Adds ability to easier find books by first letter

src/main/java/net/knarcraft/bookswithoutborders/BooksWithoutBorders.java

@@ -39,12 +39,16 @@ import org.bukkit.inventory.ItemFactory;
 import org.bukkit.plugin.PluginDescriptionFile;
 import org.bukkit.plugin.PluginManager;
 import org.bukkit.plugin.java.JavaPlugin;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
 import java.util.logging.Level;
 
@@ -61,6 +65,8 @@ public class BooksWithoutBorders extends JavaPlugin {
     private static ItemFactory itemFactory;
     private static Map<UUID, List<String>> playerBooksList;
     private static List<String> publicBooksList;
+    private static Map<Character, Integer> publicLetterIndex;
+    private static Map<UUID, Map<Character, Integer>> playerLetterIndex;
     private static BooksWithoutBorders booksWithoutBorders;
     private static ConsoleCommandSender consoleSender;
 
@@ -88,6 +94,7 @@ public class BooksWithoutBorders extends JavaPlugin {
             if (!playerBooksList.containsKey(playerUUID)) {
                 List<String> newFiles = BookFileHelper.listFiles(sender, false);
                 playerBooksList.put(playerUUID, newFiles);
+                playerLetterIndex.put(playerUUID, BookFileHelper.populateLetterIndices(newFiles));
             }
             return playerBooksList.get(playerUUID);
         } else {
@@ -95,6 +102,22 @@ public class BooksWithoutBorders extends JavaPlugin {
         }
     }
 
+    /**
+     * Gets the letter index map for public books, or a specific player's books
+     *
+     * @param playerIndex <p>The player to get the index for, or null for the public index</p>
+     * @return <p>An index mapping between a character and the first index containing that character</p>
+     */
+    @NotNull
+    public static Map<Character, Integer> getLetterIndex(@Nullable UUID playerIndex) {
+        if (playerIndex == null) {
+            return publicLetterIndex;
+        } else {
+            Map<Character, Integer> letterIndex = playerLetterIndex.get(playerIndex);
+            return Objects.requireNonNullElseGet(letterIndex, HashMap::new);
+        }
+    }
+
     /**
      * Updates available books
      *
@@ -103,10 +126,13 @@ public class BooksWithoutBorders extends JavaPlugin {
      */
     public static void updateBooks(CommandSender sender, boolean updatePublic) {
         List<String> newFiles = BookFileHelper.listFiles(sender, updatePublic);
+        newFiles.sort(Comparator.naturalOrder());
         if (updatePublic) {
             publicBooksList = newFiles;
+            publicLetterIndex = BookFileHelper.populateLetterIndices(newFiles);
         } else if (sender instanceof Player player) {
             playerBooksList.put(player.getUniqueId(), newFiles);
+            playerLetterIndex.put(player.getUniqueId(), BookFileHelper.populateLetterIndices(newFiles));
         }
     }
 
@@ -123,8 +149,10 @@ public class BooksWithoutBorders extends JavaPlugin {
         booksWithoutBorders = this;
         consoleSender = this.getServer().getConsoleSender();
         playerBooksList = new HashMap<>();
+        playerLetterIndex = new HashMap<>();
         BooksWithoutBordersConfig.initialize(this);
         publicBooksList = BookFileHelper.listFiles(consoleSender, true);
+        publicLetterIndex = BookFileHelper.populateLetterIndices(publicBooksList);
 
         PluginManager pluginManager = this.getServer().getPluginManager();
 

src/main/java/net/knarcraft/bookswithoutborders/utility/BookFileHelper.java

@@ -10,11 +10,15 @@ import net.md_5.bungee.api.chat.HoverEvent;
 import net.md_5.bungee.api.chat.TextComponent;
 import net.md_5.bungee.api.chat.hover.content.Text;
 import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
 
 import java.io.File;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.regex.Pattern;
 
