channels.clj

(ns state-examples.channels
  (:require [clojure.core.async :as async]))

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(defn- make-call
  ([acc-ch cmd]
    (make-call acc-ch cmd nil))
  ([acc-ch cmd amount]
    (let [client-ch (async/chan)]
      (async/>!! acc-ch {:client client-ch :cmd cmd :amount amount})
      (when-let [msg (async/<!! client-ch)]
        (:result msg)))))

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(defn- send-name [data client]
  (async/>!! client {:result (:name data)})
  data)

(defn- send-balance [data client]
  (async/>!! client {:result (:balance data)})
  data)

(defn- send-apply-interest [data client]
  (let [balance (:balance data)
        interest-rate (:interest-rate data)]
    (async/>!! client {:result :ok})
    (assoc data :balance (+ balance (* balance interest-rate)))))

(defn- send-withdrawl [data client amt]
  (if (<= amt (:balance data))
    (do
      (async/>!! client {:result :ok})
      (assoc data :balance (- (:balance data) amt)))
    (do
      (async/>!! client {:result :insufficient-funds})
      data)))

(defn- send-deposit [data client amt]
  (async/>!! client {:result :ok})
  (assoc data :balance (+ (:balance data) amt)))

(defn- dispatch-send
  ([data client cmd]
    (dispatch-send data client cmd nil))
  ([data client cmd amount]
    (case cmd
      :name (send-name data client)
      :balance (send-balance data client)
      :apply-interest (send-apply-interest data client)
      :withdraw (send-withdrawl data client amount)
      :deposit (send-deposit data client amount))))

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(defn new-account [name balance interest-rate]
  (let [ch (async/chan)
        data {:name name
              :balance balance
              :interest-rate interest-rate}]
    (async/go
      (loop [d data]
        (when-let [msg (async/<! ch)]
          (recur (dispatch-send
                  d (:client msg) (:cmd msg) (:amount msg))))))
    ch))

(defn get-name [acc-ch]
  (make-call acc-ch :name))

(defn get-balance [acc-ch]
  (make-call acc-ch :balance))

(defn apply-interest [acc-ch]
  (make-call acc-ch :apply-interest))

(defn withdraw [acc-ch amount]
  (make-call acc-ch :withdraw amount))

(defn deposit [acc-ch amount]
  (make-call acc-ch :deposit amount))