Implement pagination for item tags list

app/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/data/item_tag/ItemTagApi.kt

@@ -10,6 +10,7 @@ interface ItemTagApi {
   suspend fun getItemTags(
     @Path("account_id") accountId: String,
     @Path("shop_id") shopId: String,
+    @Query("page") page: Int? = null,
   ): ApiResponse<ItemTags>
 
   @GET("{account_id}/api/v1/shopkeeper/item_tags/{id}")

app/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/data/item_tag/ItemTagRepository.kt

@@ -6,6 +6,7 @@ import kotlinx.coroutines.flow.Flow
 interface ItemTagRepository {
   fun getItemTags(
     shopId: String,
+    page: Int? = null,
   ): Flow<ItemTags>
 
   fun getItemTag(

app/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/data/item_tag/ItemTagRepositoryImpl.kt

@@ -19,10 +19,12 @@ class ItemTagRepositoryImpl @Inject constructor(
 
   override fun getItemTags(
     shopId: String,
+    page: Int?,
   ) = flow {
     val response = api.getItemTags(
       mtcPreferencesDataSource.userData.first().accountId,
       shopId,
+      page,
     )
     emitApiResponse(response)
   }.flowOn(ioDispatcher)

app/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/ui/shop_settings/item_tag_list/ItemTagListView.kt

@@ -11,12 +11,14 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.itemsIndexed
+import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material.icons.filled.Add
 import androidx.compose.material.icons.filled.Delete
 import androidx.compose.material.icons.outlined.Rectangle
 import androidx.compose.material3.CenterAlignedTopAppBar
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.FloatingActionButton
 import androidx.compose.material3.HorizontalDivider
@@ -31,7 +33,10 @@ import androidx.compose.material3.pulltorefresh.PullToRefreshDefaults.Indicator
 import androidx.compose.material3.pulltorefresh.pullToRefresh
 import androidx.compose.material3.pulltorefresh.rememberPullToRefreshState
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
@@ -132,7 +137,19 @@ private fun ItemTagListContentView(
   onBackClick: () -> Unit,
 ) {
   val isEmpty: Boolean by viewModel.isEmpty().collectAsStateWithLifecycle()
-  val itemTags = uiState.itemTags.getDatumWithRelationships().toMutableList()
+  val itemTags = uiState.itemTags.toMutableList()
+  val listState = rememberLazyListState()
+
+  val prefetchDistance = 3
+  val shouldLoadMore by remember {
+    derivedStateOf {
+      val lastVisibleIndex = listState.layoutInfo.visibleItemsInfo.lastOrNull()?.index ?: 0
+      lastVisibleIndex >= itemTags.size - prefetchDistance && uiState.hasMorePages && !uiState.isLoadingMore
+    }
+  }
+  LaunchedEffect(shouldLoadMore) {
+    if (shouldLoadMore) viewModel.loadMore()
+  }
 
   Scaffold(
     topBar = {
@@ -172,7 +189,8 @@ private fun ItemTagListContentView(
           .padding(padding),
       ) {
         LazyColumn(
-          Modifier.padding(24.dp),
+          state = listState,
+          modifier = Modifier.padding(24.dp),
         ) {
           item {
             Text(
@@ -212,6 +230,18 @@ private fun ItemTagListContentView(
             }
             HorizontalDivider()
           }
+          if (uiState.isLoadingMore) {
+            item {
+              Box(
+                modifier = Modifier
+                  .fillMaxWidth()
+                  .padding(16.dp),
+                contentAlignment = Alignment.Center,
+              ) {
+                CircularProgressIndicator()
+              }
+            }
+          }
         }
         Indicator(
           modifier = Modifier.align(Alignment.TopCenter),

app/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/ui/shop_settings/item_tag_list/ItemTagListViewModel.kt

@@ -7,10 +7,11 @@ import androidx.navigation.toRoute
 import com.nativeapptemplate.nativeapptemplatefree.common.errors.codedDescription
 import com.nativeapptemplate.nativeapptemplatefree.data.item_tag.ItemTagRepository
 import com.nativeapptemplate.nativeapptemplatefree.data.shop.ShopRepository
-import com.nativeapptemplate.nativeapptemplatefree.model.ItemTags
+import com.nativeapptemplate.nativeapptemplatefree.model.Data
 import com.nativeapptemplate.nativeapptemplatefree.model.Shop
 import com.nativeapptemplate.nativeapptemplatefree.ui.shop_settings.navigation.ItemTagListRoute
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -26,12 +27,18 @@ import javax.inject.Inject
 
 data class ItemTagListUiState(
   val shop: Shop = Shop(),
-  val itemTags: ItemTags = ItemTags(),
+  val itemTags: List<Data> = emptyList(),
 
   val isLoading: Boolean = true,
   val success: Boolean = false,
   val message: String = "",
-)
+
+  val currentPage: Int = 1,
+  val totalPages: Int = 1,
+  val isLoadingMore: Boolean = false,
+) {
+  val hasMorePages: Boolean get() = currentPage < totalPages
+}
 
