RocketChat/Rocket.Chat

import type { AsyncState } from './AsyncState';
import { AsyncStatePhase } from './AsyncStatePhase';

export const loading = <T>(): AsyncState<T> => ({
    phase: AsyncStatePhase.LOADING,
    value: undefined,
    error: undefined,
});

export const updating = <T>(value: T): AsyncState<T> => ({
    phase: AsyncStatePhase.UPDATING,
    value,
    error: undefined,
});

export const resolved = <T>(value: T): AsyncState<T> => ({
    phase: AsyncStatePhase.RESOLVED,
    value,
    error: undefined,
});

export const rejected = <T>(error: Error): AsyncState<T> => ({
    phase: AsyncStatePhase.REJECTED,
    value: undefined,
    error,
});

export const reload = <T>(prevState: AsyncState<T>): AsyncState<T> => {
    switch (prevState.phase) {
        case AsyncStatePhase.LOADING:
            return prevState;

        case AsyncStatePhase.UPDATING:
        case AsyncStatePhase.RESOLVED:
            return {
                phase: AsyncStatePhase.LOADING,
                value: prevState.value,
                error: undefined,
            };

        case AsyncStatePhase.REJECTED:
            return {
                phase: AsyncStatePhase.LOADING,
                value: undefined,
                error: prevState.error,
            };
    }
};

export const update = <T>(prevState: AsyncState<T>): AsyncState<T> => {
    switch (prevState.phase) {
        case AsyncStatePhase.LOADING:
        case AsyncStatePhase.UPDATING:
            return prevState;

        case AsyncStatePhase.RESOLVED:
            return {
                phase: AsyncStatePhase.UPDATING,
                value: prevState.value,
                error: undefined,
            };

        case AsyncStatePhase.REJECTED:
            return {
                phase: AsyncStatePhase.LOADING,
                value: undefined,
                error: prevState.error,
            };
    }
};

export const resolve = <T>(prevState: AsyncState<T>, value: T): AsyncState<T> => {
    switch (prevState.phase) {
        case AsyncStatePhase.LOADING:
        case AsyncStatePhase.UPDATING:
            return {
                phase: AsyncStatePhase.RESOLVED,
                value,
                error: undefined,
            };

        case AsyncStatePhase.RESOLVED:
        case AsyncStatePhase.REJECTED:
            return prevState;
    }
};

export const reject = <T>(prevState: AsyncState<T>, error: Error): AsyncState<T> => {
    switch (prevState.phase) {
        case AsyncStatePhase.LOADING:
        case AsyncStatePhase.UPDATING:
            return {
                phase: AsyncStatePhase.REJECTED,
                value: undefined,
                error,
            };

        case AsyncStatePhase.RESOLVED:
        case AsyncStatePhase.REJECTED:
            return prevState;
    }
};

export const value = <T>(state: AsyncState<T>): T | undefined => state.value;

export const error = <T>(state: AsyncState<T>): Error | undefined => state.error;