1 files changed, 117 insertions, 0 deletions
diff --git a/java/src/main/java/org/whispersystems/libaxolotl/state/SessionRecord.java b/java/src/main/java/org/whispersystems/libaxolotl/state/SessionRecord.java
new file mode 100644
index 00000000..76c64922
--- /dev/null
+++ b/java/src/main/java/org/whispersystems/libaxolotl/state/SessionRecord.java
@@ -0,0 +1,117 @@
+package org.whispersystems.libaxolotl.state;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import static org.whispersystems.libaxolotl.state.StorageProtos.RecordStructure;
+import static org.whispersystems.libaxolotl.state.StorageProtos.SessionStructure;
+
+/**
+ * A SessionRecord encapsulates the state of an ongoing session.
+ *
+ * @author Moxie Marlinspike
+ */
+public class SessionRecord {
+
+  private static final int ARCHIVED_STATES_MAX_LENGTH = 40;
+
+  private SessionState             sessionState   = new SessionState();
+  private LinkedList<SessionState> previousStates = new LinkedList<>();
+  private boolean                  fresh          = false;
+
+  public SessionRecord() {
+    this.fresh = true;
+  }
+
+  public SessionRecord(SessionState sessionState) {
+    this.sessionState = sessionState;
+    this.fresh        = false;
+  }
+
+  public SessionRecord(byte[] serialized) throws IOException {
+    RecordStructure record = RecordStructure.parseFrom(serialized);
+    this.sessionState = new SessionState(record.getCurrentSession());
+    this.fresh        = false;
+
+    for (SessionStructure previousStructure : record.getPreviousSessionsList()) {
+      previousStates.add(new SessionState(previousStructure));
+    }
+  }
+
+  public boolean hasSessionState(int version, byte[] aliceBaseKey) {
+    if (sessionState.getSessionVersion() == version &&
+        Arrays.equals(aliceBaseKey, sessionState.getAliceBaseKey()))
+    {
+      return true;
+    }
+
+    for (SessionState state : previousStates) {
+      if (state.getSessionVersion() == version &&
+          Arrays.equals(aliceBaseKey, state.getAliceBaseKey()))
+      {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  public SessionState getSessionState() {
+    return sessionState;
+  }
+
+  /**
+   * @return the list of all currently maintained "previous" session states.
+   */
+  public List<SessionState> getPreviousSessionStates() {
+    return previousStates;
+  }
+
+
+  public boolean isFresh() {
+    return fresh;
+  }
+
+  /**
+   * Move the current {@link SessionState} into the list of "previous" session states,
+   * and replace the current {@link org.whispersystems.libaxolotl.state.SessionState}
+   * with a fresh reset instance.
+   */
+  public void archiveCurrentState() {
+    promoteState(new SessionState());
+  }
+
+  public void promoteState(SessionState promotedState) {
+    this.previousStates.addFirst(sessionState);
+    this.sessionState = promotedState;
+
+    if (previousStates.size() > ARCHIVED_STATES_MAX_LENGTH) {
+      previousStates.removeLast();
+    }
+  }
+
+  public void setState(SessionState sessionState) {
+    this.sessionState = sessionState;
+  }
+
+  /**
+   * @return a serialized version of the current SessionRecord.
+   */
+  public byte[] serialize() {
+    List<SessionStructure> previousStructures = new LinkedList<>();
+
+    for (SessionState previousState : previousStates) {
+      previousStructures.add(previousState.getStructure());
+    }
+
+    RecordStructure record = RecordStructure.newBuilder()
+                                            .setCurrentSession(sessionState.getStructure())
+                                            .addAllPreviousSessions(previousStructures)
+                                            .build();
+
+    return record.toByteArray();
+  }
+
+}