Join/Leave account groups + API calls

src/main/java/org/qora/api/model/GroupWithMemberInfo.java

@@ -6,7 +6,6 @@ import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 
-import org.qora.data.group.GroupAdminData;
 import org.qora.data.group.GroupData;
 import org.qora.data.group.GroupMemberData;
 
@@ -23,16 +22,19 @@ public class GroupWithMemberInfo {
 
 	Integer memberCount;
 
-	public List<GroupAdminData> groupAdmins;
+	@XmlElement(name = "admins")
+	public List<String> groupAdminAddresses;
+
+	@XmlElement(name = "members")
 	public List<GroupMemberData> groupMembers;
 
 	// For JAX-RS
 	protected GroupWithMemberInfo() {
 	}
 
-	public GroupWithMemberInfo(GroupData groupData, List<GroupAdminData> groupAdmins, List<GroupMemberData> groupMembers, Integer memberCount) {
+	public GroupWithMemberInfo(GroupData groupData, List<String> groupAdminAddresses, List<GroupMemberData> groupMembers, Integer memberCount) {
 		this.groupData = groupData;
-		this.groupAdmins = groupAdmins;
+		this.groupAdminAddresses = groupAdminAddresses;
 		this.groupMembers = groupMembers;
 		this.memberCount = memberCount;
 	}

src/main/java/org/qora/api/resource/GroupsResource.java

@@ -32,6 +32,7 @@ import org.qora.data.group.GroupData;
 import org.qora.data.group.GroupMemberData;
 import org.qora.data.transaction.CreateGroupTransactionData;
 import org.qora.data.transaction.JoinGroupTransactionData;
+import org.qora.data.transaction.LeaveGroupTransactionData;
 import org.qora.data.transaction.UpdateGroupTransactionData;
 import org.qora.repository.DataException;
 import org.qora.repository.Repository;
@@ -41,6 +42,7 @@ import org.qora.transaction.Transaction.ValidationResult;
 import org.qora.transform.TransformationException;
 import org.qora.transform.transaction.CreateGroupTransactionTransformer;
 import org.qora.transform.transaction.JoinGroupTransactionTransformer;
+import org.qora.transform.transaction.LeaveGroupTransactionTransformer;
 import org.qora.transform.transaction.UpdateGroupTransactionTransformer;
 import org.qora.utils.Base58;
 
@@ -137,7 +139,7 @@ public class GroupsResource {
 				groupMembers = repository.getGroupRepository().getAllGroupMembers(groupData.getGroupName());
 
 				// Strip groupName from member info
-				groupMembers = groupMembers.stream().map(groupMemberData -> new GroupMemberData(null, groupMemberData.getMember(), groupMemberData.getJoined())).collect(Collectors.toList());
+				groupMembers = groupMembers.stream().map(groupMemberData -> new GroupMemberData(null, groupMemberData.getMember(), groupMemberData.getJoined(), null)).collect(Collectors.toList());
 
 				memberCount = groupMembers.size();
 			} else {
@@ -148,10 +150,10 @@ public class GroupsResource {
 			// Always include admins
 			List<GroupAdminData> groupAdmins = repository.getGroupRepository().getAllGroupAdmins(groupData.getGroupName());
 
-			// Strip groupName from admin info
-			groupAdmins = groupAdmins.stream().map(groupAdminData -> new GroupAdminData(null, groupAdminData.getAdmin())).collect(Collectors.toList());
+			// We only need admin addresses
+			List<String> groupAdminAddresses = groupAdmins.stream().map(groupAdminData -> groupAdminData.getAdmin()).collect(Collectors.toList());
 
-			return new GroupWithMemberInfo(groupData, groupAdmins, groupMembers, memberCount);
+			return new GroupWithMemberInfo(groupData, groupAdminAddresses, groupMembers, memberCount);
 		} catch (DataException e) {
 			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
 		}
@@ -287,4 +289,47 @@ public class GroupsResource {
 		}
 	}
 
+	@POST
+	@Path("/leave")
+	@Operation(
+		summary = "Build raw, unsigned, LEAVE_GROUP transaction",
+		requestBody = @RequestBody(
+			required = true,
+			content = @Content(
+				mediaType = MediaType.APPLICATION_JSON,
+				schema = @Schema(
+					implementation = LeaveGroupTransactionData.class
+				)
+			)
+		),
+		responses = {
+			@ApiResponse(
+				description = "raw, unsigned, LEAVE_GROUP transaction encoded in Base58",
+				content = @Content(
+					mediaType = MediaType.TEXT_PLAIN,
+					schema = @Schema(
+						type = "string"
+					)
+				)
+			)
+		}
+	)
+	@ApiErrors({ApiError.TRANSACTION_INVALID, ApiError.TRANSFORMATION_ERROR, ApiError.REPOSITORY_ISSUE})
+	public String leaveGroup(LeaveGroupTransactionData transactionData) {
+		try (final Repository repository = RepositoryManager.getRepository()) {
+			Transaction transaction = Transaction.fromData(repository, transactionData);
+
+			ValidationResult result = transaction.isValidUnconfirmed();
+			if (result != ValidationResult.OK)
+				throw TransactionsResource.createTransactionInvalidException(request, result);
+
+			byte[] bytes = LeaveGroupTransactionTransformer.toBytes(transactionData);
+			return Base58.encode(bytes);
+		} catch (TransformationException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.TRANSFORMATION_ERROR, e);
+		} catch (DataException e) {
+			throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.REPOSITORY_ISSUE, e);
+		}
+	}
+
 }

src/main/java/org/qora/data/group/GroupAdminData.java

@@ -2,6 +2,7 @@ package org.qora.data.group;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
 
 // All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -10,6 +11,10 @@ public class GroupAdminData {
 	// Properties
 	private String groupName;
 	private String admin;
+	/** Reference to transaction that triggered adminship */
+	// No need to ever expose this via API
+	@XmlTransient
+	private byte[] groupReference;
 
 	// Constructors
 
@@ -17,9 +22,10 @@ public class GroupAdminData {
 	protected GroupAdminData() {
 	}
 
-	public GroupAdminData(String groupName, String admin) {
+	public GroupAdminData(String groupName, String admin, byte[] groupReference) {
 		this.groupName = groupName;
 		this.admin = admin;
+		this.groupReference = groupReference;
 	}
 
 	// Getters / setters
@@ -32,4 +38,12 @@ public class GroupAdminData {
 		return this.admin;
 	}
 
