trackdb: Create a TagStack with push() and pop() operations

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

trackdb/stack.py

@@ -0,0 +1,20 @@
+# Copyright 2021 (c) Anna Schumaker.
+from . import tags
+
+class TagStack:
+    def __init__(self):
+        self.tags = [ ]
+
+    def pop(self):
+        self.tags.pop(0)
+
+    def push(self, tag):
+        if tag == tags.User["Previous"]:
+            return
+        if tag == tags.User["Collection"]:
+            self.tags.clear()
+            return
+        if tag in self.tags:
+            self.tags.remove(tag)
+        self.tags.insert(0, tag)
+        tag.stacked()

trackdb/test_stack.py

@@ -0,0 +1,39 @@
+# Copyright 2021 (c) Anna Schumaker.
+from lib import tag
+from . import stack
+from . import tags
+import unittest
+
+class TestTagStack(unittest.TestCase):
+    def test_tag_stack_init(self):
+        s = stack.TagStack()
+        self.assertEqual(s.tags, [ ])
+
+    def test_tag_stack_pop(self):
+        s = stack.TagStack()
+        t1 = tag.Tag("Test")
+        t2 = tag.Tag("Test Two")
+        s.tags = [ t1, t2 ]
+
+        s.pop()
+        self.assertEqual(s.tags, [ t2 ])
+        s.pop()
+        self.assertEqual(s.tags, [ ])
+
+    def test_tag_stack_push(self):
+        s = stack.TagStack()
+        t1 = tag.Tag("Test")
+        t2 = tag.Tag("Test Two")
+        t1.current = 3
+
+        s.push(t1)
+        self.assertEqual(s.tags, [ t1 ])
+        self.assertEqual(t1.current, -1)
+        s.push(t2)
+        self.assertEqual(s.tags, [ t2, t1 ])
+        s.push(t1)
+        self.assertEqual(s.tags, [ t1, t2 ])
+        s.push(tags.User["Previous"])
+        self.assertEqual(s.tags, [ t1, t2 ])
+        s.push(tags.User["Collection"])
+        self.assertEqual(s.tags, [ ])