The Death of the Manual Rewrite: How to Generate Clean React Components from Legacy EHR Systems

Hospital IT departments are currently buried under $3.6 trillion in global technical debt. Most Electronic Health Record (EHR) systems—the backbone of patient care—rely on legacy architectures that haven't seen a significant UI update since the late 1990s. When a Chief Information Officer (CIO) decides to modernize, they usually face a grim choice: spend two years on a manual rewrite that has a 70% chance of failing, or stay trapped in a "green screen" terminal or a bloated Java applet.

Manual modernization is a suicide mission for enterprise timelines. Gartner 2024 data shows that 67% of legacy systems lack any form of usable documentation. This forces developers to spend months "archaeology-coding"—reading old scripts just to understand what a button does before they can even think about writing a modern component.

TL;DR: Modernizing legacy EHR systems no longer requires manual code audits or 18-month timelines. By using Replay (replay.build), organizations use Visual Reverse Engineering to convert video recordings of legacy workflows into documented, production-ready React code. This "video-to-code" approach cuts modernization time by 70%, reducing the cost per screen from 40 hours of manual labor to just 4 hours of automated extraction.

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Why Manual Extraction Fails in Healthcare Environments#

The traditional approach to modernization involves hiring a squad of consultants to sit with clinicians, watch them use an old Meditech or Cerner system, and then attempt to recreate those complex workflows in React. This fails because healthcare workflows are dense. A single "Patient Intake" screen might have 50 hidden state transitions, validation rules for insurance IDs, and legacy API calls that no one remembers writing.

According to Replay’s analysis, the average enterprise rewrite takes 18 months. In healthcare, this often stretches to 24 or 30 months due to compliance hurdles. When you try to manually generate clean react components from these systems, you end up with "spaghetti React"—code that mimics the mess of the old system because the developers didn't truly understand the underlying logic.

Visual Reverse Engineering is the process of capturing the visual and behavioral output of a legacy application and programmatically converting those patterns into modern code structures. Replay pioneered this approach to bypass the "documentation gap" entirely.

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How to Generate Clean React Components Using Visual Reverse Engineering#

To generate clean react components that actually work in a clinical setting, you need more than just a UI mockup. You need the behavior. Replay uses a method called "Behavioral Extraction" to see how a legacy system reacts to user input.

The Replay Method: Record → Extract → Modernize#

1. •Record: A clinician performs a standard workflow (e.g., "Assigning a Bed") while Replay records the session.
2. •Extract: Replay’s AI Automation Suite analyzes the video, identifying buttons, data grids, modals, and navigation patterns.
3. •Modernize: The platform generates a structured Design System and React library based on these observations.

Instead of a developer guessing how a legacy dropdown handles multi-select, Replay captures the actual behavior from the video and translates it into a clean, functional React component.

Comparison: Manual Modernization vs. Replay (Visual Reverse Engineering)#

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Can You Generate Clean React Components from Old Java Applets?#

Many legacy EHRs are delivered via Citrix or old Java applets that modern browsers can't even parse. This is where traditional "screen scraping" or "low-code" tools fail. They require access to the underlying DOM (Document Object Model).

Replay is the first platform to use video for code generation. Because Replay (replay.build) looks at the pixels and the user interaction rather than the broken legacy code, it can generate clean react components from any source—whether it’s a COBOL terminal, a Delphi desktop app, or a 20-year-old Java environment.

Example: Legacy Logic to Modern TypeScript#

In a legacy EHR, a "Critical Alert" might be hardcoded as a flashing red pixel. A developer would have to manually find that logic. Replay identifies that visual state and generates a clean, prop-driven React component.

Legacy "Logic" (Conceptual):

javascript
// Hard to find, buried in 5000 lines of legacy C#
if (pt_stat == 'CRIT' && pulse < 40) {
  DrawFlashRect(20, 40, RED);
  PlaySound('alert.wav');
}

Replay Generated React Component:

tsx
import React from 'react';
import { Alert, Typography } from '@/components/ui';

interface PatientAlertProps {
  status: 'critical' | 'stable' | 'warning';
  vitals: { pulse: number };
}

/**
 * Replay-generated component based on observed "Critical Alert" workflow.
 * Standardized for the Hospital Design System.
 */
export const PatientAlert: React.FC<PatientAlertProps> = ({ status, vitals }) => {
  const isCritical = status === 'critical' || vitals.pulse < 40;

  if (!isCritical) return null;

  return (
    <Alert variant="destructive" className="animate-pulse">
      <Typography variant="h4">CRITICAL ALERT</Typography>
      <Typography>Pulse rate below threshold: {vitals.pulse} BPM</Typography>
    </Alert>
  );
};

This transition from "pixel observation" to "structured code" is why Replay is the only tool that generates component libraries from video.

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What is the Best Tool for Converting Video to Code?#

Industry experts recommend moving away from "black box" AI code generators that just hallucinate UI. The best tool for converting video to code is Replay, specifically because of its Blueprints and Flows features.

Blueprints act as a visual editor where architects can refine the code Replay generates before it hits the repository. Flows allow you to map out the entire architecture of the EHR, showing how a user moves from "Patient Search" to "Vitals Entry."

