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109 lines
3 KiB
Clojure
109 lines
3 KiB
Clojure
(ns uxbox.rstore
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"Reactive storage management architecture helpers."
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(:require [beicon.core :as rx]))
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;; An abstraction for implement a simple state
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;; transition. The `-apply-update` function receives
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;; the state and shoudl return the transformed state.
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(defprotocol UpdateEvent
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(-apply-update [event state]))
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;; An abstraction for perform some async stuff such
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;; as communicate with api rest or other resources
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;; that implies asynchronous access.
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;; The `-apply-watch` receives the state and should
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;; return a reactive stream of events (that can be
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;; of `UpdateEvent`, `WatchEvent` or `EffectEvent`.
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(defprotocol WatchEvent
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(-apply-watch [event state]))
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;; An abstraction for perform just side effects. It
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;; receives state and its return value is completly
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;; ignored.
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(defprotocol EffectEvent
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(-apply-effect [event state]))
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(defn update?
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"Return `true` when `e` satisfies
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the UpdateEvent protocol."
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[e]
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(satisfies? UpdateEvent e))
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(defn watch?
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"Return `true` when `e` satisfies
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the WatchEvent protocol."
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[e]
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(satisfies? WatchEvent e))
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(defn effect?
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"Return `true` when `e` satisfies
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the EffectEvent protocol."
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[e]
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(satisfies? EffectEvent e))
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(defonce bus (rx/bus))
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(defn emit!
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"Emits an event or a collection of them.
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The order of events does not matters."
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([event]
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(rx/push! bus event))
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([event & events]
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(run! #(rx/push! bus %) (into [event] events))))
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(defn swap-state
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"A helper for just apply some function to state
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without a need to declare additional event."
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[f]
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(reify
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UpdateEvent
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(-apply-update [_ state]
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(f state))
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IPrintWithWriter
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(-pr-writer [mv writer _]
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(-write writer "#<event:rstore/swap-state>"))))
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(defn reset-state
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"A event that resets the internal state with
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the provided value."
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[state]
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(reify
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IPrintWithWriter
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(-pr-writer [_ writer x]
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(-write writer "#<event:rstore/reset-state ")
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(-pr-writer state writer x)
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(-write writer ">"))
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UpdateEvent
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(-apply-update [_ _]
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state)))
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(defn init
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"Initializes the stream event loop and
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return a stream with model changes."
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[state]
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(let [update-s (rx/filter update? bus)
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watch-s (rx/filter watch? bus)
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effect-s (rx/filter effect? bus)
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state-s (->> update-s
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(rx/scan #(-apply-update %2 %1) state)
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(rx/share))]
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;; Process effects: combine with the latest model to process the new effect
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(-> (rx/with-latest-from vector state-s effect-s)
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(rx/subscribe (fn [[event model]] (-apply-effect event model))))
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;; Process event sources: combine with the latest model and the result will be
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;; pushed to the event-stream bus
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(as-> (rx/with-latest-from vector state-s watch-s) $
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(rx/flat-map (fn [[event model]] (-apply-watch event model)) $)
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(rx/merge-all $)
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(rx/on-value $ emit!))
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;; Initialize the stream machinary with initial state.
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(emit! (swap-state (fn [s] (merge s state))))
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state-s))
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