feat(opds): Allow selecting the download format

When downloading a book via OPDS, the last acquisition link is chosen when there are multiple. This allows choosing which format to download when there are many. Having only one format will automatically download that.

src/activities/browser/OpdsBookBrowserActivity.h

@@ -1,7 +1,6 @@
 #pragma once
 #include <OpdsParser.h>
 
-#include <functional>
 #include <string>
 #include <vector>
 
@@ -14,7 +13,16 @@
  */
 class OpdsBookBrowserActivity final : public Activity {
  public:
-  enum class BrowserState { CHECK_WIFI, WIFI_SELECTION, LOADING, BROWSING, DOWNLOADING, ERROR, SEARCH_INPUT };
+  enum class BrowserState {
+    CHECK_WIFI,
+    WIFI_SELECTION,
+    LOADING,
+    BROWSING,
+    FORMAT_SELECTION,
+    DOWNLOADING,
+    ERROR,
+    SEARCH_INPUT
+  };
 
   explicit OpdsBookBrowserActivity(GfxRenderer& renderer, MappedInputManager& mappedInput)
       : Activity("OpdsBookBrowser", renderer, mappedInput), buttonNavigator() {}
@@ -34,6 +42,9 @@ class OpdsBookBrowserActivity final : public Activity {
   bool consumeConfirm = false;
   bool consumeBack = false;  // Added missing member
   int selectorIndex = 0;
+  int selectedBookIndex = -1;
+  int formatSelectorIndex = 0;
+  std::vector<std::string> formatSelectionLabels;
   std::string errorMessage;
   std::string statusMessage;
   size_t downloadProgress = 0;
@@ -45,7 +56,8 @@ class OpdsBookBrowserActivity final : public Activity {
   void fetchFeed(const std::string& path);
   void navigateToEntry(const OpdsEntry& entry);
   void navigateBack();
-  void downloadBook(const OpdsEntry& book);
+  void downloadBook(const OpdsEntry& book, const OpdsAcquisitionLink& acquisition);
+  void chooseBookFormat(const OpdsEntry& book);
   void fetchOsdTemplate(const std::string& osdUrl);
   void launchSearch();
   void performSearch(const std::string& query);