Implementation of memory persistence service.

This persistence service is self-contained and allows to retain data without disk/storage access.
It can be also used for items which have high update frequency and might put unecessary load on storage.

Signed-off-by: Łukasz Dywicki <luke@code-house.org>

bundles/org.connectorio.addons.persistence.memory/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ - Copyright (C) 2024-2024 ConnectorIO Sp. z o.o.
+ -
+ - Licensed under the Apache License, Version 2.0 (the "License");
+ - you may not use this file except in compliance with the License.
+ - You may obtain a copy of the License at
+ -
+ -     http://www.apache.org/licenses/LICENSE-2.0
+ -
+ - Unless required by applicable law or agreed to in writing, software
+ - distributed under the License is distributed on an "AS IS" BASIS,
+ - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ - See the License for the specific language governing permissions and
+ - limitations under the License.
+ -
+ - SPDX-License-Identifier: Apache-2.0
+ -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.connectorio.addons</groupId>
+    <artifactId>bundles</artifactId>
+    <version>3.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>org.connectorio.addons.persistence.memory</artifactId>
+  <packaging>bundle</packaging>
+
+  <name>ConnectorIO - Addons - Persistence - Memory</name>
+  <description>A memory persistence service.</description>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.openhab.core.bundles</groupId>
+      <artifactId>org.openhab.core.persistence</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.openhab.core.bundles</groupId>
+      <artifactId>org.openhab.core.config.xml</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>com.thoughtworks.xstream</groupId>
+      <artifactId>xstream</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-api</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.osgi</groupId>
+      <artifactId>osgi.core</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.osgi</groupId>
+      <artifactId>org.osgi.service.component.annotations</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-api</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-params</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.assertj</groupId>
+      <artifactId>assertj-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-junit-jupiter</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.connectorio.addons</groupId>
+      <artifactId>org.connectorio.addons.test</artifactId>
+    </dependency>
+  </dependencies>
+
+</project>

bundles/org.connectorio.addons.persistence.memory/src/main/java/org/connectorio/addons/persistence/memory/internal/MemoryBucket.java

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+/*
+ * Copyright (C) 2024-2024 ConnectorIO Sp. z o.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.connectorio.addons.persistence.memory.internal;
+
+import java.util.Comparator;
+import java.util.Date;
+import java.util.NavigableSet;
+import java.util.Objects;
+import java.util.TreeSet;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Stream;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class MemoryBucket {
+
+  private final Logger logger = LoggerFactory.getLogger(MemoryBucket.class);
+
+  private final NavigableSet<MemoryEntry> entries = new TreeSet<>(
+    Comparator.comparing(MemoryEntry::getTimestamp)
+  );
+
+  private final Lock lock = new ReentrantLock();
+  private int limit;
+
+  public MemoryBucket(int limit) {
+    this.limit = limit;
+  }
+
+  public void append(MemoryEntry entry) {
+    apply(myself -> {
+      logger.trace("Inserted entry {}. Stored entries {}, limit {}", entry, entries.size(), limit);
+      myself.entries.add(entry);
+    });
+  }
+
+  public void truncate(int limit) {
+    this.limit = limit;
+
+    apply(myself -> {
+      while (myself.entries.size() > limit) {
+        MemoryEntry entry = myself.entries.pollFirst();
+        logger.trace("Removed bucket entry {} as it exceeds limit {}", entry, limit);
+      }
+    });
+  }
+
+  public Stream<MemoryEntry> entries() {
+    return entries.stream();
+  }
+
+  public void remove(MemoryEntry entry) {
+    apply(myself -> myself.entries.remove(entry));
+  }
+
+  public Integer getSize() {
+    return entries.size();
+  }
+
+  public Date getEarliest() {
+    return entries.isEmpty() ? null : Date.from(entries.first().getTimestamp().toInstant());
+  }
+
+  public Date getOldest() {
+    return entries.isEmpty() ? null : Date.from(entries.last().getTimestamp().toInstant());
+  }
+
+  public <X> X process(Function<MemoryBucket, X> function) {
+    lock.lock();
+    try {
+      return function.apply(this);
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  private void apply(Consumer<MemoryBucket> consumer) {
+    lock.lock();
+    try {
+      consumer.accept(this);
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof MemoryBucket)) {
+      return false;
+    }
+    MemoryBucket bucket = (MemoryBucket) o;
+    return limit == bucket.limit && Objects.equals(entries, bucket.entries);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(entries, limit);
+  }
+
+}

bundles/org.connectorio.addons.persistence.memory/src/main/java/org/connectorio/addons/persistence/memory/internal/MemoryBucketInfo.java

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+/*
+ * Copyright (C) 2024-2024 ConnectorIO Sp. z o.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.connectorio.addons.persistence.memory.internal;
+
+import java.util.Date;
+import org.openhab.core.persistence.PersistenceItemInfo;
+
+public class MemoryBucketInfo implements PersistenceItemInfo {
+
+  private final String name;
+  private final Integer count;
+  private final Date earliest;
+  private final Date oldest;
+
+  public MemoryBucketInfo(String name, Integer count, Date earliest, Date oldest) {
+    this.name = name;
+    this.count = count;
+    this.earliest = earliest;
+    this.oldest = oldest;
+  }
+
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public Integer getCount() {
+    return count;
+  }
+
+  @Override
+  public Date getEarliest() {
+    return earliest;
+  }
+
+  @Override
+  public Date getLatest() {
+    return oldest;
+  }
+}

bundles/org.connectorio.addons.persistence.memory/src/main/java/org/connectorio/addons/persistence/memory/internal/MemoryEntry.java

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+/*
+ * Copyright (C) 2024-2024 ConnectorIO Sp. z o.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.connectorio.addons.persistence.memory.internal;
+
+import java.time.ZonedDateTime;
+import java.util.Objects;
+import org.openhab.core.types.State;
+
+public class MemoryEntry {
+
+  private final ZonedDateTime timestamp;
+  private final State state;
+
+  public MemoryEntry(ZonedDateTime timestamp, State state) {
+    this.timestamp = timestamp;
+    this.state = state;
+  }
+
+  public ZonedDateTime getTimestamp() {
+    return timestamp;
+  }
+
+  public State getState() {
+    return state;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof MemoryEntry)) {
+      return false;
+    }
+    MemoryEntry that = (MemoryEntry) o;
+    return Objects.equals(getTimestamp(), that.getTimestamp()) && Objects.equals(
+      getState(), that.getState());
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(getTimestamp(), getState());
+  }
+
+  public String toString() {
+    return "MemoryEntry [" + timestamp + "=" + state + "]";
+  }
+}

bundles/org.connectorio.addons.persistence.memory/src/main/java/org/connectorio/addons/persistence/memory/internal/MemoryHistoricItem.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2024-2024 ConnectorIO Sp. z o.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.connectorio.addons.persistence.memory.internal;
+
+import java.time.ZonedDateTime;
+import org.openhab.core.persistence.HistoricItem;
+import org.openhab.core.types.State;
+
+public class MemoryHistoricItem implements HistoricItem {
+  private final String name;
+  private final ZonedDateTime timestamp;
+  private final State state;
+
+  public MemoryHistoricItem(String name, ZonedDateTime timestamp, State state) {
+    this.name = name;
+    this.timestamp = timestamp;
+    this.state = state;
+  }
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public ZonedDateTime getTimestamp() {
+    return timestamp;
+  }
+
+  @Override
+  public State getState() {
+    return state;
+  }
+
+}