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

--- Returns an Observable that produces values from the original along with the most recently
-- produced value from all other specified Observables. Note that only the first argument from each
-- source Observable is used.
-- @arg {Observable...} sources - The Observables to include the most recent values from.
-- @returns {Observable}
function Observable:with(...)
    local sources = {...}

    return Observable.create(function(observer)
        local latest = setmetatable({}, {
            __len = util.constant(#sources),
        })
        local subscriptions = {}

        local function setLatest(i)
            return function(value)
                latest[i] = value
            end
        end

        local function onNext(value)
            return observer:onNext(value, util.unpack(latest))
        end

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

        local function onCompleted()
            return observer:onCompleted()
        end

        for i = 1, #sources do
            subscriptions[i] = sources[i]:subscribe(setLatest(i), util.noop, util.noop)
        end

        subscriptions[#sources + 1] = self:subscribe(onNext, onError, onCompleted)
        return Subscription.create(function()
            for i = 1, #sources + 1 do
                if subscriptions[i] then
                    subscriptions[i]:unsubscribe()
                end
            end
        end)
    end)
end