reactions... work?

src/Updux.ts

@@ -7,6 +7,7 @@ import {
     MiddlewareAPI,
     AnyAction,
     Middleware,
+    Dispatch,
 } from 'redux';
 import {
     configureStore,
@@ -19,7 +20,7 @@ import { AggregateActions, AggregateSelectors, Dux } from './types.js';
 import { buildActions } from './buildActions.js';
 import { buildInitial, AggregateState } from './initial.js';
 import { buildReducer, MutationCase } from './reducer.js';
-import { augmentGetState, buildEffectsMiddleware, EffectMiddleware } from './effects.js';
+import { augmentGetState, augmentMiddlewareApi, buildEffectsMiddleware, EffectMiddleware } from './effects.js';
 import { ToolkitStore } from '@reduxjs/toolkit/dist/configureStore.js';
 
 type MyActionCreator = { type: string } & ((...args: any) => any);
@@ -54,6 +55,17 @@ type ResolveActions<
         : never;
     };
 
+type Reaction<S = any, M extends MiddlewareAPI = MiddlewareAPI> =
+    (api: M, state: S, previousState: S, unsubscribe: () => void) => void;
+
+type AugmentedMiddlewareAPI<S, A, SELECTORS> =
+    MiddlewareAPI<Dispatch<AnyAction>, S> & {
+        dispatch: A,
+        getState: CurriedSelectors<SELECTORS>,
+        actions: A,
+        selectors: SELECTORS,
+    };
+
 export type Mutation<A extends Action<any> = Action<any>, S = any> = (
     payload: A extends {
         payload: infer P;
@@ -151,6 +163,19 @@ export default class Updux<
         ]
     }
 
+    get reactions(): any {
+        return [...this.#localReactions,
+        ...Object.entries(this.#subduxes).flatMap(
+            ([slice, { reactions }]) => reactions.map(
+                (r) => (api, unsub) => r({
+                    ...api,
+                    getState: () => api.getState()[slice],
+                }, unsub)
+            )
+        )
+        ];
+    }
+
     createStore(
         options: Partial<{
             initial: T_LocalState;
@@ -166,7 +191,7 @@ export default class Updux<
 
 
         const store = configureStore({
-            reducer: ((state) => state) as Reducer<
+            reducer: this.reducer as Reducer<
                 AggregateState<T_LocalState, T_Subduxes>,
                 AnyAction
             >,
@@ -185,20 +210,27 @@ export default class Updux<
 
         store.getState = augmentGetState(store.getState, this.selectors);
 
+        for (const reaction of this.reactions) {
+            let unsub;
+            const r = reaction(store);
+
+            unsub = store.subscribe(() => r(unsub));
+        }
+
+
         return store as ToolkitStore<
             AggregateState<T_LocalState, T_Subduxes>
-        > & {
-            dispatch: AggregateActions<
+        > & AugmentedMiddlewareAPI<
+            AggregateState<T_LocalState, T_Subduxes>,
+            AggregateActions<
                 ResolveActions<T_LocalActions>,
                 T_Subduxes
-            >;
-        } & {
-            getState: CurriedSelectors<AggregateSelectors<
+            >, AggregateSelectors<
                 T_LocalSelectors,
                 T_Subduxes,
                 AggregateState<T_LocalState, T_Subduxes>
-            >>
-        };
+            >
+        >;
     }
 
     get selectors(): AggregateSelectors<
@@ -271,5 +303,63 @@ export default class Updux<
         );
 
     }
+
+    #localReactions: any[] = [];
+    addReaction(reaction: Reaction<AggregateState<T_LocalState, T_Subduxes>,
+        AugmentedMiddlewareAPI<
+            AggregateState<T_LocalState, T_Subduxes>,
+            AggregateActions<
+                ResolveActions<T_LocalActions>,
+                T_Subduxes
+            >, AggregateSelectors<
+                T_LocalSelectors,
+                T_Subduxes,
+                AggregateState<T_LocalState, T_Subduxes>
+            >
+        >
+    >) {
+
+        let previous: any;
+
+        const memoized = (api: any) => {
+            api = augmentMiddlewareApi(api,
+                this.actions,
+                this.selectors
+            );
+            return (unsub: () => void) => {
+                const state = api.getState();
+                if (state === previous) return;
+                let p = previous;
+                previous = state;
+                reaction(api, state, p, unsub);
+            }
+        }
+            ;
+
+        this.#localReactions.push(memoized);
+    }
+
+    // internal method REMOVE
+    subscribeTo(store, subscription) {
+        const localStore = augmentMiddlewareApi({
+            ...store,
+            subscribe: (subscriber) => this.subscribeTo(store, subscriber), // TODO not sure
+        }, this.actions, this.selectors);
+
+        const subscriber = subscription(localStore);
+
+        let previous;
+        let unsub;
+
+        const memoSub = () => {
+            const state = store.getState();
+            if (state === previous) return;
+            let p = previous;
+            previous = state;
+            subscriber(state, p, unsub);
+        };
+
+        return store.subscribe(memoSub);
+    }
 }
 

src/effects.ts

@@ -32,7 +32,7 @@ const augmentDispatch = (originalDispatch, actions) => {
     return dispatch;
 };
 
