#lang racket

(require "rsound.rkt"
         "fft.rkt"
         racket/flonum
         ffi/vector
         racket/unsafe/ops)

(define twopi (* 2 pi))

(define s16max #x7fff)

(define common-sample-rate 44100)

(provide twopi 
         s16max
         sine-wave
         sawtooth-wave
         approx-sawtooth-wave
         square-wave
         harm3-wave
         ;; envelope-funs
         fader
         frisellinator
         ;; special signals
         dc-signal
         ;; signal combiners
         signal-*s
         signal-+s
         signal?
         rsound->signal/left
         rsound->signal/right
         ;; rsound makers
         make-tone
         make-squaretone
         make-sawtooth-tone
         make-zugtone
         make-harm3tone
         wavefun->tone-maker
         ding
         make-ding
         split-in-4
         times
         vectors->rsound
         fir-filter
         echo1
         rsound-fft/left
         rsound-fft/right
         rsound-max-volume
         signal
         midi-note-num->pitch
         ;; for testing:
         raw-sine-wave
         raw-square-wave
         raw-sawtooth-wave
         binary-logn
         )



;; given a length and a function, build the corresponding flvector
(define (build-flvector len fun)
  (let ([newvec (make-flvector len)])
    (for ([i (in-range len)])
      (flvector-set! newvec i (exact->inexact (fun i))))
    newvec))

(define (build-wavetable fun)
  (build-flvector common-sample-rate (fun 1 common-sample-rate)))

;; given a wavetable, make a wavetable lookup function
(define ((make-table-based-wavefun vec) pitch sample-rate)
  (let ([exact-pitch (inexact->exact pitch)])
    (lambda (i)
      (flvector-ref vec (modulo (* i exact-pitch) common-sample-rate)))))


;; given a raw function, produce a table-based version of it
;; (nat nat -> (nat -> fl)) -> (nat nat -> (nat -> fl))
(define (make-checked-wave-fun raw-wave-fun)
  (let* ([table (build-wavetable raw-wave-fun)]
         [table-based-fun (make-table-based-wavefun table)])
    (lambda (pitch sample-rate) 
      (when (= 0 pitch)
        (raise-type-error 'wave-fun "nonzero number" 0 pitch sample-rate))
      (when (= 0 sample-rate)
        (raise-type-error 'wave-fun "nonzero number" 1 pitch sample-rate))
      (cond [(and (= sample-rate common-sample-rate)
                  (integer? pitch))         
             (table-based-fun (inexact->exact pitch) sample-rate)]
            [else
             (raw-wave-fun pitch sample-rate)]))))

;; SYNTHESIS OF SINE WAVES

;; raw-sine-wave : number number -> signal
;; given a pitch and a sample rate, produce a sine wave signal
(define (raw-sine-wave pitch sample-rate)
  (let ([scalar (* twopi pitch)])
    (lambda (i)
      (let ([t (/ i sample-rate)])
        (sin (* scalar t))))))

(define sine-wave (make-checked-wave-fun raw-sine-wave))

;; SYNTHESIS OF THREE-PARTIAL SINE

(define (raw-harm3-wave pitch sample-rate)
  (let ([scalar1 (* twopi pitch)]
        [scalar2 (* twopi 2 pitch)]
        [scalar3 (* twopi 3 pitch)])
    (lambda (i)
      (let ([t (/ i sample-rate)])
        (+ (sin (* scalar1 t))
           (* 0.5 (sin (* scalar2 t)))
           (* 0.25 (sin (* scalar3 t))))))))

(define harm3-wave (make-checked-wave-fun raw-harm3-wave))

;; SYNTHESIS OF TRIANGULAR WAVES:


(define (raw-sawtooth-wave pitch sample-rate)
  (let ([scalar (exact->inexact (* 2 (* pitch (/ 1 sample-rate))))])
    (lambda (i)
      (let* ([unwrapped (+ 1.0 (* (exact->inexact i) scalar))]
             [scaled (/ unwrapped 2.0)])
        (- (* 2.0 (- scaled (floor scaled))) 1.0)))))

(define sawtooth-wave (make-checked-wave-fun raw-sawtooth-wave))


