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p61-project/presentation/presenters/_Presenter.ts

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import { produce } from "immer"
type Listener<State> = (state: State) => void
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type SetStateAction<State> = (state: State) => void
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export const FETCH_STATES = ["idle", "loading", "error", "success"] as const
export type FetchState = (typeof FETCH_STATES)[number]
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export type ErrorGlobal = "unknown" | null
export abstract class Presenter<State> {
private _state: State
private readonly _initialState: State
private readonly _listeners: Array<Listener<State>>
public constructor(initialState: State) {
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this._state = initialState
this._initialState = initialState
this._listeners = []
}
public get initialState(): State {
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return this._initialState
}
/**
* @description Set the state of the presenter.
* @param action A function that receives the current state and can update it by mutating it.
* @returns The new state.
*/
public setState(action: SetStateAction<State>): State {
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this._state = produce(this._state, action)
this.notifyListeners()
return this._state
}
public subscribe(listener: Listener<State>): void {
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this._listeners.push(listener)
}
public unsubscribe(listener: Listener<State>): void {
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const listenerIndex = this._listeners.indexOf(listener)
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this._listeners.splice(listenerIndex, 1)
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}
private notifyListeners(): void {
for (const listener of this._listeners) {
listener(this._state)
}
}
}