Implement all the playlist skipping functionality

src/cljs/airsonic_ui/audio/playlist.cljs

@@ -1,7 +1,8 @@
 (ns airsonic-ui.audio.playlist
   "Implements playlist queues that support different kinds of repetition and
   song ordering."
-  (:refer-clojure :exclude [peek]))
+  (:refer-clojure :exclude [peek])
+  (:require [airsonic-ui.utils.helpers :refer [find-where]]))
 
 (defrecord Playlist [queue playback-mode repeat-mode]
   cljs.core/ICounted
@@ -15,19 +16,17 @@
 
 (defn- playlist-queue
   [queue playing-idx]
-  (concat (take playing-idx queue)
-          [(assoc (nth queue playing-idx) :currently-playing? true)]
-          (drop (inc playing-idx) queue)))
+  (assoc-in (vec queue) [playing-idx :currently-playing?] true))
 
 (defmethod ->playlist :playback-mode/linear
   [queue playing-idx playback-mode repeat-mode]
   (let [queue (->> (playlist-queue queue playing-idx)
-                   (mapv (fn [order song] (assoc song :order order))
-                         (range (count queue))))]
+                   (mapv (fn [order song] (assoc song :order order)) (range)))]
     (->Playlist queue playback-mode repeat-mode)))
 
 (defn- -shuffle-songs [queue]
-  (mapv (fn [song order] (assoc song :order order)) queue (shuffle (range (count queue)))))
+  (->> (shuffle (range (count queue)))
+       (mapv (fn [song order] (assoc song :order order)) queue)))
 
 (defmethod ->playlist :playback-mode/shuffled
   [queue playing-idx playback-mode repeat-mode]
@@ -35,17 +34,11 @@
                    (-shuffle-songs))]
     (->Playlist queue playback-mode repeat-mode)))
 
-(defn- -current-song [playlist]
-  (first (keep-indexed (fn [idx song]
-                         (when (:currently-playing? song)
-                           [idx song]))
-                       (:queue playlist))))
-
 (defn set-playback-mode
   "Changes the playback mode of a playlist and re-shuffles it if necessary"
   [playlist playback-mode]
-  (->playlist (:queue playlist) (first (-current-song playlist))
-              playback-mode (:repeat-mode playlist)))
+  (let [[current-idx _] (find-where :currently-playing? (:queue playlist))]
+    (->playlist (:queue playlist) current-idx playback-mode (:repeat-mode playlist))))
 
 (defn set-repeat-mode
   "Allows to change the way the next and previous song of a playlist is selected"
@@ -59,45 +52,71 @@
        (filter :currently-playing?)
        (first)))
 
-(defmulti next-song :repeat-mode)
+(defn set-current-song
+  "Marks a song in the queue as currently playing, given its ID"
+  [playlist next-idx]
+  (let [[current-idx _] (find-where :currently-playing? (:queue playlist))]
+    (-> (if current-idx
+          (update-in playlist [:queue current-idx] dissoc :currently-playing?)
+          playlist)
+        (assoc-in [:queue next-idx :currently-playing?] true))))
+
+(defmulti next-song "Advances the currently playing song" :repeat-mode)
 
 (defmethod next-song :repeat-mode/none
   [playlist]
   ;; this is pretty easy; get the next song and stop playing at the at
-  (let [[current-idx _] (-current-song playlist)
-        next-idx (inc current-idx)]
+  (let [[current-idx current-song] (find-where :currently-playing? (:queue playlist))
+        [next-idx _] (find-where #(= (:order %) (inc (:order current-song))) (:queue playlist))]
     (update playlist :queue
-            (fn [queue] (cond-> queue
-                          :always (update current-idx dissoc :currently-playing?)
-                          (< next-idx (count playlist)) (assoc-in [next-idx :currently-playing?] true))))))
+            (fn [queue]
+              (cond-> queue
+                current-idx (update current-idx dissoc :currently-playing?)
+                next-idx (assoc-in [next-idx :currently-playing?] true))))))
 
 (defmethod next-song :repeat-mode/single [playlist] playlist)
 
