#(define-markup-command (print-songinfo layout props) ()
  (define (songinfo-from songId key)
    (let ((song (if (defined? 'SONG_DATA) (assoc-ref SONG_DATA songId) #f)))
      (if song
        (assoc-ref song key)
        (ly:warning (ly:format "song with id ~a not found" songId)))))

  (define (format-author authorId noDetails)
    (let ((author (if (defined? 'AUTHOR_DATA) (assoc-ref AUTHOR_DATA authorId) #f)))
      (if author
        ((ly:output-def-lookup layout 'authorFormat)
          noDetails
          (assoc-ref author "name")
          (assoc-ref author "trail_name")
          (assoc-ref author "birth_year")
          (assoc-ref author "death_year")
          (assoc-ref author "organization")
        )
        "unbekannt")))

  (define (format-poet poetId)
    (string-append (ly:output-def-lookup layout 'poetPrefix) " " (format-author poetId #f)))

  (define (format-composer composerId)
    (string-append (ly:output-def-lookup layout 'composerPrefix) " " (format-author composerId #f)))

  (define (format-poet-and-composer authorId)
    (string-append (ly:output-def-lookup layout 'poetAndComposerEqualPrefix) " " (format-author authorId #f)))

  (define (find-author-ids-by contributionType authors)
    (filter-map (lambda (authordata) (if (member contributionType (cdr authordata)) (car authordata) #f)) authors)
  )

  (define (find-author-id-with-part-numbers contributionType authors)
    (filter-map (lambda (authordata)
      (let ((contributionNumbers (filter-map (lambda (contribution) (if (and (list? contribution) (equal? contributionType (car contribution))) (cadr contribution) #f)) (cdr authordata)))
            (authorId (car authordata)))
        (if (null? contributionNumbers) #f (cons authorId contributionNumbers))
      )) authors)
  )

  (define (render-contribution-numbers contributionNumbers)
    (string-join (map (lambda (contributionNumber) (ly:format "~a." contributionNumber)) contributionNumbers) ", ")
  )
  (define (render-verse-contribution contributionNumbers)
    (string-append (render-contribution-numbers contributionNumbers) " Strophe: ")
  )

  (define (render-voice-contribution contributionNumbers)
    (string-append (render-contribution-numbers contributionNumbers) " Stimme: ")
  )

  (define (poet-and-composer-from-authors authors)
    (if authors
      (let* (
            (poetIds (find-author-ids-by 'text authors))
            (versePoetData (find-author-id-with-part-numbers 'verse authors))
            (allPoetIds (append poetIds (map car versePoetData)))
            (composerIds (find-author-ids-by 'melody authors))
            (compositionIds (find-author-ids-by 'composition authors))
            (voiceComposerData (find-author-id-with-part-numbers 'voice authors))
            (poets (append
              (map (lambda (poetId) (format-author poetId #f)) poetIds)
              (map (lambda (versePoetEntry) (string-append (render-verse-contribution (cdr versePoetEntry)) (format-author (car versePoetEntry) (member (car versePoetEntry) poetIds)))) versePoetData)
              ))
            (composers (append
              (map (lambda (composerId) (format-author composerId (member composerId allPoetIds))) composerIds)
              (map (lambda (composerId) (string-append (ly:output-def-lookup layout 'compositionPrefix) " " (format-author composerId (member composerId allPoetIds)))) compositionIds)
              (map (lambda (voiceComposerEntry) (string-append (render-voice-contribution (cdr voiceComposerEntry)) (format-author (car voiceComposerEntry) (member (car voiceComposerEntry) allPoetIds)))) voiceComposerData)
              )))
        (if (and (equal? poetIds composerIds) (null? versePoetData) (null? voiceComposerData) (null? compositionIds))
          (list (string-append (ly:output-def-lookup layout 'poetAndComposerEqualPrefix) " " (string-join poets ", ")) #f)
          (list
            (string-append (ly:output-def-lookup layout 'poetPrefix) " " (string-join poets ", "))
            (string-append (ly:output-def-lookup layout 'composerPrefix) " " (string-join composers ", ")))))
      (list #f #f)
    )
  )