+	public byte[] getGroupReference() {
+		return this.groupReference;
+	}
+
+	public void setGroupReference(byte[] groupReference) {
+		this.groupReference = groupReference;
+	}
+
 }

src/main/java/org/qora/data/group/GroupData.java

@@ -2,6 +2,7 @@ package org.qora.data.group;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
 
 // All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -14,6 +15,9 @@ public class GroupData {
 	private long created;
 	private Long updated;
 	private boolean isOpen;
+	/** Reference to transaction that created group */
+	// No need to ever expose this via API
+	@XmlTransient
 	private byte[] reference;
 
 	// Constructors

src/main/java/org/qora/data/group/GroupMemberData.java

@@ -2,6 +2,7 @@ package org.qora.data.group;
 
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
 
 // All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)
@@ -11,6 +12,10 @@ public class GroupMemberData {
 	private String groupName;
 	private String member;
 	private long joined;
+	/** Reference to transaction that triggered membership */
+	// No need to ever expose this via API
+	@XmlTransient
+	private byte[] groupReference;
 
 	// Constructors
 
@@ -18,10 +23,11 @@ public class GroupMemberData {
 	protected GroupMemberData() {
 	}
 
-	public GroupMemberData(String groupName, String member, long joined) {
+	public GroupMemberData(String groupName, String member, long joined, byte[] groupReference) {
 		this.groupName = groupName;
 		this.member = member;
 		this.joined = joined;
+		this.groupReference = groupReference;
 	}
 
 	// Getters / setters
@@ -38,4 +44,12 @@ public class GroupMemberData {
 		return this.joined;
 	}
 
+	public byte[] getGroupReference() {
+		return this.groupReference;
+	}
+
+	public void setGroupReference(byte[] groupReference) {
+		this.groupReference = groupReference;
+	}
+
 }

src/main/java/org/qora/data/transaction/JoinGroupTransactionData.java

@@ -18,7 +18,7 @@ public class JoinGroupTransactionData extends TransactionData {
 	// Properties
 	@Schema(description = "joiner's public key", example = "2tiMr5LTpaWCgbRvkPK8TFd7k63DyHJMMFFsz9uBf1ZP")
 	private byte[] joinerPublicKey;
-	@Schema(description = "which group to update", example = "my-group")
+	@Schema(description = "which group to join", example = "my-group")
 	private String groupName;
 
 	// Constructors

src/main/java/org/qora/data/transaction/LeaveGroupTransactionData.java

@@ -0,0 +1,89 @@
+package org.qora.data.transaction;
+
+import java.math.BigDecimal;
+
+import javax.xml.bind.Unmarshaller;
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlTransient;
+
+import org.qora.transaction.Transaction.TransactionType;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+// All properties to be converted to JSON via JAX-RS
+@XmlAccessorType(XmlAccessType.FIELD)
+@Schema(allOf = { TransactionData.class })
+public class LeaveGroupTransactionData extends TransactionData {
+
+	// Properties
+	@Schema(description = "leaver's public key", example = "2tiMr5LTpaWCgbRvkPK8TFd7k63DyHJMMFFsz9uBf1ZP")
+	private byte[] leaverPublicKey;
+	@Schema(description = "which group to leave", example = "my-group")
+	private String groupName;
+	// No need to ever expose this via API
+	@XmlTransient
+	private byte[] memberReference;
+	// No need to ever expose this via API
+	@XmlTransient
+	private byte[] adminReference;
+
+	// Constructors
+
+	// For JAX-RS
+	protected LeaveGroupTransactionData() {
+		super(TransactionType.LEAVE_GROUP);
+	}
+
+	public void afterUnmarshal(Unmarshaller u, Object parent) {
+		this.creatorPublicKey = this.leaverPublicKey;
+	}
+
+	public LeaveGroupTransactionData(byte[] leaverPublicKey, String groupName, byte[] memberReference, byte[] adminReference, BigDecimal fee, long timestamp, byte[] reference, byte[] signature) {
+		super(TransactionType.LEAVE_GROUP, fee, leaverPublicKey, timestamp, reference, signature);
+
+		this.leaverPublicKey = leaverPublicKey;
+		this.groupName = groupName;
+		this.memberReference = memberReference;
+		this.adminReference = adminReference;
+	}
+
+	public LeaveGroupTransactionData(byte[] leaverPublicKey, String groupName, BigDecimal fee, long timestamp, byte[] reference, byte[] signature) {
+		this(leaverPublicKey, groupName, null, null, fee, timestamp, reference, signature);
+	}
+
+	public LeaveGroupTransactionData(byte[] leaverPublicKey, String groupName, byte[] memberReference, byte[] adminReference, BigDecimal fee, long timestamp, byte[] reference) {
+		this(leaverPublicKey, groupName, memberReference, adminReference, fee, timestamp, reference, null);
+	}
+
+	public LeaveGroupTransactionData(byte[] leaverPublicKey, String groupName, BigDecimal fee, long timestamp, byte[] reference) {
+		this(leaverPublicKey, groupName, null, null, fee, timestamp, reference, null);
+	}
+
+	// Getters / setters
+
+	public byte[] getLeaverPublicKey() {
+		return this.leaverPublicKey;
+	}
+
+	public String getGroupName() {
+		return this.groupName;
+	}
+
+	public byte[] getMemberReference() {
+		return this.memberReference;
+	}
+
+	public void setMemberReference(byte[] memberReference) {
+		this.memberReference = memberReference;
+	}
+
+	public byte[] getAdminReference() {
+		return this.adminReference;
+	}
+
+	public void setAdminReference(byte[] adminReference) {
+		this.adminReference = adminReference;
+	}
+
+}

src/main/java/org/qora/data/transaction/TransactionData.java

@@ -34,7 +34,7 @@ import io.swagger.v3.oas.annotations.media.Schema.AccessMode;
 	CreateOrderTransactionData.class, CancelOrderTransactionData.class,
 	MultiPaymentTransactionData.class, DeployATTransactionData.class, MessageTransactionData.class, ATTransactionData.class,
 	CreateGroupTransactionData.class, UpdateGroupTransactionData.class,
-	JoinGroupTransactionData.class
+	JoinGroupTransactionData.class, LeaveGroupTransactionData.class
 })
 //All properties to be converted to JSON via JAX-RS
 @XmlAccessorType(XmlAccessType.FIELD)

src/main/java/org/qora/group/Group.java

@@ -1,5 +1,7 @@
 package org.qora.group;
 
