curds: Implement a node.insert_child() function

This inserts the node in sorted order

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

curds/playlist/node.py

@@ -7,3 +7,28 @@ class PlaylistNode:
         self.name     = name
         self.next     = None
         self.prev     = None
+
+    def __link_children__(self, b, c):
+        if c.prev:
+            c.prev.next = b
+        if b:
+            b.prev = c.prev
+            b.next = c
+        c.prev = b
+
+    def __lt__(self, rhs):
+        return self.name < rhs.name
+
+    def insert_child(self, child):
+        n = None
+        for i, n in enumerate(self.children):
+            if child < n:
+                self.children.insert(i, child)
+                self.__link_children__(child, n)
+                return self.children.index(child)
+        self.children.append(child)
+        self.__link_children__(n, child)
+        return self.children.index(child)
+
+    def n_children(self):
+        return len(self.children)

curds/playlist/test_node.py

@@ -14,3 +14,43 @@ class TestPlaylistNode(unittest.TestCase):
         n = node.PlaylistNode("Test Node", "test-icon")
         self.assertEqual(n.icon, "test-icon")
         self.assertEqual(n.name, "Test Node")
+
+    def test_node_less_than(self):
+        a = node.PlaylistNode("a")
+        b = node.PlaylistNode("b")
+
+        self.assertTrue( a < b)
+        self.assertFalse(b < a)
+        self.assertFalse(a < a)
+
+    def test_node_insert_child(self):
+        root = node.PlaylistNode()
+        a = node.PlaylistNode("a")
+        b = node.PlaylistNode("b")
+        c = node.PlaylistNode("c")
+        d = node.PlaylistNode("d")
+
+        self.assertEqual(root.n_children(), 0)
+        self.assertEqual(root.insert_child(b), 0)
+        self.assertEqual(root.n_children(),    1)
+        self.assertEqual(root.children, [ b ])
+
+        self.assertEqual(root.insert_child(d), 1)
+        self.assertEqual(root.n_children(),    2)
+        self.assertEqual(root.children, [ b, d ])
+        self.assertEqual(b.next, d)
+        self.assertEqual(d.prev, b)
+
+        self.assertEqual(root.insert_child(c), 1)
+        self.assertEqual(root.n_children(),    3)
+        self.assertEqual(root.children, [ b, c, d ])
+        self.assertEqual(b.next, c)
+        self.assertEqual(c.prev, b)
+        self.assertEqual(c.next, d)
+        self.assertEqual(d.prev, c)
+
+        self.assertEqual(root.insert_child(a), 0)
+        self.assertEqual(root.n_children(),    4)
+        self.assertEqual(root.children, [ a, b, c, d ])
+        self.assertEqual(a.next, b)
+        self.assertEqual(b.prev, a)