health.nhs-number-format

export function formatNhsNumber(value: string): string

import { formatNhsNumber } from "#fune/health.nhs-number-format@^1";

import { validateNhsNumber } from "./validation_nhs_number.ts";  ← from validation.nhs-number ^2.0.0 · built alongside by fune

/**
 * The NHS number in the 3-3-4 display format NHS systems use, after
 * a full check with validation.nhs-number. An invalid number is an error, not
 * a formatted string: a well-spaced wrong number looks more trustworthy than
 * a badly spaced right one. The error names the reason but never echoes the
 * number, which is a patient identifier and has no place in a log.
 */
export function formatNhsNumber(value: string): string {
  const result = validateNhsNumber(value);
  if (!result.valid || result.formatted === null) {
    throw new RangeError(`not a valid NHS number (${result.reason})`);
  }
  return result.formatted;
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add health.nhs-number-format

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./health.nhs-number-format-1.0.0-typescript.fune, or fetch it from a terminal with fune pull health.nhs-number-format@1.0.0:typescript.

The whole function, every language, is one file too: health.nhs-number-format-1.0.0.fune, 7,454 bytes, sha256 954512d1a1fc983bea7f92b75a8b24baa80192dfb610d5c18222e474c892fb80. It installs into a project of any language.

// fune: before health.nhs-number-format

// fune: after health.nhs-number-format

// fune: replace validation.nhs-number in health.nhs-number-format

// fune: step health.nhs-number-format after <n|label>

More from the author

## Why an invalid number is an error

A formatter that spaces out whatever it is given turns a mistyped number into something that looks official. So the number is checked first, and an invalid one raises `not a valid NHS number (<reason>)`, where the reason is `validation.nhs-number`'s: `empty`, `bad-character`, `bad-length`, `bad-check-digit` or `placeholder` (0000000000 and the like, which pass the arithmetic). The message deliberately does not repeat the number: it is a patient identifier, and error messages end up in logs.

A valid check digit means the number is well formed, not that it was issued or belongs to this patient; that needs a Personal Demographics Service trace.

## Level

The catalogue lists this at level 0, but it requires `validation.nhs-number`, which is level 1, and a capability may not depend on a higher level; so it is level 1.

## Source

NHS Data Model and Dictionary, *NHS NUMBER*: ten numeric digits, the tenth a check digit validated by the modulus 11 algorithm (https://www.datadictionary.nhs.uk/attributes/nhs_number.html). The check itself, and the 3-3-4 `formatted` form returned here, are `validation.nhs-number`'s; see its README. The Data Dictionary entry does not itself define the display grouping; 3-3-4 is the grouping NHS systems and correspondence conventionally use.

Files