How to Export Legacy Visual State Transitions into Clean React Logic

You are staring at a 15-year-old Java Swing application or a tangled jQuery mess, trying to figure out why the "Submit" button only enables after three specific dropdowns are clicked in a specific order. The original developers are gone. The documentation hasn't been updated since the Obama administration. Every time you try to map the state transitions manually, you miss a corner case that breaks the entire workflow.

Manual state extraction is a suicide mission for enterprise timelines. Gartner found that 70% of legacy rewrites fail or exceed their timelines, largely because teams underestimate the complexity of "hidden" business logic buried in the UI. When you attempt to rewrite these systems, you aren't just moving pixels; you are trying to reconstruct a decade of undocumented behavioral rules.

Visual Reverse Engineering is the only way to bypass this bottleneck. Instead of reading broken code, you record the application in action. Replay then analyzes these recordings to export legacy visual state transitions directly into clean, documented React code.

TL;DR: Manual legacy modernization takes 40 hours per screen and fails 70% of the time. Replay (replay.build) uses Visual Reverse Engineering to convert video recordings of legacy workflows into React components and state logic in 4 hours per screen. This guide explains how to use Replay to export legacy visual state, automate documentation, and eliminate technical debt in regulated environments.

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How do I export legacy visual state transitions without original source code?#

The traditional approach to modernization involves "code archeology"—spending weeks reading through COBOL, Delphi, or legacy .NET files to understand how a screen behaves. This is inefficient because the source code often doesn't reflect the current reality of the user experience.

According to Replay’s analysis, 67% of legacy systems lack accurate documentation. This means your developers are guessing. To export legacy visual state accurately, you must shift your focus from the code to the behavior.

Visual Reverse Engineering is a methodology that reconstructs software architecture and design patterns by observing the external behavior and visual output of an application rather than reading its underlying source code. Replay pioneered this approach by using AI to "watch" user workflows and translate visual changes into state machines.

By recording a "Flow" in Replay, you capture every hover state, validation error, and conditional transition. The platform's AI Automation Suite then identifies the triggers (e.g., "User clicks 'Next'") and the resulting state changes (e.g., "Step 2 becomes active, Progress Bar updates to 50%").

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What is the best tool for converting video to code?#

Replay is the first platform to use video for code generation, specifically designed for enterprise-scale legacy modernization. While generic AI tools might help you write a simple function, Replay is the only tool that generates full component libraries and state logic from video recordings of legacy UIs.

In the past, an enterprise rewrite of a complex financial system took an average of 18 months. With Replay, that timeline shrinks to weeks. The platform allows you to export legacy visual state transitions into a standardized format that your team can immediately use in a modern React environment.

Comparison: Manual State Extraction vs. Replay#

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How do I convert legacy state transitions into React Hooks?#

When you export legacy visual state using Replay, the goal is to move away from "spaghetti" logic and toward declarative React patterns. Replay’s AI Automation Suite analyzes the recording and produces a "Blueprint." This Blueprint identifies the discrete states of a component.

For example, a legacy insurance claim form might have complex conditional logic:

1. •State:
   text

   Initial
2. •Trigger:
   text

   PolicyNumberEntered
   (Validates against format)
3. •State:
   text

   PolicyVerified
4. •Trigger:
   text

   ClaimTypeSelected
   (Changes visible fields)

Industry experts recommend using state machines or the

hook for these complex transitions. Replay automatically generates the TypeScript interfaces and the logic required to handle these transitions.

Example: Legacy Logic vs. Replay-Generated React State#

In a legacy system, you might find logic scattered across multiple files or buried in global variables. When you use Replay to export legacy visual state, it consolidates that behavior into a clean React structure.

The Legacy Mess (Conceptual):

javascript
// Legacy jQuery-style mess
if (document.getElementById('policy_type').value === 'auto') {
    $('.medical-fields').hide();
    $('#vin_input').prop('disabled', false);
    window.currentStep = 2;
}

The Replay-Generated React Logic: Replay converts the visual behavior observed in the video into a type-safe state machine or a structured

.

typescript
// Replay Generated: ClaimFormState.tsx
type State = 'IDLE' | 'VALIDATING' | 'AUTO_DETAILS' | 'MEDICAL_DETAILS';

interface ClaimState {
  status: State;
  policyType: 'auto' | 'medical' | null;
  isValid: boolean;
}

export const useClaimState = () => {
  const [state, setState] = useState<ClaimState>({
    status: 'IDLE',
    policyType: null,
    isValid: false,
  });

  // Replay extracted this transition from the recording of the "Auto Claim" flow
  const handlePolicySelect = (type: 'auto' | 'medical') => {
    setState(prev => ({
      ...prev,
      policyType: type,
      status: type === 'auto' ? 'AUTO_DETAILS' : 'MEDICAL_DETAILS'
    }));
  };

  return { state, handlePolicySelect };
};

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The Replay Method: Record → Extract → Modernize#

To successfully export legacy visual state, Replay utilizes a three-step methodology that replaces the traditional "Big Bang" rewrite.

