Add Pagination to for Showing Reviews

app/build.gradle.kts

@@ -19,7 +19,7 @@ android {
 
     defaultConfig {
         applicationId = "in.iot.lab.teacherreview"
-        minSdk = 24
+        minSdk = 26
         targetSdk = 34
         versionCode = 1
         versionName = "1.0"
@@ -128,6 +128,10 @@ dependencies {
 
     //Implementing the design module
     implementation(project(":core:design"))
+
+    // Paging 3
+    implementation(libs.paging.runtime)
+    implementation(libs.paging.compose)
 }
 
 fun getBaseUrlInCIEnvironment(): String {

app/src/main/java/in/iot/lab/teacherreview/core/utils/Constants.kt

@@ -18,4 +18,7 @@ object Constants {
     const val LOGIN_AUTHENTICATION_ENDPOINT = "authentication"
     const val TEACHER_LIST_ENDPOINT = "faculties"
     const val POST_TEACHER_REVIEW_ENDPOINT = "reviews"
+
+    const val ITEMS_PER_PAGE = 10
+    const val PREFETCH_DISTANCE = 3
 }

app/src/main/java/in/iot/lab/teacherreview/feature_teacherlist/data/paging_source/ReviewsSource.kt

@@ -0,0 +1,41 @@
+package `in`.iot.lab.teacherreview.feature_teacherlist.data.paging_source
+
+import androidx.paging.PagingSource
+import androidx.paging.PagingState
+import `in`.iot.lab.teacherreview.core.utils.Constants
+import `in`.iot.lab.teacherreview.feature_authentication.domain.repository.AuthRepository
+import `in`.iot.lab.teacherreview.feature_teacherlist.data.remote.ReviewsApi
+import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.IndividualReviewData
+class ReviewsSource (
+    private val facultyId: String,
+    private val authRepository: AuthRepository,
+    private val reviewsApi: ReviewsApi
+) : PagingSource<Int, IndividualReviewData>() {
+    override fun getRefreshKey(state: PagingState<Int, IndividualReviewData>): Int? {
+        return state.anchorPosition
+    }
+
+    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, IndividualReviewData> {
+        return try {
+            val page = params.key ?: 0
+            val skip = page * Constants.ITEMS_PER_PAGE
+
+            val response = reviewsApi.getIndividualTeacherReviews(
+                token = authRepository.getUserIdToken().getOrDefault(""),
+                facultyId = facultyId,
+                limitValue = Constants.ITEMS_PER_PAGE,
+                skip = skip
+            )
+
+            val data = response.body()!!.individualReviewData ?: emptyList()
+
+            LoadResult.Page(
+                data = data,
+                prevKey = if (page == 0) null else page - 1,
+                nextKey = if (data.isEmpty()) null else page + 1
+            )
+        } catch (e: Exception) {
+            LoadResult.Error(e)
+        }
+    }
+}

app/src/main/java/in/iot/lab/teacherreview/feature_teacherlist/data/remote/ReviewsApi.kt

@@ -11,11 +11,13 @@ import retrofit2.http.POST
 import retrofit2.http.Query
 
 interface ReviewsApi {
-    @GET("reviews?${"$"}populate=faculty&${"$"}populate=createdBy")
+    // TODO: expose the sort query parameter as function parameter to make it more flexible
+    @GET("reviews?${"$"}populate=faculty&${"$"}populate=createdBy&${"$"}sort[createdAt]=-1")
     suspend fun getIndividualTeacherReviews(
         @Header("Authorization") token: String,
         @Query("faculty") facultyId: String,
-        @Query("${"$"}limit") limitValue: Int
+        @Query("${"$"}limit") limitValue: Int,
+        @Query("${"$"}skip") skip: Int = 0
     ): Response<ReviewData>
 
 

app/src/main/java/in/iot/lab/teacherreview/feature_teacherlist/data/repository/ReviewRepositoryImpl.kt

@@ -1,11 +1,18 @@
 package `in`.iot.lab.teacherreview.feature_teacherlist.data.repository
 
 import android.util.Log
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import `in`.iot.lab.teacherreview.core.utils.Constants
 import `in`.iot.lab.teacherreview.feature_authentication.domain.repository.AuthRepository
+import `in`.iot.lab.teacherreview.feature_teacherlist.data.paging_source.ReviewsSource
 import `in`.iot.lab.teacherreview.feature_teacherlist.data.remote.ReviewsApi
+import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.IndividualReviewData
 import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.ReviewData
 import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.ReviewPostData
 import `in`.iot.lab.teacherreview.feature_teacherlist.domain.repository.ReviewRepository
+import kotlinx.coroutines.flow.Flow
 import javax.inject.Inject
 
 class ReviewRepositoryImpl @Inject constructor(
@@ -34,36 +41,22 @@ class ReviewRepositoryImpl @Inject constructor(
         }
     }
 
