AI-Assisted Refactoring: Cleaning Up Legacy Code with Video Analysis

TL;DR: Replay leverages AI video analysis to understand user behavior within legacy code, enabling efficient and accurate refactoring by automatically generating clean, functional UI components from screen recordings.

AI-Assisted Refactoring: Breathing New Life into Legacy Code with Video Analysis#

Legacy codebases. We all have them. They're often sprawling, undocumented, and filled with technical debt. Refactoring them can feel like navigating a minefield. Traditional approaches are time-consuming, error-prone, and require deep domain knowledge. What if you could show the AI what you want, rather than tell it?

That's where video analysis comes in, and tools like Replay are revolutionizing the refactoring process. Instead of manually dissecting convoluted logic, you can simply record a video demonstrating the desired behavior, and let the AI reconstruct the UI with clean, modern code.

The Problem with Traditional Refactoring#

Refactoring legacy code is notoriously difficult. Consider these common challenges:

• •Lack of Documentation: Understanding the original intent behind the code can be nearly impossible.
• •Hidden Dependencies: Untangling the web of interconnected components can lead to unexpected breakages.
• •Fear of Regression: Changes can introduce new bugs or resurrect old ones.
• •Time-Consuming Process: Manual refactoring is a slow and tedious process, diverting valuable resources.

This is often the reality for developers:

javascript
// Legacy code - a simplified example of callback hell
const fetchData = (url, callback) => {
  setTimeout(() => {
    // Simulate network request
    const data = { message: "Data fetched from " + url };
    callback(data);
  }, 1000);
};

fetchData('/api/users', (userData) => {
  console.log('User data:', userData);
  fetchData('/api/posts?userId=' + userData.id, (postData) => {
    console.log('Post data:', postData);
    fetchData('/api/comments?postId=' + postData.id, (commentData) => {
      console.log('Comment data:', commentData);
      // More nested callbacks...
    });
  });
});

This code, while functional, is difficult to read and maintain. Refactoring this manually requires carefully tracing the execution flow and understanding the dependencies between the callbacks.

Enter AI-Assisted Refactoring with Replay#

Replay offers a radically different approach. By analyzing video recordings of user interactions with the existing application, it can infer the intended behavior and generate clean, modern UI code. This "behavior-driven reconstruction" significantly reduces the risk of introducing errors and accelerates the refactoring process.

Here's how Replay differs from traditional screenshot-to-code tools:

💡 Pro Tip: Focus on recording clear, concise videos that demonstrate the specific functionality you want to refactor. The cleaner the input, the better the output.

How Replay Works: Behavior-Driven Reconstruction#

Replay uses a sophisticated AI engine, powered by Gemini, to analyze video recordings. It identifies UI elements, tracks user interactions (clicks, scrolls, form inputs), and infers the underlying state transitions. This allows it to generate code that accurately reflects the desired behavior, even in complex, multi-page flows.

The core process involves these steps:

1. •Video Recording: Record a video of you interacting with the legacy UI, demonstrating the functionality you want to refactor.
2. •AI Analysis: Replay analyzes the video, identifying UI elements, user interactions, and state transitions.
3. •Code Generation: Replay generates clean, modern UI code (React, Vue, etc.) based on the analyzed behavior.
4. •Integration: Integrate the generated code into your existing application.

📝 Note: Replay supports various front-end frameworks, including React, Vue, and Angular.

Practical Example: Refactoring a Legacy Form#

Let's say you have a legacy form with convoluted validation logic and a clunky UI. Here's how you can use Replay to refactor it:

Step 1: Record the Interaction

Record a video of you interacting with the form. Show different scenarios:

• •Entering valid data.
• •Entering invalid data and triggering validation errors.
• •Submitting the form successfully.

Step 2: Upload to Replay

Upload the video to Replay. The AI will analyze the video and identify the form fields, validation rules, and submission process.