 (defmethod next-song :repeat-mode/all
   [playlist]
-  (let [[current-idx _] (-current-song playlist)]
+  (let [[current-idx current-song] (find-where :currently-playing? (:queue playlist))
+        [next-idx _] (find-where #(= (:order %) (inc (:order current-song))) (:queue playlist))]
     (-> (update-in playlist [:queue current-idx] dissoc :currently-playing?)
         (update :queue
                 (fn [queue]
                   ;; we need special treatment here if we're playing the last song and
                   ;; have a shuffled playlist because we need to re-shuffle
-                  (if (and (= current-idx (dec (count playlist)))
-                           (= :playback-mode/shuffled (:playback-mode playlist)))
-                    (->> (-shuffle-songs queue)
-                         (mapv #(if (= (:order %) 0) (assoc % :currently-playing? true) %)))
-                    (let [next-idx (mod (inc current-idx) (count playlist))]
-                      (assoc-in queue [next-idx :currently-playing?] true))))))))
+                  (if next-idx
+                    (assoc-in queue [next-idx :currently-playing?] true)
+                    (case (:playback-mode playlist)
+                      :playback-mode/linear (assoc-in queue [0 :currently-playing?] true)
+                      :playback-mode/shuffled (let [queue' (-shuffle-songs queue)
+                                                    [next-idx _] (find-where #(= (:order %) 0) queue')]
+                                                (assoc-in queue' [next-idx :currently-playing?] true)))))))))
 
-(defmulti previous-song :repeat-mode)
+(defmulti previous-song "Goes back along the playback queue" :repeat-mode)
 
-(defn set-current-song [playlist playing-idx]
+(defmethod previous-song :repeat-mode/single [playlist] playlist)
+
+(defmethod previous-song :repeat-mode/none [playlist]
+  (let [[current-idx current-song] (find-where :currently-playing? (:queue playlist))
+        [next-idx _] (find-where #(= (:order %) (dec (:order current-song))) (:queue playlist))]
+    (set-current-song playlist (or next-idx current-idx))))
+
+(defmethod previous-song :repeat-mode/all [playlist]
+  (let [[_ current-song] (find-where :currently-playing? (:queue playlist))
+        [next-idx _] (find-where #(= (:order %)
+                                     (rem (dec (:order current-song)) (count playlist)))
+                                 (:queue playlist))]
+    (if next-idx
+      (set-current-song playlist next-idx)
+      (if (= :playback-mode/shuffled (:playback-mode playlist))
+        (set-current-song (update playlist :queue -shuffle-songs) 0)
+        (set-current-song playlist (mod (dec (:order current-song)) (count playlist)))))))
+
+(defn enqueue-last [playlist song]
   ;; TODO: Implementation
   )
 
-(defn add-song-to-end [playlist]
-  ;; TODO: Implementation
-  )
-
-(defn add-next-song [playlist]
+(defn enqueue-next [playlist song]
   ;; TODO: Implementation
   )

src/cljs/airsonic_ui/utils/helpers.cljs

@@ -0,0 +1,10 @@
+(ns airsonic-ui.utils.helpers
+  "Assorted helper functions")
+
+(defn find-where
+  "Returns the the first item in `coll` with its index for which `(p song)`
+  is truthy"
+  [p coll]
+  (->> (map-indexed vector coll)
+       (reduce (fn [_ [idx song]]
+                 (when (p song) (reduced [idx song]))) nil)))

test/cljs/airsonic_ui/audio/playlist_test.cljs

@@ -1,26 +1,27 @@
 (ns airsonic-ui.audio.playlist-test
   (:require [cljs.test :refer [deftest testing is]]
             [airsonic-ui.audio.playlist :as playlist]
+            [airsonic-ui.utils.helpers :refer [find-where]]
             [airsonic-ui.fixtures :as fixtures]
             [airsonic-ui.test-helpers :as helpers]
             [debux.cs.core :refer-macros [dbg]]))
 
 (enable-console-print!)
 
