some beginning

app/build.gradle.kts

@@ -76,7 +76,7 @@ dependencies {
     implementation("androidx.compose.ui:ui-tooling-preview:1.6.0-beta02")
     implementation("androidx.compose.material3:material3:1.1.2")
     implementation("androidx.paging:paging-compose:3.2.1")
-    implementation("eu.bambooapps:compose-material3-pullrefresh:1.0.0")
+    implementation("eu.bambooapps:compose-material3-pullrefresh:1.0.1")
 
     // Room
     val roomVersion = "2.6.1"

app/src/main/java/com/zyzf/coffeepreorder/api/MyServerService.kt

@@ -0,0 +1,66 @@
+package com.zyzf.coffeepreorder.api
+
+import com.zyzf.coffeepreorder.api.model.CoffeeRemote
+import retrofit2.http.Body
+import retrofit2.http.DELETE
+import retrofit2.http.GET
+import retrofit2.http.POST
+import retrofit2.http.PUT
+import retrofit2.http.Path
+import retrofit2.http.Query
+
+interface MyServerService {
+    @GET("groups")
+    suspend fun getGroups(): List<GroupRemote>
+
+    @GET("coffee")
+    suspend fun getCoffees(
+        @Query("_page") page: Int,
+        @Query("_limit") limit: Int,
+    ): List<CoffeeRemote>
+
+    @GET("coffee/{id}")
+    suspend fun getCoffee(
+        @Path("id") id: Int,
+    ): CoffeeRemote
+
+    @POST("coffee")
+    suspend fun createCoffee(
+        @Body student: CoffeeRemote,
+    ): CoffeeRemote
+
+    @PUT("coffee/{id}")
+    suspend fun updateCoffee(
+        @Path("id") id: Int,
+        @Body student: CoffeeRemote,
+    ): CoffeeRemote
+
+    @DELETE("coffee/{id}")
+    suspend fun deleteCoffee(
+        @Path("id") id: Int,
+    ): CoffeeRemote
+
+    companion object {
+        private const val BASE_URL = "http://10.120.175.105:8079/"
+
+        @Volatile
+        private var INSTANCE: MyServerService? = null
+
+        fun getInstance(): MyServerService {
+            return INSTANCE ?: synchronized(this) {
+                val logger = HttpLoggingInterceptor()
+                logger.level = HttpLoggingInterceptor.Level.BASIC
+                val client = OkHttpClient.Builder()
+                    .addInterceptor(logger)
+                    .build()
+                return Retrofit.Builder()
+                    .baseUrl(BASE_URL)
+                    .client(client)
+                    .addConverterFactory(Json.asConverterFactory("application/json".toMediaType()))
+                    .build()
+                    .create(MyServerService::class.java)
+                    .also { INSTANCE = it }
+            }
+        }
+    }
+}

