import { useSession } from "@/components/session-provider";
import Icon from "@/components/ui/icon";
import { cn } from "@/lib/utils";

const FALLBACK_COLOURS = [
  "bg-teal-500",
  "bg-rose-500",
  "bg-indigo-500",
  "bg-amber-500",
  "bg-cyan-500",
  "bg-purple-500",
  "bg-lime-500",
  "bg-orange-500",
  "bg-sky-500",
  "bg-fuchsia-500",
  "bg-green-500",
  "bg-red-500",
  "bg-violet-500",
  "bg-yellow-500",
  "bg-blue-500",
  "bg-emerald-500",
  "bg-pink-500",
];

function hashStringToIndex(value: string, modulo: number) {
  let hash = 0;
  for (let i = 0; i < value.length; i++) {
    hash = (hash * 31 + value.charCodeAt(i)) >>> 0;
  }
  return modulo === 0 ? 0 : hash % modulo;
}

function getInitials(username: string) {
  username = username.trim();

  const parts = username.split(/[^a-zA-Z0-9]+/).filter(Boolean);
  if (parts.length === 0) return username.slice(0, 2).toUpperCase();

  if (parts.length === 1) return parts[0].slice(0, 2).toUpperCase();

  return `${parts[0][0]}${parts[1][0]}`.toUpperCase();
}

export default function Avatar({
  avatarURL: _avatarURL,
  name: _name,
  username,
  size,
  textClass = "text-xs",
  strong = false,
  className,
}: {
  avatarURL?: string | null;
  name?: string;
  username?: string;
  size?: number;
  textClass?: string;
  strong?: boolean;
  className?: string;
}) {
  // if the username matches the authed user, use their avatarURL and name (avoid stale data)
  const { user } = useSession();
  const avatarURL = !strong && username && user && username === user.username ? user.avatarURL : _avatarURL;
  const name = !strong && username && user && username === user.username ? user.name : _name;

  const backgroundClass = username
    ? FALLBACK_COLOURS[hashStringToIndex(username, FALLBACK_COLOURS.length)]
    : "bg-muted";

  return (
    <div
      className={cn(
        "flex items-center justify-center rounded-full",
        "text-white font-medium select-none",
        name && "border",
        !avatarURL && backgroundClass,
        "transition-colors",
        `w-${size || 6}`,
        `h-${size || 6}`,
        className,
      )}
    >
      {avatarURL ? (
        <img
          src={avatarURL}
          alt="Avatar"
          className={`rounded-full object-cover w-${size || 6} h-${size || 6}`}
        />
      ) : name ? (
        <span className={textClass}>{getInitials(name)}</span>
      ) : (
        <Icon icon="userRound" className={"size-10"} />
      )}
    </div>
  );
}