feat(atom): update History.record(), add IHistory interface

- check changed() from record() if called without arg - add IHistory for alt implementations
thi-ng · Apr 15, 2018 · cf42260 · cf42260
1 parent 3c92f7e
commit cf42260
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Showing 2 changed files with 25 additions and 5 deletions.
diff --git a/packages/atom/src/api.ts b/packages/atom/src/api.ts
@@ -48,4 +48,15 @@ export interface CursorOpts<T> {
     path: Path | [(s: any) => T, (s: any, v: T) => any];
     validate?: api.Predicate<T>;
     id?: string;
+}
+
+export interface IHistory<T> extends IAtom<T> {
+    canUndo(): boolean;
+    canRedo(): boolean;
+
+    undo(): T;
+    redo(): T;
+    clear(): void;
+
+    record(): void;
 }
diff --git a/packages/atom/src/history.ts b/packages/atom/src/history.ts
@@ -2,7 +2,7 @@ import { Predicate2, Watch } from "@thi.ng/api/api";
 import { equiv } from "@thi.ng/api/equiv";
 import { Path, getIn, setIn, updateIn } from "@thi.ng/paths";
 
-import { IAtom, SwapFn, IView, ViewTransform } from "./api";
+import { IAtom, IHistory, IView, SwapFn, ViewTransform } from "./api";
 import { View } from "./view";
 
 /**
@@ -13,7 +13,7 @@ import { View } from "./view";
  * `record()` directly.
  */
 export class History<T> implements
-    IAtom<T> {
+    IHistory<T> {
 
     state: IAtom<T>;
     maxLen: number;
@@ -137,12 +137,21 @@ export class History<T> implements
      * @param state
      */
     record(state?: T) {
-        if (this.history.length >= this.maxLen) {
-            this.history.shift();
+        const history = this.history;
+        const n = history.length;
+        if (n >= this.maxLen) {
+            history.shift();
         }
         // check for arg given and not if `state == null` we want to
         // allow null/undefined as possible values
-        this.history.push(arguments.length > 0 ? state : this.state.deref());
+        if (!arguments.length) {
+            state = this.state.deref();
+            if (!n || this.changed(history[n - 1], state)) {
+                history.push(state);
+            }
+        } else {
+            history.push(state);
+        }
         this.future.length = 0;
     }