local util = require "rx.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,
        unsubscribed = false,
    }

    return setmetatable(self, Subscription)
end

--- Unsubscribes the subscription, performing any necessary cleanup work.
function Subscription:unsubscribe()
    if self.unsubscribed then
        return
    end
    self.action(self)
    self.unsubscribed = true
end

return Subscription