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index.js
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index.js
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import ReactDOM from 'react-dom'
import React from 'react'
import R from 'ramda'
// referential equality
const eq = (a, b) => {
if (a === b) {
return true
}
if (a && a.equals && a.equals(b)) {
return true
}
return false
}
// shallow object equality
const compare = (a, b) => {
if (a === b) {
return true
}
const ak = Object.keys(a)
const bk = Object.keys(b)
if (ak.length !== bk.length) {
return false
}
for (var i = 0; i < ak.length; i++) {
const k = ak[i]
if (!eq(a[k], b[k])) {
return false
}
}
return true
}
// lazy react component
const Lazy = React.createClass({
shouldComponentUpdate: function(next) {
const props = this.props
return !eq(props.state, next.state)
|| !eq(props.dispatch, next.dispatch)
|| !compare(props.pubs, next.pubs)
|| !compare(props.props, next.props)
},
render: function() {
const {view, ...args} = this.props
return view(args)
}
})
// wrap the view function
const lazy = view => ({dispatch, state, pubs, props}) =>
<Lazy view={view} dispatch={dispatch} state={state} pubs={pubs} props={props}/>
// remember a function's arguments for comparison
const partial = fn => (...args) => {
const _fn = (...more) => fn(...args.concat(more))
_fn.fn = fn
_fn.args = args
_fn.equals = b => b
&& eq(b.fn, _fn.fn)
&& R.equals(b.args, _fn.args)
return _fn
}
// fixed arity of 2
const partial2 = fn => (a, b) => partial(fn)(a, b)
const configure = drivers => app => {
const dispatch = partial2((type, payload, ...args) => {
if (typeof payload === 'function') {
update({type, payload: payload(...args)})
} else {
update({type, payload})
}
})
let state = app.init()
const listeners = drivers.map(d => d(app, dispatch))
function update(action) {
state = app.update(state, action)
listeners.forEach(l => l(state))
}
listeners.forEach(l => l(state))
}
const mapPayload = partial((type, payload, ...args) => {
return {
type,
payload: payload(...args),
}
})
const forward = partial((dispatch, key, type, payload) => {
if (typeof payload === 'function') {
return dispatch(key, mapPayload(type, payload))
} else {
return dispatch(key, {type, payload})
}
})
// const callback = partial((fn, payload, ...args) => {
// if (typeof payload === 'function') {
// return fn(payload(...args))
// } else {
// return fn(payload)
// }
// })
const Counter = {
init: () => 0,
update: (state, action) => {
if (action.type === 'inc') {
return state + 1
}
if (action.type === 'dec') {
return state - 1
}
},
view: lazy(({dispatch, state}) => {
console.log('render Counter')
return (
<div>
<button onClick={dispatch('inc')}>{'-'}</button>
<span>{state}</span>
<button onClick={dispatch('inc')}>{'+'}</button>
</div>
)
}),
}
const twoOf = kind => ({
init: () => ({
one: kind.init(),
two: kind.init(),
}),
update: (state, action) => {
if (action.type === 'one') {
return {
one: kind.update(state.one, action.payload),
two: state.two,
}
}
if (action.type === 'two') {
return {
one: state.one,
two: kind.update(state.two, action.payload),
}
}
},
view: lazy(({dispatch, state}) => (
<div>
{kind.view({
dispatch: forward(dispatch, 'one'),
state: state.one,
})}
{kind.view({
dispatch: forward(dispatch, 'two'),
state: state.two,
})}
</div>
)),
})
const ReactDriver = (app, dispatch) => {
const root = document.getElementById('root')
return state => {
ReactDOM.render(app.view({dispatch, state}), root)
}
}
const start = configure([ReactDriver])
start(twoOf(Counter))
// start(twoOf(twoOf(Counter)))