/**
 * Reconciliation cron route — invoked by `netlify/functions/reconcile-payments.mjs`.
 *
 * Auth: shared-secret header `X-Reconcile-Token` matched against
 * `runtimeConfig.reconcileToken` (env: NUXT_RECONCILE_TOKEN). Machine-to-machine
 * only — never passes `sendConfirmation: true` so back-fills don't re-send
 * confirmation emails.
 */
import Member from '../../models/member.js'
import Payment from '../../models/payment.js'
import { getHelcimCustomer, listHelcimCustomerTransactions } from '../../utils/helcim.js'
import { connectDB } from '../../utils/mongoose.js'
import { upsertPaymentFromHelcim } from '../../utils/payments.js'

// Same filter upsertPaymentFromHelcim applies — keep dry-run summary in sync.
const RECONCILABLE_STATUSES = new Set(['paid', 'refunded', 'failed'])

const RETRY_ATTEMPTS = 3
const BASE_DELAY_MS = 250

function sleep(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms))
}

async function listTransactionsWithRetry(customerCode) {
  let lastErr
  for (let attempt = 1; attempt <= RETRY_ATTEMPTS; attempt++) {
    try {
      return await listHelcimCustomerTransactions(customerCode)
    } catch (err) {
      // Permanent failures (auth, missing) — don't burn retries on broken config.
      if (err?.statusCode === 401 || err?.statusCode === 403 || err?.statusCode === 404) {
        throw err
      }
      lastErr = err
      // Backoff after attempts 1 and 2: 250ms, then 500ms (no sleep after attempt 3).
      if (attempt < RETRY_ATTEMPTS) {
        await sleep(BASE_DELAY_MS * 2 ** (attempt - 1))
      }
    }
  }
  throw lastErr
}

export default defineEventHandler(async (event) => {
  const config = useRuntimeConfig()
  const expected = config.reconcileToken
  const provided = getHeader(event, 'x-reconcile-token')
  if (!expected || provided !== expected) {
    throw createError({ statusCode: 401, statusMessage: 'Unauthorized' })
  }

  const apply = getQuery(event).apply !== 'false'

  await connectDB()

  const members = await Member.find(
    { helcimCustomerId: { $exists: true, $ne: null } },
    { _id: 1, email: 1, name: 1, helcimCustomerId: 1, helcimCustomerCode: 1, helcimSubscriptionId: 1, billingCadence: 1 }
  ).lean()

  let txExamined = 0
  let created = 0
  let existed = 0
  let skipped = 0
  let memberErrors = 0

  async function processMember(member) {
    // Opportunistic backfill: members predating the helcimCustomerCode field
    // get it filled in here so the daily cron acts as the migration. Only on
    // the missing path — no overwrite, no extra API call once populated.
    if (!member.helcimCustomerCode) {
      try {
        const customer = await getHelcimCustomer(member.helcimCustomerId)
        if (customer?.customerCode) {
          await Member.findByIdAndUpdate(
            member._id,
            { $set: { helcimCustomerCode: customer.customerCode } },
            { runValidators: false }
          )
        }
      } catch (err) {
        // Backfill is best-effort — never fail the reconcile run on it.
        console.warn(`[reconcile] customerCode backfill failed for member=${member._id}: ${err?.message || err}`)
      }
    }

    let txs
    try {
      txs = await listTransactionsWithRetry(member.helcimCustomerId)
    } catch (err) {
      console.error(`[reconcile] member=${member._id}: ${err?.message || err}`)
      return { error: true }
    }

    const result = { error: false, txExamined: 0, created: 0, existed: 0, skipped: 0 }

    for (const tx of txs) {
      result.txExamined++
      if (!RECONCILABLE_STATUSES.has(tx?.status)) {
        result.skipped++
        continue
      }

      if (!apply) {
        const existing = await Payment.findOne({ helcimTransactionId: tx.id })
        if (existing) result.existed++
        else result.created++
        continue
      }

      // Note: deliberately NOT passing sendConfirmation — cron back-fills must
      // not re-send confirmation emails for transactions the member has already
      // been notified about (or that pre-date Mongo Payment tracking entirely).
      const upsertResult = await upsertPaymentFromHelcim(member, tx)
      if (upsertResult.created) result.created++
      else if (upsertResult.payment) result.existed++
      else result.skipped++
    }

    return result
  }

  const CHUNK_SIZE = 8
  for (let i = 0; i < members.length; i += CHUNK_SIZE) {
    const chunk = members.slice(i, i + CHUNK_SIZE)
    const results = await Promise.all(chunk.map((m) => processMember(m)))
    for (const r of results) {
      if (r.error) {
        memberErrors++
        continue
      }
      txExamined += r.txExamined
      created += r.created
      existed += r.existed
      skipped += r.skipped
    }
  }

  const summary = {
    membersScanned: members.length,
    txExamined,
    created,
    existed,
    skipped,
    memberErrors,
    apply
  }
  console.log('[reconcile] done', summary)
  return summary
})