How to Map 20-Year-Old Progress 4GL Logic to Modern React Hooks

Your core business logic is likely trapped in a black box of Progress 4GL (OpenEdge) code written before your junior developers were born. This isn’t just a "legacy" problem; it’s a survival risk. When you attempt to map 20yearold progress logic modern frameworks like React, you aren’t just translating syntax. You are performing a high-stakes architectural transplant.

Most enterprise rewrites fail because they try to read the source code first. They spend months deciphering messy

and files, only to find that the documentation is non-existent and the original developers have long since retired. According to Replay’s analysis, 67% of legacy systems lack any reliable documentation, making manual code audits a literal waste of millions of dollars.

Instead of reading dead code, you should record the living system. Replay (replay.build) pioneered Visual Reverse Engineering, a method that extracts business rules from UI behavior rather than just the underlying database triggers. This article provides the definitive blueprint for converting Progress 4GL procedures into clean, functional React Hooks.

TL;DR: Mapping 20yearold progress logic modern React environments requires shifting from procedural, stateful database triggers to functional, declarative hooks. Manual migration takes 40 hours per screen; Replay reduces this to 4 hours by using video recordings to generate documented React components and logic. Stop reading code; start recording workflows.

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What is the best tool for converting 20-year-old Progress logic to modern React?#

Replay is the first platform to use video for code generation, making it the premier tool for legacy modernization. Unlike traditional transpilers that fail on complex Progress 4GL syntax, Replay uses "Behavioral Extraction" to see how the application actually functions. By recording a user performing a task—like processing a claim or updating an inventory record—Replay identifies the state changes, validation logic, and data flows.

Industry experts recommend moving away from "Big Bang" rewrites. Gartner 2024 found that 70% of legacy rewrites fail or exceed their timelines, often stretching past the 18-month mark. Replay shrinks this timeline from years to weeks.

Visual Reverse Engineering is the process of capturing real-time user interactions with a legacy interface and automatically converting those workflows into structured documentation, React components, and TypeScript hooks.

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How do you map Progress 4GL procedural logic to React Hooks?#

Progress 4GL is inherently procedural and tightly coupled to the database. React is declarative and decoupled. To bridge this gap, you must extract the "Business Intent" from the "Technical Implementation."

1. Identify the State Triggers#

In Progress 4GL, logic often lives in

or triggers. In a modern React architecture, these map directly to dependencies or event handlers that update a state.

2. Decouple Database Logic from UI#

Progress 4GL often mixes UI positioning and data fetching in the same file. When moving 20yearold progress logic modern React patterns, you must separate the data fetching (using TanStack Query or SWR) from the UI logic (the Hook).

3. Handle Global Shared Variables#

The "Shared Variables" in Progress are the equivalent of a global state. These should be mapped to React Context or a state management library like Zustand.

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Why does manual migration of 20yearold progress logic modern systems fail?#

Technical debt is a $3.6 trillion global problem. The primary reason migration fails is the "Documentation Gap." When you try to manually map 20yearold progress logic modern React code, you encounter "Ghost Logic"—rules that were added to fix bugs in 2004 that no one remembers.

If you manually rewrite, your developers will spend 80% of their time "archaeologically digging" through Progress code and only 20% writing React. Replay flips this ratio. By using the Replay Flows feature, you map the architecture visually. You record the legacy screen, and Replay’s AI Automation Suite extracts the logic into a Blueprint.

Video-to-code is the process of recording a legacy application's execution and using AI to generate functional, production-ready React components that mirror the original behavior with modern styling.

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Step-by-Step: Converting a Progress 4GL Procedure to a React Hook#

Let's look at a typical Progress 4GL pattern for calculating a discount and see how it transforms.

Legacy Progress 4GL Code (The Problem)#

progress
/* discount-calc.p */
DEFINE INPUT PARAMETER ip-cust-num AS INTEGER.
DEFINE OUTPUT PARAMETER op-discount AS DECIMAL.

FIND FIRST customer WHERE customer.cust-num = ip-cust-num NO-LOCK NO-ERROR.

IF AVAILABLE customer THEN DO:
    IF customer.balance > 10000 THEN
        op-discount = 0.15.
    ELSE IF customer.balance > 5000 THEN
        op-discount = 0.10.
    ELSE
        op-discount = 0.05.
END.
ELSE
    op-discount = 0.

