save dialog

packages/web/src/utility/createUndoReducer.ts

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+import _ from 'lodash';
+import createReducer from './createReducer';
+
+const reducer = options => (state, action) => {
+  const { mergeNearActions } = options || {};
+
+  const useMerge =
+    action.useMerge || (mergeNearActions && state.lastActionTm && new Date().getTime() - state.lastActionTm < 100);
+
+  switch (action.type) {
+    case 'set':
+      return {
+        history: [...state.history.slice(0, useMerge ? state.current : state.current + 1), action.value],
+        current: useMerge ? state.current : state.current + 1,
+        value: action.value,
+        canUndo: true,
+        canRedo: false,
+        lastActionTm: new Date().getTime(),
+      };
+    case 'compute': {
+      const newValue = action.compute(state.history[state.current]);
+      return {
+        history: [...state.history.slice(0, useMerge ? state.current : state.current + 1), newValue],
+        current: useMerge ? state.current : state.current + 1,
+        value: newValue,
+        canUndo: true,
+        canRedo: false,
+        lastActionTm: new Date().getTime(),
+      };
+    }
+    case 'undo':
+      if (state.current > 0)
+        return {
+          history: state.history,
+          current: state.current - 1,
+          value: state.history[state.current - 1],
+          canUndo: state.current > 1,
+          canRedo: true,
+          lastActionTm: null,
+        };
+      return state;
+    case 'redo':
+      if (state.current < state.history.length - 1)
+        return {
+          history: state.history,
+          current: state.current + 1,
+          value: state.history[state.current + 1],
+          canUndo: true,
+          canRedo: state.current < state.history.length - 2,
+          lastActionTm: null,
+        };
+      return state;
+    case 'reset':
+      return {
+        history: [action.value],
+        current: 0,
+        value: action.value,
+        lastActionTm: null,
+      };
+  }
+};
+
+export default function createUndoReducer(initialValue, options = null) {
+  return createReducer(reducer(options), {
+    history: [initialValue],
+    current: 0,
+    value: initialValue,
+  });
+}