+import java.util.Arrays;
+
 import org.qora.account.Account;
 import org.qora.account.PublicKeyAccount;
 import org.qora.data.group.GroupAdminData;
@@ -7,9 +9,11 @@ import org.qora.data.group.GroupData;
 import org.qora.data.group.GroupMemberData;
 import org.qora.data.transaction.CreateGroupTransactionData;
 import org.qora.data.transaction.JoinGroupTransactionData;
+import org.qora.data.transaction.LeaveGroupTransactionData;
 import org.qora.data.transaction.TransactionData;
 import org.qora.data.transaction.UpdateGroupTransactionData;
 import org.qora.repository.DataException;
+import org.qora.repository.GroupRepository;
 import org.qora.repository.Repository;
 
 public class Group {
@@ -51,14 +55,14 @@ public class Group {
 
 	// Processing
 
-	public void create() throws DataException {
+	public void create(CreateGroupTransactionData createGroupTransactionData) throws DataException {
 		this.repository.getGroupRepository().save(this.groupData);
 
 		// Add owner as admin too
-		this.repository.getGroupRepository().save(new GroupAdminData(this.groupData.getGroupName(), this.groupData.getOwner()));
+		this.repository.getGroupRepository().save(new GroupAdminData(this.groupData.getGroupName(), this.groupData.getOwner(), createGroupTransactionData.getSignature()));
 
 		// Add owner as member too
-		this.repository.getGroupRepository().save(new GroupMemberData(this.groupData.getGroupName(), this.groupData.getOwner(), this.groupData.getCreated()));
+		this.repository.getGroupRepository().save(new GroupMemberData(this.groupData.getGroupName(), this.groupData.getOwner(), this.groupData.getCreated(), createGroupTransactionData.getSignature()));
 	}
 
 	public void uncreate() throws DataException {
@@ -71,8 +75,6 @@ public class Group {
 		if (previousTransactionData == null)
 			throw new DataException("Unable to revert group transaction as referenced transaction not found in repository");
 
-		// XXX needs code to reinstate owner as admin and member
-
 		switch (previousTransactionData.getType()) {
 			case CREATE_GROUP:
 				CreateGroupTransactionData previousCreateGroupTransactionData = (CreateGroupTransactionData) previousTransactionData;
@@ -93,9 +95,14 @@ public class Group {
 			default:
 				throw new IllegalStateException("Unable to revert group transaction due to unsupported referenced transaction");
 		}
+
+		// Previous owner will still be admin and member at this point
 	}
 
 	public void update(UpdateGroupTransactionData updateGroupTransactionData) throws DataException {
+		GroupRepository groupRepository = this.repository.getGroupRepository();
+		String groupName = updateGroupTransactionData.getGroupName();
+
 		// Update reference in transaction data
 		updateGroupTransactionData.setGroupReference(this.groupData.getReference());
 
@@ -109,15 +116,29 @@ public class Group {
 		this.groupData.setUpdated(updateGroupTransactionData.getTimestamp());
 
 		// Save updated group data
-		this.repository.getGroupRepository().save(this.groupData);
+		groupRepository.save(this.groupData);
 
-		// XXX new owner should be an admin if not already
-		// XXX new owner should be a member if not already
+		String newOwner = updateGroupTransactionData.getNewOwner();
 
-		// XXX what happens to previous owner? retained as admin?
+		// New owner should be a member if not already
+		if (!groupRepository.memberExists(groupName, newOwner)) {
+			GroupMemberData groupMemberData = new GroupMemberData(groupName, newOwner, updateGroupTransactionData.getTimestamp(), updateGroupTransactionData.getSignature());
+			groupRepository.save(groupMemberData);
+		}
+
+		// New owner should be an admin if not already
+		if (!groupRepository.adminExists(groupName, newOwner)) {
+			GroupAdminData groupAdminData = new GroupAdminData(groupName, newOwner, updateGroupTransactionData.getSignature());
+			groupRepository.save(groupAdminData);
+		}
+
+		// Previous owner retained as admin and member
 	}
 
 	public void revert(UpdateGroupTransactionData updateGroupTransactionData) throws DataException {
+		GroupRepository groupRepository = this.repository.getGroupRepository();
+		String groupName = updateGroupTransactionData.getGroupName();
+
 		// Previous group reference is taken from this transaction's cached copy
 		this.groupData.setReference(updateGroupTransactionData.getGroupReference());
 
@@ -125,21 +146,83 @@ public class Group {
 		this.revert();
 
 		// Save reverted group data
-		this.repository.getGroupRepository().save(this.groupData);
+		groupRepository.save(this.groupData);
+
+		// If ownership changed we need to do more work. Note groupData's owner is reverted at this point.
+		String newOwner = updateGroupTransactionData.getNewOwner();
+		if (!this.groupData.getOwner().equals(newOwner)) {
+			// If this update caused [what was] new owner to become admin, then revoke that now.
+			// (It's possible they were an admin prior to being given ownership so we need to retain that).
+			GroupAdminData groupAdminData = groupRepository.getAdmin(groupName, newOwner);
+			if (Arrays.equals(groupAdminData.getGroupReference(), updateGroupTransactionData.getSignature()))
+				groupRepository.deleteAdmin(groupName, newOwner);
+
+			// If this update caused [what was] new owner to become member, then revoke that now.
+			// (It's possible they were a member prior to being given ownership so we need to retain that).
+			GroupMemberData groupMemberData = groupRepository.getMember(groupName, newOwner);
+			if (Arrays.equals(groupMemberData.getGroupReference(), updateGroupTransactionData.getSignature()))
+				groupRepository.deleteMember(groupName, newOwner);
+		}
 	}
 
 	public void join(JoinGroupTransactionData joinGroupTransactionData) throws DataException {
 		Account joiner = new PublicKeyAccount(this.repository, joinGroupTransactionData.getJoinerPublicKey());
 
-		GroupMemberData groupMemberData = new GroupMemberData(joinGroupTransactionData.getGroupName(), joiner.getAddress(), joinGroupTransactionData.getTimestamp());
+		GroupMemberData groupMemberData = new GroupMemberData(joinGroupTransactionData.getGroupName(), joiner.getAddress(), joinGroupTransactionData.getTimestamp(), joinGroupTransactionData.getSignature());
 		this.repository.getGroupRepository().save(groupMemberData);
 	}
 
 	public void unjoin(JoinGroupTransactionData joinGroupTransactionData) throws DataException {
 		Account joiner = new PublicKeyAccount(this.repository, joinGroupTransactionData.getJoinerPublicKey());
 
