import type { ApplicationService } from '@adonisjs/core/types'
import { Db, MongoClient } from 'mongodb'

declare module '@adonisjs/core/types' {
  interface ContainerBindings {
    mongodb: Db
  }
}

/**
 * Singleton reference to the MongoDB Db instance.
 * Set during provider boot, used synchronously by BaseModel.
 */
let dbInstance: Db | null = null

export function getMongoDb(): Db {
  if (!dbInstance) {
    throw new Error('MongoDB is not connected. Ensure MongodbProvider has booted.')
  }
  return dbInstance
}

export default class MongodbProvider {
  private client: MongoClient | null = null

  constructor(protected app: ApplicationService) {}

  async boot() {
    const config = await import('#config/database')
    const { uri, dbName } = config.default

    this.client = new MongoClient(uri, {
      monitorCommands: true,
      serverSelectionTimeoutMS: 5000,
    })

    await this.client.connect()
    const db = this.client.db(dbName)

    dbInstance = db
    this.app.container.bindValue('mongodb', db)

    // Run pending MongoDB migrations automatically at boot
    const { MigratorRunner } = await import('../database/mongo_migrator.js')
    const migrationsPath = this.app.makePath('database/mongo_migrations')
    const migrator = new MigratorRunner(db, migrationsPath)
    const ran = await migrator.run().catch((err: Error) => {
      console.warn(`[MongoMigrator] Failed to run migrations: ${err.message}`)
      return [] as string[]
    })
    if (ran.length > 0) {
      console.info(`[MongoMigrator] Applied ${ran.length} migration(s): ${ran.join(', ')}`)
    } else {
      console.info('[MongoMigrator] Database is up to date.')
    }

    // Verify cwmp_exchanges indexes after boot
    const { verifyIndexesAtStartup } = await import('#services/exchange_index_checker')
    await verifyIndexesAtStartup(db, {
      warn: (msg: string) => console.warn(msg),
      info: (msg: string) => console.info(msg),
    }).catch((err) => {
      console.warn(`[ExchangeIndexCheck] Failed to verify indexes: ${(err as Error).message}`)
    })
  }

  async shutdown() {
    if (this.client) {
      try {
        await this.client.close()
      } catch {
        // Connection may already be closed
      }
      this.client = null
      dbInstance = null
    }
  }
}