Чтение продуктов для главного и дискаунт экранов из апишки. Великая победа над ремоут медиатором.

app/src/main/java/com/example/shawarma/AppModule.kt

@@ -50,7 +50,7 @@ object AppModule {
     @Provides
     @Singleton
     fun provideProductRepository(db: AppDatabase) : ProductRepository {
-        return ProductRepository(db.productDao(), db.orderProductDao())
+        return ProductRepository(database = db, db.productDao(), db.orderProductDao())
     }
 
     @Provides

app/src/main/java/com/example/shawarma/data/api/MyServerService.kt

@@ -1,5 +1,6 @@
 package com.example.shawarma.data.api
 
+import com.example.shawarma.data.api.models.ProductListResponse
 import com.example.shawarma.data.api.models.TokenModelRemote
 import com.example.shawarma.data.api.models.UserModelRemote
 import com.jakewharton.retrofit2.converter.kotlinx.serialization.asConverterFactory
@@ -8,7 +9,10 @@ import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.logging.HttpLoggingInterceptor
 import retrofit2.Retrofit
 import retrofit2.http.Body
+import retrofit2.http.GET
+import retrofit2.http.Header
 import retrofit2.http.POST
+import retrofit2.http.Path
 
 
 interface MyServerService {
@@ -27,6 +31,15 @@ interface MyServerService {
         @Body user: UserModelRemote
     ) :UserModelRemote?
 
+    @GET("user/products/{after}")
+    suspend fun getProductsList(@Path("after") after: Int, @Header("Authorization") token: String) : ProductListResponse
+
+    @GET("user/discounts/{after}")
+    suspend fun getDiscountsList(@Path("after") after: Int, @Header("Authorization") token: String) : ProductListResponse
+
+    @GET("user/items/{after}")
+    suspend fun getItemsList(@Path("after") after: Int, @Header("Authorization") token: String) : ProductListResponse
+
 
     companion object {
         private const val BASE_URL = "https://10.0.2.2:80/api/"

app/src/main/java/com/example/shawarma/data/api/mediators/ProductRemoteMediator.kt

@@ -0,0 +1,91 @@
+package com.example.shawarma.data.api.mediators
+
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.LoadType
+import androidx.paging.PagingState
+import androidx.paging.RemoteMediator
+import androidx.room.withTransaction
+import com.example.shawarma.data.api.MyServerService
+import com.example.shawarma.data.api.models.ProductListResponse
+import com.example.shawarma.data.api.models.toProductModel
+import com.example.shawarma.data.db.AppDatabase
+import com.example.shawarma.data.models.ProductModel
+import java.io.IOException
+
+@OptIn(ExperimentalPagingApi::class)
+class ProductRemoteMediator (
+    private val database: AppDatabase,
+    private val serverService: MyServerService,
+    private val query: String,
+    private val token: String
+) : RemoteMediator<Int, ProductModel>(){
+
+    private val productDao = database.productDao()
+
+    override suspend fun load(
+        loadType: LoadType,
+        state: PagingState<Int, ProductModel>
+    ): MediatorResult {
+        return try {
+            // The network load method takes an optional `after=<user.id>` parameter. For every
+            // page after the first, we pass the last user ID to let it continue from where it
+            // left off. For REFRESH, pass `null` to load the first page.
+            var loadKey = when (loadType) {
+                LoadType.REFRESH -> null
+                // In this example, we never need to prepend, since REFRESH will always load the
+                // first page in the list. Immediately return, reporting end of pagination.
+                LoadType.PREPEND -> return MediatorResult.Success(endOfPaginationReached = true)
+                LoadType.APPEND -> {
+                    val lastItem = state.lastItemOrNull()
+                        ?: return MediatorResult.Success(endOfPaginationReached = true)
+
+                    // We must explicitly check if the last item is `null` when appending,
+                    // since passing `null` to networkService is only valid for initial load.
+                    // If lastItem is `null` it means no items were loaded after the initial
+                    // REFRESH and there are no more items to load.
+
+                    lastItem.id
+                }
+            }
+
+            // Suspending network load via Retrofit. This doesn't need to be wrapped in a
+            // withContext(Dispatcher.IO) { ... } block since Retrofit's Coroutine CallAdapter
+            // dispatches on a worker thread.
+            if (loadKey == null) {
+                loadKey = 0
+            }
+            val response: ProductListResponse = when (query) {
+                "home" -> {
+                    serverService.getProductsList(after = loadKey, token = token)
+                }
+                "discounts" -> {
+                    serverService.getDiscountsList(after = loadKey, token = token)
+                }
+                "items" -> {
+                    serverService.getItemsList(after = loadKey, token = token)
+                }
+
+                else -> {ProductListResponse()}
+            }
+
+
+            database.withTransaction {
+                if (loadType == LoadType.REFRESH) {
+                    productDao.deleteByQuery(query)
+                }
+
+                // Insert new users into database, which invalidates the current
+                // PagingData, allowing Paging to present the updates in the DB.
+                val products = mutableListOf<ProductModel>()
+                for (prod in response.products) {
+                    products.add(prod.toProductModel())
+                }
+                productDao.insertAll(products)
+            }
+
+            MediatorResult.Success(endOfPaginationReached = response.nextKey == -1)
+        } catch (e: IOException) {
+            MediatorResult.Error(e)
+        }
+    }
+}

