56 lines
2.3 KiB
TypeScript
56 lines
2.3 KiB
TypeScript
/** Longest slug generated, so that URLs stay readable. */
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export const MAX_SLUG_LENGTH = 80;
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/** Valid slug: lowercase ASCII words separated by single hyphens. */
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export const SLUG_PATTERN = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;
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/** Letters that Unicode normalization does not split into a base letter and an accent. */
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const SPECIAL_LETTERS: Record<string, string> = { æ: 'ae', œ: 'oe', ø: 'o', ß: 'ss', đ: 'd', ł: 'l', þ: 'th' };
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/**
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* Turns a name into a slug: accents removed, lowercase, every run of other characters replaced by one hyphen,
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* cut at a word boundary to {@link MAX_SLUG_LENGTH}. "&" becomes "and" ("&TEAM" -> "and-team", not "team").
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* @returns an empty string when nothing is left (name without any latin letter or digit, e.g. in hangul).
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*/
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export function slugify(name: string, maxLength = MAX_SLUG_LENGTH): string {
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const slug = name
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.normalize('NFKD')
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.replace(/[̀-ͯ]/g, '')
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.toLowerCase()
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.replace(/[æœøßđłþ]/g, (letter) => SPECIAL_LETTERS[letter])
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.replace(/&/g, ' and ')
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.replace(/[^a-z0-9]+/g, '-')
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.replace(/^-+|-+$/g, '');
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return truncateSlug(slug, maxLength);
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}
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/** Cuts a slug to `maxLength`, at the last hyphen when there is one, never leaving a trailing hyphen. */
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function truncateSlug(slug: string, maxLength: number): string {
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if (slug.length <= maxLength) return slug;
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const cut = slug.slice(0, maxLength);
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const lastHyphen = cut.lastIndexOf('-');
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return (lastHyphen > 0 ? cut.slice(0, lastHyphen) : cut).replace(/-+$/, '');
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}
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/** Appends `-suffix` to a slug, shortening the slug so that the result fits in {@link MAX_SLUG_LENGTH}. */
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export function withSlugSuffix(slug: string, suffix: string | number): string {
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const end = `-${suffix}`;
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return truncateSlug(slug, MAX_SLUG_LENGTH - end.length) + end;
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}
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/**
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* Picks the first candidate not in `taken`. When they are all taken, numbers the last one (`-2`, `-3`...)
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* until a free slug is found.
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* @param candidates slugs by order of preference, at least one, none empty.
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*/
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export function pickAvailableSlug(candidates: string[], taken: ReadonlySet<string>): string {
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const free = candidates.find((candidate) => !taken.has(candidate));
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if (free) return free;
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const last = candidates[candidates.length - 1];
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for (let n = 2; ; n++) {
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const numbered = withSlugSuffix(last, n);
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if (!taken.has(numbered)) return numbered;
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}
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}
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