--A chat server. Supports connection/disconnection announcing and /nick command
--to let the user change her nick. Also, /kick can be used from terminal.
--Warning: there's currently hardly any security checks there.

chat_connections = {}

return {

  print_nonl = function (self, msg)
    io.stdout:write(msg)
    io.stdout:flush()
  end,

  broadcast = function (self, msg)
    self:print_nonl(msg)
    --Note that connections[k] means that we can't easily say if
    --the connection belongs to us or not. chat_connections[k]
    --would solve it, but then we'd skip the filters below the
    --connection.
    for k, v in pairs(connections) do
      connections[k]:send(msg)
    end
  end,

  connect = function (self, host, port)
    ret = self.super:connect(host, port)
    self.our_id = self:get_nick()
    msg = "* " .. self.our_id .. " connected to the server.\n"
    self:broadcast(msg)
    return ret
  end,

  close = function (self)
    msg = "* " .. self.our_id .. " disconnected from the server.\n"
    self:broadcast(msg)
    self.super:close()
  end,

  get_nick = function (self)
    for k, v in pairs(chat_connections) do
      if chat_connections[k] == self then
        return k
      end
    end
    --If we got there, we clearly aren't registered yet. Find a name.
    --We probably could have come with a cooler nick, but it's a PoC.
    local new_id = tostring(self)
    chat_connections[new_id] = self
    return new_id
  end,

  is_valid_nick = function (self, new_id)
    return chat_connections[new_id] == nil
  end,

  recv = function (self)
    local line, err = self.super:recv()
    if line == nil then
      return line, err
    end
    --During testing, this happened in UDP mode. No idea why you'd want
    --a single-user chat though since that's all you'd get without -k.
    if self.our_id == nil then
      self:connect()
    end
    local msg = '<' .. self.our_id .. '> ' .. line
    if line:sub(1, 6) == "/nick " then
      local old_id = self.our_id
      local new_id = line:sub(7):gsub("\n", "")
      if self:is_valid_nick(new_id) then
        self.our_id = new_id
        chat_connections[old_id] = nil
        chat_connections[self.our_id] = self
        msg = "* " .. old_id .. " changed nickname to " .. self.our_id .. "\n"
      else
        self:send "Nickname not allowed!\n"
        return ""
      end
    end
    self:broadcast(msg)
    return ""
  end,

  send = function (self, str)
    if str:sub(1, 6) ~= "/kick " then
      return self.super:send(str)
    end

    local kicked_nick = str:sub(7):gsub("\n", "")

    if chat_connections[kicked_nick] == nil then
      --We're not printing "no such nick" because admin would see the
      --message multiplied for each user connected.
      return
    end

    chat_connections[kicked_nick]:send "You have been kicked.\n"
    chat_connections[kicked_nick].super:close()
    chat_connections[kicked_nick] = nil
    self:broadcast(("* %s got kicked by the chat administrator.\n"):format(kicked_nick))
  end,
}