refactor: extract paging helpers

core/common/src/main/kotlin/dev/meloda/fast/common/paging/Paging.kt

@@ -0,0 +1,25 @@
+package dev.meloda.fast.common.paging
+
+fun canPaginate(pageSize: Int, loadedCount: Int): Boolean = loadedCount == pageSize
+
+fun isPaginationExhausted(
+    pageSize: Int,
+    loadedCount: Int,
+    hasExistingItems: Boolean
+): Boolean = loadedCount != pageSize && hasExistingItems
+
+fun <T> mergePage(
+    existing: List<T>,
+    page: List<T>,
+    offset: Int
+): List<T> = if (offset == 0) page else existing + page
+
+data class LoadingFlags(
+    val isLoading: Boolean,
+    val isPaginating: Boolean
+)
+
+fun loadingFlags(offset: Int, isLoading: Boolean): LoadingFlags = LoadingFlags(
+    isLoading = offset == 0 && isLoading,
+    isPaginating = offset > 0 && isLoading
+)

feature/chatmaterials/src/main/kotlin/dev/meloda/fast/chatmaterials/ChatMaterialsViewModel.kt

@@ -9,6 +9,10 @@ import dev.meloda.fast.chatmaterials.navigation.ChatMaterials
 import dev.meloda.fast.chatmaterials.util.asPresentation
 import dev.meloda.fast.common.extensions.listenValue
 import dev.meloda.fast.common.extensions.setValue
+import dev.meloda.fast.common.paging.canPaginate as canPaginatePage
+import dev.meloda.fast.common.paging.isPaginationExhausted as isPaginationExhaustedPage
+import dev.meloda.fast.common.paging.loadingFlags
+import dev.meloda.fast.common.paging.mergePage
 import dev.meloda.fast.data.State
 import dev.meloda.fast.data.VkUtils
 import dev.meloda.fast.data.processState
@@ -89,11 +93,14 @@ class ChatMaterialsViewModelImpl(
             state.processState(
                 error = ::handleError,
                 success = { response ->
-                    val itemsCountSufficient = response.size == LOAD_COUNT
+                    val itemsCountSufficient = canPaginatePage(LOAD_COUNT, response.size)
                     canPaginate.setValue { itemsCountSufficient }
 
-                    val paginationExhausted = !itemsCountSufficient
+                    val paginationExhausted = isPaginationExhaustedPage(
-                            && screenState.value.materials.isNotEmpty()
+                        pageSize = LOAD_COUNT,
+                        loadedCount = response.size,
+                        hasExistingItems = screenState.value.materials.isNotEmpty()
+                    )
 
                     val loadedMaterials = response.mapNotNull(VkAttachmentHistoryMessage::asPresentation)
 
@@ -107,24 +114,19 @@ class ChatMaterialsViewModelImpl(
                         }
                     )
 
-                    if (offset == 0) {
-                        screenState.setValue {
-                            newState.copy(materials = loadedMaterials)
-                        }
-                    } else {
                     screenState.setValue {
                         newState.copy(
-                                materials = newState.materials.plus(loadedMaterials)
+                            materials = mergePage(newState.materials, loadedMaterials, offset)
                         )
                     }
                 }
-                }
             )
 
+            val flags = loadingFlags(offset, state.isLoading())
             screenState.setValue { old ->
                 old.copy(
-                    isLoading = offset == 0 && state.isLoading(),
+                    isLoading = flags.isLoading,
-                    isPaginating = offset > 0 && state.isLoading()
+                    isPaginating = flags.isPaginating
                 )
             }
         }

feature/convos/src/main/kotlin/dev/meloda/fast/convos/ConvosViewModel.kt

@@ -14,6 +14,10 @@ import dev.meloda.fast.common.extensions.findWithIndex
 import dev.meloda.fast.common.extensions.listenValue
 import dev.meloda.fast.common.extensions.setValue
 import dev.meloda.fast.common.extensions.updateValue
+import dev.meloda.fast.common.paging.canPaginate as canPaginatePage
+import dev.meloda.fast.common.paging.isPaginationExhausted as isPaginationExhaustedPage
+import dev.meloda.fast.common.paging.loadingFlags
+import dev.meloda.fast.common.paging.mergePage
 import dev.meloda.fast.convos.model.ConvoDialog
 import dev.meloda.fast.convos.model.ConvoNavigation
 import dev.meloda.fast.convos.model.ConvosScreenState
@@ -264,17 +268,12 @@ class ConvosViewModel(
                     _baseError.update { newBaseError }
                 },
                 success = { response ->
-                    val convos = response
+                    val itemsCountSufficient = canPaginatePage(LOAD_COUNT, response.size)
-                    val fullConvos = if (offset == 0) {
+                    val paginationExhausted = isPaginationExhaustedPage(
-                        convos
+                        pageSize = LOAD_COUNT,
-                    } else {
+                        loadedCount = response.size,
-                        this.convos.value.plus(convos)
+                        hasExistingItems = this.convos.value.isNotEmpty()
-                    }
+                    )
-
-                    val itemsCountSufficient = response.size == LOAD_COUNT
-
-                    val paginationExhausted = !itemsCountSufficient &&
-                            this.convos.value.isNotEmpty()
 
