refactor: unify book cache clearing for epub, txt, and xtc files (#1875)

src/util/BookCacheUtils.cpp

@@ -0,0 +1,34 @@
+#include "BookCacheUtils.h"
+
+#include <Epub.h>
+#include <FsHelpers.h>
+#include <Logging.h>
+#include <Txt.h>
+#include <Xtc.h>
+
+bool isBookCacheDirectoryName(const char* name) {
+  if (!name) {
+    return false;
+  }
+
+  constexpr char EPUB_PREFIX[] = "epub_";
+  constexpr char TXT_PREFIX[] = "txt_";
+  constexpr char XTC_PREFIX[] = "xtc_";
+
+  return strncmp(name, EPUB_PREFIX, std::size(EPUB_PREFIX) - 1) == 0 ||
+         strncmp(name, TXT_PREFIX, std::size(TXT_PREFIX) - 1) == 0 ||
+         strncmp(name, XTC_PREFIX, std::size(XTC_PREFIX) - 1) == 0;
+}
+
+void clearBookCache(const std::string& path) {
+  if (FsHelpers::hasEpubExtension(path)) {
+    Epub(path, "/.crosspoint").clearCache();
+  } else if (FsHelpers::hasXtcExtension(path)) {
+    Xtc(path, "/.crosspoint").clearCache();
+  } else if (FsHelpers::hasTxtExtension(path)) {
+    Txt(path, "/.crosspoint").clearCache();
+  } else {
+    return;
+  }
+  LOG_DBG("BookCache", "Done checking metadata cache for: %s", path.c_str());
+}

src/util/BookCacheUtils.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <string>
+
+// Clears the reading cache for a book file if its extension is recognised
+// (EPUB, XTC, or TXT). Does nothing for other file types.
+void clearBookCache(const std::string& path);
+
+// Returns true if the directory name matches a book cache entry.
+bool isBookCacheDirectoryName(const char* name);