127 lines
3.5 KiB
TypeScript
127 lines
3.5 KiB
TypeScript
import type {$FixMe} from '../types'
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import AbstractDerivation from './AbstractDerivation'
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import type {IDerivation} from './IDerivation'
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enum UPDATE_NEEDED_FROM {
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none = 0,
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dep = 1,
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inner = 2,
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}
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const makeFlatMapDerivationClass = () => {
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class FlatMapDerivation<V, DepType> extends AbstractDerivation<V> {
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private _innerDerivation: undefined | null | IDerivation<V>
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private _staleDependency: UPDATE_NEEDED_FROM
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static displayName = 'flatMap'
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constructor(
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readonly _depDerivation: IDerivation<DepType>,
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readonly _fn: (v: DepType) => IDerivation<V> | V,
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) {
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super()
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this._innerDerivation = undefined
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this._staleDependency = UPDATE_NEEDED_FROM.dep
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this._addDependency(_depDerivation)
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return this
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}
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_recalculateHot() {
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const updateNeededFrom = this._staleDependency
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this._staleDependency = UPDATE_NEEDED_FROM.none
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if (updateNeededFrom === UPDATE_NEEDED_FROM.inner) {
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// @ts-ignore
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return this._innerDerivation.getValue()
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}
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const possibleInnerDerivation = this._fn(this._depDerivation.getValue())
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if (possibleInnerDerivation instanceof AbstractDerivation) {
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this._innerDerivation = possibleInnerDerivation
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this._addDependency(possibleInnerDerivation)
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return possibleInnerDerivation.getValue()
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} else {
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return possibleInnerDerivation
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}
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}
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protected _recalculateCold() {
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const possibleInnerDerivation = this._fn(this._depDerivation.getValue())
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if (possibleInnerDerivation instanceof AbstractDerivation) {
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return possibleInnerDerivation.getValue()
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} else {
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return possibleInnerDerivation
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}
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}
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protected _recalculate() {
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return this.isHot ? this._recalculateHot() : this._recalculateCold()
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}
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protected _reactToDependencyBecomingStale(
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msgComingFrom: IDerivation<unknown>,
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) {
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const updateNeededFrom =
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msgComingFrom === this._depDerivation
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? UPDATE_NEEDED_FROM.dep
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: UPDATE_NEEDED_FROM.inner
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if (
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updateNeededFrom === UPDATE_NEEDED_FROM.inner &&
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msgComingFrom !== this._innerDerivation
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) {
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throw Error(
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`got a _pipostale() from neither the dep nor the inner derivation`,
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)
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}
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if (this._staleDependency === UPDATE_NEEDED_FROM.none) {
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this._staleDependency = updateNeededFrom
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if (updateNeededFrom === UPDATE_NEEDED_FROM.dep) {
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this._removeInnerDerivation()
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}
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} else if (this._staleDependency === UPDATE_NEEDED_FROM.dep) {
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} else {
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if (updateNeededFrom === UPDATE_NEEDED_FROM.dep) {
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this._staleDependency = UPDATE_NEEDED_FROM.dep
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this._removeInnerDerivation()
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}
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}
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}
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private _removeInnerDerivation() {
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if (this._innerDerivation) {
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this._removeDependency(this._innerDerivation)
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this._innerDerivation = undefined
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}
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}
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protected _keepHot() {
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this._staleDependency = UPDATE_NEEDED_FROM.dep
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this.getValue()
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}
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protected _becomeCold() {
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this._staleDependency = UPDATE_NEEDED_FROM.dep
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this._removeInnerDerivation()
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}
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}
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return FlatMapDerivation
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}
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let cls: ReturnType<typeof makeFlatMapDerivationClass> | undefined = undefined
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export default function flatMap<V, R>(
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dep: IDerivation<V>,
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fn: (v: V) => R,
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): IDerivation<R extends IDerivation<infer T> ? T : R> {
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if (!cls) {
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cls = makeFlatMapDerivationClass()
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}
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return new cls(dep, fn) as $FixMe
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}
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