feat: browse page can search for books

app/src/main/java/com/cmput301f20t21/bookfriends/ui/browse/BrowseFragment.java

@@ -12,14 +12,12 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
-import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.cmput301f20t21.bookfriends.R;
 import com.cmput301f20t21.bookfriends.entities.AvailableBook;
-import com.cmput301f20t21.bookfriends.entities.Book;
 import com.cmput301f20t21.bookfriends.enums.BOOK_ERROR;
 
 import java.util.List;
@@ -33,7 +31,6 @@ public class BrowseFragment extends Fragment {
     private RecyclerView.Adapter adapter;
     private RecyclerView.LayoutManager layoutManager;
     private SearchView searchView;
-    private FragmentManager fragmentManager;
 
     /**
      *
@@ -48,7 +45,6 @@ public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup c
                                  @Nullable Bundle savedInstanceState) {
         vm = new ViewModelProvider(this).get(BrowseViewModel.class);
         setHasOptionsMenu(true);
-        inflateSearchedList();
         View view = inflater.inflate(R.layout.fragment_browse, container, false);
         return view;
     }
@@ -80,8 +76,19 @@ public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
         inflater.inflate(R.menu.browse_search_menu, menu);
         super.onCreateOptionsMenu(menu, inflater);
         searchView = (SearchView) menu.findItem(R.id.book_search_bar).getActionView();
-    }
-    private void inflateSearchedList() {
-        fragmentManager = getChildFragmentManager();
+        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
+            @Override
+            public boolean onQueryTextSubmit(String query) {
+                vm.filterBookWithKeyword(query);
+                return false;
+            }
+
+            @Override
+            public boolean onQueryTextChange(String newText) {
+                vm.filterBookWithKeyword(newText);
+                return false;
+            }
+        });
+
     }
 }

app/src/main/java/com/cmput301f20t21/bookfriends/ui/browse/BrowseViewModel.java

@@ -1,6 +1,8 @@
 package com.cmput301f20t21.bookfriends.ui.browse;
 
 
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MediatorLiveData;
 import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.ViewModel;
 
@@ -15,12 +17,22 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 public class BrowseViewModel extends ViewModel {
+    // exposed live data
+    private final MutableLiveData<BOOK_ERROR> errorMessage = new MutableLiveData<>();
     private final MutableLiveData<List<AvailableBook>> books = new MutableLiveData<>(new ArrayList<>());
-    private MutableLiveData<BOOK_ERROR> errorMessage = new MutableLiveData<>();
+    private final MutableLiveData<String> searchQuery = new MutableLiveData<>(""); // the updated search query we are using
+    // the updated/filtered/calculated book results based on changed books and/or searchQuery
+    private final MediatorLiveData<List<AvailableBook>> searchedBooks = new MediatorLiveData<>();
+
+    // raw book data
     private final List<AvailableBook> bookData = books.getValue();
+    // need this reference to keep adapter referring to the same array in memory or else it won't update
+    private final List<AvailableBook> searchedBookData = new ArrayList<>();
+
     private final IAuthRepository authRepository;
     private final IRequestRepository requestRepository;
     private final IBookRepository bookRepository;
@@ -36,17 +48,67 @@ public BrowseViewModel(IAuthRepository authRepository, IRequestRepository reques
         this.requestRepository = requestRepository;
         this.bookRepository = bookRepository;
 
+        setupSearchedBooks(); // init the searched books before we fetch anything
         fetchBooks();
     }
 
-    public MutableLiveData<List<AvailableBook>> getBooks() {
-        return books;
+    /**
+     * create the searched books live data by making it listens to two source of changes:
+     * 1. the original books list: any changes of the books will trigger it to re-calculate results
+     * 2. the search keyword/query: changes of query should filter the searched books, too
+     */
+    private void setupSearchedBooks() {
+        searchedBooks.setValue(searchedBookData);
+        searchedBooks.addSource(searchQuery, keyword -> setSearchedBooksByKeywordAndBookData(keyword, bookData)); // keyword is new
+        searchedBooks.addSource(books, bookData -> setSearchedBooksByKeywordAndBookData(searchQuery.getValue(), bookData)); // bookData is new (this is a local one!)
+    }
+
+    /**
+     * filter the original bookData (or the updated bookData) with the keyword (or the updated one)
+     * and set that value to searchedBookData and its live data wrapper
+     *
+     * @param keyword
+     * @param bookData
+     */
+    private void setSearchedBooksByKeywordAndBookData(String keyword, List<AvailableBook> bookData) {
+        Function<String, Boolean> contains = ifNotNullAndContains(keyword);
+        List<AvailableBook> newBookData = bookData
+                .stream()
+                .filter(book -> contains.apply(book.getTitle()) ||
+                        contains.apply(book.getAuthor()) ||
+                        contains.apply(book.getOwner()))
+                .collect(Collectors.toList());
+        searchedBookData.clear();
+        searchedBookData.addAll(newBookData);
+        searchedBooks.setValue(searchedBookData);
+    }
+
+    private Function<String, Boolean> ifNotNullAndContains(String keyword) {
+        return (attribute) -> {
+            if (attribute == null || keyword == null) return true;
+            return attribute.contains(keyword);
+        };
+    }
+
+    public LiveData<List<AvailableBook>> getBooks() {
+        return searchedBooks;
     }
 
-    public MutableLiveData<BOOK_ERROR> getErrorMessage() {
+    public LiveData<BOOK_ERROR> getErrorMessage() {
         return errorMessage;
     }
 
+    /**
+     * US 03.01.01
+     * As a borrower, I want to specify a keyword, and search for all books that are not currently accepted or borrowed whose **description** contains the keyword.
+     * NOTE: description here interpreted as all the basic information of the book: title, author, owner
+     *
+     * @param keyword the keyword to search with
+     */
+    public void filterBookWithKeyword(String keyword) {
+        searchQuery.setValue(keyword); // will trigger update routine for searchedBooks
+    }
+
     private void fetchBooks() {
         // get logged in user's username
         String username = authRepository.getCurrentUser().getUsername();