Code for No BT TS - Challenge 3

advanced-event-handler.ts

class EventProcessor {
  handleEvent(eventName: ..., data: ...): void {
  }

  addHandler(handler: ...) {
  }

  getProcessedEvents(): ...[] {
  }
}

interface EventMap {
  login: { user?: string; name?: string; hasSession?: boolean };
  logout: { user?: string };
}

class UserEventProcessor extends EventProcessor<EventMap> {}

const uep = new UserEventProcessor();
uep.addHandler({
  filterLogin: ({ user }) => Boolean(user),
  mapLogin: (data) => ({
    ...data,
    hasSession: Boolean(data.user && data.name),
  }),
});

uep.handleEvent("login", {
  user: null,
  name: "jack",
});
uep.handleEvent("login", {
  user: "tom",
  name: "tomas",
});
uep.handleEvent("logout", {
  user: "tom",
});

console.log(uep.getProcessedEvents());

/*
Result:

[
  {
    eventName: 'login',
    data: { user: 'tom', name: 'tomas', hasSession: true }
  },
  { eventName: 'logout', data: { user: 'tom' } }
]
*/

basic-event-handler.ts

class EventProcessor {
  handleEvent(eventName: ..., data: ...): void {
  }

  addFilter(
    eventName: ...,
    filter: (data: ...) => boolean
  ): void {
  }

  addMap(eventName: ..., map: (data: ...) => ...): void {
  }

  getProcessedEvents() {
  }
}

interface EventMap {
  login: { user?: string; name?: string; hasSession?: boolean };
  logout: { user?: string };
}

class UserEventProcessor extends EventProcessor<EventMap> {}

const uep = new UserEventProcessor();

uep.addFilter("login", ({ user }) => Boolean(user));

uep.addMap("login", (data) => ({
  ...data,
  hasSession: Boolean(data.user && data.name),
}));

uep.handleEvent("login", {
  user: null,
  name: "jack",
});
uep.handleEvent("login", {
  user: "tom",
  name: "tomas",
});
uep.handleEvent("logout", {
  user: "tom",
});

console.log(uep.getProcessedEvents());

/*
Result:

[
  {
    eventName: 'login',
    data: { user: 'tom', name: 'tomas', hasSession: true }
  },
  { eventName: 'logout', data: { user: 'tom' } }
]
*/

In the basic solution, I'd like to remove these two lines this.maps[<keyof T>eventName] ||= []; (in addMap) and this.filters[<keyof T>eventName] ||= []; (in addFilter).
Is it possible to create a constructor that initializes both arrays inside the Record in this case?

Here's the solution I came to

type EventLog<TInput> = Partial<{
  [K in keyof TInput]: TInput[K];
}>;

interface EventMap {
  login: { user?: string | null; name?: string; hasSession?: boolean };
  logout: { user?: string };
}

class EventProcessor<TInput> {
  private eventLog: EventLog<TInput>[] = [];
  private eventFilters: { [key in keyof TInput]?: (data: TInput[key]) => boolean } = {};
  private eventMaps: { [key in keyof TInput]?: (data: TInput[key]) => TInput[key] } = {};
  handleEvent(eventName: keyof TInput, data: TInput[keyof TInput]): void {
    const curEvent = {
      [eventName]: { ...data },
    } as EventLog<TInput>;
    this.eventLog.push(curEvent as EventLog<TInput>);
  }

  addFilter<U extends keyof TInput>(
    eventName: U,
    filter: (data: TInput[U]) => boolean
  ): void {
    this.eventFilters[eventName] = filter;
  }

  addMap<U extends keyof TInput, O>(
    eventName: U,
    map: (data: TInput[U]) => TInput[U]
  ): void {
    this.eventMaps[eventName] = map;
  }
  
  private runFilters(){
    return this.eventLog.filter((eventLog) => {
      const eventName = Object.keys(eventLog)[0] as keyof TInput;
      const eventData = eventLog[eventName];
      const filter = this.eventFilters[eventName];
      return !filter || filter(eventData);
    });
  }
  private runMaps(filteredObjs: Partial<{ [K in keyof TInput]: TInput[K]; }>[]){
    return filteredObjs.map((val,idx) => {
      const eventName = Object.keys(val)[0] as keyof TInput;
      const eventData = val[eventName]
      const curMapFunc = this.eventMaps[eventName]
      const mappedData = curMapFunc? curMapFunc(eventData) : eventData
      return {
        eventName,
        data:{
          ...mappedData
        }
      }
    })

  }

  getProcessedEvents() {
    return this.runMaps(this.runFilters());
  }
}




class UserEventProcessor extends EventProcessor<EventMap> {}

const uep = new UserEventProcessor();

uep.addFilter("login", ({ user }) => Boolean(user));

uep.addMap("login", (data) => ({
  ...data,
  hasSession: Boolean(data.user && data.name),
}));

uep.handleEvent("login", { user: null, name: "jack" });

uep.handleEvent("login", { user: "tom", name: "tomas" });

uep.handleEvent("logout", { user: "tom" });

console.log(uep.getProcessedEvents());

/*
Result:
[
  {
    eventName: 'login',
    data: { user: 'tom', name: 'tomas', hasSession: true }
  },
  { eventName: 'logout', data: { user: 'tom' } }
]
*/