Simple implementation of a browser history app to demonstrate application of the doubly linked list data structure. Also added a file with a few tests

browser_history_dll.py

# Creating a simple browser history app using a doubly linked list in Python is a practical project.
# Below is a basic implementation of a browser history app that allows you to navigate through visited websites using a doubly linked list:
class Node:
    def __init__(self, url):
        self.url = url
        self.prev = None
        self.next = None

    def __repr__(self) -> str:
        return self.url

class BrowserHistory:
    def __init__(self):
        self.current_page = None

    def visit(self, url):
        new_page = Node(url)
        if self.current_page:
            new_page.prev = self.current_page
            self.current_page.next = new_page
        self.current_page = new_page
        print("visited_page:", self.current_page)

    def back(self):
        if self.current_page and self.current_page.prev:
            self.current_page = self.current_page.prev
            print("current_page:", self.current_page)
        else:
            print("No page to go back to")
            print("current_page:", self.current_page)

    def forward(self):
        if self.current_page and self.current_page.next:
            self.current_page = self.current_page.next
            print("current_page:", self.current_page)
        else:
            print("No page to go forward to")
            print("current_page:", self.current_page)


    def display_current_page(self):
        if self.current_page:
            return f"Current Page: {self.current_page}"
        else:
            return "No page is currently open."


def main():
    browser_history = BrowserHistory()

    while True:
        print("\nSimple Browser History App")
        print("1. Visit a Website")
        print("2. Go Back")
        print("3. Go Forward")
        print("4. Display Current Page")
        print("5. Exit")

        choice = input("Enter your choice: ")

        if choice == "1":
            url = input("Enter the URL: ")
            browser_history.visit(url)

        elif choice == "2":
            browser_history.back()

        elif choice == "3":
            browser_history.forward()

        elif choice == "4":
            print(browser_history.display_current_page())

        elif choice == "5":
            print("Exiting the Browser History App.")
            break

        else:
            print("Invalid choice. Please try again.")        

if __name__ == "__main__":
    main()

test_browser_history.py

import unittest
from browser_history_dll import BrowserHistory, Node

class TestBrowserHistory(unittest.TestCase):
    def setUp(self):
        self.browser_history = BrowserHistory()

    def test_initial_current_page(self):
        # Test that the current page is None when the history is empty
        self.assertIsNone(self.browser_history.current_page)

    def test_visit_website(self):
        # Test visiting a website and checking if it becomes the current page
        self.browser_history.visit("https://www.example.com")
        self.assertEqual(self.browser_history.current_page.url, "https://www.example.com")

    def test_back_navigation(self):
        # Test navigating back in the history
        self.browser_history.visit("https://www.example.com")
        self.browser_history.visit("https://www.google.com")
        self.browser_history.back()
        self.assertEqual(self.browser_history.current_page.url, "https://www.example.com")

    def test_forward_navigation(self):
        # Test navigating forward in the history
        self.browser_history.visit("https://www.example.com")
        self.browser_history.visit("https://www.google.com")
        prev_url = self.browser_history.current_page.prev
        self.browser_history.current_page = prev_url
        self.browser_history.forward()
        self.assertEqual(self.browser_history.current_page.url, "https://www.google.com")

    def test_display_current_page(self):
        # Test displaying the current page
        self.browser_history.visit("https://www.example.com")
        self.assertEqual(self.browser_history.display_current_page(), "Current Page: https://www.example.com")

if __name__ == '__main__':
    unittest.main()