% Utilities for conventional input with scordablature output.

% reset the output scale (may be needed with lilypond-book)
majorScale = #'#(0 1 2 5/2 7/2 9/2 11/2)
#(ly:set-default-scale (ly:make-scale majorScale))

% The magic function that converts a standard pitch
% to a scordablature pitch.
% Number of steps to the octave = ET.
% Middle C is set to MIDI pitch midc
#(define (scorda-pitch ET midc p)
  (let* ((reg (ly:pitch-octave p))
         (semitones (+ (* 12 reg) (* 2 (+
            (vector-ref majorScale (modulo (ly:pitch-steps p) 7))
            (ly:pitch-alteration p)))))
         (diatonic-degree (ly:pitch-steps p))
         (scorda-steps (+ (- midc 60)
                          (* semitones (semitone-size ET))
                          (* diatonic-degree (diesis-size ET))))
         (scorda-reg (inexact->exact (floor (/ scorda-steps 12))))
         (scorda-semis (- scorda-steps (* 12 scorda-reg)))
         (defaultDiatonicDegrees '#(0 0 1 2 2 3 3 4 4 5 6 6))
         (scorda-degree (vector-ref defaultDiatonicDegrees 
             (round scorda-semis)))
         (alteration (- (/ scorda-semis 2)
                        (vector-ref majorScale scorda-degree)))
        )
      (ly:make-pitch scorda-reg scorda-degree alteration)))

% Finds the best size of fifth in the equal temperement with
% the given number of fifths to the octave.
% Note: different to the function in regular.ly as it returns the size
% of tempered scale steps
#(define (best-fifth ET)
    (inexact->exact (round (* ET 0.5849625007))))

% Finds the size of chromatic semitones for the given equal temperament
#(define (semitone-size ET)
    (- (* 7 (best-fifth ET)) (* 4 ET)))

% Finds the size of enharmonic dieses for the given equal temperament
#(define (diesis-size ET)
    (- (* 7 ET) (* 12 (best-fifth ET))))

% Convert all notes.
% This is copied from "Transposing music with minimum accidentals"
% In the "Pitches" snippets in the documentation.
% Transposed so middle C comes out as pitch midc
#(define (scordablarize ET midc music)
  (let* ((es (ly:music-property music 'elements))
         (e (ly:music-property music 'element))
         (p (ly:music-property music 'pitch)))
    (if (pair? es)
       (ly:music-set-property!
         music 'elements
         (map (lambda (x) (scordablarize ET midc x)) es)))
    (if (ly:music? e)
       (ly:music-set-property!
         music 'element
         (scordablarize ET midc e)))
    (if (ly:pitch? p)
       (begin
         (set! p (scorda-pitch ET midc p))
         (ly:music-set-property! music 'pitch p)))
    music))

absoluteRetune = #(define-music-function (parser location ET m)
  (integer? ly:music?)
  (scordablarize ET 70 m))

% Music expression to give middle C without note names defined:
midc = #(make-music 'EventChord
    'elements (list
        (make-music 'NoteEvent
            'duration (ly:make-duration 1 0)
            'pitch (ly:make-pitch 0 0 0))))

% Apply scordablature so that middle C becomes MIDI pitch midc
retune = #(define-music-function (parser location ET midc m)
  (integer? integer? ly:music?)
  (scordablarize ET midc m))