Introduced an endless suggestion list in search.

* With the integration of libkiwix12, we now receive full results based on the search term. Previously, we were loading the entire list, but we have now implemented pagination to enhance the search functionality.
* The libkiwix provides us with a Search object, which enables us to obtain the suggestion list using start and end indices. Consequently, we have modified our `ZimSearchResultGenerator` code to return the `Search` object instead of a list.
* To accommodate the changes, we have updated the return type of `SearchResultGenerator` to a nullable Search. This change is necessary because we initialize the `SearchState` when the search is initialized in `SearchViewModel`, and initially, we do not have the Search object available. The nullable return type allows us to pass the Search object when it becomes available.

core/detekt_baseline.xml

@@ -18,6 +18,7 @@
     <ID>MagicNumber:ArticleCount.kt$ArticleCount$3</ID>
     <ID>MagicNumber:CompatFindActionModeCallback.kt$CompatFindActionModeCallback$100</ID>
     <ID>MagicNumber:DownloadItem.kt$DownloadItem$1000L</ID>
+    <ID>MagicNumber:SearchState.kt$SearchState$100</ID>
     <ID>MagicNumber:DownloaderModule.kt$DownloaderModule$5</ID>
     <ID>MagicNumber:FetchDownloadNotificationManager.kt$FetchDownloadNotificationManager$100</ID>
     <ID>MagicNumber:FetchDownloadRequester.kt$10</ID>

core/src/main/java/org/kiwix/kiwixmobile/core/base/adapter/BaseDelegateAdapter.kt

@@ -37,6 +37,13 @@ abstract class BaseDelegateAdapter<ITEM>(
       notifyDataSetChanged()
     }
 
+  // Function to add new data to the adapter
+  fun addData(newData: List<ITEM>) {
+    val startPosition = items.size
+    items = items.toMutableList().apply { addAll(newData) }
+    notifyItemRangeInserted(startPosition, newData.size)
+  }
+
   override fun onCreateViewHolder(
     parent: ViewGroup,
     viewType: Int

core/src/main/java/org/kiwix/kiwixmobile/core/reader/ZimFileReader.kt

@@ -32,7 +32,6 @@ import org.kiwix.kiwixmobile.core.entity.LibraryNetworkEntity.Book
 import org.kiwix.kiwixmobile.core.main.UNINITIALISER_ADDRESS
 import org.kiwix.kiwixmobile.core.main.UNINITIALISE_HTML
 import org.kiwix.kiwixmobile.core.reader.ZimFileReader.Companion.CONTENT_PREFIX
-import org.kiwix.kiwixmobile.core.search.adapter.SearchListItem.ZimSearchResultListItem
 import org.kiwix.kiwixmobile.core.utils.files.FileUtils
 import org.kiwix.libkiwix.JNIKiwixException
 import org.kiwix.libzim.Archive
@@ -143,19 +142,6 @@ class ZimFileReader constructor(
       null
     }
 
-  fun getSearchResultList(search: Search?): List<ZimSearchResultListItem> {
-    val suggestionList = mutableListOf<ZimSearchResultListItem>()
-    val suggestionIterator =
-      search?.getResults(0, search.estimatedMatches.toInt())
-    suggestionIterator?.let {
-      while (it.hasNext()) {
-        val entry = it.next()
-        suggestionList.add(ZimSearchResultListItem(entry.title))
-      }
-    }
-    return suggestionList
-  }
-
   fun getPageUrlFrom(title: String): String? =
     if (jniKiwixReader.hasEntryByTitle(title))
       jniKiwixReader.getEntryByTitle(title).path

core/src/main/java/org/kiwix/kiwixmobile/core/search/SearchFragment.kt

@@ -65,6 +65,7 @@ import org.kiwix.kiwixmobile.core.utils.SimpleTextListener
 import javax.inject.Inject
 
 const val NAV_ARG_SEARCH_STRING = "searchString"
+const val LAST_VISIBLE_ITEM = 5
 
 class SearchFragment : BaseFragment() {
 
@@ -76,6 +77,8 @@ class SearchFragment : BaseFragment() {
 
   private val searchViewModel by lazy { viewModel<SearchViewModel>(viewModelFactory) }
   private var searchAdapter: SearchAdapter? = null
+  private var isLoading = false
+  private var searchState: SearchState? = null
 
