Enhance DBContext with a single variable getter, pushes forward #425

telegrambots-abilities/src/main/java/org/telegram/abilitybots/api/db/DBContext.java

@@ -39,6 +39,13 @@ public interface DBContext extends Closeable {
    */
   <T> Set<T> getSet(String name);
 
+  /**
+   * @param name the unique name of the {@link Set}
+   * @param <T>  the type that the Set holds
+   * @return the Set with the specified name
+   */
+  <T> Var<T> getVar(String name);
+
   /**
    * @return a high-level summary of the database structures (Sets, Lists, Maps, ...) present.
    */

telegrambots-abilities/src/main/java/org/telegram/abilitybots/api/db/MapDBContext.java

@@ -3,6 +3,7 @@ package org.telegram.abilitybots.api.db;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.mapdb.Atomic;
 import org.mapdb.DB;
 import org.mapdb.DBMaker;
 import org.mapdb.Serializer;
@@ -93,6 +94,11 @@ public class MapDBContext implements DBContext {
     return (Set<T>) db.<T>hashSet(name, JAVA).createOrOpen();
   }
 
+  @Override
+  public <T> Var<T> getVar(String name) {
+    return new MapDBVar<>((Atomic.Var<T>) db.atomicVar(name).createOrOpen());
+  }
+
   @Override
   public String summary() {
     return stream(db.getAllNames().spliterator(), false)

telegrambots-abilities/src/main/java/org/telegram/abilitybots/api/db/MapDBVar.java

@@ -0,0 +1,49 @@
+package org.telegram.abilitybots.api.db;
+
+import com.google.common.base.MoreObjects;
+import org.mapdb.Atomic;
+
+import java.util.Objects;
+
+/**
+ * The MapDB variant for {@link DBContext#getVar(String)}.
+ *
+ * @param <T> the type of the inner variable
+ */
+public final class MapDBVar<T> implements Var<T> {
+  private Atomic.Var<T> var;
+
+  public MapDBVar(Atomic.Var<T> var) {
+    this.var = var;
+  }
+
+  @Override
+  public T get() {
+    return var.get();
+  }
+
+  @Override
+  public void set(T var) {
+    this.var.set(var);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) return true;
+    if (o == null || getClass() != o.getClass()) return false;
+    MapDBVar<?> mapDBVar = (MapDBVar<?>) o;
+    return Objects.equals(var, mapDBVar.var);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(var);
+  }
+
+  @Override
+  public String toString() {
+    return MoreObjects.toStringHelper(this)
+        .add("var", var)
+        .toString();
+  }
+}

telegrambots-abilities/src/main/java/org/telegram/abilitybots/api/db/Var.java

@@ -0,0 +1,19 @@
+package org.telegram.abilitybots.api.db;
+
+/**
+ * The interface governing a variable for abstract getters and setters.
+ * @param <T> the type of the variable
+ *
+ * @author Abbas Abou Daya
+ */
+public interface Var<T> {
+  /**
+   * @return the variable contained
+   */
+  T get();
+
+  /**
+   * @param var the new variable value
+   */
+  void set(T var);
+}

telegrambots-abilities/src/test/java/org/telegram/abilitybots/api/db/MapDBContextTest.java

@@ -100,6 +100,23 @@ public class MapDBContextTest {
     db.info(TEST);
   }
 
+  @Test
+  public void canGetAndSetVariables() {
+    String varName = "somevar";
+    Var<User> var = db.getVar(varName);
+    var.set(CREATOR);
+    db.commit();
+
+    var = db.getVar(varName);
+    assertEquals(var.get(), CREATOR);
+
+    var.set(USER);
+    db.commit();
+
+    Var<User> changedVar = db.getVar(varName);
+    assertEquals(changedVar.get(), USER);
+  }
+
   @After
   public void tearDown() throws IOException {
     db.clear();