// ets_tracing: off

import { AtomicNumber } from "../Support/AtomicNumber/index.js"

/**
 * The identity of a Fiber, described by the time it began life, and a
 * monotonically increasing sequence number generated from an atomic counter.
 */
export interface FiberID {
  readonly _tag: "FiberID"
  readonly startTimeMillis: number
  readonly seqNumber: number
}

/**
 * Constructs a Fiber ID
 */
export function FiberID(startTimeMillis: number, seqNumber: number): FiberID {
  return {
    _tag: "FiberID",
    seqNumber,
    startTimeMillis
  }
}

/**
 * A sentinel value to indicate a fiber without identity.
 */
export const None = FiberID(0, 0)

/**
 * Checks equality of Fiber IDs
 */
export function equalsFiberID(x: FiberID, y: FiberID) {
  return x.seqNumber === y.seqNumber && x.startTimeMillis === y.startTimeMillis
}

const _fiberCounter = new AtomicNumber(0)

/**
 * Constructs a new Fiber ID using current time and global increment
 */
export function newFiberId() {
  return FiberID(new Date().getTime(), _fiberCounter.getAndIncrement())
}

/**
 * Format a fiber id
 */
export function prettyFiberId(_: FiberID) {
  return `#${_.seqNumber} (started at: ${new Date(_.startTimeMillis).toISOString()})`
}