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

--- Returns a new Observable that produces the values produced by all the specified Observables in
-- the order they are specified.
-- @arg {Observable...} sources - The Observables to concatenate.
-- @returns {Observable}
function Observable:concat(other, ...)
    if not other then
        return self
    end

    local others = {...}

    return Observable.create(function(observer)
        local function onNext(...)
            return observer:onNext(...)
        end

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

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

        local function chain()
            return other:concat(util.unpack(others)):subscribe(onNext, onError, onCompleted)
        end

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