add filter implementation

owrx/active/list/__init__.py

@@ -48,6 +48,34 @@ class ActiveListTransformationListener(ActiveListListener):
                 del self.target[change.index]
 
 
+class ActiveListFilterListener(ActiveListListener):
+    def __init__(self, filter: callable, keyMap: list, target: "ActiveList"):
+        self.filter = filter
+        self.keyMap = keyMap
+        self.target = target
+
+    def onListChange(self, changes: list[ActiveListChange]):
+        for change in changes:
+            if isinstance(change, ActiveListIndexAppended):
+                if self.filter(change.newValue):
+                    self.target.append(change.newValue)
+                    self.keyMap.append(len(self.target) - 1)
+            elif isinstance(change, ActiveListIndexUpdated):
+                if change.index in self.keyMap and not self.filter(change.newValue):
+                    idx = self.keyMap.index(change.index)
+                    del self.target[idx]
+                    del self.keyMap[idx]
+                elif change.index not in self.keyMap and self.filter(change.newValue):
+                    # TODO insert, not append
+                    self.target.append(change.newValue)
+                    self.keyMap.append(len(self.target) - 1)
+            elif isinstance(change, ActiveListIndexDeleted):
+                if change.index in self.keyMap:
+                    idx = self.keyMap.index(change.index)
+                    del self.target[idx]
+                    del self.keyMap[idx]
+
+
 class ActiveList:
     def __init__(self, elements: list = None):
         self.delegate = elements.copy() if elements is not None else []
@@ -82,6 +110,16 @@ class ActiveList:
         self.addListener(ActiveListTransformationListener(transform, res))
         return res
 
+    def filter(self, filter: callable):
+        res = ActiveList()
+        keyMap = []
+        for idx, val in enumerate(self):
+            if filter(val):
+                res.append(val)
+                keyMap.append(idx)
+        self.addListener(ActiveListFilterListener(filter, keyMap, res))
+        return res
+
     def __setitem__(self, key, value):
         if self.delegate[key] == value:
             return

test/owrx/active/list/test_active_list.py

@@ -121,3 +121,30 @@ class ActiveListTest(TestCase):
         transformedList = list.map(lambda x: "prefix-{}".format(x))
         del list[0]
         self.assertEqual(transformedList[0], "prefix-value2")
+
+    def testFilter(self):
+        list = ActiveList([1, 2, 3, 4, 5])
+        filteredList = list.filter(lambda x: x < 3)
+        self.assertEqual(len(filteredList), 2)
+        self.assertEqual(filteredList[0], 1)
+        self.assertEqual(filteredList[1], 2)
+
+    def testActiveFilterAppend(self):
+        list = ActiveList([1, 2, 3, 4, 5])
+        filteredList = list.filter(lambda x: x < 3)
+        list.append(0)
+        self.assertEqual(len(filteredList), 3)
+        self.assertEqual(filteredList[2], 0)
+
+    def testActiveFilterUpdate(self):
+        list = ActiveList([1, 2, 3, 4, 5])
+        filteredList = list.filter(lambda x: x < 3)
+        list[3] = 0
+        self.assertEqual(len(filteredList), 3)
+        self.assertEqual(filteredList[2], 0)
+
+    def testActiveFilterDelete(self):
+        list = ActiveList([1, 2, 3, 4, 5])
+        filteredList = list.filter(lambda x: x < 3)
+        del list[1]
+        self.assertEqual(len(filteredList), 1)