Task Scheduler

Prototype: NewPriorityQueue() *PriorityQueue; Add(name string,priority int) int assigns increasing IDs from 1; Pop() *QueuedTask removes highest priority then smallest numeric ID, nil empty. Names may duplicate or be empty, priorities signed.

Final: NewTaskScheduler() *TaskScheduler; AddTask(name,priority) int; AddWorker(worker string,capacity int) (bool,error) validates positive capacity before duplicate handling; duplicate preserves capacity. Worker IDs are strings, including empty. Dispatch(ts int,worker string,lease int) (*Task,error) validates positive lease before time, expires leases, returns nil for unknown/full/no pending. Success selects highest priority then smallest ID and globally increasing Token from 1; failures do not consume tokens. Running lifetime [ts,ts+lease). Complete(ts,id,token) (bool,error) expires first, succeeds only for current running matching token, then done with nil assignment fields. GetTask(ts,id) (*Task,error) and Active(ts,worker) ([]Task,error) expire first; active sorts numeric IDs, unknown worker empty. Only these timed methods accept nonnegative nondecreasing time, including valid failures. Negative/regressing timestamps error without time/state change. Expired tasks become pending with nil assignment fields; every dispatch gets a fresh token. Task snapshots contain exactly the exported fields; Status pending/running/done.

All identifiers and strings compare exactly and case-sensitively. Numeric inputs are typed int; booleans cannot be passed as amounts. Arithmetic and logical timestamps fit int. All supplied collection inputs that are retained must be copied. Every collection or pointer snapshot must be detached; separate service instances own independent state. A nil pointer or nil optional slice denotes absence, while an ordinary empty result collection is nonnil. Invalid calls leave state unchanged unless the contract explicitly accepts time and expires state on a valid unsuccessful call. The exported signatures in exercise.go are the API specification.

Edit exercise.go; retain the public types and signatures. prototype and final are separate stages. The executable tests recover panics as failures, report named checks, and exit nonzero on any failure. A successful run must execute at least one check. Tests use logical time or explicit synchronization where relevant.