// ── Client → Server messages ──

export interface HelloMessage {
  type: "hello";
  joinCode?: string;
}

export interface CreatePublicRoomMessage {
  type: "create-public-room";
}

export interface SignalMessage {
  type: "signal";
  to: string;
  data: unknown;
}

export interface LeaveMessage {
  type: "leave";
}

export type ClientMessage =
  | HelloMessage
  | CreatePublicRoomMessage
  | SignalMessage
  | LeaveMessage;

// ── Server → Client messages ──

export interface PeerInfo {
  peerId: string;
  displayName: string;
}

export interface WelcomeMessage {
  type: "welcome";
  peerId: string;
  displayName: string;
  roomId: string;
  peers: PeerInfo[];
}

export interface PublicRoomCreatedMessage {
  type: "public-room-created";
  code: string;
  url: string;
  expiresAt: string;
}

export interface PeerJoinedMessage {
  type: "peer-joined";
  peerId: string;
  displayName: string;
}

export interface PeerLeftMessage {
  type: "peer-left";
  peerId: string;
}

export interface SignalRelayMessage {
  type: "signal";
  from: string;
  data: unknown;
}

export type ErrorCode = "room-not-found" | "room-expired" | "rate-limit";

export interface ErrorMessage {
  type: "error";
  code: ErrorCode;
  message: string;
}

export type ServerMessage =
  | WelcomeMessage
  | PublicRoomCreatedMessage
  | PeerJoinedMessage
  | PeerLeftMessage
  | SignalRelayMessage
  | ErrorMessage;

// ── Data channel messages (peer-to-peer) ──

export interface FileMetaMessage {
  type: "file-meta";
  id: string;
  name: string;
  size: number;
  mime: string;
}

export interface FileEndMessage {
  type: "file-end";
  id: string;
}

export interface TextMessage {
  type: "text";
  id: string;
  content: string;
}

export interface TransferRequestMessage {
  type: "transfer-request";
  files: { id: string; name: string; size: number; mime: string }[];
  text?: string;
}

export interface TransferResponseMessage {
  type: "transfer-response";
  accepted: boolean;
}

export type DataChannelMessage =
  | FileMetaMessage
  | FileEndMessage
  | TextMessage
  | TransferRequestMessage
  | TransferResponseMessage;

// ── Constants ──

export const CHUNK_SIZE = 16 * 1024; // 16 KB
export const MAX_BUFFER = 1024 * 1024; // 1 MB backpressure threshold

export const SHORT_CODE_ALPHABET = "abcdefghjkmnpqrstuvwxyz23456789";
export const SHORT_CODE_LENGTH = 3;
export const SHORT_CODE_MAX_LENGTH = 4;
export const SHORT_CODE_MAX_RETRIES = 5;

export const PUBLIC_ROOM_TTL_MS = 10 * 60 * 1000; // 10 minutes

export const ICE_SERVERS: RTCIceServer[] = [
  { urls: "stun:stun.l.google.com:19302" },
  { urls: "stun:stun1.l.google.com:19302" },
];