curds: Clean up how nodes are inserted and linked

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/node.py

@@ -10,17 +10,25 @@ class PlaylistNode:
         self.parent     = None
         self.prev_child = None
 
-    def __link_children__(self, b, c):
-        if c.prev_child:
-            c.prev_child.next_child = b
-        if b:
-            b.prev_child = c.prev_child
-            b.next_child = c
-        c.prev_child = b
+    def __link_children__(self, a, b, c):
+        if a:
+            a.next_child = b
+        b.parent = self
+        b.prev_child = a
+        b.next_child = c
+        if c:
+            c.prev_child = b
 
     def __lt__(self, rhs):
         return self.name < rhs.name
 
+    def __insert_node__(self, child, index):
+        self.children.insert(index, child)
+        self.__link_children__(self.nth_child(index - 1), child,
+                               self.nth_child(index + 1))
+        notify.notify("node-inserted", child, index)
+        return index
+
     def __normalize__(self, name):
         return name.title()
 
@@ -28,14 +36,7 @@ class PlaylistNode:
         return f"<small>\n</small><big>{self.name}</big>"
 
     def append_child(self, child):
-        prev = None
-        if len(self.children) > 0:
-            prev = self.children[-1]
-        self.children.append(child)
-        child.parent = self
-        self.__link_children__(prev, child)
-        notify.notify("node-inserted", child, child.node_index())
-        return self.children.index(child)
+        return self.__insert_node__(child, len(self.children))
 
     def get_node(self, path):
         if len(path) == 1:
@@ -54,6 +55,12 @@ class PlaylistNode:
     def has_sibling(self):
         return (self.next_child != None) or (self.prev_child != None)
 
+    def insert_child(self, child):
+        for i, n in enumerate(self.children):
+            if child < n:
+                return self.__insert_node__(child, i)
+        return self.append_child(child)
+
     def lookup(self, name):
         name = self.__normalize__(name)
         for node in self.children:
@@ -61,26 +68,16 @@ class PlaylistNode:
                 return node
         return None
 
+    def n_children(self):
+        return len(self.children)
+
     def node_index(self):
         if self.parent == None:
             return None
         return self.parent.children.index(self)
 
-    def insert_child(self, child):
-        for i, n in enumerate(self.children):
-            if child < n:
-                self.children.insert(i, child)
-                child.parent = self
-                self.__link_children__(child, n)
-                notify.notify("node-inserted", child, child.node_index())
-                return self.children.index(child)
-        return self.append_child(child)
-
-    def n_children(self):
-        return len(self.children)
-
     def nth_child(self, n):
-        if n < len(self.children):
+        if -1 < n < len(self.children):
             return self.children[n]
         return None
 

curds/playlist/test_node.py

@@ -137,10 +137,12 @@ class TestPlaylistNode(unittest.TestCase):
         root.append_child(b)
         a.append_child(c)
 
+        self.assertIsNone(root.nth_child(-1))
         self.assertEqual( root.nth_child(0), a)
         self.assertEqual( root.nth_child(1), b)
         self.assertIsNone(root.nth_child(2))
 
+        self.assertIsNone(a.nth_child(-1))
         self.assertEqual( a.nth_child(0), c)
         self.assertIsNone(a.nth_child(1))