 /**
  * ViewModel for library view
@@ -47,39 +54,62 @@ class ItemTagListViewModel @Inject constructor(
   private val _uiState = MutableStateFlow(ItemTagListUiState())
   val uiState: StateFlow<ItemTagListUiState> = _uiState.asStateFlow()
 
+  private var fetchJob: Job? = null
+
   fun reload() {
-    fetchData()
+    fetchData(page = 1, isReload = true)
   }
 
-  fun isEmpty(): StateFlow<Boolean> = uiState.map { it.itemTags.datum.isEmpty() }
+  fun isEmpty(): StateFlow<Boolean> = uiState.map { it.itemTags.isEmpty() }
     .stateIn(
       scope = viewModelScope,
       initialValue = false,
       started = SharingStarted.WhileSubscribed(5_000),
     )
 
-  private fun fetchData() {
+  fun loadMore() {
+    val state = _uiState.value
+    if (state.isLoadingMore || !state.hasMorePages) return
+    fetchData(page = state.currentPage + 1, isReload = false)
+  }
+
+  private fun fetchData(page: Int, isReload: Boolean) {
     val shopId = shopId
 
-    _uiState.update {
-      it.copy(
-        isLoading = true,
-        success = false,
-      )
+    if (isReload) {
+      _uiState.update {
+        it.copy(
+          isLoading = true,
+          success = false,
+        )
+      }
+    } else {
+      _uiState.update {
+        it.copy(
+          isLoadingMore = true,
+        )
+      }
     }
 
-    viewModelScope.launch {
+    fetchJob?.cancel()
+    fetchJob = viewModelScope.launch {
       val shopFlow: Flow<Shop> = shopRepository.getShop(shopId)
-      val itemTagsFlow: Flow<ItemTags> = itemTagRepository.getItemTags(shopId)
+      val itemTagsFlow = itemTagRepository.getItemTags(shopId, page)
 
       combine(
         shopFlow,
         itemTagsFlow,
       ) { shop, itemTags ->
+        val newItems = itemTags.getDatumWithRelationships()
+        val allItems = if (isReload) newItems else _uiState.value.itemTags + newItems
+
         _uiState.update {
           it.copy(
             shop = shop,
-            itemTags = itemTags,
+            itemTags = allItems,
+            currentPage = itemTags.meta?.currentPage ?: page,
+            totalPages = itemTags.meta?.totalPages ?: 1,
+            isLoadingMore = false,
             success = true,
             isLoading = false,
           )
@@ -90,6 +120,7 @@ class ItemTagListViewModel @Inject constructor(
           it.copy(
             message = message,
             isLoading = false,
+            isLoadingMore = false,
           )
         }
       }.collect {

app/src/test/kotlin/com/nativeapptemplate/nativeapptemplatefree/demo/item_tag/DemoItemTagRepository.kt

@@ -36,7 +36,7 @@ class DemoItemTagRepository @Inject constructor(
     emit(itemTag)
   }.flowOn(ioDispatcher)
 
-  override fun getItemTags(shopId: String): Flow<ItemTags> = itemTagsFlow
+  override fun getItemTags(shopId: String, page: Int?): Flow<ItemTags> = itemTagsFlow
 
   override fun getItemTag(id: String): Flow<ItemTag> = itemTagFlow
 

app/src/test/kotlin/com/nativeapptemplate/nativeapptemplatefree/testing/repository/TestItemTagRepository.kt

@@ -8,15 +8,15 @@ import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.flow
 
 class TestItemTagRepository : ItemTagRepository {
-  private val itemTagsFlow: MutableSharedFlow<ItemTags> =
-    MutableSharedFlow(replay = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST)
+  private var currentItemTags: ItemTags = ItemTags()
 
   private val itemTagFlow: MutableSharedFlow<ItemTag> =
     MutableSharedFlow(replay = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST)
 
-  override fun getItemTags(shopId: String): Flow<ItemTags> = itemTagsFlow
+  override fun getItemTags(shopId: String, page: Int?): Flow<ItemTags> = flow { emit(currentItemTags) }
 
   override fun getItemTag(id: String): Flow<ItemTag> = itemTagFlow
 
@@ -34,7 +34,7 @@ class TestItemTagRepository : ItemTagRepository {
    * A test-only API.
    */
   fun sendItemTags(itemTags: ItemTags) {
-    itemTagsFlow.tryEmit(itemTags)
+    currentItemTags = itemTags
   }
 
   fun sendItemTag(itemTag: ItemTag) {

app/src/test/kotlin/com/nativeapptemplate/nativeapptemplatefree/ui/shop_settings/item_tag_list/ItemTagListViewModelTest.kt

