(ns qdis.queue
  (:use qdis.jedis))

;; settings

(def ^{:private true} queue-set  "qdis:queueset")
(def ^{:private true} queue-uuid "qdis:uuid")

(def ^{:private true} qdis-tag  "qdis:")
(def ^{:private true} queue-tag "queue:")
(def ^{:private true} uuid-tag  ":uuid:")

(defn- which-queue-name-for [queue]
  (str qdis-tag queue-tag queue))

(defn- which-item-uuid-for [queue-name uuid]
  (str queue-name uuid-tag uuid))
  
;; api

(defn enqueue [queue item]
  (with-jedis
    (do
      (let [queue-name (which-queue-name-for queue)]
        ;; create the queue (if it doesn't exists)
        (qdis.jedis/-sadd queue-set queue-name)
        ;; get a uuid to received item
        (let [item-uuid (which-item-uuid-for queue-name (qdis.jedis/-incr queue-uuid))]
          ;; bind this uuid to item's value
          (qdis.jedis/-set item-uuid item)
          ;; and finally push item's uuid to queue
          (qdis.jedis/-lpush queue-name item-uuid)
          item-uuid)))))

(defn dequeue [queue]
  (with-jedis
    (do
      (let [result (let [queue-name (which-queue-name-for queue)]
                     ;; get item's uuid from queue
                     (let [item-uuid (qdis.jedis/-rpop queue-name)]
                       (if (nil? item-uuid)
                         ;; being nil, it means that this queue doesn't exists or is empty
                         :queue-not-found-or-is-empty
                         ;; or since queue exists, get and del the item
                         (let [item (qdis.jedis/-get item-uuid)]
                           (qdis.jedis/-del item-uuid)
                           {:item-uuid item-uuid :item item}))))]
          result))))
        
;; tests

(defn run-tests []
  (qdis.jedis/initialize-pool {:host "127.0.0.1" :port 6379})

  (println "\n::: running test functions :::\n")

  (println "TEST 1   (enqueue 'padoca' 'panguan') =" (enqueue  "padoca" "panguan"))
  (println "TEST 2   (dequeue 'padocax') ="          (dequeue "padocax"))
  (println "TEST 3   (dequeue 'padoca') ="           (dequeue "padoca"))

  (println)

  (println "TEST 4.1 (enqueue 'padoca' 'panguan1') =" (enqueue  "padoca" "panguan1"))
  (println "TEST 4.2 (enqueue 'padoca' 'panguan2') =" (enqueue  "padoca" "panguan2"))
  (println "TEST 4.3 (enqueue 'padoca' 'panguan3') =" (enqueue  "padoca" "panguan3"))
  (println "TEST 4.4 (dequeue 'padoca') ="            (dequeue "padoca"))
  (println "TEST 4.5 (dequeue 'padoca') ="            (dequeue "padoca"))
  (println "TEST 4.6 (dequeue 'padoca') ="            (dequeue "padoca"))

  (println)
  
  (qdis.jedis/finalize-pool)
  
  :ok)