;; a memoized 20-term sawtooth
(define sawtooth-terms 20)
(define (raw-sawtooth-approx-wave pitch sample-rate)
  (let ([scalar (exact->inexact (* twopi (* pitch (/ 1 sample-rate))))])
    (lambda (i) 
      (for/fold ([sum 0.0])
        ([t (in-range 1 sawtooth-terms)])
        (+ sum (* (expt -1 t) (/ 1 (* twopi t)) (sin (* i scalar t))))))))

(define approx-sawtooth-wave (make-checked-wave-fun raw-sawtooth-approx-wave))



;; square waves

(define (raw-square-wave pitch sample-rate)
  (let* ([period (* sample-rate (/ 1 pitch))])
    (lambda (i)
      (let* ([scaled (/ i period)]
             [frac (- scaled (floor scaled))])
        (cond [(< frac 0.5) 1.0]
              [else -1.0])))))

(define square-wave (make-checked-wave-fun raw-square-wave))



;;fader : frames -> signal
(define (fader fade-frames)
  (let ([p (expt 0.001 (/ 1 fade-frames))])
  (lambda (i)
    (expt p i))))

;; frisellinator : frames -> signal
(define (frisellinator intro-frames)
  (lambda (i)
    (cond [(< intro-frames i) 1.0]
          [else (* 0.5 (- 1.0 (cos (* pi (/ i intro-frames)))))])))

;; dc-signal : number -> signal
(define (dc-signal volume)
  (lambda (i) volume))

(define (signal-*s lof)
  (lambda (i) (apply * (map (lambda (x) (x i)) lof))))

(define (signal-* a b) (signal-*s (list a b)))

(define (signal-+s lof)
  (lambda (i) (apply + (map (lambda (x) (x i)) lof))))

;; can this procedure be used as a signal?
(define (signal? f)
  (and (procedure? f) (procedure-arity-includes? f 1)))

;; convert a wavefun into a tone-maker; basically just keep a hash table
;; of previously generated sounds.
(define (wavefun->tone-maker wavefun)
  (let ([tone-table (make-hash)])
    (lambda (pitch volume frames sample-rate)
      (let ([key (list pitch volume sample-rate)])
        (define (compute-and-store)
          (let ([s (fun->mono-rsound frames sample-rate (wavefun pitch volume sample-rate))])
            (hash-set! tone-table key s)
            s))
        (match (hash-ref tone-table key #f)
          ;;
          [#f (compute-and-store)]
          [(and s (struct rsound (data stored-frames sample-rate)))
           (cond [(= stored-frames frames) s]
                 ;; opportunity for real laziness here:
                 [(< frames stored-frames) (rsound-clip s 0 frames)]
                 [else (compute-and-store)])])))))

;; a memoized harm3 tone
(define make-harm3tone
  (wavefun->tone-maker
   (lambda (pitch volume sample-rate)
     (signal-*s (list (fader 88200)
                      (dc-signal volume)
                      (harm3-wave pitch sample-rate))))))

;; make a monaural pitch with the given number of frames
(define make-tone
  (wavefun->tone-maker 
   (lambda (pitch volume sample-rate)
     (signal-*s (list (dc-signal volume) (sine-wave pitch sample-rate))))))

(define make-squaretone
  (wavefun->tone-maker
   (lambda (pitch volume sample-rate)
     (signal-*s (list (dc-signal volume) (square-wave pitch sample-rate))))))

(define make-zugtone
  (wavefun->tone-maker
   (lambda (pitch volume sample-rate)
     (signal-*s (list (frisellinator 8820) #;(fader 88200) (dc-signal volume) (approx-sawtooth-wave pitch sample-rate))))))




(define make-sawtooth-tone
  (wavefun->tone-maker 
   (lambda (pitch volume sample-rate)
     (signal-*s (list (dc-signal volume)
                      (sawtooth-wave pitch sample-rate))))))




;; sounds like a ding...
(define ding (fun->mono-rsound 44100 44100 (signal-*s (list (sine-wave 600 44100)
                                                            (dc-signal 0.35)
                                                            (fader 44100)))))

