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import {Container, Inject, Injectable, Instantiable} from '../../di'
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import {Awaitable, ErrorWithContext, JSONState, uuid4} from '../../util'
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import {BaseSerializer} from './serial/BaseSerializer'
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import {Event} from './types'
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/**
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* An event base class that provides its own validator and serializer implementation.
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* This is meant to streamline event creation for app-space by forcing the payload of
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* the event to be a JSONState.
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*/
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@Injectable()
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export abstract class StateEvent<T extends JSONState> implements Event {
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@Inject()
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protected readonly injector!: Container
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/** The payload of the event. */
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private state?: T
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eventUuid = uuid4()
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public get eventName(): string {
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return this.getName()
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}
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/** Validate the incoming data. */
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public abstract validate(state: JSONState): state is T
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/** Get the event's name for the bus. */
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public getName(): string {
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const ctor = this.constructor as typeof StateEvent
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return `state:${ctor.name}`
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}
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/** Get the Serializer implementation for this event. */
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public getSerializer(): StateEventSerializer {
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const ctor = this.constructor as typeof StateEvent
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return this.injector.makeNew<StateEventSerializer>(StateEventSerializer, ctor)
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}
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/** Validate & set the internal state of this event instance. */
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public setState(state: JSONState): this {
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if ( !this.validate(state) ) {
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throw new ErrorWithContext('Invalid state', {
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state,
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})
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}
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this.state = state
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return this
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}
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/** Get the internal state of this event, validated. */
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public getState(): T {
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if ( typeof this.state === 'undefined' ) {
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throw new ErrorWithContext('State has not been set on event')
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}
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return this.state
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}
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}
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/**
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* Generic serializer implementation for StateEvents.
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* Note that this is NOT registered with @ObjectSerializer() because we need to
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* create an instance of this class for EACH implementation of StateEvent.
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* Still working that one out. For now, you'll need to manually register the
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* serializer. You can do this with the `getSerializer` method.
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*
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* @example
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* ```ts
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* type MyState = {
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* id: number
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* }
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*
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* class MyStateEvent extends StateEvent<MyState> {
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* public validate(state: JSONState): state is MyState {
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* return is<MyState>(state)
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* }
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* }
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* ```
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*/
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@Injectable()
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export class StateEventSerializer extends BaseSerializer<StateEvent<JSONState>, JSONState> {
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@Inject()
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protected readonly injector!: Container
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/** The StateEvent implementation. */
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public readonly eventClass: Instantiable<StateEvent<JSONState>>;
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constructor(
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eventClass: Instantiable<StateEvent<JSONState>>,
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) {
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super()
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this.eventClass = eventClass
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}
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matchActual(some: StateEvent<JSONState>): boolean {
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return some instanceof this.eventClass
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}
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protected encodeActual(actual: StateEvent<JSONState>): Awaitable<JSONState> {
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return actual.getState()
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}
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protected decodeSerial(serial: JSONState): Awaitable<StateEvent<JSONState>> {
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const inst = this.injector.makeNew<StateEvent<JSONState>>(this.eventClass)
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if ( !inst.validate(serial) ) {
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throw new ErrorWithContext('Invalid serial state', {
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serial,
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eventClass: inst.getName(),
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})
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}
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inst.setState(serial)
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return inst
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}
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protected getName(): string {
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const inst = this.injector.makeNew<StateEvent<JSONState>>(this.eventClass)
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return `${inst.getName()}Serializer`
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}
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}
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