-(defn- playing-queue
+(defn- song-queue
   "Generates a seq of n different songs"
   [n]
   (repeatedly n #(hash-map :id (rand-int 9999)
                            :coverArt (rand-int 9999)
                            :year (+ 1900 (rand-int 118))
                            :artist (helpers/rand-str)
-                           :aristId (rand-int 100000)
+                           :artistId (rand-int 100000)
                            :title (helpers/rand-str)
                            :album (helpers/rand-str))))
 
 (def fixture
   {:audio {:current-song fixtures/song
-           :playlist (playing-queue 20)
+           :playlist (song-queue 20)
            :playback-status fixtures/playback-status}})
 
 (defn- same-song? [a b] (= (:id a) (:id b)))
@@ -28,7 +29,7 @@
 (deftest playlist-creation
   (testing "Playlist creation"
     (testing "should give us the correct current song"
-      (let [queue (playing-queue 10)
+      (let [queue (song-queue 10)
             start-idx (rand-int 10)]
         (doseq [playback-mode [:playback-mode/linear, :playback-mode/shuffled]
                 repeat-mode [:repeat-mode/none, :repeat-mode/single, :repeat-mode/all]]
@@ -37,7 +38,7 @@
                               (playlist/peek)))
               (str playback-mode ", " repeat-mode)))))
     (testing "should give us a playlist with the correct number of tracks"
-      (let [queue (playing-queue 100)
+      (let [queue (song-queue 100)
             start-idx (rand-int 100)]
         (doseq [playback-mode [:playback-mode/linear, :playback-mode/shuffled]
                 repeat-mode [:repeat-mode/none, :repeat-mode/single, :repeat-mode/all]]
@@ -48,7 +49,7 @@
 (deftest changing-playback-mode
   (testing "Changing playback mode"
     (testing "from linear to shuffled"
-      (let [queue (playing-queue 10)
+      (let [queue (song-queue 10)
             start-idx (rand-int 10)
             linear (playlist/->playlist queue start-idx :playback-mode/linear :repeat-mode/node)
             shuffled (playlist/set-playback-mode linear :playback-mode/shuffled)]
@@ -59,7 +60,7 @@
         (testing "should not change the repeat mode"
           (is (= (:repeat-mode shuffled) (:repeat-mode linear)))))
       (testing "from shuffled to linear"
-        (let [queue (playing-queue 10)
+        (let [queue (song-queue 10)
               start-idx (rand-int 10)
               shuffled (playlist/->playlist queue start-idx
                                             :playback-mode/shuffled :repeat-mode/none)
@@ -85,7 +86,7 @@
       (doseq [playback-mode [:playback-mode/linear, :playback-mode/shuffled]
               repeat-mode [:repeat-mode/none, :repeat-mode/single, :repeat-mode/all]
               next-repeat-mode [:repeat-mode/none, :repeat-mode/single, :repeat-mode/all]]
-        (let [playlist (-> (playlist/->playlist (playing-queue 1) 0
+        (let [playlist (-> (playlist/->playlist (song-queue 1) 0
                                                 playback-mode repeat-mode)
                            (playlist/set-repeat-mode next-repeat-mode))]
           (is (= playback-mode (:playback-mode playlist)))
@@ -95,7 +96,7 @@
 (deftest linear-next-song
   (testing "Should follow the same order as the queue used for creation"
     (doseq [repeat-mode [:repeat-mode/none :repeat-mode/all]]
-      (let [queue (playing-queue 5)
+      (let [queue (song-queue 5)
             playlist (playlist/->playlist queue 0 :playback-mode/linear repeat-mode)]
         (is (same-song? (nth queue 1) (-> (playlist/next-song playlist)
                                           (playlist/peek)))
@@ -106,7 +107,7 @@
             (str repeat-mode ", skipped twice")))))
   (testing "Should go back to the first song when repeat-mode is all and we played the last song")
   (testing "Should always give the same track when repeat-mode is single"
-    (let [queue (playing-queue 3)
+    (let [queue (song-queue 3)
           playing-idx (rand-int 3)
           playlist (playlist/->playlist queue playing-idx
                                         :playback-mode/linear :repeat-mode/single)
@@ -116,30 +117,31 @@
       (is (same-song? (nth queue playing-idx) (nth played-back 2)))
       (is (same-song? (nth queue playing-idx) (nth played-back 3)) "wrapping around")))
   (testing "Should stop playing at the end of the queue when repeat-mode is none"
-    (is (nil? (-> (playing-queue 1)
+    (is (nil? (-> (song-queue 1)
                   (playlist/->playlist 0 :playback-mode/linear :repeat-mode/none)
                   (playlist/next-song)
                   (playlist/peek))))))
 
