// (g) Defensive handler: retries within the limits, then a clean fallback.
// Secrets: API_KEY, a key for your API.
// A run has 2000 ms and 3 fetches by default, and each fetch may take up to
// 1500 ms before it rejects with 'fetch timed out'. So: retry only what can
// succeed on a second try (a network error, 429 or 5xx), only while a whole
// fetch still fits in the time left, and never more than the fetch limit.
// A 4xx is your API saying no: fall back at once. Check what comes back
// before you return it. There are no timers: you cannot wait between tries.

const RUN_MS = 2000 // the run's time limit (adorably://claim-handler shows the current value)
const FETCH_MS = 1500 // the longest one fetch can take
const MAX_TRIES = 3 // the fetch limit per run
const MARGIN_MS = 100 // time kept for the work after the last fetch

/** @param {HandlerInput} input @returns {Promise<HandlerOutput>} */
async function handle(input) {
  const started = Date.now()
  let last = ''
  for (let attempt = 1; attempt <= MAX_TRIES; attempt++) {
    if (attempt > 1 && Date.now() - started + FETCH_MS > RUN_MS - MARGIN_MS) break // no time for another full fetch
    let res
    try {
      res = await fetch('https://api.example.com/v1/perks', {
        method: 'POST',
        headers: { 'content-type': 'application/json', authorization: 'Bearer ' + SECRETS.API_KEY, 'idempotency-key': input.claim_id },
        body: JSON.stringify({ claim_id: input.claim_id, email: input.email, offer_id: input.offer.id }),
      })
    } catch (e) {
      last = e instanceof Error ? e.message : String(e)
      console.warn('attempt', attempt, last)
      if (last === 'fetch timed out') break // the next one would not finish in time
      continue
    }
    if (res.status === 429 || res.status >= 500) {
      last = 'perks API answered ' + res.status
      console.warn('attempt', attempt, last)
      continue
    }
    if (!res.ok) adorably.fallback('perks API refused the claim: ' + res.status)
    let body
    try {
      body = await res.json()
    } catch (e) {
      adorably.fallback('perks API answered with a body that is not JSON')
    }
    const url = body && body.url
    // adorably.allowedUrl: https, on an approved host, short enough.
    if (typeof url !== 'string' || !adorably.allowedUrl(url)) {
      adorably.fallback('perks API answered without a url this handler may return')
    }
    return { url }
  }
  adorably.fallback('perks API failed: ' + last)
}