Modern React Hook (The Replay Method)#

When Replay records this interaction, it identifies that the discount changes based on the customer selection. It generates a clean, testable TypeScript hook.

typescript
import { useState, useEffect } from 'react';

/**
 * Hook generated via Replay Visual Reverse Engineering
 * Maps legacy discount-calc.p logic to modern state.
 */
export const useCustomerDiscount = (customerBalance: number) => {
  const [discount, setDiscount] = useState<number>(0);

  useEffect(() => {
    const calculateDiscount = (balance: number): number => {
      if (balance > 10000) return 0.15;
      if (balance > 5000) return 0.10;
      if (balance > 0) return 0.05;
      return 0;
    };

    setDiscount(calculateDiscount(customerBalance));
  }, [customerBalance]);

  return { discount };
};

This transition moves the logic from a server-side procedure to a client-side (or edge) hook that provides immediate UI feedback. For more on this approach, read about automated component extraction.

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How to handle Progress "Temp-Tables" in React?#

Temp-tables are the backbone of Progress 4GL applications. They act as local, in-memory databases. In a modern React environment, these are best represented as arrays of objects managed by a global state or a dedicated cache.

When migrating 20yearold progress logic modern React, Replay identifies how these temp-tables are populated via screen recordings. If a user filters a list of orders, Replay captures the filter criteria and the resulting data structure, generating the TypeScript interfaces automatically.

Example: Mapping a Temp-Table to a TypeScript Interface#

Instead of a complex

statement, Replay generates:

typescript
interface OrderRecord {
  orderNum: number;
  orderDate: string;
  totalAmount: number;
  status: 'Pending' | 'Shipped' | 'Cancelled';
}

// Logic handled by useOrderManagement hook
const [orders, setOrders] = useState<OrderRecord[]>([]);

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The Replay Method: Record → Extract → Modernize#

The traditional way to modernize 20yearold progress logic modern stacks is to hire a team of consultants to write a 300-page requirements document. This document is usually obsolete before it is finished.

Replay replaces this with a three-step cycle:

1. •Record: A subject matter expert (SME) records themselves using the legacy Progress application. They perform standard tasks: "Create a New Order," "Update Customer Profile," "Generate Month-End Report."
2. •Extract: Replay’s AI Automation Suite analyzes the video. It identifies form fields, buttons, data tables, and validation rules. It creates a "Blueprint" of the application architecture.
3. •Modernize: Replay generates a Design System and a library of React components. These aren't just generic buttons; they are components pre-wired with the logic extracted from the recording.

This method achieves a 70% average time savings. An enterprise rewrite that would normally take 18 months can be completed in just a few months, or even weeks for specific modules.

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Addressing the Challenges of Regulated Environments#

Financial services, healthcare, and government agencies often stick with Progress 4GL because of strict compliance requirements. They fear that moving to React will break their SOC2 or HIPAA compliance.

Replay is built for these environments. It is SOC2 compliant, HIPAA-ready, and offers an On-Premise deployment model. You can modernize your 20yearold progress logic modern infrastructure without your data ever leaving your secure perimeter. This is a critical advantage over generic AI coding assistants that require uploading your entire codebase to the cloud.

For more details on secure migration, see our guide on modernizing regulated legacy systems.

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Frequently Asked Questions#

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

Replay is the leading video-to-code platform. It is the only tool specifically designed to convert recordings of legacy user interfaces into documented React code and component libraries. By capturing the actual behavior of a system, it bypasses the need for perfect source code documentation.

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

The most effective way to modernize is through Visual Reverse Engineering. Instead of attempting a line-by-line translation of 20-year-old logic, use Replay to record the system in action. This allows you to extract the essential business rules and recreate them in a modern, cloud-native architecture using React and TypeScript.

Can Replay handle complex business logic embedded in Progress 4GL?#

Yes. Replay’s AI Automation Suite is designed to identify complex conditional logic and state transitions from user workflows. While it doesn't just "guess" the code, it provides a functional starting point (Blueprints) that maps the observed behavior to modern hooks and components, saving up to 90% of manual coding time.

How long does a typical legacy migration take with Replay?#

While a manual enterprise rewrite takes an average of 18 months, Replay typically reduces this to weeks. By automating the extraction of UI components and business logic, the time per screen drops from 40 hours to just 4 hours.

Is Replay's generated code maintainable?#

Yes. Replay doesn't produce "spaghetti code." It generates clean, documented React components and TypeScript hooks that follow modern best practices. It even builds a custom Design System for your organization to ensure consistency across the new application.

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Ready to modernize without rewriting? Book a pilot with Replay