.impl;
+
+import lombok.Getter;
+import lombok.NonNull;
+import me.braydon.mc.common.packet.MinecraftPacket;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+/**
+ * This packet is sent by the client to the server to request the
+ * status of the server. The server will respond with a json object
+ * containing the server's status.
+ *
+ * @author Braydon
+ * @see <a href="https://wiki.vg/Protocol#Status_Request">Protocol Docs</a>
+ */
+@Getter
+public final class PacketStatusInStart extends MinecraftPacket {
+    private static final byte ID = 0x00; // The ID of the packet
+
+    /**
+     * The response json from the server, null if none.
+     */
+    private String response;
+
+    /**
+     * Process this packet.
+     *
+     * @param inputStream  the input stream to read from
+     * @param outputStream the output stream to write to
+     * @throws IOException if an I/O error occurs
+     */
+    @Override
+    public void process(@NonNull DataInputStream inputStream, @NonNull DataOutputStream outputStream) throws IOException {
+        // Send the status request
+        outputStream.writeByte(0x01); // Size of packet
+        outputStream.writeByte(ID);
+
+        // Read the status response
+        readVarInt(inputStream); // Size of the response
+        int id = readVarInt(inputStream);
+        if (id == -1) { // The stream was prematurely ended
+            throw new IOException("Server prematurely ended stream.");
+        } else if (id != ID) { // Invalid packet ID
+            throw new IOException("Server returned invalid packet ID.");
+        }
+
+        int length = readVarInt(inputStream); // Length of the response
+        if (length == -1) { // The stream was prematurely ended
+            throw new IOException("Server prematurely ended stream.");
+        } else if (length == 0) {
+            throw new IOException("Server returned unexpected value.");
+        }
+
+        // Get the json response
+        byte[] data = new byte[length];
+        inputStream.readFully(data);
+        response = new String(data);
+    }
+}