\version "2.22.2"

#(define (symbol-or-false-or-procedure? x) (or (symbol? x) (not x) (procedure? x)))

% An alist for saving predefined comparator functions. Could just define them and pass a reference, but this way might be a bit cleaner.
#(define orderings
   (list
    (cons 'lex-by-text
          (lambda (item1 item2)
             (let ((mkup1 (assoc-get 'text (cdr item1)))
                   (mkup2 (assoc-get 'text (cdr item2))))
                (string<?
                (markup->string mkup1)
                (markup->string mkup2)))))))

%% Copied from LilyPond's definition and modified
% @param filterfn can be
%	 A) A symbol (filter on label == filterfn)
%	 B) A procedure (filter on (filterfn tocitem))
%	 C) #f (Do not filter)
% @param cmp can be
%	 A) A symbol (use predefined procedure from orderings alist)
%	 B) A procedure (sort using (cmp tocitem1 tocitem2))
%	 C) #f (Do not sort)
#(define-markup-list-command (filtered-ordered-table-of-contents layout props filterfn cmp)
   (symbol-or-false-or-procedure? symbol-or-false-or-procedure?)
   #:properties ((baseline-skip))
   (if (symbol? cmp)
       (set! cmp (assoc-get cmp orderings cmp)))
   (if (symbol? cmp) (ly:error "Predefined ordering ~a does not exist" cmp))
   (let* ((titleMarkup (ly:output-def-lookup layout 'tocTitleMarkup))
          (indentMarkup (ly:output-def-lookup layout 'tocIndentMarkup))
          (toplevelFormatter (ly:output-def-lookup layout 'tocFormatMarkup))
          (toc-alist (toc-items))
          (filtered-toc-alist
           (if filterfn
               (if (symbol? filterfn)
                   (filter
                    (lambda (item) (eq? filterfn (assoc-get 'name (cdr item))))
                    toc-alist)
                   (filter filterfn toc-alist))
               toc-alist))
          (sorted-toc-alist
           (if cmp
               (sort filtered-toc-alist cmp)
               filtered-toc-alist)))

     (ly:output-def-set-variable! layout 'label-alist-table
                                  (append (ly:output-def-lookup layout 'label-alist-table)
                                          toc-alist))
     (cons (interpret-markup layout props titleMarkup)
           (space-lines baseline-skip
                        (map (lambda (toc-item)
                               (let* ((label (car toc-item))
                                      (alist (cdr toc-item))
                                      (toc-markup (assoc-get 'toc-markup alist))
                                      (text (assoc-get 'text alist))
                                      (level (assoc-get 'level alist)))
                                 (interpret-markup
                                  layout
                                  (cons (list
                                         (cons 'toc:page
                                               (markup #:with-link label
                                                       #:page-ref label "XXX" "?"))
                                         (cons 'toc:text (markup #:with-link label text))
                                         (cons 'toc:label label)
                                         (cons 'toc:level level)
                                         (cons 'toc:toplevel-formatter toplevelFormatter)
                                         (cons 'toc:indent
                                               (make-line-markup
                                                (make-list level indentMarkup))))
                                        props)
                                  (ly:output-def-lookup layout toc-markup))))
                             sorted-toc-alist)))))

\markup \fill-line { " " \fontsize #6 "Index by name" " " }
\markuplist \filtered-ordered-table-of-contents #'title #'lex-by-text

\markup \fill-line { " " \fontsize #6 "Index by lyrics" " " }
\markuplist \filtered-ordered-table-of-contents #'first-lyrics #'lex-by-text

\tocItem #'title \markup "Abraham ate an apple"
\tocItem #'first-lyrics \markup "O behold how marvellous"
{ c' }
\pageBreak

\tocItem #'title \markup "Cesar’s chatting computer"
\tocItem #'first-lyrics \markup "All of this works, splendid!"
{ c' }
\pageBreak

\tocItem #'title \markup "Ernest’s eery emu"
\tocItem #'first-lyrics \markup "I do not want to brag, but this is quite a thing!"
{ c' }
\pageBreak

\tocItem #'title \markup "Flying Fools frolicking funnily"
\tocItem #'first-lyrics \markup "How many pieces are there left, exactly?"
{ c' }
\pageBreak

\tocItem #'title \markup "Hernado held his hands high"
\tocItem #'first-lyrics \markup "Really I’m starting to loose inspiration for these lyrics!"
{ c' }
\pageBreak

\tocItem #'title \markup "Good Geese giggling"
\tocItem #'first-lyrics \markup "Three more to go, come on, you can do it!"
{ c' }
\pageBreak

\tocItem #'title \markup "Beethoven broke Bach’s Biathlon-Record"
\tocItem #'first-lyrics \markup "Um ... Row, row, row your boat?"
{ c' }
\pageBreak

\tocItem #'title \markup "Did not expect this, did you?"
\tocItem #'first-lyrics \markup "I’m so glad I’m FINALLY done with this ..."
{ c' }