(require '[tapestry.core :refer [fiber fiber-loop]])

;; Spawning a Fiber behaves very similarly to `future` in standard clojure, but
;; runs in a Loom Fiber and returns a tapestry.core.Fiber which implements IDeref.
@(fiber (+ 1 2 3 4))
;; => 10


;; Or, Like `core.async`'s `go-loop'

@(fiber-loop [i 0]
   (if (= i 5)
     (* 2 i)
     (do (Thread/sleep 100)
         (recur (inc i)))))
;; => 10, after aprox 500ms of sleeping

(require '[tapestry.core :refer [fiber interrupt! alive?]]')

(let [f (fiber (Thread/sleep 10000))]
  (alive? f) ;; true
  (interrupt! f)
  (alive? f) ;; false
  @f ;; Raises java.lang.InterruptedException))

(require '[tapestry.core :refer [fiber timeout! alive?]]')

(let [f (fiber (Thread/sleep 10000))]
  (timeout! f 100)
  (alive? f) ;; true
  (Thread/sleep 200)
  (alive? f) ;; false
  @f ;; Raises java.util.concurrent.TimeoutException))

(require '[tapestry.core :refer [fiber timeout! alive?]]')

(let [f (fiber (Thread/sleep 10000))]
  (timeout! f 100 :default)
  @f ;; => :default))

(require '[tapestry.core :refer [fiber alive? with-timeout]]')

(with-timeout 100 ;; Accepts a duration or number of millis
  (let [f (fiber (Thread/sleep 10000))]
    @f ;; raises java.util.concurrent.TimeoutException
    ))

(require '[tapestry.core :refer [parallelly asyncly pfor]]
         '[clj-http.client :as clj-http])

(def urls
  ["https://google.com"
   "https://bing.com"
   "https://yahoo.com"])

;; We can also run a function over a sequence, spawning a fiber for each item.
(->> urls
     (parallelly clj-http/get))

;; We can using the built in `pfor` macro to evaluate a `for` expression in parallel. Note that unlike
;; clojure.core/for, this is not lazy.
(pfor [url urls]
  (clj-http/get url))

;; Similalry, if we don't care about the order of items being maintained, and instead just want
;; to return results as quickly as possible

(doseq [resp (asyncly clj-http/get urls)]
  (println "Got Response!" (:status resp)))

;; We can control max parallelism for fibers
(require '[tapestry.core :refer [parallelly fiber]])

;; Note that you can also use `with-max-parallelism` within a fiber body
;; which will limit parallelism of all newly spawned fibers. Consider the following
;; in which we process up to 3 orders simultaneously, and each order can process up to 2
;; tasks in parallel.
(defn process-order!
  [order]
  (with-max-parallelism 2
    (let [internal-notification-success? (fiber (send-internal-notification! order))
          shipping-success?     (fiber (ship-order! order))
          receipt-success?      (fiber (send-receipt! order))]
      {:is-notified @internal-notification-success?
       :is-shipped  @shipping-success?
       :has-receipt @receipt-success?})))
(with-max-parallelism 3
  (let [order-a-summary (process-order! order-a)
        order-b-summary (process-order! order-b)
        order-c-summary (process-order! order-c)
        order-d-summary (process-order! order-d)]
    {:a @order-a-summary
     :b @order-b-summary
     :c @order-c-summary
     :d @order-d-summary})


;; You can also bound the parallelism of sequence processing functions by specifying
;; an optional bound:

(asyncly 3 clj-http/get urls)

(parallelly 3 clj-http/get urls)

(require '[manifold.stream :as s]
         '[tick.alpha.api :as t]
         '[tapestry.core :refer [periodically parallelly asyncly]])

;; tapestry.core/periodically behaves very similar to manfold's built in periodically,
;; but runs each task in a fiber. You can terminate it by closing the stream.
(let [count     (atom 0)
        generator (periodically (t/new-duration 1 :seconds) #(swap! count inc))]
    (->> generator
         (s/consume #(println "Count is now:" %)))
    (Thread/sleep 5000)
    (s/close! generator))

;; Also, `parallelly` and `asyncly` both suppport manifold streams, allowing you to describe parallel
;; execution pipelines
(->> (s/stream)
     (paralelly 5 some-operation)
     (asyncly 5 some-other-operation)
     (s/consume #(println "Got Result" %)))

{:lint-as {tapestry.core/fiber-loop clojure.core/loop
           tapestry.core/pfor       clojure.core/for}}