Step 3: Review and Customize the Generated Code

Replay will generate clean, React code for the form, including:

• •UI components for each form field.
• •Validation logic based on the observed behavior.
• •State management for handling form data and errors.
• •Submission logic for sending the data to the backend.

Here's an example of the generated code:

typescript
// Generated React component by Replay
import React, { useState } from 'react';

const RefactoredForm = () => {
  const [name, setName] = useState('');
  const [email, setEmail] = useState('');
  const [errors, setErrors] = useState({});

  const validateEmail = (email) => {
    // Simple email validation
    return String(email)
      .toLowerCase()
      .match(
        /^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/
      );
  };

  const handleSubmit = (e) => {
    e.preventDefault();
    const newErrors = {};
    if (!name) newErrors.name = 'Name is required';
    if (!email) newErrors.email = 'Email is required';
    else if (!validateEmail(email)) newErrors.email = 'Invalid email format';

    if (Object.keys(newErrors).length > 0) {
      setErrors(newErrors);
      return;
    }

    // Submit the form (replace with your actual submission logic)
    console.log('Form submitted:', { name, email });
    setErrors({}); // Clear errors
  };

  return (
    <form onSubmit={handleSubmit}>
      <div>
        <label htmlFor="name">Name:</label>
        <input type="text" id="name" value={name} onChange={(e) => setName(e.target.value)} />
        {errors.name && <span className="error">{errors.name}</span>}
      </div>
      <div>
        <label htmlFor="email">Email:</label>
        <input type="email" id="email" value={email} onChange={(e) => setEmail(e.target.value)} />
        {errors.email && <span className="error">{errors.email}</span>}
      </div>
      <button type="submit">Submit</button>
    </form>
  );
};

export default RefactoredForm;

Step 4: Integrate into Your Application

Replace the legacy form with the generated

component. You can further customize the component to match your application's styling and requirements.

Benefits of Using Replay for Refactoring#

• •Reduced Risk of Errors: Behavior-driven reconstruction ensures that the refactored code accurately reflects the desired functionality.
• •Faster Development Time: Automated code generation significantly reduces the manual effort required for refactoring.
• •Improved Code Quality: Replay generates clean, modern code that is easier to understand and maintain.
• •Enhanced Collaboration: Video recordings provide a clear and concise way to communicate the desired behavior to other developers.
• •Deeper Understanding: Observing the AI's interpretation of the video can provide valuable insights into the existing code.

⚠️ Warning: While Replay automates much of the refactoring process, it's essential to review the generated code carefully and ensure that it meets your specific requirements. Always run thorough tests after integrating the refactored code into your application.

Advanced Features: Multi-Page Generation, Supabase Integration, and Style Injection#

Replay goes beyond simple component generation and offers advanced features to streamline the refactoring process:

• •Multi-Page Generation: Replay can analyze videos that span multiple pages or screens, generating complete application flows.
• •Supabase Integration: Seamlessly integrate your generated code with Supabase for backend services.
• •Style Injection: Inject custom styles to match your application's design.
• •Product Flow Maps: Automatically generates a visual representation of the user flow, helping you understand the application's structure.

Replay vs. Manual Refactoring: A Head-to-Head Comparison#

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited features and usage. Paid plans are available for more advanced features and higher usage limits. Check the Replay pricing page for the latest details.

How is Replay different from v0.dev?#

While both tools aim to generate code, Replay focuses on behavior-driven reconstruction from video, understanding what the user is trying to achieve. v0.dev primarily uses text prompts and visual references to generate code, focusing on what the UI should look like. Replay's video analysis allows for a deeper understanding of application logic and user flows, leading to more accurate and functional code generation.

What types of videos work best with Replay?#

Clear, concise videos that demonstrate the desired functionality are ideal. Focus on showing different scenarios and edge cases. Avoid unnecessary mouse movements or distractions.

What frameworks does Replay support?#

Replay currently supports React, Vue, and Angular, with plans to add support for more frameworks in the future.

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