Rebuilding Legacy Angular Apps from Screen Recordings with Replay AI

TL;DR: Replay leverages video analysis and AI to dramatically simplify the process of rebuilding legacy Angular applications, offering a faster, more accurate alternative to traditional methods.

The Legacy Angular Nightmare: Can AI Really Help?#

Let's face it: dealing with legacy Angular applications is a pain. The codebases are often brittle, poorly documented, and maintained by teams who've long moved on. Rewriting from scratch is a massive undertaking, and traditional "screenshot-to-code" tools just don't cut it. They give you a static representation, not the dynamic behavior you need.

The problem isn't just what the application looks like, it's how users interact with it. Understanding the user flows, the edge cases, and the subtle nuances of the UI is crucial for a successful rebuild. This is where Replay comes in. Instead of relying on static images, Replay analyzes video recordings of the application in action, using Gemini-powered AI to reconstruct a fully functional UI, complete with behavior and logic.

Behavior-Driven Reconstruction: Video as the Source of Truth#

Traditional approaches focus on visual replication. Replay takes a radically different stance: behavior-driven reconstruction. This means we treat video recordings as the source of truth for understanding the application's functionality.

Here's why this is a game-changer:

• •Understands User Intent: Replay doesn't just see buttons; it sees clicks, form submissions, and page transitions.
• •Captures Complex Flows: Multi-page generation allows Replay to reconstruct entire user journeys, not just isolated components.
• •Handles Dynamic Content: Video captures the application's response to user actions, including dynamic data and state changes.

This approach allows Replay to generate code that's not only visually accurate but also functionally equivalent to the original application.

Replay vs. Traditional Methods: A Head-to-Head Comparison#

Let's see how Replay stacks up against other tools and approaches:

As you can see, Replay offers a compelling balance of speed, accuracy, and cost-effectiveness, making it an ideal solution for rebuilding legacy Angular applications.

Rebuilding an Angular Component with Replay: A Practical Example#

Let's say we have a legacy Angular component responsible for displaying a user profile. We have a video recording of a user interacting with this component. Here's how we can use Replay to rebuild it:

Step 1: Record and Upload the Video#

First, record a video of yourself interacting with the user profile component. Ensure the video captures all relevant user actions, such as scrolling, clicking buttons, and filling out forms. Upload the video to Replay.

Step 2: Replay Analyzes the Video#

Replay's AI engine analyzes the video, identifying UI elements, user interactions, and data flows. This process typically takes a few minutes, depending on the length and complexity of the video.

Step 3: Generate the Code#

Once the analysis is complete, Replay generates the Angular code for the component. This code includes:

• •HTML markup for the UI elements
• •TypeScript code for the component logic
• •CSS styles for the visual appearance

Here's an example of the generated TypeScript code:

typescript
// Generated by Replay
import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-user-profile',
  templateUrl: './user-profile.component.html',
  styleUrls: ['./user-profile.component.css']
})
export class UserProfileComponent implements OnInit {
  user: any; // Placeholder for user data

  constructor() { }

  ngOnInit(): void {
    // Fetch user data (replace with actual implementation)
    this.user = {
      name: 'John Doe',
      email: 'john.doe@example.com',
      profileImage: 'https://example.com/profile.jpg'
    };
  }

  updateProfile(): void {
    // Handle profile update logic (replace with actual implementation)
    console.log('Profile updated!');
  }
}

💡 Pro Tip: Replay often generates placeholder comments like "// Replace with actual implementation". These guide you to the areas where you need to add custom logic or connect to your backend services.

Step 4: Integrate and Customize#

The generated code is a starting point. You'll need to integrate it into your existing Angular project and customize it to fit your specific requirements. This may involve:

• •Connecting the component to your backend API
• •Adding custom validation logic
• •Refining the UI styles

📝 Note: Replay's Supabase integration can significantly streamline the process of connecting your components to a database.

Step 5: Iterate and Refine#

Use the generated code as a foundation and iterate on it until you achieve the desired functionality and appearance. You can use Replay to generate new code based on updated video recordings, allowing you to continuously refine the component.

The Power of Style Injection and Product Flow Maps#

Replay offers two additional features that are particularly useful for rebuilding legacy Angular applications:

• •Style Injection: Replay can analyze the styles used in the original application and inject them into the generated code. This helps to ensure that the rebuilt component looks and feels consistent with the rest of the application.
• •Product Flow Maps: Replay can generate visual maps of the user flows within the application. These maps provide a high-level overview of the application's functionality and can be invaluable for understanding complex user journeys.

Addressing Common Challenges in Legacy Angular Rebuilds#

Rebuilding legacy Angular applications often presents unique challenges. Here's how Replay helps overcome them:

• •Lack of Documentation: Replay's video analysis provides a visual and behavioral understanding of the application, even in the absence of documentation.
• •Complex Codebases: Replay breaks down the application into smaller, manageable components, making it easier to understand and rebuild.
• •Outdated Dependencies: Replay generates code that's compatible with modern Angular versions, allowing you to upgrade your dependencies.

⚠️ Warning: While Replay significantly accelerates the rebuilding process, it's not a magic bullet. You'll still need to have a solid understanding of Angular development and the specific requirements of your application.

Code Block Example: Fetching Data with Error Handling#

Here's a more robust example of fetching data within a generated component, including error handling:

typescript
import { Component, OnInit } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Component({
  selector: 'app-data-display',
  templateUrl: './data-display.component.html',
  styleUrls: ['./data-display.component.css']
})
export class DataDisplayComponent implements OnInit {
  data: any;
  loading: boolean = true;
  error: string = '';

  constructor(private http: HttpClient) { }

  ngOnInit(): void {
    this.fetchData();
  }

  async fetchData(): Promise<void> {
    this.loading = true;
    this.error = '';
    try {
      const response = await this.http.get('/api/data').toPromise();
      this.data = response;
    } catch (e: any) {
      this.error = 'Error fetching data: ' + e.message;
      console.error(e);
    } finally {
      this.loading = false;
    }
  }
}

This example demonstrates how Replay can help generate the basic structure for data fetching, while you add the specific API endpoint and error handling logic.

Frequently Asked Questions#

Is Replay free to use?#

Replay offers a free tier with limited features. Paid plans are available for more advanced functionality and higher usage limits.

How is Replay different from v0.dev?#

v0.dev primarily focuses on generating UI components based on text prompts. Replay, on the other hand, analyzes video recordings to understand user behavior and reconstruct entire application flows. Replay uses video as a source of truth for accurate UI reconstruction, understanding what users are doing, not just what they see.

What types of Angular applications can Replay rebuild?#

Replay can rebuild a wide range of Angular applications, from simple CRUD applications to complex enterprise systems. The key is to have clear video recordings of the application in action.

Does Replay support other frameworks besides Angular?#

Currently, Replay is optimized for Angular. Support for other frameworks is planned for future releases.

How accurate is the generated code?#

The accuracy of the generated code depends on the quality of the video recording and the complexity of the application. However, Replay consistently achieves high levels of accuracy, often exceeding 90%.

---

Ready to try behavior-driven code generation? Get started with Replay - transform any video into working code in seconds.