Merge pull request #67 from snuhcs-course/feat/android-emoji-pagination

feat: emoji pagination

android/app/src/main/java/com/goliath/emojihub/data_sources/EmojiPagingSource.kt

@@ -0,0 +1,34 @@
+package com.goliath.emojihub.data_sources
+
+import androidx.paging.PagingSource
+import androidx.paging.PagingState
+import com.goliath.emojihub.data_sources.api.EmojiApi
+import com.goliath.emojihub.models.EmojiDto
+import javax.inject.Inject
+
+class EmojiPagingSource @Inject constructor(
+    private val api: EmojiApi
+): PagingSource<Int, EmojiDto>() {
+    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, EmojiDto> {
+        val cursor = params.key ?: 1
+        val count = params.loadSize
+        return try {
+            val response = api.fetchEmojiList(1, cursor, count).body()
+            val data = response ?: listOf()
+            LoadResult.Page(
+                data = data,
+                prevKey = if (cursor == 1) null else cursor - 1,
+                nextKey = if (data.isEmpty()) null else cursor + 1
+            )
+        } catch (exception: Exception) {
+            LoadResult.Error(exception)
+        }
+    }
+
+    override fun getRefreshKey(state: PagingState<Int, EmojiDto>): Int? {
+        return state.anchorPosition?.let { anchorPosition ->
+            state.closestPageToPosition(anchorPosition)?.prevKey?.plus(1)
+                ?: state.closestPageToPosition(anchorPosition)?.nextKey?.minus(1)
+        }
+    }
+}

android/app/src/main/java/com/goliath/emojihub/repositories/remote/EmojiRepository.kt

@@ -1,11 +1,18 @@
 package com.goliath.emojihub.repositories.remote
 
 import android.util.Log
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import com.goliath.emojihub.data_sources.EmojiPagingSource
+import com.goliath.emojihub.data_sources.PostPagingSource
 import com.goliath.emojihub.data_sources.api.EmojiApi
 import com.goliath.emojihub.models.EmojiDto
 import com.goliath.emojihub.models.FetchEmojiListDto
+import com.goliath.emojihub.models.PostDto
 import com.goliath.emojihub.models.UploadEmojiDto
 import com.google.gson.Gson
+import kotlinx.coroutines.flow.Flow
 import okhttp3.MediaType
 import okhttp3.MultipartBody
 import okhttp3.RequestBody
@@ -17,7 +24,7 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 interface EmojiRepository {
-    suspend fun fetchEmojiList(numLimit: Int): List<EmojiDto>
+    suspend fun fetchEmojiList(): Flow<PagingData<EmojiDto>>
     suspend fun getEmojiWithId(id: String): EmojiDto?
     suspend fun uploadEmoji(videoFile: File, emojiDto: UploadEmojiDto): Boolean
     suspend fun saveEmoji(id: String): Response<Unit>
@@ -29,22 +36,11 @@ interface EmojiRepository {
 class EmojiRepositoryImpl @Inject constructor(
     private val emojiApi: EmojiApi
 ): EmojiRepository {
-    override suspend fun fetchEmojiList(numLimit: Int): List<EmojiDto> {
-//        val fetchEmojiListDto = FetchEmojiListDto(1, 0, 10)
-        try {
-            val response = emojiApi.fetchEmojiList(1, 1, 10)
-
-            if(response.isSuccessful && response.body() != null) {
-                Log.d("Fetch_E_L", "Successfully fetched ${response.body()!!.size} emojis")
-                return response.body()!!
-            } else {
-                val errorBody = response.errorBody()?.string() ?: "Unknown error"
-                Log.d("Fetch_E_L", "Failed to fetch emojis: $errorBody")
-            }
-        } catch(e: Exception) {
-            Log.e("Fetch_E_L", "Error fetching emojis", e)
-        }
-        return listOf()
+    override suspend fun fetchEmojiList(): Flow<PagingData<EmojiDto>> {
+        return Pager(
+            config = PagingConfig(pageSize = 10, initialLoadSize = 10, enablePlaceholders = false),
+            pagingSourceFactory = { EmojiPagingSource(emojiApi) }
+        ).flow
     }
 
     override suspend fun getEmojiWithId(id: String): EmojiDto? {

android/app/src/main/java/com/goliath/emojihub/usecases/EmojiUseCase.kt

@@ -2,23 +2,30 @@ package com.goliath.emojihub.usecases
 
 import android.net.Uri
 import android.util.Log
+import androidx.paging.PagingData
+import androidx.paging.map
 import com.goliath.emojihub.data_sources.ApiErrorController
 import com.goliath.emojihub.models.CreatedEmoji
+import com.goliath.emojihub.models.Emoji
 import com.goliath.emojihub.models.EmojiDto
+import com.goliath.emojihub.models.Post
 
 import com.goliath.emojihub.models.UploadEmojiDto
 import com.goliath.emojihub.repositories.local.X3dRepository
 import com.goliath.emojihub.repositories.remote.EmojiRepository
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.map
 import java.io.File
 import javax.inject.Inject
 import javax.inject.Singleton
 
