Add a real playlist (#20)

* Start implementing playlist

Done so far:
* Creation
* Changing playback mode
* Changing repeat mode

* Add skipping for linear playlists with all repeat modes

* Complete implementation for playlist/next-song

* Implement all the playlist skipping functionality

* Add functions to enqueue songs

* Remove start-idx parameter when constructing playlists

* Use namespaced keywords only when modifying external data

E.g. songs in the queue

src/cljs/airsonic_ui/audio.cljs

@@ -1,106 +0,0 @@
-(ns airsonic-ui.audio
-  (:require [re-frame.core :as re-frame]))
-
-;; TODO: Manage buffering
-
-(defonce audio (atom nil))
-
-(defn ->status
-  "Takes an audio object and returns a map describing its current status"
-  [elem]
-  {:ended? (.-ended elem)
-   :loop? (.-loop elem)
-   :muted? (.-muted elem)
-   :paused? (.-paused elem)
-   :current-src (.-currentSrc elem)
-   :current-time (.-currentTime elem)})
-
-; explanation of these events: https://developer.mozilla.org/en-US/Apps/Fundamentals/Audio_and_video_delivery/Cross-browser_audio_basics
-(defn attach-listeners! [el]
-  (doseq [event ["loadstart" "progress" "play" "timeupdate" "pause"]]
-    (.addEventListener el event #(re-frame/dispatch [:audio/update (->status el)]))))
-
-;; effects to be fired from event handlers
-
-(re-frame/reg-fx
- :audio/play
- (fn [song-url]
-   (when-not @audio
-     (reset! audio (js/Audio.))
-     (attach-listeners! @audio))
-   (.pause @audio)
-   (set! (.-src @audio) song-url)
-   (.play @audio)))
-
-(re-frame/reg-fx
- :audio/pause
- (fn [_]
-   (some-> @audio .pause)))
-
-(re-frame/reg-fx
- :audio/stop
- (fn [_]
-   (when-let [audio @audio]
-     (.pause audio)
-     (set! (.-currentTime audio) 0))))
-
-(re-frame/reg-fx
- :audio/toggle-play-pause
- (fn [_]
-   (if-let [a @audio]
-     (if (.-paused a)
-       (.play a)
-       (.pause a)))))
-
-;; subscriptions
-
-(defn summary
-  "Returns all information about audio that we have"
-  [db _]
-  (:audio db))
-
-(re-frame/reg-sub :audio/summary summary)
-
-(defn current-song
-  "Gives us information about the currently played song as presented by
-  the airsonic api"
-  [summary _]
-  (:current-song summary))
-
-(re-frame/reg-sub
- :audio/current-song
- (fn [_ _] (re-frame/subscribe [:audio/summary]))
- current-song)
-
-(defn playback-status
-  "Gives us information about the most recently fired html 5 audio event"
-  [summary _]
-  (:playback-status summary))
-
-(re-frame/reg-sub
- :audio/playback-status
- (fn [_ _] (re-frame/subscribe [:audio/summary]))
- playback-status)
-
-(defn is-playing?
-  "Predicate to tell us whether we currently have audio output or not"
-  [playback-status _]
-  (and (not (:paused? playback-status))
-       (not (:ended? playback-status))))
-
-(re-frame/reg-sub
- :audio/is-playing?
- (fn [_ _] (re-frame/subscribe [:audio/current-playback-status]))
- is-playing?)
-
-(comment
-  ;; NOTE: Not in use currently
-  (defn current-playlist
-    "Lists the complete playlist"
-    [summary _]
-    (:playlist summary))
-
-  (re-frame/reg-sub
-   :audio/current-playlist
-   (fn [_ _] (re-frame/subscribe [:audio/summary]))
-   current-playlist))