Merge pull request #219 from tiagonuneslx/query-cursors

Firestore query-cursors/pagination: Added Query.startAfter (Android, iOS, js)

Author: nbransby

firebase-common/src/jsMain/kotlin/dev/gitlive/firebase/externals.kt

@@ -379,6 +379,7 @@ external object firebase {
             fun limit(limit: Double): Query
             fun orderBy(field: String, direction: Any): Query
             fun orderBy(field: FieldPath, direction: Any): Query
+            fun startAfter(document: DocumentSnapshot): Query
         }
 
         open class CollectionReference : Query {

firebase-firestore/src/androidMain/kotlin/dev/gitlive/firebase/firestore/firestore.kt

@@ -354,6 +354,8 @@ actual open class Query(open val android: com.google.firebase.firestore.Query) {
 
     internal actual fun _orderBy(field: String, direction: Direction) = Query(android.orderBy(field, direction))
     internal actual fun _orderBy(field: FieldPath, direction: Direction) = Query(android.orderBy(field.android, direction))
+
+    internal actual fun _startAfter(document: DocumentSnapshot) = Query(android.startAfter(document.android))
 }
 
 actual typealias Direction = com.google.firebase.firestore.Query.Direction

firebase-firestore/src/commonMain/kotlin/dev/gitlive/firebase/firestore/firestore.kt

@@ -67,6 +67,8 @@ expect open class Query {
 
     internal fun _orderBy(field: String, direction: Direction): Query
     internal fun _orderBy(field: FieldPath, direction: Direction): Query
+
+    internal fun _startAfter(document: DocumentSnapshot): Query
 }
 
 fun Query.where(field: String, equalTo: Any?) = _where(field, equalTo)
@@ -81,6 +83,8 @@ fun Query.where(path: FieldPath, inArray: List<Any>? = null, arrayContainsAny: L
 fun Query.orderBy(field: String, direction: Direction = Direction.ASCENDING) = _orderBy(field, direction)
 fun Query.orderBy(field: FieldPath, direction: Direction = Direction.ASCENDING) = _orderBy(field, direction)
 
+fun Query.startAfter(document: DocumentSnapshot) = _startAfter(document)
+
 expect class WriteBatch {
     inline fun <reified T> set(documentRef: DocumentReference, data: T, encodeDefaults: Boolean = true, merge: Boolean = false): WriteBatch
     inline fun <reified T> set(documentRef: DocumentReference, data: T, encodeDefaults: Boolean = true, vararg mergeFields: String): WriteBatch

firebase-firestore/src/commonTest/kotlin/dev/gitlive/firebase/firestore/firestore.kt

@@ -220,6 +220,25 @@ class FirebaseFirestoreTest {
         assertEquals("AutoId", resultDoc.get("prop1"))
     }
 
+    @Test
+    fun testStartAfterDocumentSnapshot() = runTest {
+        setupFirestoreData()
+        val query = Firebase.firestore
+            .collection("FirebaseFirestoreTest")
+            .orderBy("prop1", Direction.ASCENDING)
+
+        val firstPage = query.limit(2).get().documents // First 2 results
+        assertEquals(2, firstPage.size)
+        assertEquals("aaa", firstPage[0].get("prop1"))
+        assertEquals("bbb", firstPage[1].get("prop1"))
+
+        val lastDocumentSnapshot = firstPage.lastOrNull()
+        assertNotNull(lastDocumentSnapshot)
+        val secondPage = query.startAfter(lastDocumentSnapshot).limit(2).get().documents // Second 2 results (only one left)
+        assertEquals(1, secondPage.size)
+        assertEquals("ccc", secondPage[0].get("prop1"))
+    }
+
     private suspend fun setupFirestoreData() {
         Firebase.firestore.collection("FirebaseFirestoreTest")
             .document("one")

firebase-firestore/src/iosMain/kotlin/dev/gitlive/firebase/firestore/firestore.kt

@@ -270,9 +270,10 @@ actual open class Query(open val ios: FIRQuery) {
     )
 
     internal actual fun _orderBy(field: String, direction: Direction) = Query(ios.queryOrderedByField(field, direction == Direction.DESCENDING))
-
     internal actual fun _orderBy(field: FieldPath, direction: Direction) = Query(ios.queryOrderedByFieldPath(field.ios, direction == Direction.DESCENDING))
 
+    internal actual fun _startAfter(document: DocumentSnapshot) = Query(ios.queryStartingAfterDocument(document.ios))
+
 }
 @Suppress("UNCHECKED_CAST")
 actual class CollectionReference(override val ios: FIRCollectionReference) : Query(ios) {

firebase-firestore/src/jsMain/kotlin/dev/gitlive/firebase/firestore/firestore.kt

@@ -329,6 +329,10 @@ actual open class Query(open val js: firebase.firestore.Query) {
         Query(js.orderBy(field.js, direction.jsString))
     }
 
+    internal actual fun _startAfter(document: DocumentSnapshot) = rethrow {
+        Query(js.startAfter(document.js))
+    }
+
     actual val snapshots get() = callbackFlow<QuerySnapshot> {
         val unsubscribe = rethrow {
             js.onSnapshot(