app/src/main/java/com/zyzf/coffeepreorder/api/coffee/CoffeeRemoteMediator.kt

@@ -0,0 +1,108 @@
+package com.zyzf.coffeepreorder.api.coffee
+
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.LoadType
+import androidx.paging.PagingState
+import androidx.paging.RemoteMediator
+import androidx.room.withTransaction
+import com.zyzf.coffeepreorder.api.MyServerService
+import com.zyzf.coffeepreorder.api.model.toCoffee
+import com.zyzf.coffeepreorder.database.AppDatabase
+import com.zyzf.coffeepreorder.database.model.Coffee
+import com.zyzf.coffeepreorder.database.model.RemoteKeyType
+import com.zyzf.coffeepreorder.database.model.RemoteKeys
+import com.zyzf.coffeepreorder.database.repository.OfflineCoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineRemoteKeyRepository
+import retrofit2.HttpException
+import java.io.IOException
+
+@OptIn(ExperimentalPagingApi::class)
+class CoffeeRemoteMediator(
+    private val service: MyServerService,
+    private val dbCoffeeRepository: OfflineCoffeeRepository,
+    private val dbRemoteKeyRepository: OfflineRemoteKeyRepository,
+    private val database: AppDatabase
+) : RemoteMediator<Int, Coffee>() {
+
+    override suspend fun initialize(): InitializeAction {
+        return InitializeAction.LAUNCH_INITIAL_REFRESH
+    }
+
+    override suspend fun load(
+        loadType: LoadType,
+        state: PagingState<Int, Coffee>
+    ): MediatorResult {
+        val page = when (loadType) {
+            LoadType.REFRESH -> {
+                val remoteKeys = getRemoteKeyClosestToCurrentPosition(state)
+                remoteKeys?.nextKey?.minus(1) ?: 1
+            }
+
+            LoadType.PREPEND -> {
+                val remoteKeys = getRemoteKeyForFirstItem(state)
+                remoteKeys?.prevKey
+                    ?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
+            }
+
+            LoadType.APPEND -> {
+                val remoteKeys = getRemoteKeyForLastItem(state)
+                remoteKeys?.nextKey
+                    ?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
+            }
+        }
+
+        try {
+            val coffees = service.getCoffees(page, state.config.pageSize).map { it.toCoffee() }
+            val endOfPaginationReached = coffees.isEmpty()
+            database.withTransaction {
+                if (loadType == LoadType.REFRESH) {
+                    dbRemoteKeyRepository.deleteRemoteKey(RemoteKeyType.Coffee)
+                    dbCoffeeRepository.clearCoffees()
+                }
+                val prevKey = if (page == 1) null else page - 1
+                val nextKey = if (endOfPaginationReached) null else page + 1
+                val keys = coffees.map {
+                    RemoteKeys(
+                        entityId = it.uid,
+                        type = RemoteKeyType.Coffee,
+                        prevKey = prevKey,
+                        nextKey = nextKey
+                    )
+                }
+                dbRemoteKeyRepository.createRemoteKeys(keys)
+                for (coffee in coffees) {
+                    dbCoffeeRepository.insert(coffee.name, coffee.cost, coffee.ingredients)
+                }
+            }
+            return MediatorResult.Success(endOfPaginationReached = endOfPaginationReached)
+        } catch (exception: IOException) {
+            return MediatorResult.Error(exception)
+        } catch (exception: HttpException) {
+            return MediatorResult.Error(exception)
+        }
+    }
+
+    private suspend fun getRemoteKeyForLastItem(state: PagingState<Int, Coffee>): RemoteKeys? {
+        return state.pages.lastOrNull { it.data.isNotEmpty() }?.data?.lastOrNull()
+            ?.let { coffee ->
+                dbRemoteKeyRepository.getAllRemoteKeys(coffee.uid, RemoteKeyType.Coffee)
+            }
+    }
+
+    private suspend fun getRemoteKeyForFirstItem(state: PagingState<Int, Coffee>): RemoteKeys? {
+        return state.pages.firstOrNull { it.data.isNotEmpty() }?.data?.firstOrNull()
+            ?.let { coffee ->
+                dbRemoteKeyRepository.getAllRemoteKeys(coffee.uid, RemoteKeyType.Coffee)
+            }
+    }
+
+    private suspend fun getRemoteKeyClosestToCurrentPosition(
+        state: PagingState<Int, Coffee>
+    ): RemoteKeys? {
+        return state.anchorPosition?.let { position ->
+            state.closestItemToPosition(position)?.uid?.let { coffeeUid ->
+                dbRemoteKeyRepository.getAllRemoteKeys(coffeeUid, RemoteKeyType.Coffee)
+            }
+        }
+    }
+}

app/src/main/java/com/zyzf/coffeepreorder/api/coffee/RestCoffeeRepository.kt

@@ -0,0 +1,60 @@
+package com.zyzf.coffeepreorder.api.coffee
+
+import android.util.Log
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import com.zyzf.coffeepreorder.api.MyServerService
+import com.zyzf.coffeepreorder.api.model.toCoffee
+import com.zyzf.coffeepreorder.api.model.toCoffeeRemote
+import com.zyzf.coffeepreorder.database.AppContainer
+import com.zyzf.coffeepreorder.database.AppDatabase
+import com.zyzf.coffeepreorder.database.model.Coffee
+import com.zyzf.coffeepreorder.database.repository.CoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineCoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineRemoteKeyRepository
+import kotlinx.coroutines.flow.Flow
+
+class RestCoffeeRepository(
+    private val service: MyServerService,
+    private val dbCoffeeRepository: OfflineCoffeeRepository,
+    private val dbRemoteKeyRepository: OfflineRemoteKeyRepository,
+    private val database: AppDatabase
+) : CoffeeRepository {
+    override fun getAll(): Flow<PagingData<Coffee>> {
+        Log.d(RestCoffeeRepository::class.simpleName, "Get coffees")
+
+        val pagingSourceFactory = { dbCoffeeRepository.getAllCoffeesPagingSource() }
+
+        @OptIn(ExperimentalPagingApi::class)
+        return Pager(
+            config = PagingConfig(
+                pageSize = AppContainer.LIMIT,
+                enablePlaceholders = false
+            ),
+            remoteMediator = CoffeeRemoteMediator(
+                service,
+                dbCoffeeRepository,
+                dbRemoteKeyRepository,
+                database,
+            ),
+            pagingSourceFactory = pagingSourceFactory
+        ).flow
+    }
+
+    override suspend fun getByUid(uid: Int): Coffee? =
+        service.getCoffee(uid).toCoffee()
+
+    override suspend fun insert(name: String, cost: Double, ingredients: String): Int {
+        return service.createCoffee(Coffee(name, cost, ingredients, null, 0).toCoffeeRemote()).toCoffee().uid
+    }
+
+    override suspend fun update(uid: Int, name: String, cost: Double, ingredients: String, cartId: Int?, count: Int): Int? {
+        return service.updateCoffee(uid, Coffee(uid, name, cost, ingredients, cartId, count).toCoffeeRemote()).toCoffee().uid
+    }
+
+    override suspend fun delete(coffee: Coffee) {
+        service.deleteCoffee(coffee.uid).toCoffee()
+    }
+}

