457 lines
17 KiB
Racket
457 lines
17 KiB
Racket
#lang racket/base
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(require racket-audio
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racket/file
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racket/list
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racket-mimetypes
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racket/path
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racket/string)
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(provide (struct-out music-library)
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(struct-out browser-entry)
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(struct-out track)
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(struct-out artwork)
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make-music-libraries
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library-contains-audio-file?
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browse-library
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browser-entry->tracks
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track-artwork)
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(struct music-library
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(id name root)
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#:transparent)
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(struct browser-entry
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(name kind relative-path)
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#:transparent)
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(struct track
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(file title artist album duration mime-type)
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#:transparent)
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(struct artwork
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(mime-type data)
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#:transparent)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Supporting functions
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define supported-extensions
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(audio-supported-extensions))
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(define cover-file-names
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'("cover.jpg" "cover.jpeg" "cover.png"
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"folder.jpg" "folder.jpeg" "folder.png"
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"front.jpg" "front.jpeg" "front.png"))
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;;; Checks whether a path has an extension supported by racket-audio.
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(define (audio-file? file)
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(let ((extension (path-get-extension file)))
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(if (eq? extension #f)
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#f
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(let ((extension-name
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(string-downcase
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(string-trim
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(bytes->string/utf-8 extension)
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"."))))
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(if (member extension-name supported-extensions)
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#t
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#f)))))
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;;; Checks whether the final path element starts with a dot.
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(define (hidden-name? path)
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(string-prefix? (path->string path) "."))
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;;; Derives a fallback track title from the file name without its extension.
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(define (file-title file)
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(let* ((name (file-name-from-path file))
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(without-extension
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(if name
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(path-replace-extension name #"")
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file)))
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(path->string without-extension)))
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;;; Returns a non-empty string value or the supplied fallback.
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(define (nonempty value fallback)
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(if (and (string? value)
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(not (string=? (string-trim value) "")))
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value
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fallback))
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;;; Reads audio metadata and converts a file path to a track value.
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;;; File-name and MIME-type fallbacks are used when metadata cannot be read.
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(define (path->track file)
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(let ((fallback-title (file-title file)))
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(with-handlers
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((exn:fail?
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(λ (_)
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(track file fallback-title "" "" #f
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(mimetype-for-ext file)))))
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(call-with-id3-tags
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file
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(λ (tags)
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(if (tags-valid? tags)
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(track file
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(nonempty (tags-title tags) fallback-title)
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(nonempty (tags-artist tags) "")
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(nonempty (tags-album tags) "")
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(let ((length (tags-length tags)))
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(if (and (number? length) (positive? length))
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length
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#f))
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(mimetype-for-ext file))
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(track file fallback-title "" "" #f
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(mimetype-for-ext file))))))))
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;;; Builds the filesystem path represented by a library-relative path.
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(define (library-path library relative-path)
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(if (null? relative-path)
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(music-library-root library)
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(apply build-path
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(music-library-root library)
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relative-path)))
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;;; Classifies a path as a container, supported track or unusable entry.
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(define (path-kind path)
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(cond
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((directory-exists? path) 'container)
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((and (file-exists? path)
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(audio-file? path))
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'track)
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(else #f)))
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;;; Orders browser entries with containers first and names alphabetically.
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(define (entry<? first second)
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(cond
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((and (eq? (browser-entry-kind first) 'container)
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(eq? (browser-entry-kind second) 'track))
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#t)
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((and (eq? (browser-entry-kind first) 'track)
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(eq? (browser-entry-kind second) 'container))
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#f)
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(else
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(string-ci<? (browser-entry-name first)
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(browser-entry-name second)))))
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;;; Recursively converts the browsable contents of a directory to tracks.
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(define (directory-tracks library relative-path)
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(append-map
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(λ (entry)
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(if (eq? (browser-entry-kind entry) 'container)
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(directory-tracks library
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(browser-entry-relative-path entry))
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(list
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(path->track
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(library-path library
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(browser-entry-relative-path entry))))))
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(browse-library library relative-path)))
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;;; Produces a resolved complete path, or #f when resolution fails.
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(define (complete-path/safe path)
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(with-handlers ((exn:fail? (λ (_) #f)))
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(simplify-path (path->complete-path path) #t)))
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;;; Checks whether file is located below root without traversing upward.
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(define (path-below-root? root file)
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(let* ((relative (find-relative-path root file))
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(elements (explode-path relative)))
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(and (relative-path? relative)
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(not (member 'up elements)))))
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;;; Recognizes a library specification containing a display name and path.
