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Simple Text Editor - Clojure
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| (ns metasimple.simple-editor.core | |
| (:require | |
| [clojure.string :as str])) | |
| (defn- process-op-append | |
| [{:keys [text] :as ed-state} | |
| {:keys [op-type arg]}] | |
| (-> ed-state | |
| (update :text str arg) | |
| (update :undo-history conj {:op-type op-type :text text}))) | |
| (defn undo-op-append | |
| [ed-state | |
| {:keys [text]}] | |
| (assoc ed-state :text text)) | |
| (defn- process-op-delete | |
| [{:keys [text] :as ed-state} | |
| {:keys [op-type arg]}] | |
| (-> ed-state | |
| (update :text subs 0 arg) | |
| (update :undo-history conj {:op-type op-type :text text}))) | |
| (defn undo-op-delete | |
| [ed-state | |
| {:keys [text]}] | |
| (assoc ed-state :text text)) | |
| (defn- process-op-print | |
| [ed-state {:keys [arg]}] | |
| (println (get-in ed-state [:text (dec arg)])) | |
| ed-state) | |
| (declare op-type->exec-fns) | |
| (defn- process-op-undo | |
| [{:keys [undo-history] :as ed-state} _op] | |
| (if-let [{:keys [op-type] :as undo-item} (peek undo-history)] | |
| (let [{:keys [undo-fn]} (op-type->exec-fns op-type)] | |
| (when-not undo-fn | |
| (throw (ex-info (format "No `:undo-fn` found for undo item op: %s" undo-item) | |
| {:undo-item undo-item}))) | |
| (-> ed-state | |
| (update :undo-history pop) | |
| (undo-fn undo-item))) | |
| ;; Nothing to undo. | |
| ed-state)) | |
| (defn- parse-int | |
| [^String s] | |
| (Long/parseLong s)) | |
| (defn- create-op | |
| [op-str] | |
| (let [[op arg] (str/split op-str #" ")] | |
| (case op | |
| "1" {:op-type :append :arg arg} | |
| "2" {:op-type :delete :arg (parse-int arg)} | |
| "3" {:op-type :print :arg (parse-int arg)} | |
| "4" {:op-type :undo} | |
| (throw (ex-info (format "Unsupported op given: %s" | |
| [op arg]) | |
| {:op op :arg arg :op-str op-str}))))) | |
| (def op-type->exec-fns | |
| {:append {:process-fn process-op-append | |
| :undo-fn undo-op-append} | |
| :delete {:process-fn process-op-delete | |
| :undo-fn undo-op-delete} | |
| :print {:process-fn process-op-print} | |
| :undo {:process-fn process-op-undo}}) | |
| (def ^:dynamic *with-tracing* false) | |
| (defn- print-ed-state | |
| [{:keys [text undo-history]}] | |
| (println (format "History: %s text: '%s'" undo-history text))) | |
| (defn- exec-op | |
| [ed-state {:keys [op-type] :as op}] | |
| (when *with-tracing* | |
| (println "*********************************************") | |
| (println (format "Processing op: %s" op)) | |
| (println "-- Before state:") | |
| (print-ed-state ed-state) | |
| (println "---------------")) | |
| (let [{:keys [process-fn]} (op-type->exec-fns op-type) | |
| new-ed-state (if process-fn | |
| (process-fn ed-state op) | |
| (throw (ex-info (format "No `:process-fn` found for op: %s" op) | |
| {:op op})))] | |
| (when *with-tracing* | |
| (println "---------------") | |
| (println "--- After state:") | |
| (print-ed-state new-ed-state)) | |
| new-ed-state)) | |
| (defn process-input | |
| [raw-ops] | |
| (let [ops (mapv create-op raw-ops) | |
| init-state {:text "" :undo-history []}] | |
| (reduce exec-op | |
| init-state | |
| ops))) | |
| (def input1 | |
| ["1 abc" | |
| "1 xyz" | |
| "2 3" | |
| "4" | |
| "3 6"]) | |
| (comment | |
| (do | |
| (println "*********************************************") | |
| (binding [*with-tracing* true] (process-input input1))) | |
| ) |
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