                     _screenState.updateValue {
                         copy(isPaginationExhausted = paginationExhausted)
@@ -293,16 +292,17 @@ class ConvosViewModel(
 
                     convoUseCase.storeConvos(response)
 
-                    _convos.emit(fullConvos)
+                    _convos.emit(mergePage(this.convos.value, response, offset))
                     syncUiConvos()
                     _canPaginate.setValue { itemsCountSufficient }
                 }
             )
 
+            val flags = loadingFlags(offset, state.isLoading())
             _screenState.setValue { old ->
                 old.copy(
-                    isLoading = offset == 0 && state.isLoading(),
+                    isLoading = flags.isLoading,
-                    isPaginating = offset > 0 && state.isLoading()
+                    isPaginating = flags.isPaginating
                 )
             }
         }

feature/createchat/src/main/kotlin/dev/meloda/fast/convos/CreateChatViewModel.kt

@@ -7,6 +7,10 @@ import coil.ImageLoader
 import coil.request.ImageRequest
 import dev.meloda.fast.common.extensions.listenValue
 import dev.meloda.fast.common.extensions.setValue
+import dev.meloda.fast.common.paging.canPaginate as canPaginatePage
+import dev.meloda.fast.common.paging.isPaginationExhausted as isPaginationExhaustedPage
+import dev.meloda.fast.common.paging.loadingFlags
+import dev.meloda.fast.common.paging.mergePage
 import dev.meloda.fast.convos.model.CreateChatScreenState
 import dev.meloda.fast.data.State
 import dev.meloda.fast.data.UserConfig
@@ -156,11 +160,14 @@ class CreateChatViewModel(
                 state.processState(
                 error = ::handleError,
                 success = { response ->
-                        val itemsCountSufficient = response.size == LOAD_COUNT
+                    val itemsCountSufficient = canPaginatePage(LOAD_COUNT, response.size)
                     _canPaginate.setValue { itemsCountSufficient }
 
-                        val paginationExhausted = !itemsCountSufficient &&
+                    val paginationExhausted = isPaginationExhaustedPage(
-                                screenState.value.friends.isNotEmpty()
+                        pageSize = LOAD_COUNT,
+                        loadedCount = response.size,
+                        hasExistingItems = screenState.value.friends.isNotEmpty()
+                    )
 
                         val imagesToPreload =
                             response.mapNotNull { it.photo100.takeIf { p -> !p.isNullOrEmpty() } }
@@ -182,24 +189,19 @@ class CreateChatViewModel(
                         val newState = screenState.value.copy(
                             isPaginationExhausted = paginationExhausted
                         )
-                        if (offset == 0) {
-                            _screenState.setValue {
-                                newState.copy(friends = loadedFriends)
-                            }
-                        } else {
                         _screenState.setValue {
                             newState.copy(
-                                    friends = newState.friends.plus(loadedFriends)
+                                friends = mergePage(newState.friends, loadedFriends, offset)
                             )
                         }
                     }
-                    }
                 )
 
+                val flags = loadingFlags(offset, state.isLoading())
                 _screenState.setValue { old ->
                     old.copy(
-                        isLoading = offset == 0 && state.isLoading(),
+                        isLoading = flags.isLoading,
-                        isPaginating = offset > 0 && state.isLoading()
+                        isPaginating = flags.isPaginating
                     )
                 }
             }

feature/friends/src/main/kotlin/dev/meloda/fast/friends/FriendsViewModel.kt

@@ -4,6 +4,10 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dev.meloda.fast.common.extensions.listenValue
 import dev.meloda.fast.common.extensions.setValue
+import dev.meloda.fast.common.paging.canPaginate as canPaginatePage
+import dev.meloda.fast.common.paging.isPaginationExhausted as isPaginationExhaustedPage
+import dev.meloda.fast.common.paging.loadingFlags
+import dev.meloda.fast.common.paging.mergePage
 import dev.meloda.fast.data.State
 import dev.meloda.fast.data.VkUtils
 import dev.meloda.fast.data.processState
@@ -122,11 +126,14 @@ class FriendsViewModelImpl(
             state.processState(
                 error = ::handleError,
                 success = { response ->
-                    val itemsCountSufficient = response.size == LOAD_COUNT
+                    val itemsCountSufficient = canPaginatePage(LOAD_COUNT, response.size)
                     canPaginate.setValue { itemsCountSufficient }
 
