const DB_NAME = 'nostr_paywall'
const DB_VERSION = 1
const STORE_NAME = 'article_content'

interface DBData {
  id: string
  data: any
  createdAt: number
  expiresAt?: number
}

/**
 * IndexedDB storage service for article content
 * More robust than localStorage and supports larger data sizes
 */
export class IndexedDBStorage {
  private db: IDBDatabase | null = null
  private initPromise: Promise<void> | null = null

  /**
   * Initialize the IndexedDB database
   */
  private async init(): Promise<void> {
    if (this.db) {
      return
    }

    if (this.initPromise) {
      return this.initPromise
    }

    this.initPromise = new Promise((resolve, reject) => {
      if (typeof window === 'undefined' || !window.indexedDB) {
        reject(new Error('IndexedDB is not available. This application requires IndexedDB support.'))
        return
      }

      const request = indexedDB.open(DB_NAME, DB_VERSION)

      request.onerror = () => {
        reject(new Error(`Failed to open IndexedDB: ${request.error}`))
      }

      request.onsuccess = () => {
        this.db = request.result
        resolve()
      }

      request.onupgradeneeded = (event) => {
        const db = (event.target as IDBOpenDBRequest).result

        // Create object store if it doesn't exist
        if (!db.objectStoreNames.contains(STORE_NAME)) {
          const store = db.createObjectStore(STORE_NAME, { keyPath: 'id' })
          store.createIndex('createdAt', 'createdAt', { unique: false })
          store.createIndex('expiresAt', 'expiresAt', { unique: false })
        }
      }
    })

    try {
      await this.initPromise
    } catch (error) {
      this.initPromise = null
      throw error
    }
  }

  /**
   * Store data in IndexedDB
   */
  async set(key: string, value: any, expiresIn?: number): Promise<void> {
    try {
      await this.init()

      if (!this.db) {
        throw new Error('Database not initialized')
      }

      const now = Date.now()
      const data: DBData = {
        id: key,
        data: value,
        createdAt: now,
        expiresAt: expiresIn ? now + expiresIn : undefined,
      }

      return new Promise((resolve, reject) => {
        const transaction = this.db!.transaction([STORE_NAME], 'readwrite')
        const store = transaction.objectStore(STORE_NAME)
        const request = store.put(data)

        request.onsuccess = () => resolve()
        request.onerror = () => reject(new Error(`Failed to store data: ${request.error}`))
      })
    } catch (error) {
      console.error('Error storing in IndexedDB:', error)
      throw error
    }
  }

  /**
   * Get data from IndexedDB
   */
  async get<T = any>(key: string): Promise<T | null> {
    try {
      await this.init()

      if (!this.db) {
        throw new Error('Database not initialized')
      }

      return new Promise((resolve, reject) => {
        const transaction = this.db!.transaction([STORE_NAME], 'readonly')
        const store = transaction.objectStore(STORE_NAME)
        const request = store.get(key)

        request.onsuccess = () => {
          const result = request.result as DBData | undefined

          if (!result) {
            resolve(null)
            return
          }

          // Check if expired
          if (result.expiresAt && result.expiresAt < Date.now()) {
            // Delete expired data
            this.delete(key).catch(console.error)
            resolve(null)
            return
          }

          resolve(result.data as T)
        }

        request.onerror = () => reject(new Error(`Failed to get data: ${request.error}`))
      })
    } catch (error) {
      console.error('Error getting from IndexedDB:', error)
      return null
    }
  }

  /**
   * Delete data from IndexedDB
   */
  async delete(key: string): Promise<void> {
    try {
      await this.init()

      if (!this.db) {
        throw new Error('Database not initialized')
      }

      return new Promise((resolve, reject) => {
        const transaction = this.db!.transaction([STORE_NAME], 'readwrite')
        const store = transaction.objectStore(STORE_NAME)
        const request = store.delete(key)

        request.onsuccess = () => resolve()
        request.onerror = () => reject(new Error(`Failed to delete data: ${request.error}`))
      })
    } catch (error) {
      console.error('Error deleting from IndexedDB:', error)
      throw error
    }
  }

  /**
   * Clear all expired entries
   */
  async clearExpired(): Promise<void> {
    try {
      await this.init()

      if (!this.db) {
        throw new Error('Database not initialized')
      }

      return new Promise((resolve, reject) => {
        const transaction = this.db!.transaction([STORE_NAME], 'readwrite')
        const store = transaction.objectStore(STORE_NAME)
        const index = store.index('expiresAt')
        const request = index.openCursor(IDBKeyRange.upperBound(Date.now()))

        request.onsuccess = (event) => {
          const cursor = (event.target as IDBRequest).result
          if (cursor) {
            cursor.delete()
            cursor.continue()
          } else {
            resolve()
          }
        }

        request.onerror = () => reject(new Error(`Failed to clear expired: ${request.error}`))
      })
    } catch (error) {
      console.error('Error clearing expired entries:', error)
      throw error
    }
  }

  /**
   * Check if IndexedDB is available
   */
  static isAvailable(): boolean {
    return typeof window !== 'undefined' && typeof window.indexedDB !== 'undefined'
  }
}

export const storageService = new IndexedDBStorage()