Issue mozilla-mobile#11483: Extend DefaultTopSitesStorage to accept a…

… top sites provider

components/feature/top-sites/src/main/java/mozilla/components/feature/top/sites/DefaultTopSitesStorage.kt

@@ -23,12 +23,15 @@ import kotlin.coroutines.CoroutineContext
  * @param pinnedSitesStorage An instance of [PinnedSiteStorage], used for storing pinned sites.
  * @param historyStorage An instance of [PlacesHistoryStorage], used for retrieving top frecent
  * sites from history.
+ * @param topSitesProvider An optional instance of [TopSitesProvider], used for retrieving top
+ * sites from a provider.
  * @param defaultTopSites A list containing a title to url pair of default top sites to be added
  * to the [PinnedSiteStorage].
  */
 class DefaultTopSitesStorage(
     private val pinnedSitesStorage: PinnedSiteStorage,
     private val historyStorage: PlacesHistoryStorage,
+    private val topSitesProvider: TopSitesProvider? = null,
     private val defaultTopSites: List<Pair<String, String>> = listOf(),
     coroutineContext: CoroutineContext = Dispatchers.IO
 ) : TopSitesStorage, Observable<TopSitesStorage.Observer> by ObserverRegistry() {
@@ -83,9 +86,16 @@ class DefaultTopSitesStorage(
     ): List<TopSite> {
         val topSites = ArrayList<TopSite>()
         val pinnedSites = pinnedSitesStorage.getPinnedSites().take(totalSites)
-        val numSitesRequired = totalSites - pinnedSites.size
+        var numSitesRequired = totalSites - pinnedSites.size
+
         topSites.addAll(pinnedSites)
 
+        topSitesProvider?.let { provider ->
+            val providerTopSites = provider.getTopSites()
+            topSites.addAll(providerTopSites.take(numSitesRequired))
+            numSitesRequired -= providerTopSites.size
+        }
+
         if (frecencyConfig != null && numSitesRequired > 0) {
             // Get 'totalSites' sites for duplicate entries with
             // existing pinned sites

components/feature/top-sites/src/main/java/mozilla/components/feature/top/sites/TopSitesProvider.kt

@@ -0,0 +1,16 @@
+/* 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 mozilla.components.feature.top.sites
+
+/**
+ * A contract that indicates how a top sites provider must behave.
+ */
+interface TopSitesProvider {
+
+    /**
+     * Provides a list of top sites.
+     */
+    suspend fun getTopSites(): List<TopSite>
+}

components/feature/top-sites/src/test/java/mozilla/components/feature/top/sites/DefaultTopSitesStorageTest.kt

@@ -37,10 +37,10 @@ class DefaultTopSitesStorageTest {
         )
 
         DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            defaultTopSites,
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = defaultTopSites,
+            coroutineContext = coroutineContext
         )
 
         verify(pinnedSitesStorage).addAllPinnedSites(defaultTopSites, isDefault = true)
@@ -49,10 +49,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `addPinnedSite`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
         defaultTopSitesStorage.addTopSite("Mozilla", "https://mozilla.com", isDefault = false)
 
@@ -66,10 +66,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `removeTopSite`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
 
         val frecentSite = TopSite(
@@ -111,10 +111,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `updateTopSite`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
 
         val defaultSite = TopSite(
@@ -154,10 +154,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `getTopSites returns only default and pinned sites when frecencyConfig is null`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
 
         val defaultSite = TopSite(
@@ -207,10 +207,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `getTopSites returns pinned and frecent sites when frecencyConfig is specified`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
 
         val defaultSite = TopSite(
@@ -301,10 +301,10 @@ class DefaultTopSitesStorageTest {
     @Test
     fun `getTopSites filters out frecent sites that already exist in pinned sites`() = runBlockingTest {
         val defaultTopSitesStorage = DefaultTopSitesStorage(
-            pinnedSitesStorage,
-            historyStorage,
-            listOf(),
-            coroutineContext
+            pinnedSitesStorage = pinnedSitesStorage,
+            historyStorage = historyStorage,
+            defaultTopSites = listOf(),
+            coroutineContext = coroutineContext
         )
 
         val defaultSiteFirefox = TopSite(