refactoring

private/player.rkt

@@ -15,7 +15,8 @@
          "library.rkt"
          "playlists.rkt")
 
-(provide make-player
+(provide player?
+         make-player
          player-state->jsexpr
          player-command!
          player-discover!
@@ -73,9 +74,19 @@
    [volume #:mutable]
    [repeat #:mutable]
    [error #:mutable]
-   local-music-indexes)
+  local-music-indexes)
   #:transparent)
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+; goal   : Hold the shared libraries, playback sessions, outputs and UI state.
+; pre    : make-player supplies all fields and owns construction of the value.
+; post   : Creating or recognizing a player does not start an HTTP server.
+; result : player? recognizes values accepted by the internal server API.
+; internals: make-player initializes the state and command locks, playlist
+;            contexts and playback sessions. player-command! mutates that
+;            state, player-state->jsexpr reads it, and player-close! releases
+;            the owned playback and persistence resources.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 (struct player
   (libraries
    allowed-agent-ids
@@ -373,6 +384,13 @@
    (λ ()
      (set-playback-session-error! session message))))
 
+;;; Converts an internal error value to a JSON-compatible message or key.
+(define (error->jsexpr error)
+  (cond
+    ((eq? error #f) 'null)
+    ((symbol? error) (symbol->string error))
+    (else error)))
+
 (define (clear-session-error! value session)
   (set-session-error! value session #f))
 
@@ -1372,9 +1390,9 @@
         'volume (playback-session-volume session)
         'repeat (symbol->string (playback-session-repeat session))
         'discovering (player-discovering? value)
-        'error (or (playback-session-error session)
-                   (player-error value)
-                   'null))))))))
+        'error (error->jsexpr
+                (or (playback-session-error session)
+                    (player-error value))))))))))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; goal   : Execute one browser player command.
@@ -1722,6 +1740,12 @@
   (require rackunit
            racket/file)
 
+  (check-equal? (error->jsexpr #f) 'null)
+  (check-equal?
+   (error->jsexpr 'dlna-renderer-unreachable)
+   "dlna-renderer-unreachable")
+  (check-equal? (error->jsexpr "technical error") "technical error")
+
   (define root
     (make-temporary-file "rkt-web-player-~a" 'directory))