/**
 * One-time migration: convert Member.contributionAmount from monthly-equivalent
 * to cadence-unit for billingCadence='annual' members. After this migration,
 * an annual member with contributionAmount=180 means "$180/year" (vs the old
 * interpretation "$15/month × 12 = $180/year").
 *
 * Companion to commit 5023fb1 which dropped × 12 from the server's recurringAmount
 * computation. Run AFTER deploying the new server code, BEFORE annual members
 * try to renew or update.
 *
 * IDEMPOTENT via a transient marker field (`contributionAmountConverted: true`).
 * The script only acts on rows where this flag is not set, so re-running is
 * safe — the second run will find 0 unconverted rows.
 *
 * Trade-off: this pollutes the schema with a transient field. A follow-up
 * migration can $unset `contributionAmountConverted` from all docs once every
 * environment is confirmed migrated. The field is harmless if left in place.
 * (Option A from Task 9's plan — chosen because no migration-tracking
 * collection exists in this codebase.)
 *
 * Usage:
 *   node scripts/migrate-annual-contribution-to-cadence-unit.cjs            # dry-run
 *   node scripts/migrate-annual-contribution-to-cadence-unit.cjs --apply    # writes
 */
require('dotenv').config()
const mongoose = require('mongoose')

async function run() {
  const apply = process.argv.includes('--apply')
  if (!process.env.MONGODB_URI) {
    console.error('MONGODB_URI not set in environment')
    process.exit(1)
  }

  await mongoose.connect(process.env.MONGODB_URI)
  const db = mongoose.connection.db
  const col = db.collection('members')

  // Find annual members that haven't been converted yet.
  const filter = {
    billingCadence: 'annual',
    contributionAmountConverted: { $ne: true },
  }
  const legacyCount = await col.countDocuments(filter)
  console.log(`Found ${legacyCount} annual members not yet converted`)

  if (legacyCount === 0) {
    console.log('Nothing to migrate.')
    await mongoose.disconnect()
    return
  }

  const cursor = col.find(filter)
  let updated = 0
  let skipped = 0

  while (await cursor.hasNext()) {
    const doc = await cursor.next()
    const current = doc.contributionAmount

    if (current === null || current === undefined) {
      console.warn(`  SKIP ${doc._id}: contributionAmount is ${current}`)
      skipped++
      continue
    }

    if (!Number.isInteger(current) || current < 0) {
      console.warn(
        `  SKIP ${doc._id}: contributionAmount=${JSON.stringify(current)} is not a non-negative integer`,
      )
      skipped++
      continue
    }

    const next = current * 12

    if (current === 0) {
      console.log(`  ${doc._id}: contributionAmount=0, no change (still 0 after ×12)`)
    } else {
      console.log(
        `  ${apply ? 'Update' : 'Would update'} ${doc._id}: contributionAmount ${current} → ${next}`,
      )
    }

    if (apply) {
      await col.updateOne(
        { _id: doc._id },
        {
          $set: {
            contributionAmount: next,
            contributionAmountConverted: true,
          },
        },
      )
    }
    updated++
  }

  console.log(
    `\n${apply ? 'Updated' : 'Would update'} ${updated} documents, skipped ${skipped}`,
  )
  if (!apply) console.log('Dry-run complete. Re-run with --apply to write changes.')
  await mongoose.disconnect()
}

run().catch(async (err) => {
  console.error(err)
  try {
    await mongoose.disconnect()
  } catch {}
  process.exit(1)
})