import { Int, Policy, Report, JobFailure, InvalidPolicy, Jobs, Clock } from "./contracts.eff"

const policySchema: Schema<Policy> = schema()

export const retryPolicy = (policy: Policy): RetrySchedule<JobFailure> =>
  retrySchedule((error, attempt) =>
    if (error.kind === "Transient" && attempt <= policy.retries) {
      Some(policy.retryMillis)
    } else { None })

const attempt = () =>
  using (job = {
      const id = Jobs.open()
      {
        execute: () => Jobs.execute(id),
        close: () => Jobs.close(id)
      }
    }) {
      job.execute()
    } finally {
      job.close()
    }

const cycle = (policy: Policy, completed: Int, last: Option<Int>): Report =>
  if (completed >= policy.runs) {
    { completed, last }
  } else {
    const value = retry(() => attempt(), { schedule: retryPolicy(policy) })
    const count = completed + 1
    if (count < policy.runs) { Clock.wait(policy.delayMillis) } else {}
    cycle(policy, count, Some(value))
  }

export const runWorker = (input: unknown): Report
  fails SchemaError | InvalidPolicy | JobFailure
  uses Jobs.open | Jobs.execute | Jobs.close | Clock.wait => {
    const policy = schemaDecode(policySchema, input)
    if (policy.runs < 0 || policy.delayMillis < 0 || policy.retries < 0 || policy.retryMillis < 0) {
      fail(InvalidPolicy({}))
    } else { cycle(policy, 0, None) }
  }