# rpc_client.rb
require 'ffi-rzmq'
require 'json'
require 'securerandom'
require 'timeout'

ENDPOINT = "ipc:///tmp/zmq-rpc-demo"

class RpcClient
  def initialize(endpoint, timeout_ms: 2000)
    @ctx = ZMQ::Context.new
    @req = @ctx.socket(ZMQ::REQ)
    
    @req.setsockopt(ZMQ::LINGER, 0)

    rc = @req.connect(endpoint)
    raise "connect failed: #{ZMQ::Util.error_string}" unless rc == 0
    @poller = ZMQ::Poller.new
    @poller.register_readable(@req)
    @timeout = timeout_ms
  end

  def call(method, params=nil)
    id = SecureRandom.uuid
    payload = { jsonrpc: "2.0", id: id, method: method, params: params }.to_json
    @req.send_string(payload)

    # Wait for reply with timeout
    rc = @poller.poll(@timeout)
    raise Timeout::Error, "RPC timeout after #{@timeout}ms" if rc == 0

    raw = ''
    @req.recv_string(raw)
    res = JSON.parse(raw)

    if res["error"]
      code = res["error"]["code"]
      msg  = res["error"]["message"]
      data = res["error"]["data"]
      raise StandardError, "RPC error (#{code}): #{msg}#{data ? " | #{data}" : ""}"
    end

    raise "Mismatched id" if res["id"] != id
    res["result"]
  end

  def close
    @req.close
    @ctx.terminate
  end
end