-const augmentMiddlewareApi = (api, actions, selectors) => {
+export const augmentMiddlewareApi = (api, actions, selectors) => {
     return {
         ...api,
         getState: augmentGetState(api.getState, selectors),

src/reactions.test.todo

@@ -2,26 +2,6 @@ import { test, expect, vi } from 'vitest';
 
 import { Updux } from './Updux.js';
 
-test('basic reactions', async () => {
-    const spyA = vi.fn();
-    const spyB = vi.fn();
-    const foo = new Updux({
-        initial: { i: 0 },
-        reactions: [() => spyA],
-        actions: { inc: null },
-        mutations: {
-            inc: () => (state) => ({ ...state, i: state.i + 1 }),
-        },
-    });
-
-    foo.addReaction((api) => spyB);
-
-    const store = foo.createStore();
-    store.dispatch.inc();
-
-    expect(spyA).toHaveBeenCalledOnce();
-    expect(spyB).toHaveBeenCalledOnce();
-});
 
 test('subduxes reactions', async () => {
     const spyA = vi.fn();

src/reactions.test.ts

@@ -0,0 +1,82 @@
+import { test, expect, vi } from 'vitest';
+import Updux from './index.js';
+
+test('basic reactions', () => {
+    const foo = new Updux({
+        initial: 0,
+        actions: { inc: 0, reset: 0 },
+    });
+
+    // TODO immer that stuff
+    foo.addMutation(foo.actions.inc, () => (state) => state + 1);
+    foo.addMutation(foo.actions.reset, () => (state) => 0);
+
+    foo.addReaction((api, state, _previous, unsubscribe) => {
+        if (state < 3) return;
+        unsubscribe();
+        api.dispatch.reset();
+    });
+
+    // TODO
+    //reaction: (api) => (state,previous,unsubscribe)
+
+    const store = foo.createStore();
+
+    store.dispatch.inc();
+    expect(store.getState()).toEqual(1);
+    store.dispatch.inc();
+    store.dispatch.inc();
+
+    expect(store.getState()).toEqual(0); // we've been reset
+
+    store.dispatch.inc();
+    store.dispatch.inc();
+    store.dispatch.inc();
+    store.dispatch.inc();
+
+    expect(store.getState()).toEqual(4); // we've unsubscribed
+});
+
+test('subdux reactions', () => {
+    const bar = new Updux({
+        initial: 0,
+        actions: { inc: 0, reset: 0 },
+        selectors: {
+            getIt: (x) => x,
+        },
+    });
+
+    const foo = new Updux({ actions: { notInBar: 0 }, subduxes: { bar } });
+
+    // TODO immer that stuff
+    bar.addMutation(foo.actions.inc, () => (state) => state + 1);
+    bar.addMutation(foo.actions.reset, () => (state) => 0);
+
+    let seen = 0;
+    bar.addReaction((api, state, _previous, unsubscribe) => {
+        seen++;
+        expect(api.actions).not.toHaveProperty('notInBar');
+        expect(state).toBeTypeOf('number');
+        if (state < 3) return;
+        unsubscribe();
+        api.dispatch.reset();
+    });
+
+    const store = foo.createStore();
+
+    store.dispatch.inc();
+    expect(seen).toEqual(1);
+    expect(store.getState()).toEqual({ bar: 1 });
+    expect(store.getState.getIt()).toEqual(1);
+    store.dispatch.inc();
+    store.dispatch.inc();
+
+    expect(store.getState.getIt()).toEqual(0); // we've been reset
+
+    store.dispatch.inc();
+    store.dispatch.inc();
+    store.dispatch.inc();
+    store.dispatch.inc();
+
+    expect(store.getState.getIt()).toEqual(4); // we've unsubscribed
+});

src/types.ts

@@ -12,6 +12,7 @@ export type Dux<
         action: ReturnType<ACTIONS[keyof ACTIONS]>,
     ) => STATE;
     effects: Middleware[];
+    reactions: ((...args: any[]) => void)[];
 }>;
 
 type ActionsOf<DUX> = DUX extends { actions: infer A } ? A : {};