import { BaseModel } from '#database/base_model'
import { getMongoDb } from '#providers/mongodb_provider'

export interface CwmpExchange {
  deviceId: string
  direction: 'CPE→ACS' | 'ACS→CPE'
  timestamp: string
  sessionId: string
  cwmpMethod: string
  rawXml: string
  sequenceNumber: number
  createdAt?: Date
}

export interface ExchangeMetadata {
  recordedFrom: string | null
  recordedUntil: string | null
  count: number
}

export default class ExchangeModel extends BaseModel {
  static collectionName = 'cwmp_exchanges'

  /**
   * Find exchanges for a device, ordered by timestamp ascending.
   * Supports cursor-based pagination with `after` (newer) and `before` (older) parameters.
   * When `before` is used, returns the most recent `limit` messages before that timestamp (ascending order).
   * When `latest` is true, returns the most recent `limit` messages (ascending order).
   */
  static async findByDevice(
    deviceId: string,
    options?: { limit?: number; after?: string; before?: string; latest?: boolean }
  ): Promise<CwmpExchange[]> {
    const collection = this.getCollection()
    const filter: any = { deviceId }

    if (options?.after) {
      filter.timestamp = { $gt: options.after }
    } else if (options?.before) {
      filter.timestamp = { $lt: options.before }
    }

    const limit = options?.limit ?? 200

    // When using `latest` or `before`, we want the most recent messages.
    // Query in descending order then reverse to return in ascending order.
    if (options?.latest || options?.before) {
      const results = await collection
        .find(filter)
        .sort({ timestamp: -1 })
        .limit(limit)
        .toArray() as unknown as CwmpExchange[]
      return results.reverse()
    }

    return collection
      .find(filter)
      .sort({ timestamp: 1 })
      .limit(limit)
      .toArray() as unknown as Promise<CwmpExchange[]>
  }

  /**
   * Find exchanges with sequence number greater than given value.
   * Used for SSE reconnection via Last-Event-ID.
   */
  static async findAfterSequence(deviceId: string, seqNumber: number): Promise<CwmpExchange[]> {
    const collection = this.getCollection()
    return collection
      .find({ deviceId, sequenceNumber: { $gt: seqNumber } })
      .sort({ sequenceNumber: 1 })
      .toArray() as unknown as Promise<CwmpExchange[]>
  }

  /**
   * Delete all exchanges for a device.
   * Returns the number of deleted documents.
   */
  static async deleteByDevice(deviceId: string): Promise<number> {
    const collection = this.getCollection()
    const result = await collection.deleteMany({ deviceId })
    return result.deletedCount
  }

  /**
   * Get the maximum sequence number for a device.
   * Returns 0 if no exchanges exist.
   */
  static async getMaxSequenceNumber(deviceId: string): Promise<number> {
    const collection = this.getCollection()
    const result = await collection
      .find({ deviceId })
      .sort({ sequenceNumber: -1 })
      .limit(1)
      .toArray()

    return result.length > 0 ? result[0].sequenceNumber : 0
  }

  /**
   * Count exchanges for a device.
   */
  static async countByDevice(deviceId: string): Promise<number> {
    const collection = this.getCollection()
    return collection.countDocuments({ deviceId })
  }

  /**
   * Delete oldest exchanges exceeding the cap for a device.
   * Keeps the most recent `maxCount` exchanges (by sequenceNumber).
   */
  static async deleteOldestBeyondCap(deviceId: string, maxCount: number): Promise<void> {
    const collection = this.getCollection()
    const count = await collection.countDocuments({ deviceId })

    if (count <= maxCount) return

    const toDelete = count - maxCount
    const oldest = await collection
      .find({ deviceId })
      .sort({ sequenceNumber: 1 })
      .limit(toDelete)
      .project({ sequenceNumber: 1 })
      .toArray()

    if (oldest.length === 0) return

    const maxSeqToDelete = oldest[oldest.length - 1].sequenceNumber
    await collection.deleteMany({
      deviceId,
      sequenceNumber: { $lte: maxSeqToDelete },
    })
  }

  /**
   * Check if any exchange exists for a device (ever traced).
   */
  static async hasExchanges(deviceId: string): Promise<boolean> {
    const collection = this.getCollection()
    const doc = await collection.findOne({ deviceId }, { projection: { _id: 1 } })
    return doc !== null
  }

  /**
   * Get metadata (oldest and newest timestamps, count).
   */
  static async getMetadata(deviceId: string): Promise<ExchangeMetadata> {
    const collection = this.getCollection()

    const count = await collection.countDocuments({ deviceId })
    if (count === 0) {
      return { recordedFrom: null, recordedUntil: null, count: 0 }
    }

    const [oldest] = await collection
      .find({ deviceId })
      .sort({ timestamp: 1 })
      .limit(1)
      .project({ timestamp: 1 })
      .toArray()

    const [newest] = await collection
      .find({ deviceId })
      .sort({ timestamp: -1 })
      .limit(1)
      .project({ timestamp: 1 })
      .toArray()

    return {
      recordedFrom: oldest?.timestamp ?? null,
      recordedUntil: newest?.timestamp ?? null,
      count,
    }
  }

  /**
   * Ensure required indexes exist on the cwmp_exchanges collection.
   * Creates indexes for:
   * - (deviceId, timestamp): efficient retrieval by device ordered by time
   * - (deviceId, sequenceNumber) unique: atomic sequence numbering, Last-Event-ID queries
   * - (createdAt) TTL 24h: auto-remove old exchanges
   */
  static async ensureIndexes(): Promise<void> {
    const db = getMongoDb()
    const collection = db.collection('cwmp_exchanges')

    await collection.createIndex(
      { deviceId: 1, timestamp: 1 },
      { name: 'idx_deviceId_timestamp', background: true }
    )

    await collection.createIndex(
      { deviceId: 1, sequenceNumber: 1 },
      { unique: true, name: 'idx_deviceId_sequenceNumber', background: true }
    )

    await collection.createIndex(
      { createdAt: 1 },
      { expireAfterSeconds: 86400, name: 'idx_createdAt_ttl', background: true }
    )
  }
}