@@ -6,6 +6,7 @@ import com.nativeapptemplate.nativeapptemplatefree.model.Attributes
 import com.nativeapptemplate.nativeapptemplatefree.model.Data
 import com.nativeapptemplate.nativeapptemplatefree.model.ItemTag
 import com.nativeapptemplate.nativeapptemplatefree.model.ItemTags
+import com.nativeapptemplate.nativeapptemplatefree.model.Meta
 import com.nativeapptemplate.nativeapptemplatefree.model.Shop
 import com.nativeapptemplate.nativeapptemplatefree.testing.repository.TestItemTagRepository
 import com.nativeapptemplate.nativeapptemplatefree.testing.repository.TestShopRepository
@@ -88,7 +89,7 @@ class ItemTagListViewModelTest {
     val itemTagsFromRepository = itemTagRepository.getItemTags(shopId).first()
 
     assertEquals(shopFromRepository, uiStateValue.shop)
-    assertEquals(itemTagsFromRepository, uiStateValue.itemTags)
+    assertEquals(itemTagsFromRepository.getDatumWithRelationships(), uiStateValue.itemTags)
   }
 
   @Test
@@ -105,6 +106,78 @@ class ItemTagListViewModelTest {
     val uiStateValue = viewModel.uiState.value
     assertFalse(uiStateValue.isLoading)
   }
+
+  @Test
+  fun paginationMeta_whenPresent_isReflectedInUiState() = runTest {
+    backgroundScope.launch(UnconfinedTestDispatcher()) { viewModel.uiState.collect() }
+
+    shopRepository.sendShop(testInputShop)
+    itemTagRepository.sendItemTags(testInputItemTagsPage1)
+
+    viewModel.reload()
+
+    val uiStateValue = viewModel.uiState.value
+    assertEquals(1, uiStateValue.currentPage)
+    assertEquals(2, uiStateValue.totalPages)
+    assertTrue(uiStateValue.hasMorePages)
+  }
+
+  @Test
+  fun loadMore_accumulatesItemsFromNextPage() = runTest {
+    backgroundScope.launch(UnconfinedTestDispatcher()) { viewModel.uiState.collect() }
+
+    shopRepository.sendShop(testInputShop)
+    itemTagRepository.sendItemTags(testInputItemTagsPage1)
+
+    viewModel.reload()
+    assertEquals(2, viewModel.uiState.value.itemTags.size)
+
+    itemTagRepository.sendItemTags(testInputItemTagsPage2)
+    viewModel.loadMore()
+
+    val uiStateValue = viewModel.uiState.value
+    assertEquals(3, uiStateValue.itemTags.size)
+    assertEquals(2, uiStateValue.currentPage)
+    assertEquals(2, uiStateValue.totalPages)
+    assertFalse(uiStateValue.hasMorePages)
+  }
+
+  @Test
+  fun loadMore_doesNotFire_whenNoMorePages() = runTest {
+    backgroundScope.launch(UnconfinedTestDispatcher()) { viewModel.uiState.collect() }
+
+    shopRepository.sendShop(testInputShop)
+    itemTagRepository.sendItemTags(testInputItemTagsPage2)
+
+    viewModel.reload()
+
+    val itemCountBefore = viewModel.uiState.value.itemTags.size
+    viewModel.loadMore()
+    assertEquals(itemCountBefore, viewModel.uiState.value.itemTags.size)
+    assertFalse(viewModel.uiState.value.isLoadingMore)
+  }
+
+  @Test
+  fun reload_resetsToFirstPage() = runTest {
+    backgroundScope.launch(UnconfinedTestDispatcher()) { viewModel.uiState.collect() }
+
+    shopRepository.sendShop(testInputShop)
+    itemTagRepository.sendItemTags(testInputItemTagsPage1)
+
+    viewModel.reload()
+    assertEquals(2, viewModel.uiState.value.itemTags.size)
+
+    itemTagRepository.sendItemTags(testInputItemTagsPage2)
+    viewModel.loadMore()
+    assertEquals(3, viewModel.uiState.value.itemTags.size)
+
+    itemTagRepository.sendItemTags(testInputItemTagsPage1)
+    viewModel.reload()
+
+    val uiStateValue = viewModel.uiState.value
+    assertEquals(2, uiStateValue.itemTags.size)
+    assertEquals(1, uiStateValue.currentPage)
+  }
 }
 
 private const val SHOP_TYPE = "shop"
@@ -197,3 +270,13 @@ private val testInputItemTags = ItemTags(
 private val testInputItemTag = ItemTag(
   datum = testInputItemTagsData.first(),
 )
+
+private val testInputItemTagsPage1 = ItemTags(
+  datum = listOf(testInputItemTagsData[0], testInputItemTagsData[1]),
+  meta = Meta(currentPage = 1, totalPages = 2, totalCount = 3, limit = 2),
+)
+
+private val testInputItemTagsPage2 = ItemTags(
+  datum = listOf(testInputItemTagsData[2]),
+  meta = Meta(currentPage = 2, totalPages = 2, totalCount = 3, limit = 2),
+)

model/src/main/kotlin/com/nativeapptemplate/nativeapptemplatefree/model/Meta.kt

@@ -30,4 +30,15 @@ data class Meta(
   var shopLimitCount: Int = 0,
 
   var count: Int = 0,
+
+  @SerialName("current_page")
+  val currentPage: Int? = null,
+
+  @SerialName("total_pages")
+  val totalPages: Int? = null,
+
+  @SerialName("total_count")
+  val totalCount: Int? = null,
+
+  val limit: Int? = null,
 ) : Parcelable