Graph oriented programming.
An alternative way of writing code rich of conditionals.
Instead of
(defn sell-booze
[resources data]
(let [profile (get-profile-data resources data)]
(if (got-the-id? profile)
(if (is-under-21? profile)
(dont-sell)
(let [supply (get-supply resources data)]
(if (is-enough-supply? supply)
(if (is-enough-money data)
(sell)
(not-enough-money))
(not-enough-supply))))
(dont-sell))))we do
(def sell-booze-graph
{get-profile-data {got-the-id? :check-age
flow/otherwise dont-sell}
:check-age {is-under-21? dont-sell
flow/otherwise get-supply}
get-supply {is-enough-supply? :check-money
flow/otherwise inform-not-enough-supply}
:check-money {is-enough-money? sell
flow/otherwise inform-not-enough-money}
inform-not-enough-supply inform-available-amount-of-supply
inform-not-enough-money inform-affordable-amount-of-booze})(require '[flow.core :as flow])
(defn- get-profile-data
[resources data]
(let [{:keys [id]} data
profile (get-in resources [:profiles id])]
(assoc data :profile profile)))
(defn- get-supply
[resources data]
(let [{:keys [booze]} data
{:keys [supplies]} resources
supply (get supplies booze)]
(assoc data :supply supply)))
(defn- inform-not-enough-supply
[resources data]
(assoc data :result {:status :not-enough-booze}))
(defn- inform-not-enough-money
[resources data]
(assoc data :result {:status :not-enough-money}))
(defn- inform-available-amount-of-supply
[resources data]
(let [real-amount (get-in data [:supply :amount] 0)]
(assoc-in data [:result :available] real-amount)))
(defn- inform-affordable-amount-of-booze
[resources data]
(let [{:keys [money supply]} data
{:keys [price]} supply
affordable-amount (int (/ money price))]
(assoc-in data [:result :affordable] affordable-amount)))
(defn- dont-sell
[resources data]
(assoc data :result {:status :can-not-sell}))
(defn- sell
[resources data]
(assoc data :result {:status :here-you-are}))
(defn- got-the-id?
[resources data]
(let [{:keys [profile]} data]
(not (nil? profile))))
(defn- is-under-21?
[resources data]
(let [{:keys [profile]} data
{:keys [age]} profile]
(< age 21)))
(defn- is-enough-supply?
[resources data]
(let [{:keys [amount supply]} data
{real-amount :amount} supply]
(and real-amount
(>= real-amount amount))))
(defn- is-enough-money?
[resources data]
(let [{:keys [amount money supply]} data
{real-amount :amount
:keys [price]} supply
total-price (* amount price)]
(>= money total-price)))
(def sell-booze-graph
{get-profile-data {got-the-id? :check-age
flow/otherwise dont-sell}
:check-age {is-under-21? dont-sell
flow/otherwise get-supply}
get-supply {is-enough-supply? :check-money
flow/otherwise inform-not-enough-supply}
:check-money {is-enough-money? sell
flow/otherwise inform-not-enough-money}
inform-not-enough-supply inform-available-amount-of-supply
inform-not-enough-money inform-affordable-amount-of-booze})
(deftest get-the-booze-flow
(let [resources {:supplies {"Beer" {:amount 10
:price 7}
"Wine" {:amount 5
:price 12}
"Whiskey" {:amount 2
:price 22}
"Gin" {:amount 3
:price 17}}
:profiles {"Ivan" {:age 30}
"Andrew" {:age 30}
"Eva" {:age 2}}}]
(testing "all good"
(let [data {:id "Ivan"
:money 100
:booze "Beer"
:amount 3}
{:keys [result]} (flow/execute {:graph sell-booze-graph
:start get-profile-data}
resources
data)]
(is (= {:status :here-you-are}
result))))
(testing "not enough booze"
(let [data {:id "Ivan"
:money 100
:booze "Wine"
:amount 10}
{:keys [result]} (flow/execute {:graph sell-booze-graph
:start get-profile-data}
resources
data)]
(is (= {:status :not-enough-booze
:available 5}
result))))
(testing "not enough money"
(let [data {:id "Andrew"
:money 20
:booze "Beer"
:amount 5}
{:keys [result]} (flow/execute {:graph sell-booze-graph
:start get-profile-data}
resources
data)]
(is (= {:status :not-enough-money
:affordable 2}
result))))
(testing "no ID"
(let [data {:id "Ira"
:money 1000
:booze "Whiskey"
:amount 30}
{:keys [result]} (flow/execute {:graph sell-booze-graph
:start get-profile-data}
resources
data)]
(is (= {:status :can-not-sell}
result))))
(testing "too young"
(let [data {:id "Eva"
:money 50
:booze "Whiskey"
:amount 1}
{:keys [result]} (flow/execute {:graph sell-booze-graph
:start get-profile-data}
resources
data)]
(is (= {:status :can-not-sell}
result))))))