feat: add default implementations of procedures.

Jellyfin.Plugin.SmartPlaylist/Lisp/Interpreter.cs

@@ -76,6 +76,12 @@ namespace Jellyfin.Plugin.SmartPlaylist.Lisp {
         }
     }
 
+    public class DefaultEnvironment: Environment {
+        public DefaultEnvironment() {
+            this["find"] = new Parser("(lambda (item list) (if (= list ()) nil (if (= item (car list)) (car list) (find item (cdr list)))))").parse();
+        }
+    }
+
     public class SubEnvironment : Dictionary<string, Expression>, IEnvironment<string, Expression> {
         private IEnvironment<string, Expression> _super;
         public SubEnvironment(IEnvironment<string, Expression> super) {
@@ -375,6 +381,11 @@ namespace Jellyfin.Plugin.SmartPlaylist.Lisp {
             _builtins = builtins;
             _builtinsLater = builtinsLater;
         }
+        public Executor(IEnvironment<string, Expression> environment) {
+            _environment = environment;
+            _builtins = new Builtins();
+            _builtinsLater = new BuiltinsLater();
+        }
         public Executor() {
             _environment = new Environment();
             _builtins = new Builtins();

Jellyfin.Plugin.SmartPlaylist/ScheduledTasks/GeneratePlaylist.cs

@@ -104,7 +104,7 @@ namespace Jellyfin.Plugin.SmartPlaylist.ScheduledTasks {
         private IEnumerable<Guid> FilterPlaylistItems(IEnumerable<BaseItem> items, User user, SmartPlaylistDto smartPlaylist) {
             List<Guid> results = new List<Guid>();
             Expression expression = new Parser(StringTokenStream.generate(smartPlaylist.Program)).parse();
-            Executor executor = new Executor();
+            Executor executor = new Executor(new DefaultEnvironment());
             executor.environment.Set("user", new Lisp_Object(user));
             foreach (var i in items) {
                 executor.environment.Set("item", new Lisp_Object(i));

Tests/Tests.cs

@@ -172,5 +172,12 @@ namespace Tests
             r = e.eval("(begin (define find (lambda (item list) (if (= list ()) nil (if (= item (car list)) (car list) (find item (cdr list)))))) (find 0 (1 2 3 4)))");
             Assert.Equal(string.Format("{0}", r), "nil");
         }
+
+        [Fact]
+        public static void DefaultEnvironmentTest() {
+            Executor e = new Executor(new DefaultEnvironment());
+            Assert.Equal("nil", e.eval("(find 0 (1 2 3 4))").ToString());
+            Assert.Equal("3", e.eval("(find 3 (1 2 3 4))").ToString());
+        }
     }
 }