defmodule TcpHandler do
  def start(port) do
    # 監聽端口
    {:ok, listen_socket} =
      :gen_tcp.listen(port, [
        :binary,
        packet: :line,
        reuseaddr: true,
        active: false,
        backlog: 100
      ])

    accept_loop(listen_socket)
  end

  defp accept_loop(listen_socket) do
    case :gen_tcp.accept(listen_socket) do
      {:ok, socket} ->
        spawn(__MODULE__, :handle_client, [socket])
        accept_loop(listen_socket)

      {:error, reason} ->
        IO.puts("接受連接失敗: #{reason}")
    end
  end

  def handle_client(socket) do
    # 接收數據
    case :gen_tcp.recv(socket, 0) do
      {:ok, data} ->
        IO.puts("收到: #{data}")
        :gen_tcp.send(socket, "Echo: #{data}")
        # 繼續接收
        handle_client(socket)

      {:error, :closed} ->
        IO.puts("客戶端斷開連接")

      {:error, reason} ->
        IO.puts("接收數據失敗: #{reason}")
    end
  end
end