(define (make-ding pitch)
  (fun->mono-rsound 44100 44100 (signal-*s (list (sine-wave pitch 44100)
                                                 (dc-signal 0.35)
                                                 (fader 44100)))))

(define (split-in-4 s)
  (let ([len (/ (rsound-frames s) 4)])
    (apply values (for/list ([i (in-range 4)])
                    (rsound-clip s (* i len) (* (+ 1 i) len))))))

;; play a sound 'n' times
(define (times n s)
  (rsound-append* (build-list n (lambda (x) s))))




;; put vectors together into an rsound at the given sample-rate. Ignores
;; the complex component entirely.
(define (vectors->rsound leftvec rightvec sample-rate)
  (unless (equal? (vector-length leftvec) (vector-length rightvec))
    (error 'vectors->rsound "expected vectors of equal length, given vectors of lengths ~v and ~v." 
           (vector-length leftvec) (vector-length rightvec)))
  (let* ([len (vector-length leftvec)]
         [datamax (for/fold ((max-abs 0.0))
                    ((x (in-vector leftvec))
                     [y (in-vector rightvec)])
                    (max (abs (real-part x)) 
                         (abs (real-part y))
                         max-abs))]
         [newvec (make-s16vector (* 2 len))]
         [scaling (/ s16max datamax)])
    (for ([i (in-range len)])
      (s16vector-set! newvec (* 2 i)        (inexact->exact (round (* scaling (real-part (vector-ref leftvec i))))))
      (s16vector-set! newvec (add1 (* 2 i)) (inexact->exact (round (* scaling (real-part (vector-ref rightvec i)))))))
    (rsound newvec len sample-rate)))


;; ADSR envelope (actually more of an ADS envelope)
(define (adsr frames attack-len attack-height decay-len decay-height)
  (let* ([t1 attack-len]
         [t2 (+ t1 decay-len)]
         [t3 frames])
  (lambda (i)
    (cond [(< i t1) (weighted (/ i attack-len) 0 attack-height)]
          [(< i t2) (weighted (/ (- i t1) decay-len) attack-height decay-height)]
          [(< i t3) decay-height]
          [else 0]))))

;; (1-s)*a + s*b
(define (weighted s a b)
  (+ (* a (- 1 s)) (* b s)))

;; turn a function of multiple arguments into a signal. Basically,
;; just curry w.r.t. the first argument.
(define (signal f . args)
  (lambda (t) (apply f (cons t args))))

;; FFTs

;; binary-logn; a safe version of the one that appears in the fft code
(define (binary-logn n)
  (let ((binary-logn
         (let loop ((k 1)
                    (l 0))
           (if (>= k n)
               l
               (loop (* k 2) (+ l 1))))))
    (if (= n (arithmetic-shift 1 binary-logn))
        binary-logn
        #f)))

;; return the (complex) fft of the left channel
(define (rsound-fft/left rsound)
  (channel-fft (lambda (i) (rsound-nth-sample/left rsound i)) (rsound-frames rsound)))

;; return the (complex) fft of the right channel
(define (rsound-fft/right rsound)
  (channel-fft (lambda (i) (rsound-nth-sample/right rsound i)) (rsound-frames rsound)))

;; the common left-right abstraction
(define (channel-fft accessor len)
  (let* ([v (build-vector len 
                          (lambda (i) 
                            (/ (exact->inexact (accessor i)) s16max)))])
    (if (binary-logn len)
        (fft-complex-radix2-forward v)
        (fft-complex-forward v)) 
    v))

;; make the sound as lound as possible without distortion
(define (rsound-max-volume rsound)
  (let* ([scalar (fl/ 1.0 (exact->inexact (rsound-largest-sample rsound)))])
    (funs->stereo-rsound (rsound-frames rsound)
                         (rsound-sample-rate rsound)
                         (lambda (i) (fl* scalar (exact->inexact (rsound-nth-sample/left rsound i))))
                         (lambda (i) (fl* scalar (exact->inexact (rsound-nth-sample/right rsound i)))))))


;; midi-note-num->pitch : number -> number
;; produces the pitch that corresponds to a midi note number
(define (midi-note-num->pitch note-num)
  (* 440 (expt 2 (/ (- note-num 69) 12))))