app/src/main/java/com/zyzf/coffeepreorder/api/model/CoffeeRemote.kt

@@ -0,0 +1,32 @@
+package com.zyzf.coffeepreorder.api.model
+
+import com.zyzf.coffeepreorder.database.model.Coffee
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class CoffeeRemote(
+    val id: Int = 0,
+    val name: String = "",
+    val cost: Double = 0.0,
+    val ingredients: String = "",
+    val cartId: Int? = 0,
+    val count: Int = 0
+)
+
+fun CoffeeRemote.toCoffee(): Coffee = Coffee(
+    id,
+    name,
+    cost,
+    ingredients,
+    cartId,
+    count
+)
+
+fun Coffee.toCoffeeRemote(): CoffeeRemote = CoffeeRemote(
+    uid,
+    name,
+    cost,
+    ingredients,
+    cartId,
+    count
+)

app/src/main/java/com/zyzf/coffeepreorder/api/model/UserRemote.kt

@@ -0,0 +1,32 @@
+package com.zyzf.coffeepreorder.api.model
+
+import com.zyzf.coffeepreorder.database.model.User
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class UserRemote(
+    val id: Int = 0,
+    val login: String = "",
+    val fio: String = "",
+    val phone: String = "",
+    val password: String = "",
+    val role: String = "user"
+)
+
+fun UserRemote.toUser(): User = User(
+    id,
+    login,
+    fio,
+    phone,
+    password,
+    role
+)
+
+fun User.toUserRemote(): UserRemote = UserRemote(
+    uid,
+    login,
+    fio,
+    phone,
+    password,
+    role
+)

app/src/main/java/com/zyzf/coffeepreorder/api/user/RestUserRepository.kt

@@ -0,0 +1,64 @@
+package com.zyzf.coffeepreorder.api.user
+
+import android.util.Log
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import com.zyzf.coffeepreorder.api.MyServerService
+import com.zyzf.coffeepreorder.api.coffee.CoffeeRemoteMediator
+import com.zyzf.coffeepreorder.api.model.toCoffee
+import com.zyzf.coffeepreorder.api.model.toCoffeeRemote
+import com.zyzf.coffeepreorder.database.AppContainer
+import com.zyzf.coffeepreorder.database.AppDatabase
+import com.zyzf.coffeepreorder.database.model.Coffee
+import com.zyzf.coffeepreorder.database.model.User
+import com.zyzf.coffeepreorder.database.repository.CoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineCoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineRemoteKeyRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineUserRepository
+import com.zyzf.coffeepreorder.database.repository.UserRepository
+import kotlinx.coroutines.flow.Flow
+
+class RestUserRepository(
+    private val service: MyServerService,
+    private val dbUserRepository: OfflineUserRepository,
+    private val dbRemoteKeyRepository: OfflineRemoteKeyRepository,
+    private val database: AppDatabase
+) : UserRepository {
+    override fun getAll(): Flow<PagingData<User>> {
+        Log.d(RestUserRepository::class.simpleName, "Get users")
+
+        val pagingSourceFactory = { dbUserRepository.getAllUserPagingSource() }
+
+        @OptIn(ExperimentalPagingApi::class)
+        return Pager(
+            config = PagingConfig(
+                pageSize = AppContainer.LIMIT,
+                enablePlaceholders = false
+            ),
+            remoteMediator = UserRemoteMediator(
+                service,
+                dbUserRepository,
+                dbRemoteKeyRepository,
+                database,
+            ),
+            pagingSourceFactory = pagingSourceFactory
+        ).flow
+    }
+
+    override suspend fun getByUid(uid: Int): User? =
+        service.getUser(uid).toUser()
+
+    override suspend fun insert(name: String, cost: Double, ingredients: String): Int {
+        return service.createCoffee(Coffee(name, cost, ingredients, null, 0).toCoffeeRemote()).toCoffee().uid
+    }
+
+    override suspend fun update(uid: Int, name: String, cost: Double, ingredients: String, cartId: Int?, count: Int): Int? {
+        return service.updateCoffee(uid, Coffee(uid, name, cost, ingredients, cartId, count).toCoffeeRemote()).toCoffee().uid
+    }
+
+    override suspend fun delete(coffee: Coffee) {
+        service.deleteCoffee(coffee.uid).toCoffee()
+    }
+}

