Function makeEventEmitter

packages/effect/src/internal/executionPlan.ts:28–84

(
  onEvent: (event: Api.Event<any>) => Effect<void, never, any>,
  currentMetadata: () => Api.Metadata
)

/** @internal */
export const makeEventEmitter = (
  onEvent: (event: Api.Event<any>) => Effect<void, never, any>,
  currentMetadata: () => Api.Metadata
): EventEmitter => {
  let lastStepIndex = -1
  let stepAttempt = 0
  const emit = (event: Api.Event<any>) => effect.ignoreCause(onEvent(event))
  return {
    begin: effect.clockWith((clock) =>
      effect.suspend(() => {
        const meta = currentMetadata()
        if (meta.stepIndex !== lastStepIndex) {
          lastStepIndex = meta.stepIndex
          stepAttempt = 0
        }
        stepAttempt++
        const state: AttemptState = {
          attempt: meta.attempt,
          stepAttempt,
          stepIndex: meta.stepIndex,
          startNanos: clock.monotonicTimeNanosUnsafe()
        }
        return effect.as(
          emit({
            _tag: "AttemptStart",
            attempt: state.attempt,
            stepAttempt: state.stepAttempt,
            stepIndex: state.stepIndex
          }),
          state
        )
      })
    ),
    end: (state, exit) =>
      effect.clockWith((clock) => {
        const duration = Duration.nanos(clock.monotonicTimeNanosUnsafe() - state.startNanos)
        return emit(
          exit._tag === "Success"
            ? {
              _tag: "AttemptSuccess",
              attempt: state.attempt,
              stepAttempt: state.stepAttempt,
              stepIndex: state.stepIndex,
              duration
            }
            : {
              _tag: "AttemptFailure",
              attempt: state.attempt,
              stepAttempt: state.stepAttempt,
              stepIndex: state.stepIndex,
              duration,
              cause: exit.cause
            }
        )
      })
  }
}