Handling of Epic labels and links

src/main/java/org/hibernate/infra/replicate/jira/JiraConfig.java

@@ -61,7 +61,7 @@ interface JiraProjectGroup {
 		 * Mapping of upstream issue types to downstream ones. Please make sure to
 		 * review your project scheme to see which issue types are available.
 		 */
-		ValueMapping issueTypes();
+		IssueTypeValueMapping issueTypes();
 
 		/**
 		 * Depending on your downstream JIRA permission schema configuration, Service
@@ -234,6 +234,35 @@ interface IssueLinkTypeValueMapping extends ValueMapping {
 		String parentLinkType();
 	}
 
+	interface IssueTypeValueMapping extends ValueMapping {
+		/**
+		 * @return the name of the custom field that represents the epic link field.
+		 *         Apparently there is no clean way to attach issues to an epic, and a
+		 *         possible workaround is to use the custom filed (that differs from
+		 *         instance to instance) that represents the Epic link key.
+		 *         <p>
+		 *         A possible alternative could've been <a href=
+		 *         "https://developer.atlassian.com/server/jira/platform/rest/v10000/api-group-epic/#api-agile-1-0-epic-epicidorkey-issue-post">Move
+		 *         issues to a specific epic</a> but it might not be available on all
+		 *         instance types.
+		 *         <p>
+		 *         If value is not provided in the configuration, then tickets will not
+		 *         be linked to epics during the sync.
+		 */
+		Optional<String> epicLinkKeyCustomFieldName();
+
+		/**
+		 * @return The name of a custom field that represents the "epic name" i.e.
+		 *         epic-short-label in the upstream (source) Jira instance.
+		 */
+		Optional<String> epicLinkSourceLabelCustomFieldName();
+		/**
+		 * @return The name of a custom field that represents the "epic name" i.e.
+		 *         epic-short-label in the downstream (destination) Jira instance.
+		 */
+		Optional<String> epicLinkDestinationLabelCustomFieldName();
+	}
+
 	interface UserValueMapping extends ValueMapping {
 		/**
 		 * @return the name of the property to apply the assignee value to. With Jira

src/main/java/org/hibernate/infra/replicate/jira/service/jira/handler/JiraIssueAbstractEventHandler.java

@@ -6,6 +6,7 @@
 import java.util.Objects;
 import java.util.Optional;
 
+import org.hibernate.infra.replicate.jira.JiraConfig;
 import org.hibernate.infra.replicate.jira.service.jira.HandlerProjectContext;
 import org.hibernate.infra.replicate.jira.service.jira.client.JiraRestException;
 import org.hibernate.infra.replicate.jira.service.jira.model.rest.JiraFields;
@@ -128,6 +129,24 @@ protected JiraIssue issueToCreate(JiraIssue sourceIssue) {
 			destinationIssue.fields.assignee = JiraUser.unassigned(context.projectGroup().users().mappedPropertyName());
 		}
 
+		if (!isSubTaskIssue(sourceIssue.fields.issuetype) && sourceIssue.fields.parent != null) {
+			if (isEpicIssue(sourceIssue.fields.parent.fields.issuetype)) {
+				JiraConfig.IssueTypeValueMapping issueTypes = context.projectGroup().issueTypes();
+				issueTypes.epicLinkKeyCustomFieldName().ifPresent(epicLinkCustomFieldName -> destinationIssue.fields
+						.properties().put(epicLinkCustomFieldName, toDestinationKey(sourceIssue.fields.parent.key)));
+			}
+		}
+		if (isEpicIssue(sourceIssue.fields.issuetype)) {
+			// Try to set an epic label ... obviously it is a custom field >_< ...
+			JiraConfig.IssueTypeValueMapping issueTypes = context.projectGroup().issueTypes();
+			Object sourceEpicLabel = issueTypes.epicLinkSourceLabelCustomFieldName()
+					.map(sourceIssue.fields.properties()::get).orElse(sourceIssue.fields.summary);
+
+			issueTypes.epicLinkDestinationLabelCustomFieldName()
+					.ifPresent(epicLinkDestinationLabelCustomFieldName -> destinationIssue.fields.properties()
+							.put(epicLinkDestinationLabelCustomFieldName, sourceEpicLabel));
+		}
+
 		return destinationIssue;
 	}
 
@@ -140,7 +159,10 @@ private Optional<JiraTransition> prepareTransition(JiraIssue sourceIssue) {
 	}
 
 	protected Optional<JiraIssueLink> prepareParentLink(String destinationKey, JiraIssue sourceIssue) {
-		if (sourceIssue.fields.parent != null) {
+		// we only add a link for sub-tasks (the ones that have a corresponding types).
+		// Issues assigned to an epic, can also have a parent.
+		// but for those we won't add an extra link:
+		if (sourceIssue.fields.parent != null && isSubTaskIssue(sourceIssue.fields.issuetype)) {
 			String parent = toDestinationKey(sourceIssue.fields.parent.key);
 			// we don't really need it, but as usual we are making sure that the issue is
 			// available downstream:
@@ -164,6 +186,20 @@ protected Optional<JiraIssueLink> prepareParentLink(String destinationKey, JiraI
 		}
 	}
 
+	private boolean isSubTaskIssue(JiraSimpleObject issueType) {
+		if (issueType == null) {
+			return false;
+		}
+		return Boolean.parseBoolean(Objects.toString(issueType.properties().get("subtask"), null));
+	}
+
+	private boolean isEpicIssue(JiraSimpleObject issueType) {
+		if (issueType == null) {
+			return false;
+		}
+		return "epic".equalsIgnoreCase(issueType.name);
+	}
+
 	private String prepareDescriptionQuote(JiraIssue issue) {
 		URI issueUri = createJiraIssueUri(issue);