/*
 * A TypeScript mirror of shared/provision's slug rules, used ONLY to preview the
 * host a rename would move an instance to while the customer types.
 *
 * It is a second implementation of Slugify, BaseSlug and ReservedSlugs, and it
 * must change in the same commit as the Go one — the same hazard as
 * web/lib/targets.ts. The preview is a courtesy; the server's 409 is the
 * boundary, and the two are allowed to disagree without anything breaking.
 */

/** Mirrors provision.MinSlugLength / MaxSlugLength. */
export const MIN_SLUG_LENGTH = 3;
export const MAX_SLUG_LENGTH = 40;

/** Mirrors provision.ReservedSlugs. */
const RESERVED = new Set([
    "www", "api", "app", "admin", "auth",
    "install", "static", "_next", "default",
]);

/*
 * The tenant subdomain namespace. Also hardcoded in InstanceRecord.tsx and the
 * customer instance page; those predate this file and are left alone rather than
 * refactored under a rename change.
 */
export const INSTANCE_DOMAIN = "vantage.hostxtra.co.uk";

/** Mirrors provision.Slugify. */
export function slugify(name: string): string {
    return name
        .toLowerCase()
        .replace(/[^a-z0-9]+/g, "-")
        .replace(/^-+|-+$/g, "");
}

/** Mirrors provision.BaseSlug's truncation. */
export function baseSlug(name: string): string {
    return slugify(name).slice(0, MAX_SLUG_LENGTH);
}

/** The reason a name cannot become a slug, or undefined when it can. */
export function slugError(name: string): string | undefined {
    const base = slugify(name);
    if (base.length < MIN_SLUG_LENGTH) {
        return `Needs at least ${MIN_SLUG_LENGTH} letters or digits.`;
    }
    if (RESERVED.has(base.slice(0, MAX_SLUG_LENGTH))) {
        return "That name is reserved.";
    }
    return undefined;
}

/** The host an instance on this slug is reached at. */
export function hostFor(slug: string): string {
    return `${slug}.${INSTANCE_DOMAIN}`;
}