@glion/decode-escapes

unified plugin to decode HL7v2 escape sequences in literal values.

What is this?

@glion/decode-escapes is a unified plugin that traverses an HL7v2 syntax tree (produced by a parser such as @glion/ast) and decodes HL7v2 escape sequences in all literal values (subcomponent nodes).

It preserves the original raw value and replaces the value property with the decoded text, handling:

HL7 delimiter escapes (\F\, \S\, \R\, \T\, \E\)
Hexadecimal escapes (\Xdddd\)
Line break directives (\.br\)
Strips highlighting markers (\H\, \N\)

When should I use this?

Use this plugin when you need:

Human-readable HL7v2 values with escape sequences decoded.
To process or display HL7v2 message content where \F\ and similar escapes should be expanded.

If you need to parse HL7v2 messages first, use @glion/ast before applying this plugin.

Install

This package is ESM only.

In Node.js (version 16+), install with npm:

npm install @glion/decode-escapes

Use

Say we have an HL7v2 message with escapes:

import { unified } from "unified";
import { hl7v2Parse } from "@glion/ast";
import { hl7v2DecodeLiterals } from "@glion/decode-escapes";

const msg = `OBX|1|TX|ID123||Patient allergic to \\F\\Peanuts\\F\\ and \\.br\\Severe reaction`;

const file = await unified()
  .use(hl7v2Parse)
  .use(hl7v2DecodeLiterals)
  .process(msg);

console.log(String(file));

Before decoding, the subcomponent.value contains the raw HL7 text:

{
  "type": "subcomponent",
  "index": 1,
  "value": "Patient allergic to \\F\\Peanuts\\F\\ and \\.br\\Severe reaction"
}

After this plugin runs:

{
  "type": "subcomponent",
  "index": 1,
  "value": "Patient allergic to |Peanuts| and \rSevere reaction"
}

API

`unified().use(hl7v2DecodeLiterals[, options])`

Decode HL7v2 escape sequences in literal nodes.

Parameters

options.delimiters (optional) — Override delimiters. If omitted, the plugin reads them from Root.data.delimiters (set by the parser). Defaults to the HL7 standard (| ^ ~ & \).

Returns

Nothing (undefined). Mutates the AST in-place.

Behavior

Preserves original text in node.data.raw.
Decodes into node.value.
Uses Root.data.delimiters (preferred) or options.delimiters.
Falls back to defaults if neither is present.

Security

This plugin only transforms AST nodes and does not execute code. Ensure you trust the source of HL7v2 messages before processing.

Contributing

We welcome contributions! Please see our Contributing Guide for more details.

Fork the repository
Create your feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add some amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

Code of Conduct

To ensure a welcoming and positive environment, we have a Code of Conduct that all contributors and participants are expected to adhere to.

License

This program is licensed to you under the terms of the MIT License. This program is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the LICENSE file for details.