 (deftest shuffled-next-song
   (testing "Should play every track once when called for the entire queue"
-    (doseq [repeat-mode '(:repeat-mode/none :repeat-mode/all)]
-      (let [length 10
-            playlist (playlist/->playlist (playing-queue length) 0
-                                          :playback-mode/shuffled repeat-mode)
-            played-tracks (->> (iterate playlist/next-song playlist)
-                               (map playlist/peek)
-                               (take length))]
-        (is (= (count played-tracks) (count (set played-tracks)))
-            (str repeat-mode)))))
+    (with-redefs [shuffle reverse]
+      (doseq [repeat-mode '(:repeat-mode/none :repeat-mode/all)]
+        (let [length 10
+              playlist (playlist/->playlist (song-queue length) 9
+                                            :playback-mode/shuffled repeat-mode)
+              played-tracks (->> (iterate playlist/next-song playlist)
+                                 (map playlist/peek)
+                                 (take length))]
+          (is (= (count played-tracks) (count (set played-tracks)))
+              (str repeat-mode))))))
   (testing "Should re-shuffle the playlist when wrapping around and repeat-mode is all"
-    (let [length 100
-          playlist (playlist/->playlist (playing-queue length) (dec length)
-                                        :playback-mode/shuffled :repeat-mode/all)]
+    (let [playlist (playlist/->playlist (song-queue 100) 0 :playback-mode/shuffled :repeat-mode/all)
+          [last-idx _] (find-where #(= (:order %) 99) (:queue playlist))]
       (is (not= (map :order (:queue playlist))
-                (map :order (:queue (playlist/next-song playlist)))))))
+                (map :order (:queue (-> (playlist/set-current-song playlist last-idx)
+                                        (playlist/next-song))))))))
   (testing "Should always give the same track when repeat-mode is single"
-    (let [queue (playing-queue 3)
+    (let [queue (song-queue 3)
           playing-idx (rand-int 3)
           playlist (playlist/->playlist queue playing-idx
                                         :playback-mode/shuffled :repeat-mode/single)
@@ -149,10 +151,85 @@
       (is (same-song? (nth queue playing-idx) (nth played-back 2)))
       (is (same-song? (nth queue playing-idx) (nth played-back 3)) "wrapping around")))
   (testing "Should stop playing at the end of the queue when repeat-mode is none"
-    (is (nil? (-> (playing-queue 1)
+    (is (nil? (-> (song-queue 1)
                   (playlist/->playlist 0 :playback-mode/linear :repeat-mode/none)
                   (playlist/next-song)
                   (playlist/peek))))))
 