-                    val paginationExhausted = !itemsCountSufficient
+                    val paginationExhausted = isPaginationExhaustedPage(
-                            && screenState.value.friends.isNotEmpty()
+                        pageSize = LOAD_COUNT,
+                        loadedCount = response.size,
+                        hasExistingItems = screenState.value.friends.isNotEmpty()
+                    )
 
                     imagesToPreload.setValue {
                         response.mapNotNull(VkUser::photo100)
@@ -142,24 +149,20 @@ class FriendsViewModelImpl(
                         isPaginationExhausted = paginationExhausted
                     )
 
-                    if (offset == 0) {
+                    friends.emit(mergePage(friends.value, response, offset))
-                        friends.emit(response)
                     screenState.setValue {
-                            newState.copy(friends = loadedFriends)
+                        newState.copy(
-                        }
+                            friends = mergePage(newState.friends, loadedFriends, offset)
-                    } else {
+                        )
-                        friends.emit(friends.value.plus(response))
-                        screenState.setValue {
-                            newState.copy(friends = newState.friends.plus(loadedFriends))
-                        }
                     }
                 }
             )
 
+            val flags = loadingFlags(offset, state.isLoading())
             screenState.setValue { old ->
                 old.copy(
-                    isLoading = offset == 0 && state.isLoading(),
+                    isLoading = flags.isLoading,
-                    isPaginating = offset > 0 && state.isLoading()
+                    isPaginating = flags.isPaginating
                 )
             }
         }
@@ -197,10 +200,14 @@ class OnlineFriendsViewModelImpl(
                                 }
                             )
 
+                            val flags = loadingFlags(
+                                offset = offset,
+                                isLoading = onlineState.isLoading() || state.isLoading()
+                            )
                             screenState.setValue { old ->
                                 old.copy(
-                                    isLoading = offset == 0 && (onlineState.isLoading() || state.isLoading()),
+                                    isLoading = flags.isLoading,
-                                    isPaginating = offset > 0 && (onlineState.isLoading() || state.isLoading())
+                                    isPaginating = flags.isPaginating
                                 )
                             }
                         }

feature/messageshistory/src/main/kotlin/dev/meloda/fast/messageshistory/MessagesHistoryViewModelImpl.kt

@@ -31,6 +31,10 @@ import dev.meloda.fast.common.extensions.orDots
 import dev.meloda.fast.common.extensions.removeIfCompat
 import dev.meloda.fast.common.extensions.setValue
 import dev.meloda.fast.common.provider.ResourceProvider
+import dev.meloda.fast.common.paging.canPaginate as canPaginatePage
+import dev.meloda.fast.common.paging.isPaginationExhausted as isPaginationExhaustedPage
+import dev.meloda.fast.common.paging.loadingFlags
+import dev.meloda.fast.common.paging.mergePage
 import dev.meloda.fast.data.State
 import dev.meloda.fast.data.UserConfig
 import dev.meloda.fast.data.VkUtils
@@ -915,11 +919,7 @@ class MessagesHistoryViewModelImpl(
                 error = ::handleError,
                 success = { response ->
                     val messages = response.messages
-                    val fullMessages = if (offset == 0) {
+                    val fullMessages = mergePage(this.messages.value, messages, offset).sorted()
-                        messages
-                    } else {
-                        this.messages.value.plus(messages)
-                    }.sorted()
 
                     val convos = response.convos
 
@@ -930,10 +930,12 @@ class MessagesHistoryViewModelImpl(
                     messagesUseCase.storeMessages(messages)
                     convoUseCase.storeConvos(convos)
 
-                    val itemsCountSufficient = messages.size == MESSAGES_LOAD_COUNT
+                    val itemsCountSufficient = canPaginatePage(MESSAGES_LOAD_COUNT, messages.size)
-
+                    val paginationExhausted = isPaginationExhaustedPage(
-                    val paginationExhausted = !itemsCountSufficient &&
+                        pageSize = MESSAGES_LOAD_COUNT,
-                            this.messages.value.isNotEmpty()
+                        loadedCount = messages.size,
+                        hasExistingItems = this.messages.value.isNotEmpty()
+                    )
                     screenState.setValue { old ->
                         old.copy(isPaginationExhausted = paginationExhausted)
                     }
@@ -944,10 +946,11 @@ class MessagesHistoryViewModelImpl(
                 }
             )
 
+            val flags = loadingFlags(offset, state.isLoading())
             screenState.setValue { old ->
                 old.copy(
-                    isLoading = offset == 0 && state.isLoading(),
+                    isLoading = flags.isLoading,
-                    isPaginating = offset > 0 && state.isLoading()
+                    isPaginating = flags.isPaginating
                 )
             }
         }