TypeDrop

2026-05-23 Challenge

2026-05-23 Easy

Typed Task Priority Queue

You're building the scheduling layer for a project management tool. Tasks arrive as `unknown` from a REST API; your engine must validate them, insert them into a typed priority queue, and drain them in order — returning a strongly-typed execution plan with zero `any`.

Goals

Implement `isValidPriority` as a proper type-guard that narrows `unknown` to `Priority`.
Implement `validateTask` to parse `unknown` input into a well-typed `Task`, throwing descriptive `TypeError`s for each invalid field.
Implement `TaskQueue` with `insert`, `drain` (stable priority sort), and a `size` getter — using no `any`.
Implement `buildExecutionPlan` to validate all raw tasks, drain the queue in priority order, and return a fully-typed `ExecutionPlan` where every `Priority` key is present in `taskCountByPriority`.

          
          challenge.ts

/** Raw priority levels accepted by the API. */
type Priority = "low" | "medium" | "high" | "critical";

type Task = {
  id:          string;
  title:       string;
  priority:    Priority;
  durationMin: number;        // must be > 0
  tags:        readonly string[];
};

type ExecutionPlan = {
  orderedTasks:         readonly Task[];   // critical → high → medium → low
  totalDurationMin:     number;
  taskCountByPriority:  Record<Priority, number>;
};

/** Ordered priority levels — highest first. */
const PRIORITY_ORDER = ["critical", "high", "medium", "low"] as const;

// Your main entry point:
function buildExecutionPlan(rawTasks: unknown[]): ExecutionPlan { /* TODO */ }

Hints (click to reveal)

Hints

Use `PRIORITY_ORDER.indexOf(a.priority) - PRIORITY_ORDER.indexOf(b.priority)` as your sort comparator — a stable sort preserves insertion order for equal priorities.
To ensure every `Priority` key is always present in `taskCountByPriority`, initialise the `Record` with all four keys set to `0` before counting.
Inside `validateTask`, narrow `raw` to `Record<string, unknown>` after the non-null object check so you can safely access named fields without `any`.

Useful resources

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CodeSandbox

Or clone locally

git clone -b challenge/2026-05-23 https://github.com/niltonheck/typedrop.git