static IResourceLoader resourceLoaderFromJar(File mainJar, File unpackDir) {
  print("Unpacking to: " + unpackDir);
  
  SS titles = cast safeUnstructure(loadTextFileFromZip(mainJar, "snippet-titles.struct"));
  assertNempty("Snippet titles", titles);
  Map<S, Int> types = cast safeUnstructure(loadTextFileFromZip(mainJar, "snippet-types.struct"));

  ret new IResourceLoader {
    public S loadSnippet(S snippetID) {
      ret loadTextFileFromZip(mainJar, psI(snippetID) + ".text");
    }
    
    public S getTranspiled(S snippetID) {
      S src = loadTextFileFromZip(mainJar, psI(snippetID) + ".transpiled");
      if (empty(src))
        print("Warning: Transpilation for " + snippetID + " not found");
      ret src;
    }
    
    public int getSnippetType(S snippetID) {
      ret or0(types.get(fsI(snippetID)));
    }
    
    public S getSnippetTitle(S snippetID) {
      ret titles.get(fsI(snippetID));
    }
    
    public File loadLibrary(S snippetID) {
      long id = psI(snippetID);
      ret optExtractFileFromZipToDir(mainJar, unpackDir, id +
        (isImageServerSnippet(id) ? ".png" : ".bin"));
    }
    
    public File pathToJavaXJar() {
      ret mainJar;
    }
    
    public File getSnippetJar(S snippetID, S transpiledSrc) {
      null; // just compile through CompilerBot
    }
  };
}