-		GroupMemberData groupMemberData = new GroupMemberData(joinGroupTransactionData.getGroupName(), joiner.getAddress(), joinGroupTransactionData.getTimestamp());
-		this.repository.getGroupRepository().delete(groupMemberData);
+		this.repository.getGroupRepository().deleteMember(joinGroupTransactionData.getGroupName(), joiner.getAddress());
+	}
+
+	public void leave(LeaveGroupTransactionData leaveGroupTransactionData) throws DataException {
+		GroupRepository groupRepository = this.repository.getGroupRepository();
+		String groupName = leaveGroupTransactionData.getGroupName();
+		Account leaver = new PublicKeyAccount(this.repository, leaveGroupTransactionData.getLeaverPublicKey());
+
+		// Potentially record reference to transaction that restores previous admin state.
+		// Owners can't leave as that would leave group ownerless and in unrecoverable state.
+
+		// Owners are also admins, so skip if owner
+		if (!leaver.getAddress().equals(this.groupData.getOwner())) {
+			// Fetch admin data for leaver
+			GroupAdminData groupAdminData = groupRepository.getAdmin(groupName, leaver.getAddress());
+
+			if (groupAdminData != null) {
+				// Leaver is admin - use promotion transaction reference as restore-state reference
+				leaveGroupTransactionData.setAdminReference(groupAdminData.getGroupReference());
+
+				// Remove as admin
+				groupRepository.deleteAdmin(groupName, leaver.getAddress());
+			}
+		}
+
+		// Save membership transaction reference
+		GroupMemberData groupMemberData = groupRepository.getMember(groupName, leaver.getAddress());
+		leaveGroupTransactionData.setMemberReference(groupMemberData.getGroupReference());
+
+		// Remove as member
+		groupRepository.deleteMember(leaveGroupTransactionData.getGroupName(), leaver.getAddress());
+	}
+
+	public void unleave(LeaveGroupTransactionData leaveGroupTransactionData) throws DataException {
+		GroupRepository groupRepository = this.repository.getGroupRepository();
+		String groupName = leaveGroupTransactionData.getGroupName();
+		Account leaver = new PublicKeyAccount(this.repository, leaveGroupTransactionData.getLeaverPublicKey());
+
+		// Rejoin as member
+		TransactionData membershipTransactionData = this.repository.getTransactionRepository().fromSignature(leaveGroupTransactionData.getMemberReference());
+		groupRepository.save(new GroupMemberData(groupName, leaver.getAddress(), membershipTransactionData.getTimestamp(), membershipTransactionData.getSignature()));
+
+		// Put back any admin state based on referenced group-related transaction
+		byte[] adminTransactionSignature = leaveGroupTransactionData.getAdminReference();
+		if (adminTransactionSignature != null) {
+			GroupAdminData groupAdminData = new GroupAdminData(leaveGroupTransactionData.getGroupName(), leaver.getAddress(), adminTransactionSignature);
+			groupRepository.save(groupAdminData);
+		}
 	}
 
 }

src/main/java/org/qora/repository/GroupRepository.java

@@ -24,15 +24,21 @@ public interface GroupRepository {
 
 	// Group Admins
 
+	public GroupAdminData getAdmin(String groupName, String address) throws DataException;
+
+	public boolean adminExists(String groupName, String address) throws DataException;
+
 	public List<GroupAdminData> getAllGroupAdmins(String groupName) throws DataException;
 
 	public void save(GroupAdminData groupAdminData) throws DataException;
 
-	public void delete(GroupAdminData groupAdminData) throws DataException;
+	public void deleteAdmin(String groupName, String address) throws DataException;
 
 	// Group Members
 
-	public boolean memberExists(String groupName, String member) throws DataException;
+	public GroupMemberData getMember(String groupName, String address) throws DataException;
+
+	public boolean memberExists(String groupName, String address) throws DataException;
 
 	public List<GroupMemberData> getAllGroupMembers(String groupName) throws DataException;
 
@@ -41,6 +47,6 @@ public interface GroupRepository {
 
 	public void save(GroupMemberData groupMemberData) throws DataException;
 
-	public void delete(GroupMemberData groupMemberData) throws DataException;
+	public void deleteMember(String groupName, String address) throws DataException;
 
 }

src/main/java/org/qora/repository/hsqldb/HSQLDBDatabaseUpdates.java

@@ -416,12 +416,13 @@ public class HSQLDBDatabaseUpdates {
 					stmt.execute("CREATE INDEX AccountGroupOwnerIndex on AccountGroups (owner)");
 
 					// Admins
-					stmt.execute("CREATE TABLE AccountGroupAdmins (group_name GroupName, admin QoraAddress, PRIMARY KEY (group_name, admin))");
+					stmt.execute("CREATE TABLE AccountGroupAdmins (group_name GroupName, admin QoraAddress, group_reference Signature NOT NULL, PRIMARY KEY (group_name, admin))");
 					// For finding groups that address administrates
 					stmt.execute("CREATE INDEX AccountGroupAdminIndex on AccountGroupAdmins (admin)");
 
 					// Members
-					stmt.execute("CREATE TABLE AccountGroupMembers (group_name GroupName, address QoraAddress, joined TIMESTAMP WITH TIME ZONE NOT NULL, PRIMARY KEY (group_name, address))");
+					stmt.execute("CREATE TABLE AccountGroupMembers (group_name GroupName, address QoraAddress, joined TIMESTAMP WITH TIME ZONE NOT NULL, group_reference Signature NOT NULL, "
+							+ "PRIMARY KEY (group_name, address))");
 					// For finding groups that address is member
 					stmt.execute("CREATE INDEX AccountGroupMemberIndex on AccountGroupMembers (address)");
 
@@ -450,13 +451,12 @@ public class HSQLDBDatabaseUpdates {
 					stmt.execute("CREATE TABLE UpdateGroupTransactions (signature Signature, owner QoraPublicKey NOT NULL, group_name GroupName NOT NULL, "
 							+ "new_owner QoraAddress NOT NULL, new_description GenericDescription NOT NULL, new_is_open BOOLEAN NOT NULL, group_reference Signature, "
 							+ "PRIMARY KEY (signature), FOREIGN KEY (signature) REFERENCES Transactions (signature) ON DELETE CASCADE)");
-					break;
 
