[#32] feat(core): add Entity Operation interface and Entity name iden…

…tifier (#33)

### What changes were proposed in this pull request?

This PR is a preconditional PR to support REST API for Graviton. This PR
defines:

1. Entity's name identifier to distinguish between entities.
2. Entity operation interfaces. We will later on implement this
interface to manipulate the entities.

### Why are the changes needed?

This PR is a preconditional PR to support REST API for Graviton.

Fix: #32 

### Does this PR introduce _any_ user-facing change?

N/A

### How was this patch tested?

New UTs to cover the test.

core/src/main/java/com/datastrato/graviton/EntityOperations.java

@@ -0,0 +1,45 @@
+package com.datastrato.graviton;
+
+import com.datastrato.graviton.schema.Entity;
+import com.datastrato.graviton.schema.HasIdentifier;
+import com.datastrato.graviton.schema.NameIdentifier;
+
+public interface EntityOperations<T extends Entity & HasIdentifier> {
+
+  /**
+   * Creates the entity.
+   *
+   * @param t the entity to create.
+   */
+  default void create(T t) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Gets the entity by name identifier.
+   *
+   * @param nameIdentifier the name identifier of the entity.
+   * @return the entity.
+   */
+  default T get(NameIdentifier nameIdentifier) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Updates the entity.
+   *
+   * @param t the entity to update.
+   */
+  default void update(T t) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+
+  /**
+   * Deletes the entity by name identifier.
+   *
+   * @param nameIdentifier the name identifier of the entity.
+   */
+  default void delete(NameIdentifier nameIdentifier) {
+    throw new UnsupportedOperationException("Not implemented yet");
+  }
+}

core/src/main/java/com/datastrato/graviton/schema/Column.java

@@ -16,7 +16,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public final class Column implements Entity, Auditable {
+public final class Column implements Entity, Auditable, HasIdentifier {
 
   public static final Field ID =
       Field.required("id", Integer.class, "The unique identifier of the column");
@@ -88,6 +88,11 @@ public AuditInfo auditInfo() {
     return auditInfo;
   }
 
+  @Override
+  public String name() {
+    return name;
+  }
+
   public static class Builder {
     private final Column column;
 

core/src/main/java/com/datastrato/graviton/schema/hasExtraInfo.java → core/src/main/java/com/datastrato/graviton/schema/HasExtraInfo.java

@@ -4,7 +4,7 @@
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 
 /** Interface for entities that have extra info. */
-public interface hasExtraInfo {
+public interface HasExtraInfo {
 
   @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
   @JsonSubTypes({@JsonSubTypes.Type(value = VirtualTableInfo.class, name = "VIRTUAL")})

core/src/main/java/com/datastrato/graviton/schema/HasIdentifier.java

@@ -0,0 +1,22 @@
+package com.datastrato.graviton.schema;
+
+public interface HasIdentifier {
+
+  /**
+   * Return the name of the entity.
+   *
+   * @return A String with the name of the entity.
+   */
+  String name();
+
+  /**
+   * Returns the name identifier of the entity.
+   *
+   * @return NameIdentifier of the entity.
+   */
+  default NameIdentifier nameIdentifier(Namespace namespace) {
+    return NameIdentifier.of(namespace, name());
+  }
+
+  // TODO. Returns a binary compact unique identifier of the entity. @Jerry
+}

core/src/main/java/com/datastrato/graviton/schema/Lakehouse.java

@@ -12,7 +12,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public class Lakehouse implements Entity, Auditable {
+public class Lakehouse implements Entity, Auditable, HasIdentifier {
 
   public static final Field ID =
       Field.required("id", Long.class, "The unique identifier of the lakehouse");
@@ -61,6 +61,11 @@ public AuditInfo auditInfo() {
     return auditInfo;
   }
 
