yay-machine/dist/MachineEvent.d.ts

A modern, simple, lightweight, zero-dependency, TypeScript state-machine library

/**
 * The base type for all machine states.
 * User-defined states do not need to extend this interface, just conform to its shape,
 * and can also have their own arbitrary properties.
 */
export interface MachineEvent<Type extends string = string> {
    /**
     * The unique type (or types if a string-union) of the state.
     */
    readonly type: Type;
}
/**
 * Extracts the specific event type from a union of events.
 */
export type ExtractEvent<EventType extends MachineEvent, Type extends EventType["type"]> = Extract<EventType, {
    type: Type;
}> extends never ? ExtractComplexEvent<EventType, Type> : Extract<EventType, {
    type: Type;
}>;
/**
 * Extracts a concrete event type from type whose `type` field is a `string` union
 */
type ExtractComplexEvent<EventType extends MachineEvent, Type extends EventType["type"]> = EventType extends {
    type: infer N;
} ? Type extends N ? EventType : never : never;
/**
 * Extracts the "payload" (ie, everything but the `type` field) of a specific event type.
 */
export type EventPayload<EventType extends MachineEvent, Type extends EventType["type"] = EventType["type"]> = keyof Omit<ExtractEvent<EventType, Type>, "type"> extends never ? never : Omit<ExtractEvent<EventType, Type>, "type">;
export {};
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