import type { Member } from "../stores/member.ts";

export type MentionOption =
  | { kind: "special"; id: string; label: string; description: string }
  | { kind: "user"; member: Member };

interface MentionDropdownProps {
  query: string;
  members: Member[];
  selectedIndex: number;
  onSelect: (username: string) => void;
  canMentionEveryone?: boolean;
}

const SPECIALS: { id: string; label: string; description: string }[] = [
  { id: "everyone", label: "everyone", description: "Notify the entire server" },
  { id: "channel", label: "channel", description: "Notify everyone in this channel" },
];

export function buildMentionOptions(
  query: string,
  members: Member[],
  canMentionEveryone: boolean,
): MentionOption[] {
  const q = query.toLowerCase();
  const options: MentionOption[] = [];

  if (canMentionEveryone) {
    for (const s of SPECIALS) {
      if (!q || s.id.startsWith(q) || s.label.startsWith(q)) {
        options.push({ kind: "special", id: s.id, label: s.label, description: s.description });
      }
    }
  }

  const users = members
    .filter(
      (m) =>
        m.username.toLowerCase().includes(q) ||
        m.display_name?.toLowerCase().includes(q),
    )
    .slice(0, 6)
    .map((m): MentionOption => ({ kind: "user", member: m }));

  return [...options, ...users].slice(0, 8);
}

export function MentionDropdown({
  query,
  members,
  selectedIndex,
  onSelect,
  canMentionEveryone = false,
}: MentionDropdownProps) {
  const options = buildMentionOptions(query, members, canMentionEveryone);

  if (options.length === 0) return null;

  return (
    <div className="absolute bottom-full left-0 mb-1 z-50 w-72 max-h-48 overflow-y-auto bg-gb-bg-s border border-gb-bg-t shadow-lg">
      <div className="px-2 py-1 text-xs text-gb-fg-s font-mono border-b border-gb-bg-t">
        MENTION
      </div>
      {options.map((opt, i) => {
        const active = i === selectedIndex;
        if (opt.kind === "special") {
          return (
            <button
              key={opt.id}
              type="button"
              onMouseDown={(e) => {
                e.preventDefault();
                onSelect(opt.label);
              }}
              className={`w-full px-2 py-1.5 text-left text-sm font-mono flex items-center gap-2 transition-colors ${
                active ? "bg-gb-orange text-gb-bg" : "hover:bg-gb-orange hover:text-gb-bg"
              }`}
            >
              <span className={active ? "text-gb-bg" : "text-gb-orange"}>@</span>
              <span className="font-bold">{opt.label}</span>
              <span className={`text-xs truncate ${active ? "text-gb-bg" : "text-gb-fg-f"}`}>
                {opt.description}
              </span>
            </button>
          );
        }
        const m = opt.member;
        return (
          <button
            key={m.id}
            type="button"
            onMouseDown={(e) => {
              e.preventDefault();
              onSelect(m.username);
            }}
            className={`w-full px-2 py-1 text-left text-sm font-mono flex items-center gap-2 transition-colors ${
              active ? "bg-gb-orange text-gb-bg" : "hover:bg-gb-orange hover:text-gb-bg"
            }`}
          >
            <span className={active ? "text-gb-bg" : "text-gb-green"}>●</span>
            <span className="truncate">{m.display_name || m.username}</span>
            {m.display_name && m.display_name !== m.username && (
              <span className={`text-xs ${active ? "text-gb-bg" : "text-gb-fg-f"}`}>
                ({m.username})
              </span>
            )}
          </button>
        );
      })}
    </div>
  );
}