app/src/main/java/com/zyzf/coffeepreorder/api/user/UserRemoteMediator.kt

@@ -0,0 +1,110 @@
+package com.zyzf.coffeepreorder.api.user
+
+import androidx.paging.ExperimentalPagingApi
+import androidx.paging.LoadType
+import androidx.paging.PagingState
+import androidx.paging.RemoteMediator
+import androidx.room.withTransaction
+import com.zyzf.coffeepreorder.api.MyServerService
+import com.zyzf.coffeepreorder.api.model.toCoffee
+import com.zyzf.coffeepreorder.database.AppDatabase
+import com.zyzf.coffeepreorder.database.model.Coffee
+import com.zyzf.coffeepreorder.database.model.RemoteKeyType
+import com.zyzf.coffeepreorder.database.model.RemoteKeys
+import com.zyzf.coffeepreorder.database.model.User
+import com.zyzf.coffeepreorder.database.repository.OfflineCoffeeRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineRemoteKeyRepository
+import com.zyzf.coffeepreorder.database.repository.OfflineUserRepository
+import retrofit2.HttpException
+import java.io.IOException
+
+@OptIn(ExperimentalPagingApi::class)
+class UserRemoteMediator(
+    private val service: MyServerService,
+    private val dbUserRepository: OfflineUserRepository,
+    private val dbRemoteKeyRepository: OfflineRemoteKeyRepository,
+    private val database: AppDatabase
+) : RemoteMediator<Int, User>() {
+
+    override suspend fun initialize(): InitializeAction {
+        return InitializeAction.LAUNCH_INITIAL_REFRESH
+    }
+
+    override suspend fun load(
+        loadType: LoadType,
+        state: PagingState<Int, User>
+    ): MediatorResult {
+        val page = when (loadType) {
+            LoadType.REFRESH -> {
+                val remoteKeys = getRemoteKeyClosestToCurrentPosition(state)
+                remoteKeys?.nextKey?.minus(1) ?: 1
+            }
+
+            LoadType.PREPEND -> {
+                val remoteKeys = getRemoteKeyForFirstItem(state)
+                remoteKeys?.prevKey
+                    ?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
+            }
+
+            LoadType.APPEND -> {
+                val remoteKeys = getRemoteKeyForLastItem(state)
+                remoteKeys?.nextKey
+                    ?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
+            }
+        }
+
+        try {
+            val coffees = service.getUsers(page, state.config.pageSize).map { it.toCoffee() }
+            val endOfPaginationReached = coffees.isEmpty()
+            database.withTransaction {
+                if (loadType == LoadType.REFRESH) {
+                    dbRemoteKeyRepository.deleteRemoteKey(RemoteKeyType.User)
+                    dbUserRepository.clearCoffees()
+                }
+                val prevKey = if (page == 1) null else page - 1
+                val nextKey = if (endOfPaginationReached) null else page + 1
+                val keys = coffees.map {
+                    RemoteKeys(
+                        entityId = it.uid,
+                        type = RemoteKeyType.User,
+                        prevKey = prevKey,
+                        nextKey = nextKey
+                    )
+                }
+                dbRemoteKeyRepository.createRemoteKeys(keys)
+                for (user in coffees) {
+                    dbUserRepository.insert()
+                }
+            }
+            return MediatorResult.Success(endOfPaginationReached = endOfPaginationReached)
+        } catch (exception: IOException) {
+            return MediatorResult.Error(exception)
+        } catch (exception: HttpException) {
+            return MediatorResult.Error(exception)
+        }
+    }
+
+    private suspend fun getRemoteKeyForLastItem(state: PagingState<Int, User>): RemoteKeys? {
+        return state.pages.lastOrNull { it.data.isNotEmpty() }?.data?.lastOrNull()
+            ?.let { user ->
+                dbRemoteKeyRepository.getAllRemoteKeys(user.uid, RemoteKeyType.User)
+            }
+    }
+
+    private suspend fun getRemoteKeyForFirstItem(state: PagingState<Int, User>): RemoteKeys? {
+        return state.pages.firstOrNull { it.data.isNotEmpty() }?.data?.firstOrNull()
+            ?.let { user ->
+                dbRemoteKeyRepository.getAllRemoteKeys(user.uid, RemoteKeyType.User)
+            }
+    }
+
+    private suspend fun getRemoteKeyClosestToCurrentPosition(
+        state: PagingState<Int, User>
+    ): RemoteKeys? {
+        return state.anchorPosition?.let { position ->
+            state.closestItemToPosition(position)?.uid?.let { userUid ->
+                dbRemoteKeyRepository.getAllRemoteKeys(userUid, RemoteKeyType.User)
+            }
+        }
+    }
+}

