feat: Add core-site.xml builder

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: maltesander

rust/operator-binary/src/controller/build/properties/core_site.rs

@@ -1 +1,117 @@
-//! placeholder — implemented in a later task
+//! Builder for `core-site.xml`.
+//!
+//! Only emitted when Kerberos is enabled and there is no HDFS backend (i.e. S3),
+//! in which case `hadoop.security.authentication=kerberos` is required.
+
+use std::collections::BTreeMap;
+
+use crate::crd::v1alpha1;
+
+const HADOOP_SECURITY_AUTHENTICATION: &str = "hadoop.security.authentication";
+
+/// Returns the `core-site.xml` properties, or `None` if the file should be omitted.
+pub fn build(hive: &v1alpha1::HiveCluster) -> Option<BTreeMap<String, Option<String>>> {
+    if hive.has_kerberos_enabled() && hive.spec.cluster_config.hdfs.is_none() {
+        let mut data = BTreeMap::new();
+        data.insert(
+            HADOOP_SECURITY_AUTHENTICATION.to_string(),
+            Some("kerberos".to_string()),
+        );
+        Some(data)
+    } else {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn hive_cluster(yaml: &str) -> v1alpha1::HiveCluster {
+        stackable_operator::utils::yaml_from_str_singleton_map(yaml).expect("valid HiveCluster YAML")
+    }
+
+    const NO_KERBEROS_YAML: &str = r#"
+        apiVersion: hive.stackable.tech/v1alpha1
+        kind: HiveCluster
+        metadata:
+          name: simple-hive
+          namespace: default
+        spec:
+          image:
+            productVersion: "4.0.0"
+          clusterConfig:
+            metadataDatabase:
+              derby: {}
+          metastore:
+            roleGroups:
+              default:
+                replicas: 1
+        "#;
+
+    const KERBEROS_S3_YAML: &str = r#"
+        apiVersion: hive.stackable.tech/v1alpha1
+        kind: HiveCluster
+        metadata:
+          name: simple-hive
+          namespace: default
+        spec:
+          image:
+            productVersion: "4.0.0"
+          clusterConfig:
+            authentication:
+              kerberos:
+                secretClass: kerberos
+            metadataDatabase:
+              derby: {}
+          metastore:
+            roleGroups:
+              default:
+                replicas: 1
+        "#;
+
+    const KERBEROS_HDFS_YAML: &str = r#"
+        apiVersion: hive.stackable.tech/v1alpha1
+        kind: HiveCluster
+        metadata:
+          name: simple-hive
+          namespace: default
+        spec:
+          image:
+            productVersion: "4.0.0"
+          clusterConfig:
+            authentication:
+              kerberos:
+                secretClass: kerberos
+            metadataDatabase:
+              derby: {}
+            hdfs:
+              configMap: hdfs
+          metastore:
+            roleGroups:
+              default:
+                replicas: 1
+        "#;
+
+    #[test]
+    fn omitted_without_kerberos() {
+        let hive = hive_cluster(NO_KERBEROS_YAML);
+        assert!(build(&hive).is_none());
+    }
+
+    #[test]
+    fn emitted_with_kerberos_and_no_hdfs() {
+        let hive = hive_cluster(KERBEROS_S3_YAML);
+        let data = build(&hive).expect("core-site present");
+        assert_eq!(
+            data.get("hadoop.security.authentication"),
+            Some(&Some("kerberos".to_string()))
+        );
+    }
+
+    #[test]
+    fn omitted_with_kerberos_but_hdfs_backend() {
+        let hive = hive_cluster(KERBEROS_HDFS_YAML);
+        assert!(build(&hive).is_none());
+    }
+}