<script>
<![CDATA[

require("json")
require("tprint")

-- GMCP and Telnet Request/Subnegotiation info
local CLIENT_ID = {client="MUSHclient", version=Version()}
local codes = {
  IAC_SB_GMCP = "\255\250\201", -- begins a GMCP packet
  IAC_SE      = "\255\240",     -- ends a GMCP packet
  GMCP        = 201,            -- GMCP protocol number
}
local SB_GMCP = codes.IAC_SB_GMCP .. "%s" .. codes.IAC_SE

-- GMCP modules supported by this plugin
local GMCP_options = {
  "Core 1",
  "Char 1",
  "Char.Skills 1",
  "Char.Items 1",
  "Comm.Channel 1",
  "Room 1",
  "Redirect 1",
  "IRE.Rift 1",
  "IRE.Composer 1",
}

function SendGMCP(message, content)
  if type(message) ~= "string" then
    return nil, "Message name must be a string."
  end
  
  if content ~= nil then
    content = json.encode({content})
    if content == nil then
      return nil, "Invalid input."
    end
    message = ("%s %s"):format(message, content:sub(2, #content-1))
  end
  
  SendPkt(SB_GMCP:format(message))
  return true
end

function OnPluginTelnetRequest (opt, data)
  if opt ~= 201 then
    return false
  end
  
  if data == "SENT_DO" then
    Note("GMCP enabled.\n")
    
    SendGMCP("Core.Hello ", CLIENT_ID)
    SendGMCP("Core.Supports.Set ", GMCP_options)
  end
  
  return true
end

function OnPluginTelnetSubnegotiation (opt, data)
  if opt ~= codes.GMCP then
    return
  end

ColourNote ("blue", "white", data)
  
  local msg, content = unpack(utils.split(data, " ", 1))
  if not content or content:len() == 0 then
    content = nil
  else
    -- Not every JSON parser allows any top-level value to be valid.
    -- Ensuring that a non-object non-array value is at least within
    -- an array makes this code parser-agnostic.
    local err
    content, err = json.decode(("[%s]"):format(content))
    if content ~= nil then
      content = content[1]
    else
      error("Invalid message: " .. err)
    end
  end
  
function toggle_debug()
  gmcpdebug = not gmcpdebug
  Note(("GMCP Debugging is %s"):format(gmcpdebug and "Enabled" or "Disabled"))
end

]]>
</script>