import { Db } from 'mongodb'
import { getMongoDb } from '#providers/mongodb_provider'

/**
 * Expected indexes on the `cwmp_exchanges` collection.
 * Each entry describes the index name and key pattern for verification.
 */
const EXPECTED_INDEXES = [
  {
    name: 'idx_deviceId_timestamp',
    key: { deviceId: 1, timestamp: 1 },
    description: 'Compound index (deviceId, timestamp)',
  },
  {
    name: 'idx_deviceId_sequenceNumber',
    key: { deviceId: 1, sequenceNumber: 1 },
    description: 'Unique index (deviceId, sequenceNumber)',
  },
  {
    name: 'idx_createdAt_ttl',
    key: { createdAt: 1 },
    description: 'TTL index (createdAt, 86400s)',
  },
]

export interface IndexCheckResult {
  name: string
  description: string
  exists: boolean
}

export interface IndexVerificationResult {
  collection: string
  allPresent: boolean
  indexes: IndexCheckResult[]
}

/**
 * Verifies that all expected indexes exist on the cwmp_exchanges collection.
 * Returns a structured result with per-index status.
 */
export async function verifyCwmpExchangesIndexes(db?: Db): Promise<IndexVerificationResult> {
  const database = db ?? getMongoDb()
  const collection = database.collection('cwmp_exchanges')

  let existingIndexes: { name?: string }[]
  try {
    existingIndexes = await collection.indexes()
  } catch {
    // Collection may not exist yet
    existingIndexes = []
  }

  const existingNames = new Set(existingIndexes.map((idx) => idx.name))

  const indexes: IndexCheckResult[] = EXPECTED_INDEXES.map((expected) => ({
    name: expected.name,
    description: expected.description,
    exists: existingNames.has(expected.name),
  }))

  const allPresent = indexes.every((idx) => idx.exists)

  return {
    collection: 'cwmp_exchanges',
    allPresent,
    indexes,
  }
}

/**
 * Runs index verification at startup and logs warnings for missing indexes.
 * Intended to be called after MongoDB provider has booted.
 */
export async function verifyIndexesAtStartup(db: Db, log: { warn: (msg: string) => void; info: (msg: string) => void }): Promise<void> {
  const result = await verifyCwmpExchangesIndexes(db)

  if (result.allPresent) {
    log.info('[ExchangeIndexCheck] All cwmp_exchanges indexes verified OK')
    return
  }

  const missing = result.indexes.filter((idx) => !idx.exists)
  for (const idx of missing) {
    log.warn(`[ExchangeIndexCheck] Missing index on cwmp_exchanges: ${idx.name} (${idx.description})`)
  }
}