app/src/main/java/com/zyzf/coffeepreorder/database/AppContainer.kt

@@ -12,6 +12,11 @@ interface AppContainer {
     val coffeeRepository: CoffeeRepository
     val userRepository: UserRepository
     val cartRepository: CartRepository
+
+    companion object {
+        const val TIMEOUT = 5000L
+        const val LIMIT = 10
+    }
 }
 
 class AppDataContainer(private val context: Context) : AppContainer {
@@ -24,9 +29,4 @@ class AppDataContainer(private val context: Context) : AppContainer {
     override val cartRepository: CartRepository by lazy {
         OfflineCartRepository(AppDatabase.getInstance(context).cartDao())
     }
-
-    companion object {
-        const val TIMEOUT = 5000L
-        const val LIMIT = 10
-    }
 }

app/src/main/java/com/zyzf/coffeepreorder/database/dao/CartDao.kt

@@ -1,16 +1,24 @@
 package com.zyzf.coffeepreorder.database.dao
 
+import androidx.paging.PagingSource
 import androidx.room.Dao
 import androidx.room.Insert
 import androidx.room.Query
 import androidx.room.Update
 import com.zyzf.coffeepreorder.database.model.Cart
+import com.zyzf.coffeepreorder.database.model.Coffee
 
 @Dao
 interface CartDao {
     @Query("select * from cart limit 1")
     suspend fun get(): Cart
 
+    @Query("select * from coffee where cart_id is not null and count > 0 order by name collate nocase asc")
+    fun getAllInCart(): PagingSource<Int, Coffee>
+
+    @Query("select sum(cost) from coffee where cart_id is not null and count > 0")
+    fun getSumInCart(): Double
+
     @Insert
     suspend fun insert(cart: Cart)
 

app/src/main/java/com/zyzf/coffeepreorder/database/dao/CoffeeDao.kt

@@ -5,28 +5,24 @@ import androidx.room.Dao
 import androidx.room.Delete
 import androidx.room.Query
 import com.zyzf.coffeepreorder.database.model.Coffee
-import com.zyzf.coffeepreorder.database.model.CoffeeWithCart
 
 @Dao
 interface CoffeeDao {
     @Query("select * from coffee order by name collate nocase asc")
     fun getAll(): PagingSource<Int, Coffee>
 
-    @Query("select * from coffee where cart_id is not null and count > 0 order by name collate nocase asc")
+    @Query("select coffee.uid, name, cost, ingredients, cart_id, count from coffee where coffee.uid = :uid")
-    fun getAllInCart(): PagingSource<Int, Coffee>
+    suspend fun getByUid(uid: Int): Coffee?
-
-    @Query("select sum(cost) from coffee where cart_id is not null and count > 0")
-    fun getSumInCart(): Double
-
-    @Query("select coffee.uid, name, cost, ingredients, cart_id, count, cart.uid as cart_uid from coffee left join cart on coffee.cart_id = cart.uid where coffee.uid = :uid")
-    suspend fun getByUid(uid: Int): CoffeeWithCart?
 
     @Query("insert into coffee (name, cost, ingredients, count) values (:name, :cost, :ingredients, 0)")
-    suspend fun insert(name: String, cost: Double, ingredients: String): Long
+    suspend fun insert(name: String, cost: Double, ingredients: String): Int
 
     @Query("update coffee set name = :name, cost = :cost, ingredients = :ingredients, cart_id = :cartId, count = :count where uid = :uid")
     suspend fun update(uid: Int, name: String, cost: Double, ingredients: String, cartId: Int?, count: Int): Int?
 
     @Delete
     suspend fun delete(coffee: Coffee)
+
+    @Query("delete from coffee")
+    suspend fun deleteAll()
 }

app/src/main/java/com/zyzf/coffeepreorder/database/dao/RemoteKeysDao.kt

@@ -0,0 +1,20 @@
+package com.zyzf.coffeepreorder.database.dao
+
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+import com.zyzf.coffeepreorder.database.model.RemoteKeyType
+import com.zyzf.coffeepreorder.database.model.RemoteKeys
+
+@Dao
+interface RemoteKeysDao {
+    @Query("SELECT * FROM remote_keys WHERE entityId = :entityId AND type = :type")
+    suspend fun getRemoteKeys(entityId: Int, type: RemoteKeyType): RemoteKeys?
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun insertAll(remoteKey: List<RemoteKeys>)
+
+    @Query("DELETE FROM remote_keys WHERE type = :type")
+    suspend fun clearRemoteKeys(type: RemoteKeyType)
+}

app/src/main/java/com/zyzf/coffeepreorder/database/dao/UserDao.kt

@@ -1,15 +1,17 @@
 package com.zyzf.coffeepreorder.database.dao
 
+import androidx.paging.PagingSource
 import androidx.room.Dao
 import androidx.room.Insert
 import androidx.room.Query
+import com.zyzf.coffeepreorder.database.model.Coffee
 import com.zyzf.coffeepreorder.database.model.User
 import kotlinx.coroutines.flow.Flow
 
