add effects

docs/tutorial-effects.test.js

@@ -0,0 +1,44 @@
+import { test, expect } from 'vitest';
+
+import u from 'updeep';
+import { action, Updux } from '../src/index.js';
+
+const addTodoWithId = action('addTodoWithId');
+const incNextId = action('incNextId');
+const addTodo = action('addTodo');
+
+const addTodoEffect = ({ getState, dispatch }) => next => action => {
+    const id = getState.nextId();
+
+    dispatch.incNextId();
+
+    next(action);
+
+    dispatch.addTodoWithId({ description: action.payload, id });
+}
+
+const todosDux = new Updux({
+    initial: { nextId: 1, todos: [] },
+    actions: { addTodo, incNextId, addTodoWithId },
+    selectors: {
+        nextId: ({nextId}) => nextId,
+    },
+    mutations: {
+        addTodoWithId: (todo) => u({ todos:  (todos) => [...todos, todo] }),
+        incNextId: () => u({ nextId: id => id+1 }),
+    },
+    effects: {
+        'addTodo': addTodoEffect
+    }
+});
+
+const store = todosDux.createStore();
+
+test( "tutorial example", async () => {
+    store.dispatch.addTodo('Do the thing');
+
+    expect( store.getState() ).toMatchObject({
+        nextId:2, todos: [ 'Do the thing' ]
+    })
+
+});