@@ -119,11 +123,21 @@ public final class BookFileHelper {
      */
     public static void printBooks(@NotNull CommandSender sender, boolean listPublic, @NotNull String command, int page) {
         List<String> availableBooks = BooksWithoutBorders.getAvailableBooks(sender, listPublic);
+
+        Map<Character, Integer> firstInstances;
+        if (listPublic) {
+            firstInstances = BooksWithoutBorders.getLetterIndex(null);
+        } else if (sender instanceof Player player) {
+            firstInstances = BooksWithoutBorders.getLetterIndex(player.getUniqueId());
+        } else {
+            firstInstances = new HashMap<>();
+        }
+
         int totalPages = (int) Math.ceil((double) availableBooks.size() / booksPerPage);
         if (page > totalPages) {
             sender.sendMessage(ChatColor.GRAY + "No such page");
         } else {
-            showBookMenu(sender, command, page, totalPages, availableBooks);
+            showBookMenu(sender, command, page, totalPages, availableBooks, firstInstances);
         }
     }
 
@@ -135,11 +149,28 @@ public final class BookFileHelper {
      * @param page           <p>The currently selected page</p>
      * @param totalPages     <p>The total amount of pages</p>
      * @param availableBooks <p>All books available to the sender</p>
+     * @param firstInstances <p>The map between a character, and the index of the first instance of that character in the book list</p>
      */
     private static void showBookMenu(@NotNull CommandSender sender, @NotNull String command, int page,
-                                     int totalPages, @NotNull List<String> availableBooks) {
+                                     int totalPages, @NotNull List<String> availableBooks,
+                                     @NotNull Map<Character, Integer> firstInstances) {
         ComponentBuilder headerComponent = new ComponentBuilder();
         headerComponent.append("Books page " + page + " of " + totalPages).color(ChatColor.GREEN);
+
+        // Display links to first page where a letter can be found
+        for (int characterIndex = 0; characterIndex <= 25; characterIndex++) {
+            char character = (char) ('a' + characterIndex);
+            if (firstInstances.containsKey(character)) {
+                int pageIndex = (firstInstances.get(character) / booksPerPage) + 1;
+                headerComponent.append(" ", ComponentBuilder.FormatRetention.NONE).append(character + "").color(
+                        ChatColor.AQUA).event(new ClickEvent(ClickEvent.Action.RUN_COMMAND,
+                        "/" + command + " page" + pageIndex)).event(new HoverEvent(
+                        HoverEvent.Action.SHOW_TEXT, new Text("To page " + pageIndex)));
+            } else {
+                headerComponent.append(" " + character, ComponentBuilder.FormatRetention.NONE).color(ChatColor.GRAY);
+            }
+        }
+
         sender.spigot().sendMessage(headerComponent.create());
 
         // Print the previous page button
@@ -148,26 +179,30 @@ public final class BookFileHelper {
             String fullCommand = "/" + command + " page" + (page - 1);
             HoverEvent prevPagePreview = new HoverEvent(HoverEvent.Action.SHOW_TEXT, new Text("To page " + (page - 1)));
             ClickEvent prevPageClick = new ClickEvent(ClickEvent.Action.RUN_COMMAND, fullCommand);
-            previousComponent.append("Previous [<] " + ChatColor.DARK_GRAY + fullCommand).event(prevPagePreview).event(prevPageClick);
+            previousComponent.append("Previous [<]").event(prevPagePreview).event(prevPageClick).append(" " +
+                    ChatColor.DARK_GRAY + fullCommand, ComponentBuilder.FormatRetention.NONE);
         } else {
             previousComponent.append("Previous [<]").color(ChatColor.GRAY);
         }
         sender.spigot().sendMessage(previousComponent.create());
 
