#(use-modules (ice-9 receive))
#(define (format-author layout 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 (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-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-poet poetId)
    (string-append (ly:output-def-lookup layout 'poetPrefix) " " (format-author layout poetId #f)))

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

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

  (define (numbered-contribution-prefix contributionNumbers prefixLookup)
    (string-append
      (string-join (map (lambda (contributionNumber) (ly:format "~a." contributionNumber)) contributionNumbers) ", ")
      " "
      (ly:output-def-lookup layout prefixLookup)
    )
  )

  (define referencedAuthors '())

  (define (format-authors authorIds)
    (map (lambda (authorId)
      (format-author
        layout
        authorId
        (if (member authorId referencedAuthors)
          #t
          (begin
            (set! referencedAuthors (cons authorId referencedAuthors))
            #f)))
    ) authorIds)
  )

  (define (render-contribution-group contributionPrefix authorIds)
    (if (null? authorIds)
      ""
      (string-append contributionPrefix " " (string-join (format-authors authorIds) ", ")))
  )

  (define (render-partial-contribution-group prefixLookup authorData)
    (if (null? authorData)
      ""
      (let ((firstAuthorContributions (cdar authorData)))
        (receive (authorDataSame authorDataOther)
            (partition (lambda (authorEntry) (equal? (cdr authorEntry) firstAuthorContributions)) authorData)
          (string-append
            (render-contribution-group (numbered-contribution-prefix firstAuthorContributions prefixLookup) (map car authorDataSame))
            " "
            (render-partial-contribution-group prefixLookup authorDataOther)
          ))))
  )

  (define (join-present items joiner)
    (string-join (filter (lambda (item) (and (string? item) (not (string-null? (string-trim-both item))))) items) joiner)
  )

  (define (poet-and-composer-from-authors authors)
    (if authors
      (let (
            (poetIds (find-author-ids-by 'text authors))
            (translatorIds (find-author-ids-by 'translation authors))
            (versePoetData (find-author-id-with-part-numbers 'verse authors))
            (composerIds (find-author-ids-by 'melody authors))
            (verseComposerData (find-author-id-with-part-numbers 'meloverse authors))
            (voiceComposerData (find-author-id-with-part-numbers 'voice authors))
            (compositionIds (find-author-ids-by 'composition authors))
            (bridgeIds (find-author-ids-by 'bridge authors))
            (interludeIds (find-author-ids-by 'interlude authors))
            (year_text (chain-assoc-get 'header:year_text props #f))
            (year_translation (chain-assoc-get 'header:year_translation props #f))
            (year_melody (chain-assoc-get 'header:year_melody props #f))
            (year_composition (chain-assoc-get 'header:year_composition props #f))
            )
        (if (and (equal? poetIds composerIds) (null? translatorIds) (null? versePoetData) (null? verseComposerData) (null? voiceComposerData) (null? compositionIds) (null? bridgeIds) (null? interludeIds))
          (list
            (join-present (list
              (render-contribution-group (ly:output-def-lookup layout 'poetAndComposerEqualPrefix) poetIds)
              (if (equal? year_text year_melody) year_text (join-present (list year_text year_melody) "/"))
            ) ", ")
            #f)
          (list
            (if (and (null? poetIds) (null? versePoetData) (null? translatorIds)) #f
              (string-append
                (ly:output-def-lookup layout 'poetPrefix)
                " "
                (join-present (list
                  (join-present (list
                    (render-contribution-group "" poetIds)
                    year_text
                  ) ", ")
                  (render-partial-contribution-group 'versePrefix versePoetData)
                  (join-present (list
                    (render-contribution-group (ly:output-def-lookup layout 'translationPrefix) translatorIds)
                    year_translation
                  ) ", ")
                ) "; ")
              ))
            (if (and (null? composerIds) (null? compositionIds) (null? verseComposerData) (null? voiceComposerData) (null? bridgeIds) (null? interludeIds)) #f
              (string-append
                (ly:output-def-lookup layout 'composerPrefix)
                " "
                (join-present (list
                  (join-present (list
                    (render-contribution-group "" composerIds)
                    year_melody
                  ) ", ")
                  (render-partial-contribution-group 'versePrefix verseComposerData)
                  (render-partial-contribution-group 'voicePrefix voiceComposerData)
                  (join-present (list
                    (render-contribution-group (ly:output-def-lookup layout 'compositionPrefix) compositionIds)
                    year_composition
                  ) ", ")
                  (render-contribution-group (ly:output-def-lookup layout 'bridgePrefix) bridgeIds)
                  (render-contribution-group (ly:output-def-lookup layout 'interludePrefix) interludeIds)
                ) "; ")
              )))))
      (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 (if (string? (car poet-and-composers)) #f (chain-assoc-get 'header:year_text props #f)))
            (year_melody (if (string? (car poet-and-composers)) #f (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 songInfoLineWidthFraction) (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 }
    }
  }
}