/**
 * Identity resolution. Bridges the existing top-level didResolver helpers
 * with the explorer's "give me {did, handle, pds}" needs.
 *
 *   resolveHandle(handle) — appview first, falls back to bsky.social.
 *   resolveIdentifier(input) — accepts handle | did | at://… and returns
 *     the canonical identity bundle the explorer pages depend on.
 */

import { resolvePdsEndpoint } from '../didResolver';
import { APPVIEW, HANDLE_RESOLVER_FALLBACK } from './config';
import { describeRepo } from './pdsClient';
import { TTLMap } from './cache';

export type IdentityBundle = {
  did: string;
  handle: string | null;
  pds: string;
};

const HANDLE_TTL = 5 * 60_000;
const handleToDidCache = new TTLMap<string, string>(HANDLE_TTL);

async function tryFetchJson<T>(url: string): Promise<T | null> {
  try {
    const res = await fetch(url);
    if (!res.ok) return null;
    return (await res.json()) as T;
  } catch {
    return null;
  }
}

/**
 * Resolve a handle to a DID. Tries the AppView first, falls back to the
 * bsky.social PDS (which can resolve handles served via DNS even when the
 * appview hasn't seen them yet).
 */
export async function resolveHandle(handle: string): Promise<string | null> {
  if (!handle) return null;
  if (handle.startsWith('did:')) return handle;
  const cached = handleToDidCache.get(handle);
  if (cached) return cached;

  const qs = `handle=${encodeURIComponent(handle)}`;
  const resolved =
    (await tryFetchJson<{ did?: string }>(
      `${APPVIEW}/xrpc/com.atproto.identity.resolveHandle?${qs}`,
    ))?.did ??
    (await tryFetchJson<{ did?: string }>(
      `${HANDLE_RESOLVER_FALLBACK}/xrpc/com.atproto.identity.resolveHandle?${qs}`,
    ))?.did ??
    null;

  if (resolved) handleToDidCache.set(handle, resolved);
  return resolved;
}

/**
 * Normalize a user-supplied identifier (handle, DID, or at://… URI) into
 * `{ did, handle, pds }`. Throws on failure.
 */
export async function resolveIdentifier(input: string): Promise<IdentityBundle> {
  const trimmed = String(input || '').trim();
  if (!trimmed) throw new Error('resolveIdentifier: empty input');

  // at:// URI shortcut — extract the repo segment.
  let target = trimmed;
  if (target.startsWith('at://')) {
    const m = target.match(/^at:\/\/([^/]+)/);
    if (m) target = m[1];
  }

  const resolved = await resolvePdsEndpoint(target);
  if (!resolved) throw new Error(`Could not resolve ${trimmed}`);

  let handle: string | null = null;
  try {
    const desc = await describeRepo(resolved.pdsEndpoint.replace(/\/$/, ''), resolved.did);
    handle = desc?.handle || null;
  } catch {
    // describeRepo failures are non-fatal — the explorer still works by DID.
  }
  return {
    did: resolved.did,
    handle,
    pds: resolved.pdsEndpoint.replace(/\/$/, ''),
  };
}