app/src/main/java/com/example/shawarma/data/api/models/ProductModelRemote.kt

@@ -8,13 +8,19 @@ data class ProductModelRemote(
     val id: Int = 0,
     val title: String = "",
     val price: Int = 0,
-    val oldPrice: Int? = null
+    val old_price: Int? = null
+)
+
+@Serializable
+data class ProductListResponse(
+    val products: List<ProductModelRemote> = listOf(),
+    val nextKey: Int? = null
 )
 
 fun ProductModelRemote.toProductModel(): ProductModel = ProductModel(
-    id, title, price, oldPrice
+    id, title, price, old_price
 )
 
 fun ProductModel.toProductModelRemote(): ProductModelRemote = ProductModelRemote(
-    title = title, price = price, oldPrice = oldPrice
+    title = title, price = price, old_price = oldPrice
 )

app/src/main/java/com/example/shawarma/data/interfaces/dao/ProductDao.kt

@@ -13,6 +13,12 @@ interface ProductDao {
     @Insert
     suspend fun insert(product: ProductModel)
 
+    suspend fun insertAll(products: List<ProductModel>) {
+        for (product in products) {
+            insert(product)
+        }
+    }
+
     @Update
     suspend fun update(product: ProductModel)
 
@@ -39,4 +45,25 @@ interface ProductDao {
 
     @Query("select * from products")
     fun getPagedItems(): PagingSource<Int, ProductModel>
+
+    @Query("delete from products where products.product_old_price is null")
+    fun deleteAllProducts()
+
+    @Query("delete from products where products.product_old_price is not null")
+    fun deleteAllDiscountProducts()
+
+    @Query("delete from products")
+    fun deleteAllItems()
+
+    fun deleteByQuery(query: String) {
+        if (query == "home") {
+            deleteAllProducts()
+        }
+        if (query == "discounts") {
+            deleteAllDiscountProducts()
+        }
+        if (query == "items") {
+            deleteAllItems()
+        }
+    }
 }

app/src/main/java/com/example/shawarma/data/repos/ProductRepository.kt

@@ -1,8 +1,12 @@
 package com.example.shawarma.data.repos
 
+import androidx.paging.ExperimentalPagingApi
 import androidx.paging.Pager
 import androidx.paging.PagingConfig
 import androidx.paging.PagingData
+import com.example.shawarma.data.api.MyServerService
+import com.example.shawarma.data.api.mediators.ProductRemoteMediator
+import com.example.shawarma.data.db.AppDatabase
 import com.example.shawarma.data.interfaces.dao.OrderProductDao
 import com.example.shawarma.data.interfaces.dao.ProductDao
 import com.example.shawarma.data.models.ProductModel
@@ -10,6 +14,7 @@ import kotlinx.coroutines.flow.Flow
 import javax.inject.Inject
 
