#lang racket/base

;; FFI binding to taglibc

(require ffi/unsafe
	 ffi/unsafe/define
         (only-in unstable/contract option/c)
         (rename-in racket/contract [-> ->/c]))

(provide (struct-out tag)
         (struct-out audio-properties)

         (contract-out
           ;; get tag and audio props for the given file
           [get-metadata
             (->/c path-string?
                   (option/c (list/c tag/c audio-properties/c)))])

         ;; Low-level API
         taglib_set_strings_unicode
         taglib_set_string_management_enabled

         taglib_file_new
         taglib_file_new_type
         taglib_file_free
         taglib_file_is_valid
         taglib_file_tag
         taglib_file_audioproperties
         taglib_file_save

         taglib_tag_title
         taglib_tag_artist
         taglib_tag_album
         taglib_tag_comment
         taglib_tag_genre
         taglib_tag_year
         taglib_tag_track

         taglib_tag_set_title
         taglib_tag_set_artist
         taglib_tag_set_album
         taglib_tag_set_comment
         taglib_tag_set_genre
         taglib_tag_set_year
         taglib_tag_set_track

         taglib_tag_free_strings

         taglib_audioproperties_length
         taglib_audioproperties_bitrate
         taglib_audioproperties_samplerate
         taglib_audioproperties_channels

         _TagLib_ID3v2_Encoding

         taglib_id3v2_set_default_text_encoding)

;; Racket representation of tags and audio
(struct tag (title artist album comment genre year track)
  #:transparent)

(struct audio-properties (length bitrate samplerate channels)
  #:transparent)

(define tag/c
  (struct/c tag
            string? string? string? string? string?
            exact-nonnegative-integer?
            exact-nonnegative-integer?))

(define audio-properties/c
  (struct/c audio-properties
            exact-nonnegative-integer?
            exact-nonnegative-integer?
            exact-nonnegative-integer?
            exact-nonnegative-integer?))

;; FFI stuff
(define taglib (ffi-lib "libtag_c"))
(define-ffi-definer define-tl taglib)

(define _TagLib_File (_cpointer/null 'TagLib_File))
(define _TagLib_Tag  (_cpointer 'TagLib_Tag))
(define _TagLib_AudioProperties (_cpointer 'TagLib_AudioProperties))

(define _TagLib_File_Type
  (_enum '(mpeg oggvorbis flac mpc
           oggflac wavpack speex trueaudio
	   mp4 asf type)))

;; Racket API
(define (get-metadata path)
  (unless (path-string? path)
    (raise-type-error 'get-metadata "path-string" path))
  (define file (taglib_file_new path))
  (dynamic-wind
   void
   (lambda ()
     (and file
          (taglib_file_is_valid file)
          (let* ([ctag (taglib_file_tag file)]
                 [ap (taglib_file_audioproperties file)]
                 [the-tag
                  (tag
                   (taglib_tag_title ctag)
                   (taglib_tag_artist ctag)
                   (taglib_tag_album ctag)
                   (taglib_tag_comment ctag)
                   (taglib_tag_genre ctag)
                   (taglib_tag_year ctag)
                   (taglib_tag_track ctag))]
                 [audio-props
                  (audio-properties
                   (taglib_audioproperties_length ap)
                   (taglib_audioproperties_bitrate ap)
                   (taglib_audioproperties_samplerate ap)
                   (taglib_audioproperties_channels ap))])
            (begin
             (taglib_tag_free_strings ctag)
             (list the-tag audio-props)))))
   (lambda ()
     (taglib_file_free file))))

;; Low Level C API

(define-tl taglib_set_strings_unicode (_fun _bool -> _void))
(define-tl taglib_set_string_management_enabled (_fun _bool -> _void))

;; File API
(define-tl taglib_file_new (_fun _path -> _TagLib_File))
(define-tl taglib_file_new_type (_fun _path _TagLib_File_Type -> _TagLib_File))
(define-tl taglib_file_free (_fun _TagLib_File -> _void))
(define-tl taglib_file_is_valid (_fun _TagLib_File -> _bool))
(define-tl taglib_file_tag (_fun _TagLib_File -> _TagLib_Tag))
(define-tl taglib_file_audioproperties (_fun _TagLib_File -> _TagLib_AudioProperties))
(define-tl taglib_file_save (_fun _TagLib_File -> _bool))

;; Tag API
(define-tl taglib_tag_title   (_fun _TagLib_Tag -> _string))
(define-tl taglib_tag_artist  (_fun _TagLib_Tag -> _string))
(define-tl taglib_tag_album   (_fun _TagLib_Tag -> _string))
(define-tl taglib_tag_comment (_fun _TagLib_Tag -> _string))
(define-tl taglib_tag_genre   (_fun _TagLib_Tag -> _string))
(define-tl taglib_tag_year    (_fun _TagLib_Tag -> _uint))
(define-tl taglib_tag_track   (_fun _TagLib_Tag -> _uint))

(define-tl taglib_tag_set_title   (_fun _TagLib_Tag _string -> _void))
(define-tl taglib_tag_set_artist  (_fun _TagLib_Tag _string -> _void))
(define-tl taglib_tag_set_album   (_fun _TagLib_Tag _string -> _void))
(define-tl taglib_tag_set_comment (_fun _TagLib_Tag _string -> _void))
(define-tl taglib_tag_set_genre   (_fun _TagLib_Tag _string -> _void))
(define-tl taglib_tag_set_year    (_fun _TagLib_Tag _uint -> _void))
(define-tl taglib_tag_set_track   (_fun _TagLib_Tag _uint -> _void))

(define-tl taglib_tag_free_strings (_fun _TagLib_Tag -> _void))

;; Audio Properties API
(define-tl taglib_audioproperties_length     (_fun _TagLib_AudioProperties -> _int))
(define-tl taglib_audioproperties_bitrate    (_fun _TagLib_AudioProperties -> _int))
(define-tl taglib_audioproperties_samplerate (_fun _TagLib_AudioProperties -> _int))
(define-tl taglib_audioproperties_channels   (_fun _TagLib_AudioProperties -> _int))

;; ID3v2
(define _TagLib_ID3v2_Encoding
  (_enum '(latin1 utf16 utf16be utf8)))

(define-tl taglib_id3v2_set_default_text_encoding (_fun _TagLib_ID3v2_Encoding -> _void))