-				case 32:
 					// Account group join/leave transactions
 					stmt.execute("CREATE TABLE JoinGroupTransactions (signature Signature, joiner QoraPublicKey NOT NULL, group_name GroupName NOT NULL, "
 							+ "PRIMARY KEY (signature), FOREIGN KEY (signature) REFERENCES Transactions (signature) ON DELETE CASCADE)");
 					stmt.execute("CREATE TABLE LeaveGroupTransactions (signature Signature, leaver QoraPublicKey NOT NULL, group_name GroupName NOT NULL, "
+							+ "member_reference Signature, admin_reference Signature, "
 							+ "PRIMARY KEY (signature), FOREIGN KEY (signature) REFERENCES Transactions (signature) ON DELETE CASCADE)");
 					break;
 

src/main/java/org/qora/repository/hsqldb/HSQLDBGroupRepository.java

@@ -125,9 +125,9 @@ public class HSQLDBGroupRepository implements GroupRepository {
 		Long updated = groupData.getUpdated();
 		Timestamp updatedTimestamp = updated == null ? null : new Timestamp(updated);
 
-		saveHelper.bind("owner", groupData.getOwner()).bind("group_name", groupData.getGroupName())
-				.bind("description", groupData.getDescription()).bind("created", new Timestamp(groupData.getCreated())).bind("updated", updatedTimestamp)
-				.bind("reference", groupData.getReference()).bind("is_open", groupData.getIsOpen());
+		saveHelper.bind("owner", groupData.getOwner()).bind("group_name", groupData.getGroupName()).bind("description", groupData.getDescription())
+				.bind("created", new Timestamp(groupData.getCreated())).bind("updated", updatedTimestamp).bind("reference", groupData.getReference())
+				.bind("is_open", groupData.getIsOpen());
 
 		try {
 			saveHelper.execute(this.repository);
@@ -156,18 +156,43 @@ public class HSQLDBGroupRepository implements GroupRepository {
 
 	// Group Admins
 
+	@Override
+	public GroupAdminData getAdmin(String groupName, String address) throws DataException {
+		try (ResultSet resultSet = this.repository.checkedExecute("SELECT admin, group_reference FROM AccountGroupAdmins WHERE group_name = ?", groupName)) {
+			if (resultSet == null)
+				return null;
+
+			String admin = resultSet.getString(1);
+			byte[] groupReference = resultSet.getBytes(2);
+
+			return new GroupAdminData(groupName, admin, groupReference);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch group admin from repository", e);
+		}
+	}
+
+	@Override
+	public boolean adminExists(String groupName, String address) throws DataException {
+		try {
+			return this.repository.exists("AccountGroupAdmins", "group_name = ? AND admin = ?", groupName, address);
+		} catch (SQLException e) {
+			throw new DataException("Unable to check for group admin in repository", e);
+		}
+	}
+
 	@Override
 	public List<GroupAdminData> getAllGroupAdmins(String groupName) throws DataException {
 		List<GroupAdminData> admins = new ArrayList<>();
 
-		try (ResultSet resultSet = this.repository.checkedExecute("SELECT admin FROM AccountGroupAdmins WHERE group_name = ?", groupName)) {
+		try (ResultSet resultSet = this.repository.checkedExecute("SELECT admin, group_reference FROM AccountGroupAdmins WHERE group_name = ?", groupName)) {
 			if (resultSet == null)
 				return admins;
 
 			do {
 				String admin = resultSet.getString(1);
+				byte[] groupReference = resultSet.getBytes(2);
 
-				admins.add(new GroupAdminData(groupName, admin));
+				admins.add(new GroupAdminData(groupName, admin, groupReference));
 			} while (resultSet.next());
 
 			return admins;
@@ -180,7 +205,8 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	public void save(GroupAdminData groupAdminData) throws DataException {
 		HSQLDBSaver saveHelper = new HSQLDBSaver("AccountGroupAdmins");
 
-		saveHelper.bind("group_name", groupAdminData.getGroupName()).bind("admin", groupAdminData.getAdmin());
+		saveHelper.bind("group_name", groupAdminData.getGroupName()).bind("admin", groupAdminData.getAdmin()).bind("group_reference",
+				groupAdminData.getGroupReference());
 
 		try {
 			saveHelper.execute(this.repository);
@@ -190,9 +216,9 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	}
 
 	@Override
-	public void delete(GroupAdminData groupAdminData) throws DataException {
+	public void deleteAdmin(String groupName, String address) throws DataException {
 		try {
-			this.repository.delete("AccountGroupAdmins", "group_name = ? AND admin = ?", groupAdminData.getGroupName(), groupAdminData.getAdmin());
+			this.repository.delete("AccountGroupAdmins", "group_name = ? AND admin = ?", groupName, address);
 		} catch (SQLException e) {
 			throw new DataException("Unable to delete group admin info from repository", e);
 		}
@@ -201,9 +227,26 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	// Group Members
 
 	@Override
-	public boolean memberExists(String groupName, String member) throws DataException {
+	public GroupMemberData getMember(String groupName, String address) throws DataException {
+		try (ResultSet resultSet = this.repository.checkedExecute("SELECT address, joined, group_reference FROM AccountGroupMembers WHERE group_name = ?",
+				groupName)) {
+			if (resultSet == null)
+				return null;
+
+			String member = resultSet.getString(1);
+			long joined = resultSet.getTimestamp(2, Calendar.getInstance(HSQLDBRepository.UTC)).getTime();
+			byte[] groupReference = resultSet.getBytes(3);
+
+			return new GroupMemberData(groupName, member, joined, groupReference);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch group members from repository", e);
+		}
+	}
+
+	@Override
+	public boolean memberExists(String groupName, String address) throws DataException {
 		try {
-			return this.repository.exists("AccountGroupMembers", "group_name = ? AND address = ?", groupName, member);
+			return this.repository.exists("AccountGroupMembers", "group_name = ? AND address = ?", groupName, address);
 		} catch (SQLException e) {
 			throw new DataException("Unable to check for group member in repository", e);
 		}
@@ -213,15 +256,17 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	public List<GroupMemberData> getAllGroupMembers(String groupName) throws DataException {
 		List<GroupMemberData> members = new ArrayList<>();
 
-		try (ResultSet resultSet = this.repository.checkedExecute("SELECT address, joined FROM AccountGroupMembers WHERE group_name = ?", groupName)) {
+		try (ResultSet resultSet = this.repository.checkedExecute("SELECT address, joined, group_reference FROM AccountGroupMembers WHERE group_name = ?",
+				groupName)) {
 			if (resultSet == null)
 				return members;
 
 			do {
 				String member = resultSet.getString(1);
 				long joined = resultSet.getTimestamp(2, Calendar.getInstance(HSQLDBRepository.UTC)).getTime();
+				byte[] groupReference = resultSet.getBytes(3);
 
-				members.add(new GroupMemberData(groupName, member, joined));
+				members.add(new GroupMemberData(groupName, member, joined, groupReference));
 			} while (resultSet.next());
 
 			return members;
@@ -232,7 +277,8 @@ public class HSQLDBGroupRepository implements GroupRepository {
 