   override fun inject(baseActivity: BaseActivity) {
     baseActivity.cachedComponent.inject(this)
@@ -104,6 +107,22 @@ class SearchFragment : BaseFragment() {
       adapter = searchAdapter
       layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)
       setHasFixedSize(true)
+      // Add scroll listener to detect when the last item is reached
+      addOnScrollListener(object : RecyclerView.OnScrollListener() {
+        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
+          super.onScrolled(recyclerView, dx, dy)
+
+          val layoutManager = recyclerView.layoutManager as LinearLayoutManager
+          val totalItemCount = layoutManager.itemCount
+          val lastVisibleItem = layoutManager.findLastVisibleItemPosition()
+
+          // Check if the user is about to reach the last item
+          if (!isLoading && totalItemCount <= (lastVisibleItem + LAST_VISIBLE_ITEM)) {
+            // Load more data when the last item is almost visible
+            loadMoreSearchResult()
+          }
+        }
+      })
     }
     lifecycleScope.launchWhenCreated {
       searchViewModel.effects.collect { it.invokeWith(this@SearchFragment.coreMainActivity) }
@@ -111,6 +130,27 @@ class SearchFragment : BaseFragment() {
     handleBackPress()
   }
 
+  private fun loadMoreSearchResult() {
+    if (isLoading) {
+      return
+    }
+    val startIndex = searchAdapter?.itemCount ?: 0
+    // Set isLoading flag to true to prevent multiple load requests at once
+    isLoading = true
+    val fetchMoreSearchResults = searchState?.getVisibleResults(startIndex)
+    if (fetchMoreSearchResults?.isNotEmpty() == true) {
+      // Check if there is no duplicate entry, this is specially added for searched history items.
+      val nonDuplicateResults = fetchMoreSearchResults.filter { newItem ->
+        searchAdapter?.items?.any { it != newItem } == true
+      }
+
+      // Append new data (non-duplicate items) to the existing dataset
+      searchAdapter?.addData(nonDuplicateResults)
+
+      isLoading = false // Set isLoading to false when data is loaded successfully
+    }
+  }
+
   private fun handleBackPress() {
     activity?.onBackPressedDispatcher?.addCallback(
       viewLifecycleOwner,
@@ -136,6 +176,7 @@ class SearchFragment : BaseFragment() {
 
   override fun onDestroyView() {
     super.onDestroyView()
+    searchState = null
     activity?.intent?.action = null
     searchView = null
     searchInTextMenuItem = null
@@ -194,11 +235,13 @@ class SearchFragment : BaseFragment() {
   }
 
   private fun render(state: SearchState) {
+    searchState = state
     searchInTextMenuItem?.isVisible = state.searchOrigin == FromWebView
     searchInTextMenuItem?.isEnabled = state.searchTerm.isNotBlank()
     fragmentSearchBinding?.searchLoadingIndicator?.isShowing(state.isLoading)
-    fragmentSearchBinding?.searchNoResults?.isVisible = state.visibleResults.isEmpty()
-    searchAdapter?.items = state.visibleResults
+    fragmentSearchBinding?.searchNoResults?.isVisible =
+      state.getVisibleResults(0).isEmpty()
+    searchAdapter?.items = state.getVisibleResults(0)
   }
 
   private fun onItemClick(it: SearchListItem) {

core/src/main/java/org/kiwix/kiwixmobile/core/search/viewmodel/SearchResultGenerator.kt

@@ -22,14 +22,14 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import kotlinx.coroutines.yield
 import org.kiwix.kiwixmobile.core.reader.ZimFileReader
-import org.kiwix.kiwixmobile.core.search.adapter.SearchListItem
+import org.kiwix.libzim.Search
 import javax.inject.Inject
 
 interface SearchResultGenerator {
   suspend fun generateSearchResults(
     searchTerm: String,
     zimFileReader: ZimFileReader?
-  ): List<SearchListItem>
+  ): Search?
 }
 