  (interpret-markup layout props
    (if (chain-assoc-get 'page:is-bookpart-last-page props #f)
    (let* ((authors (chain-assoc-get 'header:authors props #f))
           (poet-and-composers (poet-and-composer-from-authors authors))
           (songId (chain-assoc-get 'header:songId props #f))
           (poetId (chain-assoc-get 'header:poetId props (if songId (songinfo-from songId "poet") #f)))
           (composerId (chain-assoc-get 'header:composerId props (if songId (songinfo-from songId "composer") #f)))
           (poet-and-composer-same (equal? poetId composerId)))
      (let ((infotext (chain-assoc-get 'header:infotext props (chain-assoc-get 'header:songinfo props #f)))
            (poet-maybe-with-composer (chain-assoc-get 'header:poet props (if poetId (if poet-and-composer-same (format-poet-and-composer poetId) (format-poet poetId)) (car poet-and-composers))))
            (composer (chain-assoc-get 'header:composer props (if (and composerId (not poet-and-composer-same)) (format-composer composerId) (cadr poet-and-composers))))
            (copyright (chain-assoc-get 'header:copyright props #f))
            (translation (chain-assoc-get 'header:translation props #f))
            (pronunciation (chain-assoc-get 'header:pronunciation props #f))
            (year_text (chain-assoc-get 'header:year_text props #f))
            (year_melody (chain-assoc-get 'header:year_melody props #f)))
            (markup
              #:override (cons 'songinfo:poet-maybe-with-composer
                (if (and poet-maybe-with-composer (not (and (string? poet-maybe-with-composer) (string-null? poet-maybe-with-composer)))) poet-maybe-with-composer #f))
              #:override (cons 'songinfo:composer
                (if (and composer (not (and (string? composer) (string-null? composer)))) composer #f))
              #:override (cons 'songinfo:copyright
                (if (and copyright (not (and (string? copyright) (string-null? copyright)))) copyright #f))
              #:override (cons 'songinfo:infotext
                (if (and infotext (not (and (string? infotext) (string-null? infotext)))) infotext #f))
              #:override (cons 'songinfo:translation
                (if (and translation (not (and (string? translation) (string-null? translation)))) translation #f))
              #:override (cons 'songinfo:pronunciation
                (if (and pronunciation (not (and (string? pronunciation) (string-null? pronunciation)))) pronunciation #f))
              #:override (cons 'songinfo:year_text
                (if (and year_text (not (and (string? year_text) (string-null? year_text)))) year_text #f))
              #:override (cons 'songinfo:year_melody
                (if (and year_melody (not (and (string? year_melody) (string-null? year_melody)))) year_melody #f))
              #:override '(baseline-skip . 3.0)
              #:fontsize songInfoFontSize
              #:sans
              (ly:output-def-lookup layout 'songinfoMarkup)
            )))
      (make-null-markup)))
)

#(define-markup-command (print-pagenumber layout props)()
  (let ((label (chain-assoc-get 'header:myindexlabel props #f)))
   (interpret-markup layout props
     (markup #:large #:bold
        (if label
         (make-custom-page-number-markup label (chain-assoc-get 'page:page-number props 0))
         (make-fromproperty-markup 'page:page-number-string)
        )
   ))))

#(define-markup-command (fractional-line-width layout props arg)(markup?)
  (interpret-markup layout props
    (make-override-markup
      `(line-width . ,(* (chain-assoc-get 'header:songinfo-size-factor props 0.9) (ly:output-def-lookup layout 'line-width)))
      arg)))

\paper {
  print-first-page-number = ##t
  first-page-number = #0

  oddFooterMarkup = \markup {
    \fill-line {
      \line { \null }
      \line { \general-align #Y #DOWN \fractional-line-width \print-songinfo }
      \line { \if \should-print-page-number \print-pagenumber }
    }
  }
  evenFooterMarkup  = \markup {
    \fill-line {
      \line { \if \should-print-page-number \print-pagenumber }
      \line { \general-align #Y #DOWN \fractional-line-width \print-songinfo }
      \line { \null }
    }
  }
}