local Observable = require "rx.observable"
local util = require "rx.util"

--- Returns a new Observable that only produces the last result of the original.
-- @returns {Observable}
function Observable:last()
    return Observable.create(function(observer)
        local value
        local empty = true

        local function onNext(...)
            value = {...}
            empty = false
        end

        local function onError(e)
            return observer:onError(e)
        end

        local function onCompleted()
            if not empty then
                observer:onNext(util.unpack(value or {}))
            end

            return observer:onCompleted()
        end

        return self:subscribe(onNext, onError, onCompleted)
    end)
end