 class ZimSearchResultGenerator @Inject constructor() : SearchResultGenerator {
@@ -37,7 +37,7 @@ class ZimSearchResultGenerator @Inject constructor() : SearchResultGenerator {
   override suspend fun generateSearchResults(searchTerm: String, zimFileReader: ZimFileReader?) =
     withContext(Dispatchers.IO) {
       if (searchTerm.isNotEmpty()) readResultsFromZim(searchTerm, zimFileReader)
-      else emptyList()
+      else null
     }
 
   private suspend fun readResultsFromZim(
@@ -46,8 +46,4 @@ class ZimSearchResultGenerator @Inject constructor() : SearchResultGenerator {
   ) =
     reader.also { yield() }
       ?.searchSuggestions(searchTerm)
-      .also { yield() }
-      .run {
-        reader?.getSearchResultList(this) ?: emptyList()
-      }
 }

core/src/main/java/org/kiwix/kiwixmobile/core/search/viewmodel/SearchState.kt

@@ -26,9 +26,25 @@ data class SearchState(
   val recentResults: List<SearchListItem.RecentSearchListItem>,
   val searchOrigin: SearchOrigin
 ) {
-  val visibleResults = when {
-    searchTerm.isNotEmpty() -> searchResultsWithTerm.results
-    else -> recentResults
+  fun getVisibleResults(startIndex: Int): List<SearchListItem.RecentSearchListItem> =
+    if (searchTerm.isEmpty()) {
+      recentResults
+    } else {
+      searchResultsWithTerm.search?.let {
+        val maximumResults = it.estimatedMatches
+        val safeEndIndex =
+          if ((startIndex + 100) < maximumResults) startIndex + 100 else maximumResults
+        val searchIterator =
+          it.getResults(startIndex, safeEndIndex.toInt())
+        val searchResults = mutableListOf<SearchListItem.RecentSearchListItem>()
+        while (searchIterator.hasNext()) {
+          val entry = searchIterator.next()
+          searchResults.add(SearchListItem.RecentSearchListItem(entry.title))
+        }
+        searchResults
+      } ?: kotlin.run {
+        recentResults
+      }
     }
 
   val isLoading = searchTerm != searchResultsWithTerm.searchTerm

core/src/main/java/org/kiwix/kiwixmobile/core/search/viewmodel/SearchViewModel.kt

@@ -59,6 +59,7 @@ import org.kiwix.kiwixmobile.core.search.viewmodel.effects.SearchInPreviousScree
 import org.kiwix.kiwixmobile.core.search.viewmodel.effects.ShowDeleteSearchDialog
 import org.kiwix.kiwixmobile.core.search.viewmodel.effects.ShowToast
 import org.kiwix.kiwixmobile.core.search.viewmodel.effects.StartSpeechInput
+import org.kiwix.libzim.Search
 import javax.inject.Inject
 
 @OptIn(ExperimentalCoroutinesApi::class)
@@ -69,7 +70,15 @@ class SearchViewModel @Inject constructor(
 ) : ViewModel() {
 
   private val initialState: SearchState =
-    SearchState("", SearchResultsWithTerm("", emptyList()), emptyList(), FromWebView)
+    SearchState(
+      "",
+      SearchResultsWithTerm(
+        "",
+        null
+      ),
+      emptyList(),
+      FromWebView
+    )
   val state: MutableStateFlow<SearchState> = MutableStateFlow(initialState)
   private val _effects = Channel<SideEffect<*>>()
   val effects = _effects.receiveAsFlow()
@@ -165,4 +174,4 @@ class SearchViewModel @Inject constructor(
   }
 }
 
-data class SearchResultsWithTerm(val searchTerm: String, val results: List<SearchListItem>)
+data class SearchResultsWithTerm(val searchTerm: String, val search: Search?)

core/src/test/java/org/kiwix/kiwixmobile/core/search/viewmodel/SearchStateTest.kt

@@ -35,7 +35,7 @@ internal class SearchStateTest {
         SearchResultsWithTerm("", results),
         emptyList(),
         FromWebView
-      ).visibleResults
+      ).getVisibleResults(0)
     ).isEqualTo(results)
   }
 
@@ -48,7 +48,7 @@ internal class SearchStateTest {
         SearchResultsWithTerm("", emptyList()),
         results,
         FromWebView
-      ).visibleResults
+      ).getVisibleResults(0)
     ).isEqualTo(results)
   }