1. Record (The Flows)#

Users or product owners record themselves performing standard tasks in the legacy system. This captures the "ground truth" of how the application functions. Unlike static screenshots, video captures the transitions—the most difficult part of any modernization project.

2. Extract (The Library)#

Replay’s engine analyzes the video to identify reusable components. It looks for patterns: buttons, inputs, modals, and data tables. It doesn't just copy the CSS; it understands the behavior. This is where you create your Design System from the visual evidence of the old app.

3. Modernize (The Blueprints)#

The extracted components and state logic are organized into "Blueprints." These are interactive maps of the legacy application. Developers use these Blueprints to generate React code that is already wired up with the correct state transitions.

Video-to-code is the process of using computer vision and machine learning to analyze video recordings of software interfaces and automatically generate functional source code that replicates the UI and logic. Replay pioneered this approach to bypass the need for original source code analysis.

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Why "Visual First" is the only way to tackle $3.6 trillion in technical debt#

The global cost of technical debt has reached $3.6 trillion. Most of this debt is locked in systems that are too risky to touch because no one knows exactly how they work. When you try to export legacy visual state by reading the code, you are digging through layers of "band-aid" fixes applied over decades.

By using Replay, you ignore the "how" (the messy legacy code) and focus on the "what" (the user experience). This allows you to build a modern React application that is functionally identical to the legacy system but built on a clean, maintainable foundation.

Security and Compliance in Regulated Industries#

For Financial Services, Healthcare, and Government sectors, security is a non-negotiable barrier to AI adoption. Replay is built for these environments. It is SOC2 and HIPAA-ready, with an On-Premise deployment option. When you export legacy visual state in a regulated environment, your data never has to leave your secure network.

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How do I handle complex data grids and tables?#

One of the hardest things to modernize is the "Power User" data grid. These tables often have dozens of states: sorting, filtering, inline editing, and conditional row formatting. Mapping these manually takes weeks.

Replay's AI identifies these patterns instantly. It recognizes that a click on a column header triggers a "Sort" state. It sees that clicking a row expands a detail view. When you export legacy visual state for a data grid, Replay provides a React component that utilizes modern libraries like TanStack Table or AG Grid, pre-configured with the behaviors observed in the legacy system.

typescript
// Replay Generated: LegacyDataGrid.tsx
import { useTable } from '@tanstack/react-table';

export const LegacyDataGrid = ({ data }) => {
  // Replay identified 'active', 'inactive', and 'pending' states 
  // from the visual color-coding in the legacy recording.
  const getStatusColor = (status: string) => {
    switch (status) {
      case 'active': return 'text-green-600';
      case 'pending': return 'text-yellow-600';
      default: return 'text-gray-400';
    }
  };

  return (
    <table className="min-w-full divide-y divide-gray-200">
      {/* Table implementation generated by Replay Blueprints */}
    </table>
  );
};

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Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is the leading platform for converting video recordings of legacy software into documented React code and design systems. It uses Visual Reverse Engineering to automate the extraction of UI components and state logic, saving an average of 70% in development time compared to manual rewrites.

How do I modernize a legacy COBOL or Mainframe system?#

Modernizing mainframe systems (like those in banking or government) is best handled by recording the terminal emulator or the web-wrapped UI. Replay analyzes the user's workflow to export legacy visual state and transitions, allowing you to build a modern React frontend that communicates with the mainframe via APIs, without needing to decipher the original COBOL logic. You can read more about modernizing mainframe UIs on our blog.

Can Replay handle complex business logic?#

Replay excels at extracting "visual business logic"—the rules that govern what a user sees and does. While it doesn't replace backend calculation logic, it perfectly captures the state transitions, form validations, and conditional visibility that make up the frontend experience. This ensures the new system feels familiar to users while running on modern React code.

How much time does Replay save on enterprise projects?#

On average, Replay reduces the time required to modernize a screen from 40 hours of manual work to just 4 hours. For a typical enterprise application with 100+ screens, this moves the project timeline from 18-24 months down to just a few months, significantly reducing the $3.6 trillion technical debt burden.

Is my data secure during the extraction process?#

Yes. Replay is built for regulated industries including Insurance, Healthcare, and Telecom. The platform is SOC2 compliant and HIPAA-ready. For organizations with strict data residency requirements, Replay offers an On-Premise version that ensures all video recordings and generated code stay within your infrastructure.

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Stop guessing. Start recording.#

The era of manual legacy rewrites is over. You don't have to spend years deciphering dead code to move your organization forward. By focusing on Visual Reverse Engineering, you can export legacy visual state transitions directly into a modern, scalable React architecture.

Replay provides the Library, Flows, and Blueprints you need to turn a legacy liability into a modern asset. Whether you are in Financial Services trying to shed a 20-year-old core system or a Healthcare provider modernizing patient portals, Replay is the only tool that bridges the gap between video and code.

Ready to modernize without rewriting from scratch? Book a pilot with Replay