 	@Override
 	public Integer countGroupMembers(String groupName) throws DataException {
-		try (ResultSet resultSet = this.repository.checkedExecute("SELECT group_name, COUNT(*) FROM AccountGroupMembers WHERE group_name = ? GROUP BY group_name", groupName)) {
+		try (ResultSet resultSet = this.repository
+				.checkedExecute("SELECT group_name, COUNT(*) FROM AccountGroupMembers WHERE group_name = ? GROUP BY group_name", groupName)) {
 			if (resultSet == null)
 				return null;
 
@@ -246,7 +292,8 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	public void save(GroupMemberData groupMemberData) throws DataException {
 		HSQLDBSaver saveHelper = new HSQLDBSaver("AccountGroupMembers");
 
-		saveHelper.bind("group_name", groupMemberData.getGroupName()).bind("address", groupMemberData.getMember()).bind("joined", new Timestamp(groupMemberData.getJoined()));
+		saveHelper.bind("group_name", groupMemberData.getGroupName()).bind("address", groupMemberData.getMember())
+				.bind("joined", new Timestamp(groupMemberData.getJoined())).bind("group_reference", groupMemberData.getGroupReference());
 
 		try {
 			saveHelper.execute(this.repository);
@@ -256,9 +303,9 @@ public class HSQLDBGroupRepository implements GroupRepository {
 	}
 
 	@Override
-	public void delete(GroupMemberData groupMemberData) throws DataException {
+	public void deleteMember(String groupName, String address) throws DataException {
 		try {
-			this.repository.delete("AccountGroupMembers", "group_name = ? AND address = ?", groupMemberData.getGroupName(), groupMemberData.getMember());
+			this.repository.delete("AccountGroupMembers", "group_name = ? AND address = ?", groupName, address);
 		} catch (SQLException e) {
 			throw new DataException("Unable to delete group member info from repository", e);
 		}

src/main/java/org/qora/repository/hsqldb/transaction/HSQLDBLeaveGroupTransactionRepository.java

@@ -0,0 +1,52 @@
+package org.qora.repository.hsqldb.transaction;
+
+import java.math.BigDecimal;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+import org.qora.data.transaction.LeaveGroupTransactionData;
+import org.qora.data.transaction.TransactionData;
+import org.qora.repository.DataException;
+import org.qora.repository.hsqldb.HSQLDBRepository;
+import org.qora.repository.hsqldb.HSQLDBSaver;
+
+public class HSQLDBLeaveGroupTransactionRepository extends HSQLDBTransactionRepository {
+
+	public HSQLDBLeaveGroupTransactionRepository(HSQLDBRepository repository) {
+		this.repository = repository;
+	}
+
+	TransactionData fromBase(byte[] signature, byte[] reference, byte[] creatorPublicKey, long timestamp, BigDecimal fee) throws DataException {
+		try (ResultSet resultSet = this.repository
+				.checkedExecute("SELECT group_name, member_reference, admin_reference FROM LeaveGroupTransactions WHERE signature = ?", signature)) {
+			if (resultSet == null)
+				return null;
+
+			String groupName = resultSet.getString(1);
+			byte[] memberReference = resultSet.getBytes(2);
+			byte[] adminReference = resultSet.getBytes(3);
+
+			return new LeaveGroupTransactionData(creatorPublicKey, groupName, memberReference, adminReference, fee, timestamp, reference, signature);
+		} catch (SQLException e) {
+			throw new DataException("Unable to fetch leave group transaction from repository", e);
+		}
+	}
+
+	@Override
+	public void save(TransactionData transactionData) throws DataException {
+		LeaveGroupTransactionData leaveGroupTransactionData = (LeaveGroupTransactionData) transactionData;
+
+		HSQLDBSaver saveHelper = new HSQLDBSaver("LeaveGroupTransactions");
+
+		saveHelper.bind("signature", leaveGroupTransactionData.getSignature()).bind("leaver", leaveGroupTransactionData.getLeaverPublicKey())
+				.bind("group_name", leaveGroupTransactionData.getGroupName()).bind("member_reference", leaveGroupTransactionData.getMemberReference())
+				.bind("admin_reference", leaveGroupTransactionData.getAdminReference());
+
+		try {
+			saveHelper.execute(this.repository);
+		} catch (SQLException e) {
+			throw new DataException("Unable to save leave group transaction into repository", e);
+		}
+	}
+
+}

src/main/java/org/qora/repository/hsqldb/transaction/HSQLDBTransactionRepository.java

@@ -44,6 +44,7 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 	private HSQLDBCreateGroupTransactionRepository createGroupTransactionRepository;
 	private HSQLDBUpdateGroupTransactionRepository updateGroupTransactionRepository;
 	private HSQLDBJoinGroupTransactionRepository joinGroupTransactionRepository;
+	private HSQLDBLeaveGroupTransactionRepository leaveGroupTransactionRepository;
 
 	public HSQLDBTransactionRepository(HSQLDBRepository repository) {
 		this.repository = repository;
@@ -68,6 +69,7 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 		this.createGroupTransactionRepository = new HSQLDBCreateGroupTransactionRepository(repository);
 		this.updateGroupTransactionRepository = new HSQLDBUpdateGroupTransactionRepository(repository);
 		this.joinGroupTransactionRepository = new HSQLDBJoinGroupTransactionRepository(repository);
+		this.leaveGroupTransactionRepository = new HSQLDBLeaveGroupTransactionRepository(repository);
 	}
 
 	protected HSQLDBTransactionRepository() {
@@ -203,6 +205,9 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 			case JOIN_GROUP:
 				return this.joinGroupTransactionRepository.fromBase(signature, reference, creatorPublicKey, timestamp, fee);
 
+			case LEAVE_GROUP:
+				return this.leaveGroupTransactionRepository.fromBase(signature, reference, creatorPublicKey, timestamp, fee);
+
 			default:
 				throw new DataException("Unsupported transaction type [" + type.name() + "] during fetch from HSQLDB repository");
 		}
@@ -535,6 +540,10 @@ public class HSQLDBTransactionRepository implements TransactionRepository {
 				this.joinGroupTransactionRepository.save(transactionData);
 				break;
 
+			case LEAVE_GROUP:
+				this.leaveGroupTransactionRepository.save(transactionData);
+				break;
+
 			default:
 				throw new DataException("Unsupported transaction type [" + transactionData.getType().name() + "] during save into HSQLDB repository");
 		}

src/main/java/org/qora/transaction/CreateGroupTransaction.java

@@ -113,7 +113,7 @@ public class CreateGroupTransaction extends Transaction {
 	public void process() throws DataException {
 		// Create Group
 		Group group = new Group(this.repository, createGroupTransactionData);
-		group.create();
+		group.create(createGroupTransactionData);
 
