From bfcabb4cc1e3a5cd1a14f751d7e0910bf79c1a07 Mon Sep 17 00:00:00 2001
From: Xceptions <agbokenechukwu.k@gmail.com>
Date: Thu, 24 Oct 2024 17:05:54 +0100
Subject: [PATCH 1/2] added the backend of the browser history

---
 BrowserHistory/backend.py | 47 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 BrowserHistory/backend.py

diff --git a/BrowserHistory/backend.py b/BrowserHistory/backend.py
new file mode 100644
index 00000000000..20ee0005c13
--- /dev/null
+++ b/BrowserHistory/backend.py
@@ -0,0 +1,47 @@
+class DLL:
+    def __init__(self, val: str =None):
+        self.val = val
+        self.nxt = None
+        self.prev = None
+
+
+class BrowserHistory:
+    """
+        This class designs the operations of a
+        broswer history
+    """
+
+    def __init__(self, homepage: str):
+        self.head = DLL(homepage)
+        self.curr = self.head
+        
+    def visit(self, url: str) -> None:
+        url_node = DLL(url)
+        self.curr.nxt = url_node
+        url_node.prev = self.curr
+        
+        self.curr = url_node
+        
+
+    def back(self, steps: int) -> str:
+        while steps > 0 and self.curr.prev:
+            self.curr = self.curr.prev
+            steps -= 1
+        return self.curr.val
+        
+
+    def forward(self, steps: int) -> str:
+        while steps > 0 and self.curr.nxt:
+            self.curr = self.curr.nxt
+            steps -= 1
+        return self.curr.val
+        
+
+if __name__ == "__main__":
+    obj = BrowserHistory("google.com")
+    obj.visit("twitter.com")
+    param_2 = obj.back(1)
+    param_3 = obj.forward(1)
+
+    print(param_2)
+    print(param_3)
\ No newline at end of file

From fe60f2c95a4e13ea8d3fa9b2d60eebcf9f18bd37 Mon Sep 17 00:00:00 2001
From: Xceptions <agbokenechukwu.k@gmail.com>
Date: Thu, 24 Oct 2024 17:57:11 +0100
Subject: [PATCH 2/2] added comments to code

---
 BrowserHistory/backend.py | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/BrowserHistory/backend.py b/BrowserHistory/backend.py
index 20ee0005c13..5eed004cbf2 100644
--- a/BrowserHistory/backend.py
+++ b/BrowserHistory/backend.py
@@ -1,4 +1,9 @@
 class DLL:
+    """
+        a doubly linked list that holds the current page,
+        next page, and previous page.
+        Used to enforce order in operations
+    """
     def __init__(self, val: str =None):
         self.val = val
         self.nxt = None
@@ -7,15 +12,30 @@ def __init__(self, val: str =None):
 
 class BrowserHistory:
     """
-        This class designs the operations of a
-        broswer history
+    This class designs the operations of a browser history
+
+    It works by using a doubly linked list to hold the urls
     """
 
     def __init__(self, homepage: str):
+        """
+        Returns - None
+        Input - None
+        ----------
+        - Initialize doubly linked list which will serve as the
+            browser history and sets the current page
+        """
         self.head = DLL(homepage)
         self.curr = self.head
         
     def visit(self, url: str) -> None:
+        """
+        Returns - None
+        Input - str
+        ----------
+        - Adds the current url to the DLL
+        - sets both the next and previous values
+        """
         url_node = DLL(url)
         self.curr.nxt = url_node
         url_node.prev = self.curr
@@ -24,6 +44,13 @@ def visit(self, url: str) -> None:
         
 
     def back(self, steps: int) -> str:
+        """
+        Returns - str
+        Input - int
+        ----------
+        - Iterates through the DLL backwards `step` number of times
+        - returns the appropriate value
+        """
         while steps > 0 and self.curr.prev:
             self.curr = self.curr.prev
             steps -= 1
@@ -31,6 +58,13 @@ def back(self, steps: int) -> str:
         
 
     def forward(self, steps: int) -> str:
+        """
+        Returns - str
+        Input - int
+        ----------
+        - Iterates through the DLL forewards `step` number of times
+        - returns the appropriate value
+        """
         while steps > 0 and self.curr.nxt:
             self.curr = self.curr.nxt
             steps -= 1