local Observable = require "rx.observable"

--- Returns an Observable that produces the average of all values produced by the original.
-- @returns {Observable}
function Observable:average()
    return Observable.create(function(observer)
        local sum, count = 0, 0

        local function onNext(value)
            sum = sum + value
            count = count + 1
        end

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

        local function onCompleted()
            if count > 0 then
                observer:onNext(sum / count)
            end

            observer:onCompleted()
        end

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