import {Expect, Equal} from "../types/utils"
import { expect, it } from 'vitest';
type PayloadsToDiscriminatedUnion<T extends Record<string, any>> = {
[K in keyof T]: { type: K } & T[K];
}[keyof T];
export class DynamicReducer<
TState,
TPayloadMap extends Record<string, any> = {}
> {
private handlers = {} as Record<
string,
(state: TState, payload: any) => TState
>;
addHandler<TType extends string, TPayload extends object>(
type: TType,
handler: (state: TState, payload: TPayload) => TState
): DynamicReducer<TState, TPayloadMap & Record<TType, TPayload>> {
this.handlers[type] = handler;
return this;
}
reduce(
state: TState,
action: PayloadsToDiscriminatedUnion<TPayloadMap>
): TState {
const handler = this.handlers[action.type];
if (!handler) {
return state;
}
return handler(state, action);
}
}
interface State {
username: string;
password: string;
}
const reducer = new DynamicReducer<State>()
.addHandler(
"LOG_IN",
(state, action: { username: string; password: string }) => {
return {
username: action.username,
password: action.password,
};
}
)
.addHandler("LOG_OUT", () => {
return {
username: "",
password: "",
};
})
.addHandler("UPDATE_USERNAME", (state, action: { username: string }) => {
return {
...state,
username: action.username,
};
});
it("Should return the new state after LOG_IN", () => {
const state = reducer.reduce(
{ username: "", password: "" },
{
type: "UPDATE_USERNAME",
username: "awdawdawd",
}
);
type test = [Expect<Equal<typeof state, State>>];
expect(state).toEqual({ username: "foo", password: "bar" });
});
it("Should return the new state after LOG_OUT", () => {
const state = reducer.reduce(
{ username: "foo", password: "bar" },
{ type: "LOG_OUT" }
);
type test = [Expect<Equal<typeof state, State>>];
expect(state).toEqual({ username: "", password: "" });
});
it("Should error if you pass it an incorrect action", () => {
const state = reducer.reduce(
{ username: "foo", password: "bar" },
{
// @ts-expect-error
type: "NOT_ALLOWED",
}
);
});
it("Should error if you pass an incorrect payload", () => {
const state = reducer.reduce(
{ username: "foo", password: "bar" },
// @ts-expect-error
{
type: "LOG_IN",
}
);
});