+  @Override
+  public String name() {
+    return name;
+  }
+
   public static class Builder {
     private final Lakehouse lakehouse;
 

core/src/main/java/com/datastrato/graviton/schema/NameIdentifier.java

@@ -0,0 +1,81 @@
+package com.datastrato.graviton.schema;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Splitter;
+import com.google.common.collect.Iterables;
+import java.util.Arrays;
+
+public class NameIdentifier {
+
+  private static final Splitter DOT = Splitter.on('.');
+
+  private final Namespace namespace;
+
+  private final String name;
+
+  public static NameIdentifier of(String... names) {
+    Preconditions.checkArgument(names != null, "Cannot create a NameIdentifier with null names");
+    Preconditions.checkArgument(names.length > 0, "Cannot create a NameIdentifier with no names");
+
+    return new NameIdentifier(
+        Namespace.of(Arrays.copyOf(names, names.length - 1)), names[names.length - 1]);
+  }
+
+  public static NameIdentifier of(Namespace namespace, String name) {
+    return new NameIdentifier(namespace, name);
+  }
+
+  public static NameIdentifier parse(String identifier) {
+    Preconditions.checkArgument(
+        identifier != null && !identifier.isEmpty(), "Cannot parse a null or empty identifier");
+
+    Iterable<String> parts = DOT.split(identifier);
+    return NameIdentifier.of(Iterables.toArray(parts, String.class));
+  }
+
+  private NameIdentifier(Namespace namespace, String name) {
+    Preconditions.checkArgument(
+        namespace != null, "Cannot create a NameIdentifier with null namespace");
+    Preconditions.checkArgument(
+        name != null && !name.isEmpty(), "Cannot create a NameIdentifier with null or empty name");
+
+    this.namespace = namespace;
+    this.name = name;
+  }
+
+  public boolean hasNamespace() {
+    return !namespace.isEmpty();
+  }
+
+  public Namespace namespace() {
+    return namespace;
+  }
+
+  public String name() {
+    return name;
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (other == null || !(other instanceof NameIdentifier)) {
+      return false;
+    }
+
+    NameIdentifier otherNameIdentifier = (NameIdentifier) other;
+    return namespace.equals(otherNameIdentifier.namespace) && name.equals(otherNameIdentifier.name);
+  }
+
+  @Override
+  public int hashCode() {
+    return Arrays.hashCode(new int[] {namespace.hashCode(), name.hashCode()});
+  }
+
+  @Override
+  public String toString() {
+    if (hasNamespace()) {
+      return namespace.toString() + "." + name;
+    } else {
+      return name;
+    }
+  }
+}

core/src/main/java/com/datastrato/graviton/schema/Namespace.java

@@ -0,0 +1,72 @@
+package com.datastrato.graviton.schema;
+
+import com.google.common.base.Joiner;
+import com.google.common.base.Preconditions;
+import java.util.Arrays;
+
+public class Namespace {
+
+  private static final Namespace EMPTY = new Namespace(new String[0]);
+  private static final Joiner DOT = Joiner.on('.');
+
+  private final String[] levels;
+
+  public static Namespace empty() {
+    return EMPTY;
+  }
+
+  public static Namespace of(String... levels) {
+    Preconditions.checkArgument(levels != null, "Cannot create a namespace with null levels");
+    if (levels.length == 0) {
+      return empty();
+    }
+
+    for (String level : levels) {
+      Preconditions.checkArgument(
+          level != null && !level.isEmpty(), "Cannot create a namespace with null or empty level");
+    }
+
+    return new Namespace(levels);
+  }
+
+  private Namespace(String[] levels) {
+    this.levels = levels;
+  }
+
+  public String[] levels() {
+    return levels;
+  }
+
+  public String level(int pos) {
+    Preconditions.checkArgument(pos >= 0 && pos < levels.length, "Invalid level position");
+    return levels[pos];
+  }
+
+  public int length() {
+    return levels.length;
+  }
+
+  public boolean isEmpty() {
+    return levels.length == 0;
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (other == null || !(other instanceof Namespace)) {
+      return false;
+    }
+
+    Namespace otherNamespace = (Namespace) other;
+    return Arrays.equals(levels, otherNamespace.levels);
+  }
+
+  @Override
+  public int hashCode() {
+    return Arrays.hashCode(levels);
+  }
+
+  @Override
+  public String toString() {
+    return DOT.join(levels);
+  }
+}

