(defn perform-request! [url]
  (let [output (chan)]
    (http/get url {} (fn [{:keys [status]}]
      (>! output status)))
    output))

(defn start-requester! [{:keys [url name]} timeout-value aggr-ch]
  (go
    (alts!
      (timeout timeout-value)
        ([_] (>! aggr-ch {:url url :name name :status 408}))

      (perform-request! url)
        ([status] (>! aggr-ch {:url url :name name :status status})))))


(defn start-aggregator! [init-count aggr-ch result-ch]
  (go-loop [count init-count
            state []]
    (if (> count 0)
      (recur
        (dec count)
        (conj state (<! aggr-ch)))
      (>! state result-ch))))

(defn check-availabilities [mappings global-timeout]
  (let [input (map (fn [[k v]] {:name k :url v}) mappings)
        size (count input)
        aggr-ch (chan)
        result-ch (chan)]

  (do-seq [item input] (start-requester! item 250 aggr-ch))
  (start-aggregator! size aggr-ch result-ch)

  (alt!!
    result-ch                ([result] result)
    (timeout global-timeout) ([_] {:error :timeout}))))