 class ProductRepository @Inject constructor(
+    private val database: AppDatabase,
     private val productDao: ProductDao,
     private val orderProductDao: OrderProductDao
 ) {
@@ -26,20 +31,24 @@ class ProductRepository @Inject constructor(
     fun getById(id: Int): Flow<ProductModel> {
         return productDao.getById(id)
     }
-    fun getAllProductsPaged(): Flow<PagingData<ProductModel>> = Pager(
+    @OptIn(ExperimentalPagingApi::class)
+    fun getAllProductsPaged(token: String): Flow<PagingData<ProductModel>> = Pager(
         config = PagingConfig(
             pageSize = 6,
             enablePlaceholders = false
         ),
-        pagingSourceFactory = productDao::getPaged
+        pagingSourceFactory = productDao::getPaged,
+        remoteMediator = ProductRemoteMediator(database = database, serverService = MyServerService.getInstance(), query = "home", token = token)
     ).flow
 
-    fun getAllDiscountsPaged(): Flow<PagingData<ProductModel>> = Pager(
+    @OptIn(ExperimentalPagingApi::class)
+    fun getAllDiscountsPaged(token: String): Flow<PagingData<ProductModel>> = Pager(
         config = PagingConfig(
             pageSize = 6,
             enablePlaceholders = false
         ),
-        pagingSourceFactory = productDao::getPagedDiscounts
+        pagingSourceFactory = productDao::getPagedDiscounts,
+        remoteMediator = ProductRemoteMediator(database = database, serverService = MyServerService.getInstance(), query = "discounts", token = token)
     ).flow
 
     fun getAllItemsPaged(): Flow<PagingData<ProductModel>> = Pager(

app/src/main/java/com/example/shawarma/screens/discount/DiscountScreen.kt

@@ -58,9 +58,13 @@ fun DiscountScreen() {
 
 @Composable
 fun DiscountList(){
+    val preferencesManager = PreferencesManager(LocalContext.current)
+    val searchToken = preferencesManager.getData("token", "")
+
     val homeViewModel: HomeViewModel = hiltViewModel<HomeViewModel>()
 
-    val productsListUiState = homeViewModel.discountListUiState.collectAsLazyPagingItems()
+
+    val productsListUiState = homeViewModel.getDiscountList(searchToken).collectAsLazyPagingItems()
 
     Box(
         modifier = Modifier

app/src/main/java/com/example/shawarma/screens/home/HomeScreen.kt

@@ -57,9 +57,13 @@ fun HomeScreen() {
 
 @Composable
 fun HomeList(){
+    val preferencesManager = PreferencesManager(LocalContext.current)
+    val searchToken = preferencesManager.getData("token", "")
+
     val homeViewModel: HomeViewModel = hiltViewModel<HomeViewModel>()
 
-    val productsListUiState = homeViewModel.productListUiState.collectAsLazyPagingItems()
+
+    val productsListUiState = homeViewModel.getProductList(searchToken).collectAsLazyPagingItems()
 
 
     Box(

app/src/main/java/com/example/shawarma/viewmodels/HomeViewModel.kt

@@ -25,9 +25,13 @@ class HomeViewModel @Inject constructor(
     private val orderProductRepository: OrderProductRepository
 ) : ViewModel() {
 
-    val productListUiState: Flow<PagingData<ProductModel>> = productRepository.getAllProductsPaged()
+    fun getProductList(token:String): Flow<PagingData<ProductModel>> {
+        return productRepository.getAllProductsPaged(token)
+    }
 
-    val discountListUiState: Flow<PagingData<ProductModel>> = productRepository.getAllDiscountsPaged()
+    fun getDiscountList(token: String): Flow<PagingData<ProductModel>> {
+        return productRepository.getAllDiscountsPaged(token)
+    }
 
 
     fun addProductToCart(productId: Int, userId: String) {