// === WebSocket Protocol Types (xterm.js + node-pty) ===

// Binary frame header for terminal data multiplexing:
// [1 byte direction][36 bytes chatId ASCII][...payload]
// Direction: 0x01 = PTY output (proxy→backend→frontend)
//            0x02 = user input (frontend→backend→proxy)
export const DIR_PTY_OUTPUT = 0x01;
export const DIR_USER_INPUT = 0x02;
export const CHAT_ID_LENGTH = 36; // UUID length

export function encodeBinaryFrame(direction: number, chatId: string, data: Buffer): Buffer {
  const header = Buffer.alloc(1 + CHAT_ID_LENGTH);
  header[0] = direction;
  header.write(chatId, 1, CHAT_ID_LENGTH, 'ascii');
  return Buffer.concat([header, data]);
}

export function decodeBinaryFrame(frame: Buffer): { direction: number; chatId: string; data: Buffer } {
  const direction = frame[0];
  const chatId = frame.subarray(1, 1 + CHAT_ID_LENGTH).toString('ascii');
  const data = frame.subarray(1 + CHAT_ID_LENGTH);
  return { direction, chatId, data };
}

// JSON control messages

export type BackendMessageType =
  | 'sync_state'
  | 'create_pty'
  | 'kill_pty'
  | 'resize'
  | 'list_directories'
  | 'list_sessions';

export type ProxyMessageType =
  | 'pty_ready'
  | 'pty_closed'
  | 'directories'
  | 'sessions_list'
  | 'error';

export type WsMessageType = BackendMessageType | ProxyMessageType;

export interface WsMessage {
  type: WsMessageType;
  requestId?: string;
  payload: unknown;
}

// === Payload types ===

export interface SyncStatePayload {
  chats: AgentChatInfo[];
}

export interface AgentChatInfo {
  id: string;
  workDir: string | null;
  sessionId: string | null;
  cols?: number;
  rows?: number;
}

export interface CreatePtyPayload {
  chatId: string;
  dir: string;
  resumeSessionId?: string;
  cols: number;
  rows: number;
}

export interface KillPtyPayload {
  chatId: string;
}

export interface ResizePayload {
  chatId: string;
  cols: number;
  rows: number;
}

export interface PtyReadyPayload {
  chatId: string;
}

export interface PtyClosedPayload {
  chatId: string;
  exitCode: number;
}

export interface ListDirectoriesPayload {
  path: string;
}

export interface DirectoryEntry {
  name: string;
  isDirectory: boolean;
}

export interface DirectoriesPayload {
  requestId: string;
  entries: DirectoryEntry[];
}

export interface ErrorPayload {
  chatId?: string;
  message: string;
}