 @Dao
 interface UserDao {
     @Query("select * from user")
-    fun getAll(): Flow<List<User>>
+    fun getAll(): PagingSource<Int, User>
 
     @Query("select * from user where login = :login and password = :password")
     suspend fun tryLogin(login: String, password: String): User?

app/src/main/java/com/zyzf/coffeepreorder/database/model/CoffeeWithCart.kt

@@ -1,11 +0,0 @@
-package com.zyzf.coffeepreorder.database.model
-
-import androidx.room.ColumnInfo
-import androidx.room.Embedded
-
-data class CoffeeWithCart(
-    @Embedded
-    val coffee: Coffee,
-    @ColumnInfo(name = "cart_uid")
-    val cartUid: Int
-)

app/src/main/java/com/zyzf/coffeepreorder/database/model/RemoteKeys.kt

@@ -0,0 +1,26 @@
+package com.zyzf.coffeepreorder.database.model
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+import androidx.room.TypeConverter
+import androidx.room.TypeConverters
+
+enum class RemoteKeyType(private val type: String) {
+    Coffee(Coffee::class.simpleName ?: "Coffee"),
+    User(User::class.simpleName ?: "User");
+
+    @TypeConverter
+    fun toRemoteKeyType(value: String) = RemoteKeyType.values().first { it.type == value }
+
+    @TypeConverter
+    fun fromRemoteKeyType(value: RemoteKeyType) = value.type
+}
+
+@Entity(tableName = "remote_keys")
+data class RemoteKeys(
+    @PrimaryKey val entityId: Int,
+    @TypeConverters(RemoteKeyType::class)
+    val type: RemoteKeyType,
+    val prevKey: Int?,
+    val nextKey: Int?
+)

app/src/main/java/com/zyzf/coffeepreorder/database/model/User.kt

@@ -8,7 +8,7 @@ import androidx.room.PrimaryKey
 @Entity(tableName = "user")
 data class User(
     @PrimaryKey(autoGenerate = true)
-    val uid: Int?,
+    val uid: Int = 0,
     @ColumnInfo(name = "login")
     var login: String,
     @ColumnInfo(name = "fio")
@@ -27,7 +27,20 @@ data class User(
         phone: String,
         password: String,
         role: String
-    ) : this(null, login, fio, phone, password, role)
+    ) : this(0, login, fio, phone, password, role)
+
+    companion object {
+        fun getUser(index: Int = 0): User {
+            return User(
+                index,
+                "",
+                "",
+                "",
+                "",
+                "user"
+            )
+        }
+    }
 
     override fun equals(other: Any?): Boolean {
         if (this === other) return true

app/src/main/java/com/zyzf/coffeepreorder/database/repository/CartRepository.kt

@@ -1,10 +1,15 @@
 package com.zyzf.coffeepreorder.database.repository
 
+import androidx.paging.PagingData
 import com.zyzf.coffeepreorder.database.model.Cart
+import com.zyzf.coffeepreorder.database.model.Coffee
+import kotlinx.coroutines.flow.Flow
 
 interface CartRepository {
     suspend fun get(): Cart
     suspend fun insert(cart: Cart)
+    fun getAllInCart(): Flow<PagingData<Coffee>>
+    fun getSumInCart(): Double
     suspend fun insertCoffee(cartId: Int, coffeeId: Int, count: Int)
     suspend fun deleteCoffee(coffeeId: Int, count: Int)
     suspend fun update(cart: Cart)

app/src/main/java/com/zyzf/coffeepreorder/database/repository/CoffeeRepository.kt