core/src/main/java/com/datastrato/graviton/schema/Table.java

@@ -10,7 +10,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public class Table implements Entity, Auditable, hasExtraInfo {
+public class Table implements Entity, Auditable, HasExtraInfo, HasIdentifier {
   public enum TableType {
     VIRTUAL("VIRTUAL"),
     VIEW("VIEW"),
@@ -45,7 +45,7 @@ public String getTypeStr() {
   public static final Field AUDIT_INFO =
       Field.required("audit_info", AuditInfo.class, "The audit info of the table");
   public static final Field EXTRA_INFO =
-      Field.required("extra_info", hasExtraInfo.ExtraInfo.class, "The extra info of the table");
+      Field.required("extra_info", HasExtraInfo.ExtraInfo.class, "The extra info of the table");
 
   @JsonProperty("id")
   private Long id;
@@ -74,7 +74,7 @@ public String getTypeStr() {
   private AuditInfo auditInfo;
 
   @JsonProperty("extra_info")
-  private hasExtraInfo.ExtraInfo extraInfo;
+  private HasExtraInfo.ExtraInfo extraInfo;
 
   @JsonProperty("columns")
   private List<Column> columns;
@@ -103,10 +103,15 @@ public AuditInfo auditInfo() {
   }
 
   @Override
-  public hasExtraInfo.ExtraInfo extraInfo() {
+  public HasExtraInfo.ExtraInfo extraInfo() {
     return extraInfo;
   }
 
+  @Override
+  public String name() {
+    return name;
+  }
+
   public static class Builder {
     private final Table table;
 
@@ -154,7 +159,7 @@ public Builder withAuditInfo(AuditInfo auditInfo) {
       return this;
     }
 
-    public Builder withExtraInfo(hasExtraInfo.ExtraInfo extraInfo) {
+    public Builder withExtraInfo(HasExtraInfo.ExtraInfo extraInfo) {
       table.extraInfo = extraInfo;
       return this;
     }

core/src/main/java/com/datastrato/graviton/schema/Tenant.java

@@ -12,7 +12,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public final class Tenant implements Entity, Auditable {
+public final class Tenant implements Entity, Auditable, HasIdentifier {
 
   public static final Field ID =
       Field.required("id", Integer.class, "The unique identifier of the tenant");
@@ -59,6 +59,11 @@ public AuditInfo auditInfo() {
     return auditInfo;
   }
 
+  @Override
+  public String name() {
+    return name;
+  }
+
   public static class Builder {
     private final Tenant tenant;
 

core/src/main/java/com/datastrato/graviton/schema/VirtualTableInfo.java

@@ -11,7 +11,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public final class VirtualTableInfo implements hasExtraInfo.ExtraInfo {
+public final class VirtualTableInfo implements HasExtraInfo.ExtraInfo {
 
   public static final Field CONNECTION_ID =
       Field.required("connection_id", Integer.class, "The unique identifier of the connection");

core/src/main/java/com/datastrato/graviton/schema/Zone.java

@@ -12,7 +12,7 @@
 @Getter
 @EqualsAndHashCode
 @ToString
-public class Zone implements Entity, Auditable {
+public class Zone implements Entity, Auditable, HasIdentifier {
 
   public static final Field ID =
       Field.required("id", Long.class, "The unique identifier of the zone");
@@ -66,6 +66,11 @@ public AuditInfo auditInfo() {
     return auditInfo;
   }
 
+  @Override
+  public String name() {
+    return name;
+  }
+
   public static class Builder {
     private final Zone zone;