 		// Save this transaction
 		this.repository.getTransactionRepository().save(createGroupTransactionData);

src/main/java/org/qora/transaction/LeaveGroupTransaction.java

@@ -0,0 +1,143 @@
+package org.qora.transaction;
+
+import java.math.BigDecimal;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.qora.account.Account;
+import org.qora.account.PublicKeyAccount;
+import org.qora.asset.Asset;
+import org.qora.data.transaction.LeaveGroupTransactionData;
+import org.qora.data.group.GroupData;
+import org.qora.data.transaction.TransactionData;
+import org.qora.group.Group;
+import org.qora.repository.DataException;
+import org.qora.repository.Repository;
+
+import com.google.common.base.Utf8;
+
+public class LeaveGroupTransaction extends Transaction {
+
+	// Properties
+	private LeaveGroupTransactionData leaveGroupTransactionData;
+
+	// Constructors
+
+	public LeaveGroupTransaction(Repository repository, TransactionData transactionData) {
+		super(repository, transactionData);
+
+		this.leaveGroupTransactionData = (LeaveGroupTransactionData) this.transactionData;
+	}
+
+	// More information
+
+	@Override
+	public List<Account> getRecipientAccounts() throws DataException {
+		return Collections.emptyList();
+	}
+
+	@Override
+	public boolean isInvolved(Account account) throws DataException {
+		String address = account.getAddress();
+
+		if (address.equals(this.getLeaver().getAddress()))
+			return true;
+
+		return false;
+	}
+
+	@Override
+	public BigDecimal getAmount(Account account) throws DataException {
+		String address = account.getAddress();
+		BigDecimal amount = BigDecimal.ZERO.setScale(8);
+
+		if (address.equals(this.getLeaver().getAddress()))
+			amount = amount.subtract(this.transactionData.getFee());
+
+		return amount;
+	}
+
+	// Navigation
+
+	public Account getLeaver() throws DataException {
+		return new PublicKeyAccount(this.repository, this.leaveGroupTransactionData.getLeaverPublicKey());
+	}
+
+	// Processing
+
+	@Override
+	public ValidationResult isValid() throws DataException {
+		// Check group name size bounds
+		int groupNameLength = Utf8.encodedLength(leaveGroupTransactionData.getGroupName());
+		if (groupNameLength < 1 || groupNameLength > Group.MAX_NAME_SIZE)
+			return ValidationResult.INVALID_NAME_LENGTH;
+
+		// Check group name is lowercase
+		if (!leaveGroupTransactionData.getGroupName().equals(leaveGroupTransactionData.getGroupName().toLowerCase()))
+			return ValidationResult.NAME_NOT_LOWER_CASE;
+
+		GroupData groupData = this.repository.getGroupRepository().fromGroupName(leaveGroupTransactionData.getGroupName());
+
+		// Check group exists
+		if (groupData == null)
+			return ValidationResult.GROUP_DOES_NOT_EXIST;
+
+		Account leaver = getLeaver();
+
+		// Can't leave if group owner
+		if (leaver.getAddress().equals(groupData.getOwner()))
+			return ValidationResult.GROUP_OWNER_CANNOT_LEAVE;
+
+		if (!this.repository.getGroupRepository().memberExists(leaveGroupTransactionData.getGroupName(), leaver.getAddress()))
+			return ValidationResult.NOT_GROUP_MEMBER;
+
+		// Check fee is positive
+		if (leaveGroupTransactionData.getFee().compareTo(BigDecimal.ZERO) <= 0)
+			return ValidationResult.NEGATIVE_FEE;
+
+		if (!Arrays.equals(leaver.getLastReference(), leaveGroupTransactionData.getReference()))
+			return ValidationResult.INVALID_REFERENCE;
+
+		// Check creator has enough funds
+		if (leaver.getConfirmedBalance(Asset.QORA).compareTo(leaveGroupTransactionData.getFee()) < 0)
+			return ValidationResult.NO_BALANCE;
+
+		return ValidationResult.OK;
+	}
+
+	@Override
+	public void process() throws DataException {
+		// Update Group Membership
+		Group group = new Group(this.repository, leaveGroupTransactionData.getGroupName());
+		group.leave(leaveGroupTransactionData);
+
+		// Save this transaction with updated member/admin references to transactions that can help restore state
+		this.repository.getTransactionRepository().save(leaveGroupTransactionData);
+
+		// Update leaver's balance
+		Account leaver = getLeaver();
+		leaver.setConfirmedBalance(Asset.QORA, leaver.getConfirmedBalance(Asset.QORA).subtract(leaveGroupTransactionData.getFee()));
+
+		// Update leaver's reference
+		leaver.setLastReference(leaveGroupTransactionData.getSignature());
+	}
+
+	@Override
+	public void orphan() throws DataException {
+		// Revert group membership
+		Group group = new Group(this.repository, leaveGroupTransactionData.getGroupName());
+		group.unleave(leaveGroupTransactionData);
+
+		// Delete this transaction itself
+		this.repository.getTransactionRepository().delete(leaveGroupTransactionData);
+
+		// Update leaver's balance
+		Account leaver = getLeaver();
+		leaver.setConfirmedBalance(Asset.QORA, leaver.getConfirmedBalance(Asset.QORA).add(leaveGroupTransactionData.getFee()));
+
+		// Update leaver's reference
+		leaver.setLastReference(leaveGroupTransactionData.getReference());
+	}
+
+}

src/main/java/org/qora/transaction/Transaction.java

@@ -129,6 +129,8 @@ public abstract class Transaction {
 		GROUP_DOES_NOT_EXIST(49),
 		INVALID_GROUP_OWNER(50),
 		ALREADY_GROUP_MEMBER(51),
+		GROUP_OWNER_CANNOT_LEAVE(52),
+		NOT_GROUP_MEMBER(53),
 		NOT_YET_RELEASED(1000);
 
 		public final int value;
@@ -237,6 +239,9 @@ public abstract class Transaction {
 			case JOIN_GROUP:
 				return new JoinGroupTransaction(repository, transactionData);
 
+			case LEAVE_GROUP:
+				return new LeaveGroupTransaction(repository, transactionData);
+
 			default:
 				throw new IllegalStateException("Unsupported transaction type [" + transactionData.getType().value + "] during fetch from repository");
 		}

src/main/java/org/qora/transform/transaction/LeaveGroupTransactionTransformer.java