@@ -2,15 +2,12 @@ package com.zyzf.coffeepreorder.database.repository
 
 import androidx.paging.PagingData
 import com.zyzf.coffeepreorder.database.model.Coffee
-import com.zyzf.coffeepreorder.database.model.CoffeeWithCart
 import kotlinx.coroutines.flow.Flow
 
 interface CoffeeRepository {
     fun getAll(): Flow<PagingData<Coffee>>
-    fun getAllInCart(): Flow<PagingData<Coffee>>
+    suspend fun getByUid(uid: Int): Coffee?
-    fun getSumInCart(): Double
+    suspend fun insert(name: String, cost: Double, ingredients: String): Int
-    suspend fun getByUid(uid: Int): CoffeeWithCart?
-    suspend fun insert(name: String, cost: Double, ingredients: String): Long
     suspend fun update(uid: Int, name: String, cost: Double, ingredients: String, cartId: Int?, count: Int): Int?
     suspend fun delete(coffee: Coffee)
 }

app/src/main/java/com/zyzf/coffeepreorder/database/repository/OfflineCartRepository.kt

@@ -1,9 +1,23 @@
 package com.zyzf.coffeepreorder.database.repository
 
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import com.zyzf.coffeepreorder.database.AppContainer
 import com.zyzf.coffeepreorder.database.dao.CartDao
 import com.zyzf.coffeepreorder.database.model.Cart
+import com.zyzf.coffeepreorder.database.model.Coffee
+import kotlinx.coroutines.flow.Flow
 
 class OfflineCartRepository(private val cartDao: CartDao) : CartRepository {
+    override fun getAllInCart(): Flow<PagingData<Coffee>> = Pager(
+        config = PagingConfig(
+            pageSize = AppContainer.LIMIT,
+            enablePlaceholders = false
+        ),
+        pagingSourceFactory = cartDao::getAllInCart
+    ).flow
+    override fun getSumInCart(): Double = cartDao.getSumInCart()
     override suspend fun get(): Cart = cartDao.get()
     override suspend fun insert(cart: Cart) = cartDao.insert(cart)
     override suspend fun insertCoffee(cartId: Int, coffeeId: Int, count: Int) = cartDao.insertCoffee(cartId, coffeeId, count)

app/src/main/java/com/zyzf/coffeepreorder/database/repository/OfflineCoffeeRepository.kt

@@ -3,30 +3,25 @@ package com.zyzf.coffeepreorder.database.repository
 import androidx.paging.Pager
 import androidx.paging.PagingConfig
 import androidx.paging.PagingData
-import com.zyzf.coffeepreorder.database.AppDataContainer
+import androidx.paging.PagingSource
+import com.zyzf.coffeepreorder.database.AppContainer
 import com.zyzf.coffeepreorder.database.dao.CoffeeDao
 import com.zyzf.coffeepreorder.database.model.Coffee
-import com.zyzf.coffeepreorder.database.model.CoffeeWithCart
 import kotlinx.coroutines.flow.Flow
 
 class OfflineCoffeeRepository(private val coffeeDao: CoffeeDao) : CoffeeRepository {
     override fun getAll(): Flow<PagingData<Coffee>> = Pager(
         config = PagingConfig(
-            pageSize = AppDataContainer.LIMIT,
+            pageSize = AppContainer.LIMIT,
             enablePlaceholders = false
         ),
         pagingSourceFactory = coffeeDao::getAll
     ).flow
-    override fun getAllInCart(): Flow<PagingData<Coffee>> = Pager(
+
-        config = PagingConfig(
+    fun getAllCoffeesPagingSource(): PagingSource<Int, Coffee> = coffeeDao.getAll()
-            pageSize = AppDataContainer.LIMIT,
+    suspend fun clearCoffees() = coffeeDao.deleteAll()
-            enablePlaceholders = false
+    override suspend fun getByUid(uid: Int): Coffee? = coffeeDao.getByUid(uid)
-        ),
+    override suspend fun insert(name: String, cost: Double, ingredients: String): Int = coffeeDao.insert(name, cost, ingredients)
-        pagingSourceFactory = coffeeDao::getAllInCart
-    ).flow
-    override fun getSumInCart(): Double = coffeeDao.getSumInCart()
-    override suspend fun getByUid(uid: Int): CoffeeWithCart? = coffeeDao.getByUid(uid)
-    override suspend fun insert(name: String, cost: Double, ingredients: String): Long = coffeeDao.insert(name, cost, ingredients)
     override suspend fun update(uid: Int, name: String, cost: Double, ingredients: String, cartId: Int?, count: Int): Int? = coffeeDao.update(uid, name, cost, ingredients, cartId, count)
     override suspend fun delete(coffee: Coffee) = coffeeDao.delete(coffee)
 }

app/src/main/java/com/zyzf/coffeepreorder/database/repository/OfflineRemoteKeyRepository.kt