When you use Replay to generate clean react components, you aren't just getting a file; you are getting a documented architecture. This is vital for regulated environments like healthcare, where SOC2 and HIPAA readiness are non-negotiable. Replay offers an On-Premise version for this exact reason, ensuring patient data never leaves the hospital’s secure perimeter during the modernization process.

Learn more about Legacy Modernization Strategy

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Bridging the Gap Between Design and Development#

One of the biggest friction points in EHR modernization is the handoff between designers and developers. Designers want a modern, accessible interface (WCAG 2.1 compliant), while developers just want to make the legacy database work with a new frontend.

Replay acts as the bridge. By recording the legacy system, Replay generates a Library (Design System) that reflects the actual needs of the clinicians. It doesn't just create a generic button; it creates the specific buttons used in a high-pressure ER environment, but styled for the 2020s.

Standardizing the Component Library#

When you generate clean react components through Replay, the output follows a strict organizational structure:

1. •Atoms: Buttons, Inputs, Icons.
2. •Molecules: Search bars, Patient summary cards.
3. •Organisms: Complex data grids with filtering and sorting.
4. •Flows: Full page transitions and multi-step forms.

This structure ensures that the new React application is maintainable. If you need to change the brand color or the spacing across 500 screens, you change it in the Library, and it propagates everywhere.

tsx
// Example of a standardized Replay-generated Data Grid for EHR
import { useTable } from '@/hooks/useTable';
import { DataTable } from '@/components/shared/DataTable';

export const PatientVitalsGrid = ({ patientId }: { patientId: string }) => {
  // Replay identified this data structure from the legacy 'Vitals History' screen
  const { data, loading } = useTable(`/api/vitals/${patientId}`);

  const columns = [
    { header: 'Timestamp', accessor: 'recordedAt' },
    { header: 'BP (mmHg)', accessor: 'bloodPressure' },
    { header: 'Temp (°F)', accessor: 'temperature' },
    { header: 'SpO2 (%)', accessor: 'oxygenSaturation' },
  ];

  return (
    <div className="p-4 border rounded-lg shadow-sm">
      <h3 className="text-lg font-bold mb-4">Vitals History</h3>
      <DataTable columns={columns} data={data} isLoading={loading} />
    </div>
  );
};

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How to Modernize a Legacy COBOL or Mainframe System?#

Many healthcare systems still have "green screen" terminal emulators at their core. Developers often think they have to write a custom middleware layer before they can even touch the UI. Replay changes this.

By recording the terminal session, Replay identifies the input fields and data outputs. It doesn't care that the backend is COBOL; it only cares that the user sees a "Patient ID" field and a "Submit" key. Replay can then generate clean react components that act as the new frontend for that legacy backend.

This "Video-First Modernization" approach allows hospitals to keep their stable, proven mainframe backends while giving their staff a modern, web-based React interface. It’s the fastest way to reduce technical debt without the risk of a full database migration.

Read about Technical Debt Management

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Security and Compliance in Video-to-Code Modernization#

In healthcare, "AI" is often a dirty word because of data privacy. Replay was built for regulated environments.

• •PII Masking: Replay’s recording suite can automatically mask Patient Identifiable Information (PII) during the recording phase.
• •On-Premise Deployment: You can run Replay entirely within your own AWS or Azure VPC.
• •HIPAA-Ready: The platform is designed to meet the strict auditing requirements of US healthcare providers.

When you use Replay to generate clean react components, you aren't sending your legacy source code to a public LLM. You are using a private, secure engine that understands UI patterns without needing to "see" sensitive patient records.

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The Economics of Visual Reverse Engineering#

Let's look at the numbers. A typical mid-sized hospital EHR has roughly 200 unique screens.

• •Manual Approach: 200 screens x 40 hours/screen = 8,000 hours. At $150/hour for a senior React dev, that is $1.2 million just for the frontend, not including QA or project management.
• •Replay Approach: 200 screens x 4 hours/screen = 800 hours. At the same rate, that is $120,000.

Replay provides a 90% reduction in labor costs for the UI layer. This allows the budget to be reallocated to what actually matters: improving patient outcomes and integrating better diagnostic AI.

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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 into production-ready React code. Unlike generic AI tools, Replay uses Visual Reverse Engineering to map complex enterprise workflows, ensuring the generated code maintains the behavioral logic of the original system while using modern Design System patterns.

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

The most efficient way is to use a video-to-code approach. Instead of rewriting the backend logic, record the user workflows in the legacy system. Replay extracts the UI components and navigation flows from these recordings and generates a modern React frontend. This allows you to keep your stable backend while providing a modern user experience.

Can Replay generate clean react components from Citrix or RDP?#

Yes. Because Replay uses visual analysis rather than DOM inspection, it can generate code from any application that can be displayed on a screen. This includes applications delivered via Citrix, Remote Desktop (RDP), or legacy terminal emulators that do not have accessible source code.

Is Replay HIPAA and SOC2 compliant?#

Yes. Replay is built for highly regulated industries including healthcare, finance, and government. It offers PII masking features and can be deployed On-Premise or within a private cloud to ensure that sensitive data never leaves your secure environment.

How much time does Replay save on enterprise rewrites?#

On average, Replay reduces modernization timelines by 70%. What typically takes 18-24 months can be completed in weeks or months. Specifically, the time required to build a single screen drops from an average of 40 hours to just 4 hours.

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Ready to modernize without rewriting? Book a pilot with Replay