subscription.lua

local util = require 'util'

--- @class Subscription
-- @description A handle representing the link between an Observer and an Observable, as well as any
-- work required to clean up after the Observable completes or the Observer unsubscribes.
local Subscription = {}
Subscription.__index = Subscription
Subscription.__tostring = util.constant('Subscription')

--- Creates a new Subscription.
-- @arg {function=} action - The action to run when the subscription is unsubscribed. It will only
--                           be run once.
-- @returns {Subscription}
function Subscription.create(action)
  local self = {
    action = action or util.noop,
  }

  return setmetatable(self, Subscription)
end

--- Unsubscribes the subscription, performing any necessary cleanup work.
function Subscription:unsubscribe()
  action = self.action
  self.action = util.noop
  action(self)
end

return Subscription