import type { DashboardGuild, SessionUser } from '@nexumi/shared';

function discordDefaultAvatarUrl(userId: string): string {
  try {
    const index = Number((BigInt(userId) >> 22n) % 6n);
    return `https://cdn.discordapp.com/embed/avatars/${index}.png`;
  } catch {
    return 'https://cdn.discordapp.com/embed/avatars/0.png';
  }
}

function userAvatarUrl(user: SessionUser): string {
  return user.avatar
    ? `https://cdn.discordapp.com/avatars/${user.id}/${user.avatar}.png?size=256`
    : discordDefaultAvatarUrl(user.id);
}

function guildIconUrl(guild: DashboardGuild): string {
  return guild.icon
    ? `https://cdn.discordapp.com/icons/${guild.id}/${guild.icon}.png?size=128`
    : discordDefaultAvatarUrl(guild.id);
}

/** Preview placeholders from the logged-in dashboard user and current guild. */
export function buildWelcomePreviewVars(
  user: SessionUser,
  guild: DashboardGuild
): Record<string, string> {
  const displayName = user.globalName?.trim() || user.username;
  return {
    user: `@${displayName}`,
    'user.name': displayName,
    'user.tag': user.username,
    'user.id': user.id,
    'user.avatar': userAvatarUrl(user),
    server: guild.name,
    'server.icon': guildIconUrl(guild),
    memberCount: '—'
  };
}