@@ -0,0 +1,16 @@
+package com.zyzf.coffeepreorder.database.repository
+
+import com.zyzf.coffeepreorder.database.dao.RemoteKeysDao
+import com.zyzf.coffeepreorder.database.model.RemoteKeyType
+import com.zyzf.coffeepreorder.database.model.RemoteKeys
+
+class OfflineRemoteKeyRepository(private val remoteKeysDao: RemoteKeysDao) : RemoteKeyRepository {
+    override suspend fun getAllRemoteKeys(id: Int, type: RemoteKeyType) =
+        remoteKeysDao.getRemoteKeys(id, type)
+
+    override suspend fun createRemoteKeys(remoteKeys: List<RemoteKeys>) =
+        remoteKeysDao.insertAll(remoteKeys)
+
+    override suspend fun deleteRemoteKey(type: RemoteKeyType) =
+        remoteKeysDao.clearRemoteKeys(type)
+}

app/src/main/java/com/zyzf/coffeepreorder/database/repository/OfflineUserRepository.kt

@@ -1,11 +1,24 @@
 package com.zyzf.coffeepreorder.database.repository
 
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import androidx.paging.PagingSource
+import com.zyzf.coffeepreorder.database.AppContainer
 import com.zyzf.coffeepreorder.database.dao.UserDao
+import com.zyzf.coffeepreorder.database.model.Coffee
 import com.zyzf.coffeepreorder.database.model.User
 import kotlinx.coroutines.flow.Flow
 
 class OfflineUserRepository(private val userDao: UserDao) : UserRepository {
-    override fun getAll(): Flow<List<User>> = userDao.getAll()
+    override fun getAll(): Flow<PagingData<User>> = Pager(
+        config = PagingConfig(
+            pageSize = AppContainer.LIMIT,
+            enablePlaceholders = false
+        ),
+        pagingSourceFactory = userDao::getAll
+    ).flow
+    fun getAllUserPagingSource(): PagingSource<Int, User> = userDao.getAll()
     override suspend fun tryLogin(login: String, password: String): User? = userDao.tryLogin(login, password)
     override suspend fun getByUid(uid: Int): User? = userDao.getByUid(uid)
     override suspend fun getLogined(): User? = userDao.getLogined()

app/src/main/java/com/zyzf/coffeepreorder/database/repository/RemoteKeyRepository.kt

@@ -0,0 +1,10 @@
+package com.zyzf.coffeepreorder.database.repository
+
+import com.zyzf.coffeepreorder.database.model.RemoteKeyType
+import com.zyzf.coffeepreorder.database.model.RemoteKeys
+
+interface RemoteKeyRepository {
+    suspend fun getAllRemoteKeys(id: Int, type: RemoteKeyType): RemoteKeys?
+    suspend fun createRemoteKeys(remoteKeys: List<RemoteKeys>)
+    suspend fun deleteRemoteKey(type: RemoteKeyType)
+}

app/src/main/java/com/zyzf/coffeepreorder/database/repository/UserRepository.kt

@@ -1,10 +1,11 @@
 package com.zyzf.coffeepreorder.database.repository
 
+import androidx.paging.PagingData
 import com.zyzf.coffeepreorder.database.model.User
 import kotlinx.coroutines.flow.Flow
 
 interface UserRepository {
-    fun getAll(): Flow<List<User>>
+    fun getAll(): Flow<PagingData<User>>
     suspend fun tryLogin(login: String, password: String): User?
     suspend fun getByUid(uid: Int): User?
     suspend fun getLogined(): User?

app/src/main/java/com/zyzf/coffeepreorder/ui/cart/CartViewModel.kt

@@ -8,10 +8,9 @@ import com.zyzf.coffeepreorder.database.repository.CoffeeRepository
 import kotlinx.coroutines.flow.Flow
 
 class CartViewModel(
-    private val coffeeRepository: CoffeeRepository,
     private val cartRepository: CartRepository
 ) : ViewModel() {
-    val coffeeListUiState: Flow<PagingData<Coffee>> = coffeeRepository.getAllInCart()
+    val coffeeListUiState: Flow<PagingData<Coffee>> = cartRepository.getAllInCart()
 
     suspend fun deleteCoffeeFromCart(coffee: Coffee) {
         cartRepository.deleteCoffee(coffee.uid, 1)

app/src/main/java/com/zyzf/coffeepreorder/ui/coffee/CoffeeListViewModel.kt

@@ -36,7 +36,7 @@ class CoffeeListViewModel(
         cart.uid?.let { cartRepository.insertCoffee(it, coffeeUid, 1) }
     }
     suspend fun createCoffee(coffee: Coffee, imageUri: Uri, context: Context) {
-        val newCoffee: Long = coffeeRepository.insert(coffee.name, coffee.cost, coffee.ingredients)
+        val newCoffee: Int = coffeeRepository.insert(coffee.name, coffee.cost, coffee.ingredients)
         val inputStream = context.contentResolver.openInputStream(imageUri)
         val bitmap = BitmapFactory.decodeStream(inputStream)