-#_(deftest linear-previous-song)
-#_(deftest shuffled-previous-song)
+(deftest linear-previous-song
+  (testing "Should always give the same track when repeat-mode is single"
+    (let [queue (song-queue 3)
+          playing-idx (rand-int 3)
+          playlist (playlist/->playlist queue playing-idx
+                                        :playback-mode/linear :repeat-mode/single)
+          played-back (map playlist/peek (iterate playlist/next-song playlist))]
+      (is (same-song? (nth queue playing-idx) (nth played-back 0)))
+      (is (same-song? (nth queue playing-idx) (nth played-back 1)))
+      (is (same-song? (nth queue playing-idx) (nth played-back 2)))
+      (is (same-song? (nth queue playing-idx) (nth played-back 3)) "wrapping around")))
+  (testing "Should keep the linear order when repeat-mode is not single"
+    (doseq [repeat-mode '(:repeat-mode/none :repeat-mode/all)]
+      (let [queue (song-queue 3)
+            playlist (playlist/->playlist queue 0 :playback-mode/linear repeat-mode)]
+        (is (same-song? (nth queue 1) (-> (playlist/next-song playlist)
+                                          (playlist/next-song)
+                                          (playlist/previous-song)
+                                          (playlist/peek)))))))
+  (testing "Should repeatedly give the first song when repeat-mode is none"
+    (let [queue (song-queue 3)
+          playlist (playlist/->playlist queue 0 :playback-mode/linear :repeat-mode/none)]
+      (is (same-song? (first queue) (-> (playlist/previous-song playlist)
+                                        (playlist/peek))))))
+  (testing "Should wrap around to last song when repeat-mode is all"
+    (let [queue (song-queue 3)
+          playlist (playlist/->playlist queue 0 :playback-mode/linear :repeat-mode/all)]
+      (is (same-song? (last queue) (-> (playlist/previous-song playlist)
+                                       (playlist/peek)))))))
+
+(deftest shuffled-previous-song
+  (with-redefs [shuffle reverse]
+    (testing "Should always give the same track when repeat-mode is single"
+      (let [queue (song-queue 3)
+            playing-idx (rand-int 3)
+            playlist (playlist/->playlist queue playing-idx
+                                          :playback-mode/shuffled :repeat-mode/single)
+            played-back (map playlist/peek (iterate playlist/next-song playlist))]
+        (is (same-song? (nth queue playing-idx) (nth played-back 0)))
+        (is (same-song? (nth queue playing-idx) (nth played-back 1)))
+        (is (same-song? (nth queue playing-idx) (nth played-back 2)))
+        (is (same-song? (nth queue playing-idx) (nth played-back 3)) "wrapping around")))
+    (testing "Should keep the playing order when repeat-mode is not single"
+      (doseq [repeat-mode '(:repeat-mode/none :repeat-mode/all)]
+        (let [queue (song-queue 3)
+              playlist' (playlist/->playlist queue 0 :playback-mode/shuffled repeat-mode)
+              [first-idx _] (find-where #(= (:order %) 0) (:queue playlist'))
+              playlist (playlist/set-current-song playlist' first-idx)]
+          (is (same-song? (playlist/peek playlist)
+                          (-> playlist
+                              (playlist/next-song)
+                              (playlist/previous-song)
+                              (playlist/peek)))
+              (str "for repeat mode " repeat-mode))
+          (is (same-song? (-> (playlist/next-song playlist)
+                              (playlist/peek))
+                          (-> (playlist/next-song playlist)
+                              (playlist/next-song)
+                              (playlist/previous-song)
+                              (playlist/peek)))
+                (str "for repeat mode " repeat-mode)))))
+    (testing "Should re-shuffle when repeat-mode is all and we pass the start"
+      (with-redefs [shuffle identity]
+        (let [playlist (playlist/->playlist (song-queue 2) 0 :playback-mode/shuffled :repeat-mode/all)
+              playlist' (with-redefs [shuffle reverse]
+                          (playlist/previous-song playlist))]
+          (is (not= (map :order (:queue playlist)) (map :order (:queue playlist')))))))))
+
+(deftest set-current-song
+  (testing "Should correctly set the new song"
+    (let [queue (song-queue 3)
+          playlist (playlist/->playlist queue 0 :playback-mode/shuffled :repeat-mode/single)
+          current-track (first queue)
+          next-track (-> (playlist/set-current-song playlist 1)
+                         (playlist/peek))]
+      (is (not (nil? next-track)))
+      (is (not (same-song? current-track next-track))))))

test/cljs/airsonic_ui/utils/helpers_test.cljs

@@ -0,0 +1,14 @@
+(ns airsonic-ui.utils.helpers-test
+  (:require [cljs.test :refer [deftest testing is]]
+            [airsonic-ui.utils.helpers :as helpers]))
+
+(deftest find-where
+  (testing "Finds the correct item and index"
+    (is (= [0 1] (helpers/find-where (partial = 1) (range 1 10))))
+    (is (= [2 {:foo true, :bar false}] (helpers/find-where :foo '({}
+                                                                  {:foo false
+                                                                   :bar true}
+                                                                  {:foo true
+                                                                   :bar false})))))
+  (testing "Returns nil when nothing is found"
+    (is (nil? (helpers/find-where (partial = 2) (range 2))))))