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(define (named-library-specification? specification)
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(and (list? specification)
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(= (length specification) 2)
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(string? (car specification))
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(path-string? (cadr specification))))
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;;; Extracts the optional display name and path from a library specification.
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(define (specification-values specification)
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(cond
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((named-library-specification? specification)
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(values (string-trim (car specification))
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(cadr specification)))
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((path-string? specification)
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(values #f specification))
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(else
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(raise-argument-error
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'make-music-libraries
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"(or/c path-string? (list/c string? path-string?))"
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specification))))
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;;; Reads embedded ID3 artwork from a track, returning #f when unavailable.
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(define (embedded-artwork item)
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(with-handlers ((exn:fail? (λ (_) #f)))
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(call-with-id3-tags
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(track-file item)
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(λ (tags)
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(if (not (tags-valid? tags))
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#f
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(let ((picture (tags-picture tags)))
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(if (eq? picture #f)
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#f
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(let ((mime (id3-picture-mimetype picture)))
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(artwork
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(if (and (string? mime)
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(not (string=? mime "")))
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mime
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"application/octet-stream")
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(id3-picture-bytes picture))))))))))
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;;; Checks whether a path names an existing conventional cover image.
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(define (cover-file? candidate)
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(let ((name (file-name-from-path candidate)))
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(cond
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((eq? name #f) #f)
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((not (file-exists? candidate)) #f)
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((member (path->string name)
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cover-file-names
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string-ci=?) #t)
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(else #f))))
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;;; Searches the track directory for a conventional cover image.
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(define (cover-artwork item)
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(with-handlers ((exn:fail? (λ (_) #f)))
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(let* ((track-directory (path-only (track-file item)))
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(directory (if (eq? track-directory #f)
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(current-directory)
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track-directory))
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(cover (findf cover-file?
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(directory-list directory #:build? #t))))
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(if (eq? cover #f)
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#f
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(let ((mime (mimetype-for-ext cover)))
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(artwork (if (string? mime)
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mime
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"application/octet-stream")
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(file->bytes cover)))))))
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;;; Validates one normalized library root and constructs its public value.
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(define (named-root->music-library named-root index)
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(let ((configured-name (car named-root))
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(root (cadr named-root)))
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(unless (directory-exists? root)
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(raise-arguments-error
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'make-music-libraries
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"music library is not an existing directory"
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"path" root))
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(let* ((name (file-name-from-path root))
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(default-name (if (eq? name #f)
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(path->string root)
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(path->string name))))
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(music-library
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(format "library-~a" index)
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(cond
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((eq? configured-name #f) default-name)
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((string=? configured-name "") default-name)
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(else configured-name))
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root))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Provided functions
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; goal : Check whether a supported audio file belongs to a music library.
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; pre : Libraries contains music-library values; file may be any value.
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; post : The file system remains unchanged.
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; result : #t when file exists below a configured root, otherwise #f.
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; internals: audio-file? first rejects unsupported files. complete-path/safe
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; resolves the candidate and each library root. The named loop calls
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; path-below-root? until one root contains the file; that helper uses
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; find-relative-path and rejects paths containing an 'up element.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (library-contains-audio-file? libraries file)
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(cond
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((not (path-string? file)) #f)
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((not (file-exists? file)) #f)
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((not (audio-file? file)) #f)
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(else
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(let ((full-file (complete-path/safe file)))
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(if (eq? full-file #f)
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#f
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(let loop ((remaining libraries))
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(if (null? remaining)
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#f
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(let ((root
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(complete-path/safe
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(music-library-root (car remaining)))))
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(cond
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((eq? root #f)
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(loop (cdr remaining)))
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((path-below-root? root full-file) #t)
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(else
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(loop (cdr remaining))))))))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; goal : Turn configured directory paths into music libraries.
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; pre : Every value is a path or a (display-name path) list.
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; post : No directory contents or audio metadata have been read.
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; result : Libraries in configuration order, without duplicate roots.
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; internals: specification-values separates each optional name from its path.
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; map normalizes the paths and remove-duplicates compares their
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; roots. The named loop calls named-root->music-library to validate
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; each directory and assign its sequential library id.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (make-music-libraries specifications)
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(let ((roots
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(remove-duplicates
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(map (λ (specification)
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(let-values (((name path)
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(specification-values specification)))
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(list name
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(normal-case-path
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(path->complete-path path)))))
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specifications)
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(λ (first second)
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(equal? (cadr first) (cadr second))))))
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(let loop ((remaining roots)
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(index 0))
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(if (null? remaining)
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'()
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(cons (named-root->music-library (car remaining) index)
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(loop (cdr remaining) (add1 index)))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; goal : Read the artwork associated with a track.
