import { useCallback, useEffect, useRef, useState } from 'react';
import { RefreshCw } from 'lucide-react';
import { useClient } from 'hooks/useClient';
import { readableError } from './errors';
import { useNpmChanged } from './channel';

/**
 * The four sections that are a list and nothing more — redirections, streams, 404 hosts, access lists.
 *
 * One component rather than four near-identical ones. Each differs only in what a row SAYS, so that is the
 * one thing passed in; everything around it — loading, failure, empty, refresh — is the same problem four
 * times over and was not worth writing four times.
 *
 * Proxy hosts and certificates are deliberately NOT here. They have real behaviour of their own: a
 * selection with an enable/disable action, and expiry arithmetic that decides the colour of a row. Folding
 * them in would mean a props bag that is a worse version of both.
 */

type Row = { id: number } & Record<string, unknown>;

export type ListSectionProps = {
  /** Plugin route, e.g. `/proxy-manager/streams`. */
  path: string;
  /** What this is, shown when there are none. */
  emptyText: string;
  /** The row's heading — usually a domain or a port. */
  primary: (row: Row) => string;
  /** The line under it — where it goes, or what it holds. */
  secondary: (row: Row) => string;
  /** Dimmed when false. NPM's `enabled` is 0/1, and some of these have no such field at all. */
  isEnabled?: (row: Row) => boolean;
};

const Centred = ({ children }: { children: React.ReactNode }) => (
  <div className="flex size-full items-center justify-center p-6 text-center text-sm text-muted-foreground">
    {children}
  </div>
);

export const ListSection = ({ path, emptyText, primary, secondary, isEnabled }: ListSectionProps) => {
  const client = useClient();
  const clientRef = useRef(client);
  clientRef.current = client;

  const [rows, setRows] = useState<Row[] | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [connectionSignal] = useNpmChanged();

  const load = useCallback(async () => {
    try {
      const next = await clientRef.current.get<Row[]>(path);
      setRows(Array.isArray(next) ? next : []);
      setError(null);
    } catch (caught) {
      setError(readableError(caught, 'Could not load this.'));
      setRows(null);
    }
  }, [path]);

  useEffect(() => {
    void load();
  }, [load, connectionSignal]);

  if (error) return <Centred>{error}</Centred>;
  if (!rows) return <Centred>Loading…</Centred>;

  return (
    <div className="flex size-full flex-col">
      <header className="flex items-center justify-between border-b px-3 py-2">
        <span className="text-sm font-medium">
          {rows.length} {rows.length === 1 ? 'entry' : 'entries'}
        </span>
        <button type="button" onClick={() => void load()} className="text-muted-foreground hover:text-foreground">
          <RefreshCw className="size-4" />
        </button>
      </header>

      {rows.length === 0 ? (
        <Centred>{emptyText}</Centred>
      ) : (
        <ul className="flex-1 overflow-auto">
          {rows.map((row) => (
            <li
              key={row.id}
              className={`border-b px-3 py-2 ${isEnabled && !isEnabled(row) ? 'opacity-50' : ''}`}
            >
              <span className="block truncate text-sm">{primary(row)}</span>
              <span className="block truncate text-xs text-muted-foreground">{secondary(row)}</span>
            </li>
          ))}
        </ul>
      )}
    </div>
  );
};

/** NPM's `enabled` is an integer. Absent on the kinds that cannot be switched off. */
const enabled = (row: Row) => row.enabled !== 0;

const domains = (row: Row) => (Array.isArray(row.domain_names) ? (row.domain_names as string[]).join(', ') : '—');

/**
 * The four, with only the parts that differ.
 *
 * Field names are NPM's, straight off the wire — `docs/npm-api.md` has the shapes. Nothing is renamed on
 * the way through, so a value that looks wrong here is a value that looks the same in NPM's own UI.
 */
export const REDIRECTIONS: ListSectionProps = {
  path: '/proxy-manager/redirections',
  emptyText: 'No redirections. These send a domain somewhere else rather than serving it.',
  primary: domains,
  secondary: (r) => `→ ${String(r.forward_scheme ?? 'auto')}://${String(r.forward_domain_name ?? '?')}`,
  isEnabled: enabled,
};

export const STREAMS: ListSectionProps = {
  path: '/proxy-manager/streams',
  emptyText: 'No streams. These forward a raw TCP or UDP port rather than HTTP.',
  primary: (r) => `port ${String(r.incoming_port ?? '?')}`,
  secondary: (r) =>
    `→ ${String(r.forwarding_host ?? '?')}:${String(r.forwarding_port ?? '?')}` +
    `${r.tcp_forwarding ? ' · TCP' : ''}${r.udp_forwarding ? ' · UDP' : ''}`,
  isEnabled: enabled,
};

export const DEAD_HOSTS: ListSectionProps = {
  path: '/proxy-manager/dead-hosts',
  emptyText: 'No 404 hosts. These serve a domain deliberately as nothing.',
  primary: domains,
  secondary: (r) => (r.certificate_id ? 'HTTPS' : 'HTTP only'),
  isEnabled: enabled,
};

export const ACCESS_LISTS: ListSectionProps = {
  path: '/proxy-manager/access-lists',
  emptyText: 'No access lists. These decide who may reach a host.',
  primary: (r) => String(r.name ?? '(unnamed)'),
  secondary: (r) => {
    const users = Array.isArray(r.items) ? r.items.length : 0;
    const clients = Array.isArray(r.clients) ? r.clients.length : 0;
    return `${users} user${users === 1 ? '' : 's'} · ${clients} client rule${clients === 1 ? '' : 's'}`;
  },
};