;; rsound->signal/either : (rsound number -> number) -> rsound -> signal
;; an abstraction over left/right channels for the following two functions.
;; it has to appear before them, unfortunately.
(define ((rsound->signal/either ith-fun) rsound)
  (unless (rsound? rsound)
    (raise-type-error 'rsound->signal "rsound" 0 rsound))
  (let ([len (rsound-frames rsound)])
    (lambda (t)
      (cond [(< t len) (ith-fun rsound t)]
            [else 0.0]))))

;; rsound->signal/left : rsound -> signal
;; produce the signal that corresponds to the rsound's left channel, followed by silence.
(define rsound->signal/left (rsound->signal/either rsound-ith/left))

;; rsound->signal/right : rsound -> signal
;; produce the signal that corresponds to the rsound's right channel, followed by silence.
(define rsound->signal/right (rsound->signal/either rsound-ith/right))


;; FIR filters

;; fir-filter : (listof (list/c delay amplitude)) -> signal -> signal
;; filter the input signal using the delay values and amplitudes given for an FIR filter
(define (fir-filter params)
  (match params
    [`((,delays ,amplitudes) ...)
     (unless (andmap (lambda (d) (and (exact-integer? d) (< 0 d))) delays)
       (raise-type-error 'fir-filter "exact integer delays greater than zero" 0 params))
     (unless (andmap real? amplitudes)
       (raise-type-error 'fir-filter "real number amplitudes" 0 params))
     (lambda (signal)
       ;; use a minimum vector length of 1:
       (let* ([max-delay (apply max (cons 1 delays))]
              ;; set up buffer to delay the signal
              [delay-buf (make-vector max-delay 0.0)]
              [next-idx 0]
              ;; ugh... we must be called sequentially:
              [last-t -1])
         (lambda (t)
           (unless (= t (add1 last-t))
             (error 'fir-filter "called with t=~s, expecting t=~s. Sorry about that limitation." 
                    t
                    (add1 last-t)))
           (let ([this-val (signal t)])
             (begin0
               (for/fold ([sum this-val])
                         ([d (in-list delays)]
                          [a (in-list amplitudes)])
                         (+ sum (* a (vector-ref delay-buf (modulo (- next-idx d) max-delay)))))
               (vector-set! delay-buf next-idx this-val)
               (set! last-t (add1 last-t))
               (set! next-idx (modulo (add1 next-idx) max-delay)))))))]
    [other (raise-type-error 'fir-filter "(listof (list number number))" 0 params)]))

;; apply a filter to a sound
(define delay 8820)
(define echo1
  (let* ([vec-len (* 3 delay)]
         [echovec (make-flvector vec-len 0.0)]
         [vec-ptr 0])
    (define (nth-echo n)
      (flvector-ref echovec (modulo (- vec-ptr (* n delay)) vec-len)))
    (lambda (in)
      (let ([out (+ in (* 0.5 (nth-echo 1)) (* 0.25 (nth-echo 2)) (* 0.125 (nth-echo 3)))])
        (flvector-set! echovec vec-ptr (exact->inexact in))
        (set! vec-ptr (modulo (+ vec-ptr 1) vec-len))
        out))))

#;(define (try-wave-fun fun)
  (fun->mono-rsound (* 4 44100) 44100 (signal-*s (list (dc-signal 0.35)
                                                 (fun 100 44100)))))


#;(play-rsound (try-wave-fun square-wave))

#;(define (gug pitch)
  (signal-+s (list (signal-*s (list (dc-signal 0.25)
                                    (square-wave pitch 44100)))
                   (signal-*s (list
                               (dc-signal 0.25)
                               (sine-wave .5 44100)
                               (square-wave (* 2 pitch) 44100))))))

#;(change-loop
 (rsound-append* (list (fun->mono-rsound (* 2 44100) 44100 (gug 100))
                       (fun->mono-rsound (* 2 44100) 44100 (gug 75))
                       (fun->mono-rsound (* 2 44100) 44100 (gug 79))
                       (fun->mono-rsound (* 2 44100) 44100 (gug 89)))))