         // Print the main list of all book indexes and titles
-        HoverEvent interactSuggestion = new HoverEvent(HoverEvent.Action.SHOW_TEXT, new Text("Click me"));
         int startIndex = (page - 1) * booksPerPage;
         for (int bookIndex = startIndex; bookIndex < Math.min(startIndex + booksPerPage, availableBooks.size()); bookIndex++) {
             ComponentBuilder bookComponent = new ComponentBuilder();
-            TextComponent indexComponent = new TextComponent("[" + (bookIndex + 1) + "] ");
+            TextComponent indexComponent = new TextComponent("[" + (bookIndex + 1) + "]");
             indexComponent.setColor(ChatColor.GOLD);
             bookComponent.append(indexComponent).event(new ClickEvent(ClickEvent.Action.SUGGEST_COMMAND,
-                    "/" + command + " " + (bookIndex + 1))).event(interactSuggestion);
+                    "/" + command + " " + (bookIndex + 1))).event(new HoverEvent(HoverEvent.Action.SHOW_TEXT,
+                    new Text("Select book by index")));
 
-            TextComponent bookNameComponent = new TextComponent(availableBooks.get(bookIndex));
+            bookComponent.append(" ", ComponentBuilder.FormatRetention.NONE);
+
+            TextComponent bookNameComponent = new TextComponent(getNiceName(availableBooks.get(bookIndex)));
             bookNameComponent.setColor(ChatColor.WHITE);
             bookComponent.append(bookNameComponent).event(new ClickEvent(ClickEvent.Action.SUGGEST_COMMAND,
-                    "/" + command + " " + availableBooks.get(bookIndex))).event(interactSuggestion);
+                    "/" + command + " " + availableBooks.get(bookIndex))).event(
+                    new HoverEvent(HoverEvent.Action.SHOW_TEXT, new Text("Select book by path")));
             sender.spigot().sendMessage(bookComponent.create());
         }
 
@@ -177,13 +212,49 @@ public final class BookFileHelper {
             String fullCommand = "/" + command + " page" + (page + 1);
             HoverEvent nextPagePreview = new HoverEvent(HoverEvent.Action.SHOW_TEXT, new Text("To page " + (page + 1)));
             ClickEvent nextPageClick = new ClickEvent(ClickEvent.Action.RUN_COMMAND, fullCommand);
-            nextComponent.append("Next [>] " + ChatColor.DARK_GRAY + fullCommand).event(nextPagePreview).event(nextPageClick);
+            nextComponent.append("Next [>]").event(nextPagePreview).event(nextPageClick).append(" " +
+                    ChatColor.DARK_GRAY + fullCommand, ComponentBuilder.FormatRetention.NONE);
         } else {
             nextComponent.append("Next [>]").color(ChatColor.GRAY);
         }
         sender.spigot().sendMessage(nextComponent.create());
     }
 
+    /**
+     * Gets a nice name from a book's path
+     *
+     * @param bookPath <p>The path of a book</p>
+     * @return <p>The prettified book name</p>
+     */
+    @NotNull
+    private static String getNiceName(@NotNull String bookPath) {
+        return bookPath.substring(0, bookPath.length() - 4).replace(",", " by ").replace("_", " ");
+    }
+
+    /**
+     * Gets a map between characters, and the first instance of a book's title starting with that character
+     *
+     * @param books <p>The books to look through</p>
+     * @return <p>The map of the first index containing each character</p>
+     */
+    @NotNull
+    public static Map<Character, Integer> populateLetterIndices(@NotNull List<String> books) {
+        List<Character> firstCharacter = new ArrayList<>(books.size());
+        for (String bookIdentifier : books) {
+            firstCharacter.add(bookIdentifier.toLowerCase().charAt(0));
+        }
+
+        Map<Character, Integer> firstEncounter = new HashMap<>();
+        for (int characterIndex = 0; characterIndex <= 25; characterIndex++) {
+            char character = (char) ('a' + characterIndex);
+            int index = Collections.binarySearch(firstCharacter, character);
+            if (index >= 0) {
+                firstEncounter.put(character, index);
+            }
+        }
+        return firstEncounter;
+    }
+
     /**
      * Lists available files
      *