Protocol/src/main/java/org/openautonomousconnection/protocol/packets/OACPacket.java

package org.openautonomousconnection.protocol.packets;

import dev.unlegitdqrk.unlegitlibrary.network.system.packets.Packet;
import lombok.Getter;
import org.openautonomousconnection.protocol.versions.ProtocolVersion;
import org.openautonomousconnection.protocol.versions.v1_0_0.beta.INSResponseStatus;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.*;

/**
 * Abstract class representing a packet in the Open Autonomous Connection (OAC) protocol.
 * This class extends the base Packet class and includes additional functionality specific to OAC.
 */
public abstract class OACPacket extends Packet {

    /**
     * The protocol version associated with this packet.
     */
    @Getter
    private final List<ProtocolVersion> compatibleVersions;
    private final int id;
    /**
     * The response code for the packet, defaulting to RESPONSE_NOT_REQUIRED.
     */
    private INSResponseStatus responseCode = INSResponseStatus.RESPONSE_NOT_REQUIRED;

    /**
     * Constructor for OACPacket.
     *
     * @param id              The unique identifier for the packet.
     * @param supportedVersions The protocol version associated with this packet.
     */
    public OACPacket(int id, ProtocolVersion... supportedVersions) {
        this.id = id;
        this.compatibleVersions = List.of(supportedVersions);
    }

    @Override
    public int getPacketID() {
        return id;
    }

    /**
     * Gets the response code for the packet.
     *
     * @return The INSResponseCode associated with the packet.
     */
    protected final INSResponseStatus getResponseCode() {
        return responseCode;
    }

    /**
     * Sets the response code for the packet.
     *
     * @param responseCode The INSResponseCode to set for the packet.
     */
    protected final void setResponseCode(INSResponseStatus responseCode) {
        this.responseCode = responseCode;
    }

    /**
     * Writes the packet data to the output stream.
     *
     * @param outputStream The output stream to write the packet data to.
     * @throws IOException If an I/O error occurs.
     */
    @Override
    public final void write(DataOutputStream outputStream) throws IOException {
        // Write the specific packet data
        onWrite(outputStream);

        // Write the response code if the protocol version is not classic
        if (!compatibleVersions.contains(ProtocolVersion.PV_1_0_0_CLASSIC)) outputStream.writeUTF(responseCode.name());
    }

    @Override
    public final void read(DataInputStream inputStream, UUID clientID) throws IOException {
        // Read the specific packet data
        onRead(inputStream, clientID);

        // Read the response code if the protocol version is not classic
        if (!compatibleVersions.contains(ProtocolVersion.PV_1_0_0_CLASSIC))
            responseCode = INSResponseStatus.valueOf(inputStream.readUTF());
        else responseCode = INSResponseStatus.RESPONSE_NOT_REQUIRED;

        // Call the response code read handler
        onResponseCodeRead(inputStream, clientID);
    }

    /**
     * Abstract method to be implemented by subclasses for writing specific packet data.
     *
     * @param outputStream The output stream to write the packet data to.
     * @throws IOException If an I/O error occurs.
     */
    public abstract void onWrite(DataOutputStream outputStream) throws IOException;

    /**
     * Abstract method to be implemented by subclasses for reading specific packet data.
     *
     * @param inputStream The input stream to read the packet data from.
     * @throws IOException If an I/O error occurs.
     */
    public abstract void onRead(DataInputStream inputStream, UUID clientID) throws IOException;

    /**
     * Method called after the response code has been read from the input stream.
     * Subclasses can override this method to handle any additional logic based on the response code.
     *
     * @param inputStream The input stream from which the response code was read.
     */
    protected void onResponseCodeRead(DataInputStream inputStream, UUID clientID) {
    }

    /**
     * Writes a string map in a deterministic way (no Java object serialization).
     *
     * @param out output stream
     * @param map map to write (may be null)
     * @throws IOException on I/O errors
     */
    protected final void writeStringMap(DataOutputStream out, Map<String, String> map) throws IOException {
        if (map == null || map.isEmpty()) {
            out.writeInt(0);
            return;
        }

        out.writeInt(map.size());
        for (Map.Entry<String, String> e : map.entrySet()) {
            // Null keys/values are normalized to empty strings to keep the wire format stable.
            out.writeUTF((e.getKey() != null) ? e.getKey() : "");
            out.writeUTF((e.getValue() != null) ? e.getValue() : "");
        }
    }

    /**
     * Reads a string map in a deterministic way (no Java object serialization).
     *
     * @param in input stream
     * @return headers map (never null)
     * @throws IOException on I/O errors / invalid sizes
     */
    protected final Map<String, String> readStringMap(DataInputStream in) throws IOException {
        int size = in.readInt();
        if (size < 0) {
            throw new IOException("Negative map size");
        }
        if (size == 0) {
            return Collections.emptyMap();
        }

        Map<String, String> map = new LinkedHashMap<>(Math.max(16, size * 2));
        for (int i = 0; i < size; i++) {
            String key = in.readUTF();
            String value = in.readUTF();
            map.put(key, value);
        }
        return map;
    }
}