docs/tutorial.md

@@ -72,3 +72,54 @@ todosDux.setMutation( 'addTodo', description => ({next_id: id, todos}) => ({
     todos: [...todos, { description, id, done: false }]
 }));
 ```
+## Effects
+
+In addition to mutations, Updux also provides action-specific middleware, here
+called effects.
+
+Effects use the usual Redux middleware signature, plus a few goodies.
+The `getState` and `dispatch` functions are augmented with the dux selectors,
+and actions, respectively. The selectors and actions are also available 
+from the api object.
+
+```js
+import u from 'updeep';
+import { action, Updux } from 'updux';
+
+// we want to decouple the increment of next_id and the creation of
+// a new todo. So let's use a new version of the action 'addTodo'.
+
+const addTodoWithId = action('addTodoWithId');
+const incNextId = action('incNextId');
+const addTodo = action('addTodo');
+
+const addTodoEffect = ({ getState, dispatch }) => next => action => {
+    const id = getState.nextId();
+
+    dispatch.incNextId();
+
+    next(action);
+
+    dispatch.addTodoWithId({ description: action.payload, id });
+}
+
+const todosDux = new Updux({
+    initial: { nextId: 1, todos: [] },
+    actions: { addTodo, incNextId, addTodoWithId },
+    selectors: {
+        nextId: ({nextId}) => nextId,
+    },
+    mutations: {
+        addTodoWithId: (todo) => u({ todos: (todos) => [...todos, todo] }),
+        incNextId: () => u({ nextId: id => id+1 }),
+    },
+    effects: {
+        'addTodo': addTodoEffect
+    }
+});
+
+const store = todosDux.createStore();
+
+store.dispatch.addTodo('Do the thing');
+```
+

src/Updux.js

@@ -4,11 +4,7 @@ import { createStore as reduxCreateStore } from 'redux';
 
 import { buildSelectors } from './selectors.js';
 import { buildUpreducer } from './upreducer.js';
-import { action } from './actions.js';
-
-function isActionGen(action) {
-    return typeof action === 'function' && action.type;
-}
+import { action, isActionGen } from './actions.js';
 
 /**
  * Updux configuration object
@@ -23,6 +19,7 @@ export class Updux {
     #mutations = {};
     #config = {};
     #selectors = {};
+    #effects = {};
 
     constructor(config = {}) {
         this.#config = config;
@@ -36,6 +33,10 @@ export class Updux {
             this.#addSubduxActions(slice, sub),
         );
 
+        Object.entries(config.mutations ?? {}).forEach((args) =>
+            this.setMutation(...args),
+        );
+
         this.#selectors = buildSelectors(
             config.selectors,
             config.splatSelectors,

src/actions.js

@@ -1,3 +1,7 @@
+function isActionGen(action) {
+    return typeof action === 'function' && action.type;
+}
+
 export function action(type, payloadFunction, transformer) {
     let generator = function (...payloadArg) {
         const result = { type };

src/index.js

@@ -1 +1,2 @@
 export { Updux, dux } from './Updux.js';
+export { action } from './actions.js';

src/middleware.js

@@ -0,0 +1,82 @@
+import R from 'remeda';
+
+const composeMw = (mws) => (api) => (original_next) =>
+    mws.reduceRight((next, mw) => mw(api)(next), original_next);
+
+export function augmentMiddlewareApi(api, actions, selectors) {
+    const getState = () => api.getState();
+    const dispatch = (action) => api.dispatch(action);
+
+    Object.assign(
+        getState,
+        R.mapValues(selectors, (selector) => {
+            return (...args) => {
+                let result = selector(api.getState());
+
+                if (typeof result === 'function') return result(...args);
+
+                return result;
+            };
+        }),
+    );
+
+    Object.assign(
+        dispatch,
+        R.mapValues(actions, (action) => {
+            return (...args) => api.dispatch(action(...args));
+        }),
+    );
+
+    return {
+        ...api,
+        getState,
+        dispatch,
+        actions,
+        selectors,
+    };
+}
+
+const sliceMw = (slice, mw) => (api) => {
+    const getSliceState = () => get(api.getState(), slice);
+    return mw({ ...api, getState: getSliceState });
+};
+
+const middlewareFor = (type, middleware) => (api) => (next) => (action) => {
+    if (type !== '*' && action.type !== type) return next(action);
+
+    return middleware(api)(next)(action);
+};
+
+export const effectToMiddleware = (effect, actions, selectors) => {
+    let mw = effect;
+    let action = '*';
+
+    if (Array.isArray(effect)) {
+        action = effect[0];
+        mw = effect[1];
+        mw = middlewareFor(action, mw);
+    }
+
+    return (api) => mw(augmentMiddlewareApi(api, actions, selectors));
+};
+
+export function buildMiddleware(
+    effects = [],
+    actions = {},
+    selectors = {},
+    subduxes = {},
+) {
+    let inner = R.compact(
+        Object.entries(subduxes).map((slice, [{ middleware }]) =>
+            slice !== '*' && middleware ? sliceMw(slice, middleware) : null,
+        ),
+    );
+
+    const local = effects.map((effect) =>
+        effectToMiddleware(effect, actions, selectors),
+    );
+
+    let mws = [...local, ...inner];
+
+    return composeMw(mws);
+}

src/middleware.test.js

@@ -0,0 +1,48 @@
+import { test, expect, vi } from 'vitest';
+
+import { buildMiddleware } from './middleware.js';
+import { action } from './actions.js';
+
+test('buildMiddleware, effects', async () => {
+    const effectMock = vi.fn();
+
+    const mw = buildMiddleware([
+        ['*', (api) => (next) => (action) => effectMock()],
+    ]);
+
+    mw({})(() => {})({});
+
+    expect(effectMock).toHaveBeenCalledOnce();
+});
+
+test('buildMiddleware, augmented api', async () => {
+    const myAction = action('myAction');
+
+    const mw = buildMiddleware(
+        [
+            [
+                '*',
+                (api) => (next) => (action) => {
+                    expect(api.getState.mySelector()).toEqual(13);
+                    api.dispatch(myAction());
+                    next();
+                },
+            ],
+        ],
+        {
+            myAction,
+        },
+        {
+            mySelector: (state) => state?.selected,
+        },
+    );
+
+    const dispatch = vi.fn();
+    const getState = vi.fn(() => ({ selected: 13 }));
+    const next = vi.fn();
+
+    mw({ dispatch, getState })(next)(myAction());
+
+    expect(next).toHaveBeenCalledOnce();
+    expect(dispatch).toHaveBeenCalledWith(myAction());
+});