// SkateSpots NIP-05 names — `you@skate-spots.org`.
//
// This is a *convenience* namespace we hand out for free so a new skater has a
// human handle from the first minute. It is deliberately NOT a gate: NIP-05 is a
// public label (a domain maps a name → pubkey), never an account, and the app
// works fine without one. Users are always free to bring a handle from any other
// domain instead.
//
// The registry itself lives server-side (netlify/functions/nip05.mjs); this
// module holds the shared, client-side rules so the form can validate before it
// ever talks to the network.

import { isNativePlatform } from '@/lib/platform';

/** The domain SkateSpots issues handles under. */
export const SKATE_NIP05_DOMAIN = 'skate-spots.org';

/** Names the registry refuses (impersonation / infrastructure words). */
const RESERVED = new Set([
  'admin', 'administrator', 'abuse', 'api', 'bot', 'help', 'mail', 'mod',
  'moderator', 'official', 'postmaster', 'root', 'security', 'staff', 'support',
  'system', 'test', 'undefined', 'null', 'webmaster', 'www',
  'skate-spots', 'skatespots',
]);

// Keep in sync with NAME_RE in netlify/functions/nip05.mjs.
const NAME_RE = /^[a-z0-9][a-z0-9._-]{1,28}[a-z0-9]$/;

export interface SkateNip05Validation {
  ok: boolean;
  /** Normalized (lowercased, trimmed, leading @ stripped) name. */
  name: string;
  reason?: string;
}

/** Lowercase, trim, and drop a leading `@` so `@Tony` and `tony` agree. */
export function normalizeSkateNip05Name(raw: string): string {
  return (raw ?? '').trim().toLowerCase().replace(/^@/, '');
}

/** Validate a local part (the bit before `@skate-spots.org`). */
export function validateSkateNip05Name(raw: string): SkateNip05Validation {
  const name = normalizeSkateNip05Name(raw);
  if (!name) return { ok: false, name, reason: 'Enter a name.' };
  if (name.length < 3) return { ok: false, name, reason: 'Use at least 3 characters.' };
  if (name.length > 30) return { ok: false, name, reason: 'Use at most 30 characters.' };
  if (!NAME_RE.test(name)) {
    return {
      ok: false,
      name,
      reason: 'Letters, numbers, dots, dashes and underscores only — start and end with a letter or number.',
    };
  }
  if (RESERVED.has(name)) return { ok: false, name, reason: 'That name is reserved.' };
  return { ok: true, name };
}

/** Suggest a handle from a display name: "Tony Hawk!" → "tony-hawk". */
export function deriveSkateNip05Handle(displayName: string): string {
  return (displayName ?? '')
    .trim()
    .toLowerCase()
    .normalize('NFKD')
    .replace(/[\u0300-\u036f]/g, '')
    .replace(/[^a-z0-9._-]+/g, '-')
    .replace(/^[-._]+|[-._]+$/g, '')
    .slice(0, 30);
}

/** `tony` → `tony@skate-spots.org`. */
export function buildSkateNip05(name: string): string {
  return `${normalizeSkateNip05Name(name)}@${SKATE_NIP05_DOMAIN}`;
}

/** If `nip05` is on our domain, return the handle; otherwise null. */
export function parseSkateNip05(nip05: string | undefined | null): string | null {
  const value = (nip05 ?? '').trim().toLowerCase();
  const suffix = `@${SKATE_NIP05_DOMAIN}`;
  return value.endsWith(suffix) ? value.slice(0, -suffix.length) : null;
}

/**
 * Absolute base for `/api` calls. Relative paths break inside the native shell
 * (it is served from `https://localhost`), so native must hit the real origin.
 */
export function skateApiBase(): string {
  return isNativePlatform() ? 'https://skate-spots.org' : '';
}