Merge pull request #2509 from SidMehta/Test

Update backend.py

Author: geekcomputers

Diff for: BrowserHistory/backend.py

@@ -2,7 +2,7 @@ class DLL:
     """
         a doubly linked list that holds the current page,
         next page, and previous page.
-        Used to enforce order in operations
+        Used to enforce order in operations.
     """
     def __init__(self, val: str =None):
         self.val = val
@@ -14,61 +14,82 @@ class BrowserHistory:
     """
     This class designs the operations of a browser history
 
-    It works by using a doubly linked list to hold the urls
+    It works by using a doubly linked list to hold the urls with optimized
+    navigation using step counters and memory management
     """
 
     def __init__(self, homepage: str):
         """
         Returns - None
-        Input - None
+        Input - str
         ----------
         - Initialize doubly linked list which will serve as the
             browser history and sets the current page
+        - Initialize navigation counters
         """
-        self.head = DLL(homepage)
-        self.curr = self.head
+        self._head = DLL(homepage)
+        self._curr = self._head
+        self._back_count = 0
+        self._forward_count = 0
 
     def visit(self, url: str) -> None:
         """
         Returns - None
         Input - str
         ----------
         - Adds the current url to the DLL
-        - sets both the next and previous values
+        - Sets both the next and previous values
+        - Cleans up forward history to prevent memory leaks
+        - Resets forward count and increments back count
         """
-        url_node = DLL(url)
-        self.curr.nxt = url_node
-        url_node.prev = self.curr
+        # Clear forward history to prevent memory leaks
+        self._curr.nxt = None
+        self._forward_count = 0
 
-        self.curr = url_node
+        # Create and link new node
+        url_node = DLL(url)
+        self._curr.nxt = url_node
+        url_node.prev = self._curr
 
+        # Update current node and counts
+        self._curr = url_node
+        self._back_count += 1
 
     def back(self, steps: int) -> str:
         """
         Returns - str
         Input - int
         ----------
-        - Iterates through the DLL backwards `step` number of times
-        - returns the appropriate value
+        - Moves backwards through history up to available steps
+        - Updates navigation counters
+        - Returns current page URL
         """
-        while steps > 0 and self.curr.prev:
-            self.curr = self.curr.prev
+        # Only traverse available nodes
+        steps = min(steps, self._back_count)
+        while steps > 0:
+            self._curr = self._curr.prev
             steps -= 1
-        return self.curr.val
-        
+            self._back_count -= 1
+            self._forward_count += 1
+        return self._curr.val
 
     def forward(self, steps: int) -> str:
         """
         Returns - str
         Input - int
         ----------
-        - Iterates through the DLL forewards `step` number of times
-        - returns the appropriate value
+        - Moves forward through history up to available steps
+        - Updates navigation counters
+        - Returns current page URL
         """
-        while steps > 0 and self.curr.nxt:
-            self.curr = self.curr.nxt
+        # Only traverse available nodes
+        steps = min(steps, self._forward_count)
+        while steps > 0:
+            self._curr = self._curr.nxt
             steps -= 1
-        return self.curr.val
+            self._forward_count -= 1
+            self._back_count += 1
+        return self._curr.val
 
 
 if __name__ == "__main__":
@@ -78,4 +99,4 @@ def forward(self, steps: int) -> str:
     param_3 = obj.forward(1)
 
     print(param_2)
-    print(param_3)
+    print(param_3)

Diff for: BrowserHistory/tests/test_browser_history.py

@@ -0,0 +1,91 @@
+import unittest
+import sys
+import os
+
+# Add parent directory to path to import backend
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+from backend import BrowserHistory
+
+class TestBrowserHistory(unittest.TestCase):
+    def setUp(self):
+        """Set up test cases"""
+        self.browser = BrowserHistory("homepage.com")
+
+    def test_initialization(self):
+        """Test proper initialization of BrowserHistory"""
+        self.assertEqual(self.browser._curr.val, "homepage.com")
+        self.assertEqual(self.browser._back_count, 0)
+        self.assertEqual(self.browser._forward_count, 0)
+        self.assertIsNone(self.browser._curr.nxt)
+        self.assertIsNone(self.browser._curr.prev)
+
+    def test_visit(self):
+        """Test visit functionality and forward history cleanup"""
+        self.browser.visit("page1.com")
+        self.assertEqual(self.browser._curr.val, "page1.com")
+        self.assertEqual(self.browser._back_count, 1)
+        self.assertEqual(self.browser._forward_count, 0)
+
+        # Test forward history cleanup
+        self.browser.visit("page2.com")
+        self.browser.back(1)
+        self.browser.visit("page3.com")  # Should clear forward history
+        self.assertIsNone(self.browser._curr.nxt)
+        self.assertEqual(self.browser._forward_count, 0)
+
+    def test_back_navigation(self):
+        """Test back navigation with counter validation"""
+        # Setup history
+        self.browser.visit("page1.com")
+        self.browser.visit("page2.com")
+        
+        # Test normal back navigation
+        result = self.browser.back(1)
+        self.assertEqual(result, "page1.com")
+        self.assertEqual(self.browser._back_count, 1)
+        self.assertEqual(self.browser._forward_count, 1)
+
+        # Test back with more steps than available
+        result = self.browser.back(5)  # Should only go back 1 step
+        self.assertEqual(result, "homepage.com")
+        self.assertEqual(self.browser._back_count, 0)
+        self.assertEqual(self.browser._forward_count, 2)
+
+    def test_forward_navigation(self):
+        """Test forward navigation with counter validation"""
+        # Setup history and position
+        self.browser.visit("page1.com")
+        self.browser.visit("page2.com")
+        self.browser.back(2)  # Go back to homepage
+        
+        # Test normal forward navigation
+        result = self.browser.forward(1)
+        self.assertEqual(result, "page1.com")
+        self.assertEqual(self.browser._forward_count, 1)
+        self.assertEqual(self.browser._back_count, 1)
+
+        # Test forward with more steps than available
+        result = self.browser.forward(5)  # Should only go forward remaining 1 step
+        self.assertEqual(result, "page2.com")
+        self.assertEqual(self.browser._forward_count, 0)
+        self.assertEqual(self.browser._back_count, 2)
+
+    def test_complex_navigation(self):
+        """Test complex navigation patterns"""
+        self.browser.visit("page1.com")
+        self.browser.visit("page2.com")
+        self.browser.visit("page3.com")
+        
+        # Back navigation
+        self.assertEqual(self.browser.back(2), "page1.com")
+        
+        # New visit should clear forward history
+        self.browser.visit("page4.com")
+        self.assertEqual(self.browser._forward_count, 0)
+        self.assertIsNone(self.browser._curr.nxt)
+        
+        # Verify we can't go forward to cleared history
+        self.assertEqual(self.browser.forward(1), "page4.com")
+
+if __name__ == '__main__':
+    unittest.main()