1 files changed, 186 insertions, 0 deletions
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MultiMap.java b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MultiMap.java
new file mode 100644
index 0000000000..ff26d99dea
--- /dev/null
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/MultiMap.java
@@ -0,0 +1,186 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Defines a map that holds a collection of values against each key.
+ *
+ * @param <K> Key type
+ * @param <T> Value type
+ */
+public class MultiMap<K, T> {
+  private HashMap<K, List<T>> mMap;
+  private final List<T> mEmptyList = Collections.unmodifiableList(new ArrayList<>());
+
+  /**
+   * Creates a MultiMap with specified initial capacity.
+   *
+   * @param count Initial capacity
+   */
+  public MultiMap(final int count) {
+    mMap = new HashMap<>(count);
+  }
+
+  /** Creates a MultiMap with default initial capacity. */
+  public MultiMap() {
+    mMap = new HashMap<>();
+  }
+
+  private void ensure(final K key) {
+    if (!mMap.containsKey(key)) {
+      mMap.put(key, new ArrayList<>());
+    }
+  }
+
+  /**
+   * @return A map of key to the list of values associated to it
+   */
+  public Map<K, List<T>> asMap() {
+    return mMap;
+  }
+
+  /**
+   * @return The number of keys present in this map
+   */
+  public int size() {
+    return mMap.size();
+  }
+
+  /**
+   * @return whether this map is empty or not
+   */
+  public boolean isEmpty() {
+    return mMap.isEmpty();
+  }
+
+  /**
+   * Checks if a key is present in this map.
+   *
+   * @param key the key to check
+   * @return True if the map contains this key, false otherwise.
+   */
+  public boolean containsKey(final @Nullable K key) {
+    return mMap.containsKey(key);
+  }
+
+  /**
+   * Checks if a (key, value) pair is present in this map.
+   *
+   * @param key the key to check
+   * @param value the value to check
+   * @return true if there is a value associated to the given key, false otherwise
+   */
+  public boolean containsEntry(final @Nullable K key, final @Nullable T value) {
+    if (!mMap.containsKey(key)) {
+      return false;
+    }
+
+    return mMap.get(key).contains(value);
+  }
+
+  /**
+   * Gets the values associated with the given key.
+   *
+   * @param key the key to check
+   * @return the list of values associated with keys, an empty list if no values are associated with
+   *     key.
+   */
+  @NonNull
+  public List<T> get(final @Nullable K key) {
+    if (!mMap.containsKey(key)) {
+      return mEmptyList;
+    }
+
+    return mMap.get(key);
+  }
+
+  /**
+   * Add a (key, value) mapping to this map.
+   *
+   * @param key the key to add
+   * @param value the value to add
+   */
+  @Nullable
+  public void add(final @NonNull K key, final @NonNull T value) {
+    ensure(key);
+    mMap.get(key).add(value);
+  }
+
+  /**
+   * Add a list of values to the given key.
+   *
+   * @param key the key to add
+   * @param values the list of values to add
+   * @return the final list of values or null if no value was added
+   */
+  @Nullable
+  public List<T> addAll(final @NonNull K key, final @NonNull List<T> values) {
+    if (values == null || values.isEmpty()) {
+      return null;
+    }
+
+    ensure(key);
+
+    final List<T> result = mMap.get(key);
+    result.addAll(values);
+    return result;
+  }
+
+  /**
+   * Remove all mappings for the given key.
+   *
+   * @param key the key
+   * @return values associated with the key or null if no values was present.
+   */
+  @Nullable
+  public List<T> remove(final @Nullable K key) {
+    return mMap.remove(key);
+  }
+
+  /**
+   * Remove a (key, value) mapping from this map
+   *
+   * @param key the key to remove
+   * @param value the value to remove
+   * @return true if the (key, value) mapping was present, false otherwise
+   */
+  @Nullable
+  public boolean remove(final @Nullable K key, final @Nullable T value) {
+    if (!mMap.containsKey(key)) {
+      return false;
+    }
+
+    final List<T> values = mMap.get(key);
+    final boolean wasPresent = values.remove(value);
+
+    if (values.isEmpty()) {
+      mMap.remove(key);
+    }
+
+    return wasPresent;
+  }
+
+  /** Remove all mappings from this map. */
+  public void clear() {
+    mMap.clear();
+  }
+
+  /**
+   * @return a set with all the keys for this map.
+   */
+  @NonNull
+  public Set<K> keySet() {
+    return mMap.keySet();
+  }
+}