Starlight_Lancher/apps/app-frontend/src/helpers/font-family.ts

/**
 * Font family plumbing shared by the appearance settings pickers and the theme
 * store. Kept free of imports so `node --test` can load it directly.
 */

/** Mirrors `--font-standard` in `packages/assets/styles/defaults.scss`. */
export const DEFAULT_UI_FONT_STACK =
	'Inter, -apple-system, BlinkMacSystemFont, Segoe UI, Oxygen, Ubuntu, Roboto, Cantarell, Fira Sans, Droid Sans, Helvetica Neue, sans-serif'

/** Mirrors `--mono-font` in `packages/assets/styles/defaults.scss`. */
export const DEFAULT_MONO_FONT_STACK =
	'ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, Liberation Mono, monospace'

/** Picker value for "follow the launcher default"; persisted as `null`. */
export const FOLLOW_DEFAULT_FONT = ''

export interface SystemFontFamily {
	family: string
	monospaced: boolean
}

export interface FontFamilyOption {
	value: string
	label: string
	subLabel?: string
	searchTerms?: string[]
}

export type FontFamilyOptionOrDivider = FontFamilyOption | { type: 'divider' }

export interface FontFamilyOptionsConfig {
	defaultLabel: string
	selected?: string | null
	missingLabel?: string
	monospaceLabel?: string
	groupMonospaced?: boolean
}

const MAX_FONT_FAMILY_LENGTH = 128

/**
 * Quotes and escapes an installed family name so it cannot break out of the
 * font-family declaration it is spliced into. Returns null when the name has
 * nothing usable left.
 */
export function cssFontFamilyName(name: string): string | null {
	const trimmed = name.replace(/\p{Cc}/gu, '').trim()

	if (!trimmed || trimmed.length > MAX_FONT_FAMILY_LENGTH) {
		return null
	}

	return `"${trimmed.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`
}

/**
 * The value written into `--font-standard` / `--mono-font`. The launcher stack
 * always trails the chosen family so an unresolvable name degrades to the
 * previous default instead of the user agent's own font.
 */
export function resolveFontFamily(
	setting: string | null | undefined,
	fallbackStack: string,
): string {
	if (!setting) {
		return fallbackStack
	}

	const family = cssFontFamilyName(setting)

	return family ? `${family}, ${fallbackStack}` : fallbackStack
}

export function fontSettingToOptionValue(setting: string | null | undefined): string {
	return setting ?? FOLLOW_DEFAULT_FONT
}

export function optionValueToFontSetting(value: string): string | null {
	const trimmed = value.trim()

	return trimmed === FOLLOW_DEFAULT_FONT ? null : trimmed
}

function compareFamilies(first: SystemFontFamily, second: SystemFontFamily): number {
	const left = first.family.toLowerCase()
	const right = second.family.toLowerCase()

	if (left === right) {
		return 0
	}

	return left < right ? -1 : 1
}

function toOption(family: SystemFontFamily, monospaceLabel?: string): FontFamilyOption {
	return {
		value: family.family,
		label: family.family,
		...(family.monospaced && monospaceLabel
			? { subLabel: monospaceLabel, searchTerms: [monospaceLabel] }
			: {}),
	}
}

/**
 * The spelling the font list uses for a stored family. Font names are matched
 * case-insensitively so a stored value that only differs in case still selects
 * its option instead of leaving the picker blank.
 */
export function canonicalFontFamily(
	fonts: SystemFontFamily[],
	setting: string | null | undefined,
): string {
	const selected = optionValueToFontSetting(setting ?? '')
	if (!selected) {
		return FOLLOW_DEFAULT_FONT
	}

	const listed = fonts.find((font) => font.family.trim().toLowerCase() === selected.toLowerCase())

	return listed ? listed.family.trim() : selected
}

/**
 * Builds the picker options for the installed font collection: the default
 * entry first, the current selection re-added when it is no longer installed,
 * and — for the monospace picker — monospaced families ahead of the rest.
 */
export function buildFontFamilyOptions(
	fonts: SystemFontFamily[],
	config: FontFamilyOptionsConfig,
): FontFamilyOptionOrDivider[] {
	const families = new Map<string, SystemFontFamily>()
	for (const font of fonts) {
		const family = font.family.trim()

		if (!family) {
			continue
		}

		const key = family.toLowerCase()
		const known = families.get(key)

		if (known) {
			known.monospaced ||= font.monospaced
		} else {
			families.set(key, { family, monospaced: font.monospaced })
		}
	}

	const sorted = [...families.values()].sort(compareFamilies)
	const selected = optionValueToFontSetting(config.selected ?? '')
	const options: FontFamilyOptionOrDivider[] = [
		{ value: FOLLOW_DEFAULT_FONT, label: config.defaultLabel },
	]

	if (selected && !families.has(selected.toLowerCase()) && config.missingLabel) {
		options.push({ value: selected, label: selected, subLabel: config.missingLabel })
	}

	if (config.groupMonospaced) {
		const monospaced = sorted.filter((font) => font.monospaced)
		const proportional = sorted.filter((font) => !font.monospaced)

		options.push(...monospaced.map((font) => toOption(font, config.monospaceLabel)))

		if (monospaced.length > 0 && proportional.length > 0) {
			options.push({ type: 'divider' })
		}

		options.push(...proportional.map((font) => toOption(font, config.monospaceLabel)))

		return options
	}

	options.push(...sorted.map((font) => toOption(font)))

	return options
}