 interface EmojiUseCase {
-    val emojiListState: StateFlow<List<EmojiDto>>
-    suspend fun fetchEmojiList(numInt: Int)
+    val emojiList: StateFlow<PagingData<Emoji>>
+    suspend fun updateEmojiList(data: PagingData<Emoji>)
+    suspend fun fetchEmojiList(): Flow<PagingData<Emoji>>
     suspend fun createEmoji(videoUri: Uri, topK: Int): List<CreatedEmoji>
     suspend fun uploadEmoji(emojiUnicode: String, emojiLabel: String, videoFile: File): Boolean
     suspend fun saveEmoji(id: String): Boolean
@@ -32,18 +39,15 @@ class EmojiUseCaseImpl @Inject constructor(
     private val errorController: ApiErrorController
 ): EmojiUseCase {
 
-    private val _emojiListState = MutableStateFlow<List<EmojiDto>>(emptyList())
-    override val emojiListState: StateFlow<List<EmojiDto>>
-        get() = _emojiListState.asStateFlow()
+    private val _emojiList = MutableStateFlow<PagingData<Emoji>>(PagingData.empty())
+    override val emojiList: StateFlow<PagingData<Emoji>>
+        get() = _emojiList
 
-    override suspend fun fetchEmojiList(numInt: Int) {
-        try{
-            val emojiList = emojiRepository.fetchEmojiList(numInt)
-            _emojiListState.emit(emojiList)
-            Log.d("Fetch_E_L", "USECASE DONE: $emojiList")
-        } catch (e: Exception) {
-            errorController.setErrorState(-1)
-        }
+    override suspend fun updateEmojiList(data: PagingData<Emoji>) {
+        _emojiList.emit(data)
+    }
+    override suspend fun fetchEmojiList(): Flow<PagingData<Emoji>> {
+        return emojiRepository.fetchEmojiList().map { it.map { dto -> Emoji(dto) } }
     }
 
     override suspend fun createEmoji(videoUri: Uri, topK: Int): List<CreatedEmoji> {

android/app/src/main/java/com/goliath/emojihub/viewmodels/EmojiViewModel.kt

@@ -7,6 +7,7 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import androidx.paging.cachedIn
 import com.goliath.emojihub.models.CreatedEmoji
 import com.goliath.emojihub.models.Emoji
 import com.goliath.emojihub.usecases.EmojiUseCase
@@ -28,19 +29,18 @@ class EmojiViewModel @Inject constructor(
     var currentEmoji: Emoji? = null
     var isBottomSheetShown by mutableStateOf(false)
 
-    private val _emojiList = MutableStateFlow<List<Emoji>>(emptyList())
-    val emojiList: StateFlow<List<Emoji>> = _emojiList.asStateFlow()
+    val emojiList = emojiUseCase.emojiList
 
     private val _topK = 3
 
-    fun fetchEmojiList(numInt: Int)
+    fun fetchEmojiList()
     {
         viewModelScope.launch {
-            emojiUseCase.fetchEmojiList(numInt)
-
-            val emojis = emojiUseCase.emojiListState.value.map { dto -> Emoji(dto) }
-            _emojiList.emit(emojis)
-            Log.d("Fetch_E_L", "VIEWMODEL DONE: $emojis")
+            emojiUseCase.fetchEmojiList()
+                .cachedIn(viewModelScope)
+                .collect {
+                    emojiUseCase.updateEmojiList(it)
+                }
         }
     }
 

android/app/src/main/java/com/goliath/emojihub/views/EmojiPage.kt

@@ -34,6 +34,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.sp
 import androidx.core.content.ContextCompat
 import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.paging.compose.collectAsLazyPagingItems
 import com.goliath.emojihub.LocalNavController
 import com.goliath.emojihub.NavigationDestination
 import com.goliath.emojihub.models.createDummyEmoji
@@ -64,13 +65,13 @@ fun EmojiPage(
         }
     }
 
+    val emojiList = viewModel.emojiList.collectAsLazyPagingItems()
+
     LaunchedEffect(Unit)
     {
-        viewModel.fetchEmojiList(10)
+        viewModel.fetchEmojiList()
     }
 
-    val emojiList = viewModel.emojiList.collectAsState().value
-
     Column(Modifier.background(White)) {
         TopNavigationBar("Emoji", shouldNavigate = false) {
             IconButton(onClick = {
@@ -107,10 +108,12 @@ fun EmojiPage(
                 horizontalArrangement = Arrangement.spacedBy(4.dp),
                 verticalArrangement = Arrangement.spacedBy(4.dp),
             ) {
-                items(emojiList, key = { it.id }) { emoji ->
-                    EmojiCell(emoji = emoji) {
-                        viewModel.currentEmoji = emoji
-                        navController.navigate(NavigationDestination.PlayEmojiVideo)
+                items(emojiList.itemCount) { index ->
+                    emojiList[index]?.let{
+                        EmojiCell(emoji = it) { selectedEmoji ->
+                            viewModel.currentEmoji = selectedEmoji
+                            navController.navigate(NavigationDestination.PlayEmojiVideo)
+                        }
                     }
                 }
             }