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; pre : Item names a local audio file.
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; post : The audio file and optional neighbouring image remain unchanged.
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; result : Embedded artwork, a conventional folder cover, or #f.
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; internals: embedded-artwork first reads the picture stored in the audio tags.
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; Only when that returns #f does cover-artwork search the track's
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; directory for one of the names in cover-file-names.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (track-artwork item)
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(let ((embedded (embedded-artwork item)))
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(if (eq? embedded #f)
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(cover-artwork item)
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embedded)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; goal : List the immediate folders and supported audio files in a library.
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; pre : Relative-path was produced by a previous browse result.
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; post : Child directories are listed before tracks; metadata is not read.
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; result : Browser entries for one directory level.
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; internals: library-path resolves the requested directory. directory-list and
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; path-kind supply filter-map with usable children; hidden-name?
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; removes hidden containers. sort uses entry<? to put containers
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; first and compare names without regard to case.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (browse-library library relative-path)
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(let ((path (library-path library relative-path)))
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(unless (directory-exists? path)
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(raise-arguments-error
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'browse-library
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"library directory does not exist"
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"path" path))
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(sort
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(filter-map
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(λ (name)
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(let* ((full-path (build-path path name))
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(kind (path-kind full-path)))
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(cond
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((eq? kind #f) #f)
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((eq? kind 'container)
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(if (hidden-name? name)
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#f
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(browser-entry
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(path->string name)
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kind
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(append relative-path (list name)))))
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(else
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(browser-entry
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(path->string name)
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kind
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(append relative-path (list name)))))))
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(directory-list path))
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entry<?)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; goal : Resolve a selected browser entry to playable tracks.
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; pre : Entry belongs to library and was produced by browse-library.
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; post : Track metadata is read; containers are traversed recursively.
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; result : One track, or all supported tracks below the selected container.
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; internals: A track entry is resolved by library-path and read by path->track.
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; A container is passed to directory-tracks, which recursively calls
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; browse-library and path->track in browser sort order.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (browser-entry->tracks library entry)
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(if (eq? (browser-entry-kind entry) 'container)
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(directory-tracks library
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(browser-entry-relative-path entry))
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(list
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(path->track
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(library-path library
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(browser-entry-relative-path entry))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Tests for module library.rkt
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(module+ test
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(require rackunit)
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(define root
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(make-temporary-file "rkt-web-library-~a" 'directory))
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(define outside-file
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(make-temporary-file "rkt-web-outside-~a.mp3"))
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(dynamic-wind
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void
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(λ ()
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(make-directory (build-path root "Album"))
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(make-directory (build-path root ".Hidden"))
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(call-with-output-file
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(build-path root "Album" "inside.mp3") void)
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(call-with-output-file (build-path root "track.mp3") void)
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(call-with-output-file (build-path root "cover.jpg") void)
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(call-with-output-file (build-path root "ignored.txt") void)
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(let* ((libraries (make-music-libraries (list root)))
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(entries (browse-library (car libraries) '())))
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(check-equal? (length libraries) 1)
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(check-equal? (length entries) 2)
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(check-equal? (browser-entry-name (car entries)) "Album")
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(check-eq? (browser-entry-kind (car entries)) 'container)
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(check-equal? (browser-entry-name (cadr entries)) "track.mp3")
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(check-eq? (browser-entry-kind (cadr entries)) 'track)
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(check-equal?
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(length
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(browser-entry->tracks (car libraries) (car entries)))
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1)
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(check-true
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(library-contains-audio-file?
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libraries
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(build-path root "track.mp3")))
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(check-true
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(library-contains-audio-file?
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libraries
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(build-path root "Album" "inside.mp3")))
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(check-false
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(library-contains-audio-file?
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libraries
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(build-path root "cover.jpg")))
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(check-false
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(library-contains-audio-file?
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libraries
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outside-file))
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(check-equal?
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(length (make-music-libraries (list root root)))
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1)
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(check-equal?
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(music-library-name
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(car (make-music-libraries
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(list (list "Luisterkamer" root)))))
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"Luisterkamer")
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(check-equal?
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(artwork-mime-type
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(track-artwork
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(track (build-path root "track.mp3")
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"Track" "" "" #f "audio/mpeg")))
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"image/jpeg")))
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(λ ()
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(delete-directory/files root)
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(delete-file outside-file))))
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