@@ -0,0 +1,99 @@
+package org.qora.transform.transaction;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.nio.ByteBuffer;
+
+import org.json.simple.JSONObject;
+import org.qora.account.PublicKeyAccount;
+import org.qora.data.transaction.LeaveGroupTransactionData;
+import org.qora.data.transaction.TransactionData;
+import org.qora.group.Group;
+import org.qora.transform.TransformationException;
+import org.qora.utils.Serialization;
+
+import com.google.common.base.Utf8;
+import com.google.common.hash.HashCode;
+import com.google.common.primitives.Ints;
+import com.google.common.primitives.Longs;
+
+public class LeaveGroupTransactionTransformer extends TransactionTransformer {
+
+	// Property lengths
+	private static final int JOINER_LENGTH = PUBLIC_KEY_LENGTH;
+	private static final int NAME_SIZE_LENGTH = INT_LENGTH;
+
+	private static final int TYPELESS_DATALESS_LENGTH = BASE_TYPELESS_LENGTH + JOINER_LENGTH + NAME_SIZE_LENGTH;
+
+	static TransactionData fromByteBuffer(ByteBuffer byteBuffer) throws TransformationException {
+		long timestamp = byteBuffer.getLong();
+
+		byte[] reference = new byte[REFERENCE_LENGTH];
+		byteBuffer.get(reference);
+
+		byte[] leaverPublicKey = Serialization.deserializePublicKey(byteBuffer);
+
+		String groupName = Serialization.deserializeSizedString(byteBuffer, Group.MAX_NAME_SIZE);
+
+		BigDecimal fee = Serialization.deserializeBigDecimal(byteBuffer);
+
+		byte[] signature = new byte[SIGNATURE_LENGTH];
+		byteBuffer.get(signature);
+
+		return new LeaveGroupTransactionData(leaverPublicKey, groupName, fee, timestamp, reference, signature);
+	}
+
+	public static int getDataLength(TransactionData transactionData) throws TransformationException {
+		LeaveGroupTransactionData leaveGroupTransactionData = (LeaveGroupTransactionData) transactionData;
+
+		int dataLength = TYPE_LENGTH + TYPELESS_DATALESS_LENGTH + Utf8.encodedLength(leaveGroupTransactionData.getGroupName());
+
+		return dataLength;
+	}
+
+	public static byte[] toBytes(TransactionData transactionData) throws TransformationException {
+		try {
+			LeaveGroupTransactionData leaveGroupTransactionData = (LeaveGroupTransactionData) transactionData;
+
+			ByteArrayOutputStream bytes = new ByteArrayOutputStream();
+
+			bytes.write(Ints.toByteArray(leaveGroupTransactionData.getType().value));
+			bytes.write(Longs.toByteArray(leaveGroupTransactionData.getTimestamp()));
+			bytes.write(leaveGroupTransactionData.getReference());
+
+			bytes.write(leaveGroupTransactionData.getCreatorPublicKey());
+			Serialization.serializeSizedString(bytes, leaveGroupTransactionData.getGroupName());
+
+			Serialization.serializeBigDecimal(bytes, leaveGroupTransactionData.getFee());
+
+			if (leaveGroupTransactionData.getSignature() != null)
+				bytes.write(leaveGroupTransactionData.getSignature());
+
+			return bytes.toByteArray();
+		} catch (IOException | ClassCastException e) {
+			throw new TransformationException(e);
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	public static JSONObject toJSON(TransactionData transactionData) throws TransformationException {
+		JSONObject json = TransactionTransformer.getBaseJSON(transactionData);
+
+		try {
+			LeaveGroupTransactionData leaveGroupTransactionData = (LeaveGroupTransactionData) transactionData;
+
+			byte[] leaverPublicKey = leaveGroupTransactionData.getLeaverPublicKey();
+
+			json.put("leaver", PublicKeyAccount.getAddress(leaverPublicKey));
+			json.put("leaverPublicKey", HashCode.fromBytes(leaverPublicKey).toString());
+
+			json.put("groupName", leaveGroupTransactionData.getGroupName());
+		} catch (ClassCastException e) {
+			throw new TransformationException(e);
+		}
+
+		return json;
+	}
+
+}

src/main/java/org/qora/transform/transaction/TransactionTransformer.java

@@ -103,6 +103,9 @@ public class TransactionTransformer extends Transformer {
 				case JOIN_GROUP:
 					return JoinGroupTransactionTransformer.fromByteBuffer(byteBuffer);
 
+				case LEAVE_GROUP:
+					return LeaveGroupTransactionTransformer.fromByteBuffer(byteBuffer);
+
 				default:
 					throw new TransformationException("Unsupported transaction type [" + type.value + "] during conversion from bytes");
 			}
@@ -173,6 +176,9 @@ public class TransactionTransformer extends Transformer {
 			case JOIN_GROUP:
 				return JoinGroupTransactionTransformer.getDataLength(transactionData);
 
+			case LEAVE_GROUP:
+				return LeaveGroupTransactionTransformer.getDataLength(transactionData);
+
 			default:
 				throw new TransformationException("Unsupported transaction type [" + transactionData.getType().value + "] when requesting byte length");
 		}
@@ -240,6 +246,9 @@ public class TransactionTransformer extends Transformer {
 			case JOIN_GROUP:
 				return JoinGroupTransactionTransformer.toBytes(transactionData);
 
+			case LEAVE_GROUP:
+				return LeaveGroupTransactionTransformer.toBytes(transactionData);
+
 			default:
 				throw new TransformationException("Unsupported transaction type [" + transactionData.getType().value + "] during conversion to bytes");
 		}
@@ -316,6 +325,9 @@ public class TransactionTransformer extends Transformer {
 			case JOIN_GROUP:
 				return JoinGroupTransactionTransformer.toBytesForSigningImpl(transactionData);
 
+			case LEAVE_GROUP:
+				return LeaveGroupTransactionTransformer.toBytesForSigningImpl(transactionData);
+
 			default:
 				throw new TransformationException(
 						"Unsupported transaction type [" + transactionData.getType().value + "] during conversion to bytes for signing");
@@ -404,6 +416,9 @@ public class TransactionTransformer extends Transformer {
 			case JOIN_GROUP:
 				return JoinGroupTransactionTransformer.toJSON(transactionData);
 
+			case LEAVE_GROUP:
+				return LeaveGroupTransactionTransformer.toJSON(transactionData);
+
 			default:
 				throw new TransformationException("Unsupported transaction type [" + transactionData.getType().value + "] during conversion to JSON");
 		}