// How a measured imaging figure reads, decided in exactly one place.
//
// The figure is rendered twice for the same measurement and the two renderings are compared BY EYE:
// one is what the viewer currently has on screen, the other is what the patient's chart holds for it.
// That comparison is the whole reason a clinician can tell a caliper they nudged from one they did
// not. Two copies of the rounding, or two spellings of the same unit, would make identical
// measurements read as a discrepancy - and the action that invites is amending a finding that never
// changed.
//
// Deliberately free of React, of Cornerstone and of the viewport directory, so both sides can use it:
// a bundle-isolation test forbids anything outside src/components/DicomViewport/ from importing that
// directory at all, which is what would otherwise pull the imaging packages into every page.

// Cornerstone keeps display units; the chart keeps UCUM. Same physical unit, different spelling.
// A unit not listed here is shown exactly as it arrived rather than blanked or guessed at: an
// unfamiliar unit spelled out is honest, a figure with no unit at all is not.
const DISPLAY_BY_UCUM: Readonly<Record<string, string>> = Object.freeze({
    'mm2': 'mm²',
    "[hnsf'U]": 'HU',
    // An angle is charted in UCUM 'deg' and drawn on the image with the degree sign. Left unmapped,
    // the drawn "37.2°" and the charted "37.2 deg" are the same measurement rendered two ways, which
    // reads on the row as a chart that disagrees with the image - on every charted angle, forever.
    'deg': '°'
});

export const measurementDisplayUnit = (unit: string): string => DISPLAY_BY_UCUM[unit] ?? unit;

// UNITS THAT BIND DIRECTLY TO THE NUMBER. Every unit here is written with a space before it -
// "24.6 mm" - except the degree sign, which is set tight against the figure in every clinical
// display and in Cornerstone's own on-image label. Handled inside the formatter rather than by
// letting the angle bypass it: a figure formatted anywhere else is a second spelling waiting to
// happen, which is the one thing this module exists to prevent.
const TIGHT_UNITS: readonly string[] = ['°'];

// Two decimals at most, with no trailing zeros - close enough to the figure Cornerstone draws on the
// image itself that a row and the drawing it names read as the same measurement.
const round = (value: number): string => String(Math.round(value * 100) / 100);

export const measurementFigure = (value: number, unit: string): string => {
    const display = measurementDisplayUnit(unit);

    return TIGHT_UNITS.includes(display)
        ? `${round(value)}${display}`
        : `${round(value)} ${display}`.trim();
};