-    override suspend fun getTeacherReviews(facultyId: String, limitValue: Int): Result<ReviewData> {
+    override suspend fun getTeacherReviews(facultyId: String): Result<Flow<PagingData<IndividualReviewData>>> {
         try {
-            val response = reviewsApi.getIndividualTeacherReviews(
-                limitValue = limitValue,
-                facultyId = facultyId,
-                token = getToken()
-            )
-            Log.d(TAG, response.toString())
-            if (!response.isSuccessful) {
-                throw Exception("Error Connecting to the Server")
-            }
-
-            // TODO: Maybe cache the response here
-            val reviewData = response.body()!!
-
-            val sortedReviews = reviewData.individualReviewData?.sortedByDescending {
-                it.createdAt
-            }
-
-            val sortedResponse = ReviewData(
-                avgAttendanceRating = reviewData.avgAttendanceRating,
-                avgMarkingRating = reviewData.avgMarkingRating,
-                avgTeachingRating = reviewData.avgTeachingRating,
-                total = reviewData.total,
-                limit = reviewData.limit,
-                skip = reviewData.skip,
-                individualReviewData = sortedReviews
-            )
+            val pager = Pager(
+                config = PagingConfig(
+                    pageSize = Constants.ITEMS_PER_PAGE,
+                    prefetchDistance = Constants.PREFETCH_DISTANCE,
+                )
+            ) {
+                ReviewsSource(
+                    facultyId = facultyId,
+                    authRepository = authRepository,
+                    reviewsApi = reviewsApi
+                )
+            }.flow
 
-            return Result.success(sortedResponse)
+            return Result.success(pager)
         } catch (e: Exception) {
             e.printStackTrace()
             return Result.failure(e)

app/src/main/java/in/iot/lab/teacherreview/feature_teacherlist/domain/repository/ReviewRepository.kt

@@ -1,11 +1,14 @@
 package `in`.iot.lab.teacherreview.feature_teacherlist.domain.repository
 
+import androidx.paging.PagingData
+import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.IndividualReviewData
 import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.ReviewData
 import `in`.iot.lab.teacherreview.feature_teacherlist.domain.models.remote.ReviewPostData
+import kotlinx.coroutines.flow.Flow
 
 interface ReviewRepository {
     suspend fun postReview(review: ReviewPostData): Result<ReviewPostData>
-    suspend fun getTeacherReviews(facultyId: String, limitValue: Int): Result<ReviewData>
+    suspend fun getTeacherReviews(facultyId: String): Result<Flow<PagingData<IndividualReviewData>>>
     suspend fun getStudentsReviewHistory(studentId: String, limitValue: Int): Result<ReviewData>
 
     // TODO: To be added in the next release (maybe ?)

app/src/main/java/in/iot/lab/teacherreview/feature_teacherlist/ui/navigation/TeacherListNavGraph.kt

@@ -8,6 +8,7 @@ import androidx.navigation.NavHostController
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
+import androidx.paging.compose.collectAsLazyPagingItems
 import `in`.iot.lab.teacherreview.feature_bottom_navigation.navigation.BottomNavRoutes
 import `in`.iot.lab.teacherreview.feature_teacherlist.ui.screen.HomeScreenControl
 import `in`.iot.lab.teacherreview.feature_teacherlist.ui.screen.IndividualTeacherControl
@@ -46,12 +47,14 @@ fun TeacherListNavGraph(
                 TeacherListRoutes.IndividualTeacherRoute.route,
                 content = {
                     val currentUserId by teacherListViewModel.currentUserId.collectAsStateWithLifecycle()
+                    val lazyPagingItems = teacherListViewModel.pagingFlow.collectAsLazyPagingItems()
+
                     IndividualTeacherControl(
                         navController = navController,
                         selectedTeacher = teacherListViewModel.selectedTeacher!!,
-                        action = teacherListViewModel::action,
-                        individualTeacherReviewApiCall = teacherListViewModel.individualTeacherReviewApiCall,
                         currentUserId = currentUserId,
+                        lazyPagingItems = lazyPagingItems,
+                        action = teacherListViewModel::action
                     )
                 }
             )