TypeDrop

2026-07-09 Challenge

2026-07-09 Easy

Typed Task Queue Prioritizer

You're building the task scheduling module for a background job runner. Raw task definitions arrive as `unknown` from a job submission API; your module must validate them into strongly-typed `Task` records, sort them by priority and submission time, and return a fully-typed `ScheduleResult` — with zero `any`.

Goals

Implement `validateTask` to narrow `unknown` → `Task` with ordered field checks, returning a descriptive error string on the first failure found.
Implement `buildSchedule` to process a batch of raw inputs, collecting typed `ValidationError` entries for each invalid item.
Sort valid tasks by priority tier (critical → normal → low) and then by `submittedAt` ascending within the same tier.
Populate `countByPriority` as a `Record<Priority, number>` tallying valid tasks per tier.

          
          challenge.ts

export type Priority = "critical" | "normal" | "low";

export interface Task {
  id: string;
  name: string;
  priority: Priority;
  submittedAt: string;       // ISO-8601
  timeoutMs: number;         // must be > 0
  metadata: Record<string, string>;
}

export interface ScheduleResult {
  queue: Task[];             // sorted: critical → normal → low, then oldest-first
  errors: ValidationError[];
  totalReceived: number;
  countByPriority: Record<Priority, number>;
}

// Validate one raw unknown value → Task on success, error string on failure
export function validateTask(raw: unknown): Task | string { ... }

// Process a batch of raw inputs into a fully-typed ScheduleResult
export function buildSchedule(raws: unknown[]): ScheduleResult { ... }

Hints (click to reveal)

Hints

Use `PRIORITY_ORDER.includes(...)` to check if a value is a valid `Priority` — you may need a type predicate or a cast-free membership check via `(PRIORITY_ORDER as readonly string[]).includes(val)`.
For metadata validation, `Object.entries` lets you iterate key-value pairs and check that every value satisfies `typeof v === 'string'`.
The sort comparator can look up each task's tier weight with `PRIORITY_ORDER.indexOf(task.priority)`, then fall back to a `Date` comparison for tie-breaking.

Useful resources

StackBlitz

CodeSandbox

Or clone locally

git clone -b challenge/2026-07-09 https://github.com/niltonheck/typedrop.git