Extract a type for sets of reviewers, and store timestamp

Change-Id: I946b3d89ff9b77a2eecb077b7c76735a8511eab1

gerrit-server/src/main/java/com/google/gerrit/server/ReviewerSet.java

@@ -0,0 +1,115 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// 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.
+
+package com.google.gerrit.server;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.gerrit.server.notedb.ReviewerStateInternal.CC;
+import static com.google.gerrit.server.notedb.ReviewerStateInternal.REVIEWER;
+
+import com.google.common.collect.HashBasedTable;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Table;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
+
+import java.sql.Timestamp;
+
+/**
+ * Set of reviewers on a change.
+ * <p>
+ * A given account may appear in multiple states and at different timestamps. No
+ * reviewers with state {@link ReviewerStateInternal#REMOVED} are ever exposed
+ * by this interface.
+ */
+public class ReviewerSet {
+  private static final ReviewerSet EMPTY = new ReviewerSet(
+      ImmutableTable.<ReviewerStateInternal, Account.Id, Timestamp>of());
+
+  public static ReviewerSet fromApprovals(
+      Iterable<PatchSetApproval> approvals) {
+    PatchSetApproval first = null;
+    Table<ReviewerStateInternal, Account.Id, Timestamp> reviewers =
+        HashBasedTable.create();
+    for (PatchSetApproval psa : approvals) {
+      if (first == null) {
+        first = psa;
+      } else {
+        checkArgument(
+            first.getKey().getParentKey().getParentKey().equals(
+              psa.getKey().getParentKey().getParentKey()),
+            "multiple change IDs: %s, %s", first.getKey(), psa.getKey());
+      }
+      Account.Id id = psa.getAccountId();
+      if (psa.getValue() != 0) {
+        reviewers.put(REVIEWER, id, psa.getGranted());
+        reviewers.remove(CC, id);
+      } else if (!reviewers.contains(REVIEWER, id)) {
+        reviewers.put(CC, id, psa.getGranted());
+      }
+    }
+    return new ReviewerSet(reviewers);
+  }
+
+  public static ReviewerSet fromTable(
+      Table<ReviewerStateInternal, Account.Id, Timestamp> table) {
+    return new ReviewerSet(table);
+  }
+
+  public static ReviewerSet empty() {
+    return EMPTY;
+  }
+
+  private final ImmutableTable<ReviewerStateInternal, Account.Id, Timestamp>
+      table;
+  private ImmutableSet<Account.Id> accounts;
+
+  private ReviewerSet(Table<ReviewerStateInternal, Account.Id, Timestamp> table) {
+    this.table = ImmutableTable.copyOf(table);
+  }
+
+  public ImmutableSet<Account.Id> all() {
+    if (accounts == null) {
+      // Idempotent and immutable, don't bother locking.
+      accounts = ImmutableSet.copyOf(table.columnKeySet());
+    }
+    return accounts;
+  }
+
+  public ImmutableSet<Account.Id> byState(ReviewerStateInternal state) {
+    return table.row(state).keySet();
+  }
+
+  public ImmutableTable<ReviewerStateInternal, Account.Id, Timestamp>
+      asTable() {
+    return table;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return (o instanceof ReviewerSet) && table.equals(((ReviewerSet) o).table);
+  }
+
+  @Override
+  public int hashCode() {
+    return table.hashCode();
+  }
+
+  @Override
+  public String toString() {
+    return getClass().getSimpleName() + table;
+  }
+}