/**
 * IndexedDB cache for Nostr objects (authors, series, publications, reviews)
 * Objects are indexed by their hash ID for fast retrieval
 * One database per object type
 */

import type { Event } from 'nostr-tools'
import type { AuthorPresentationArticle } from '@/types/nostr'
import { buildObjectId } from './urlGenerator'

export type ObjectType = 'author' | 'series' | 'publication' | 'review' | 'purchase' | 'sponsoring' | 'review_tip'

interface CachedObject {
  id: string // Format: <hash>_<index>_<version>
  hash: string // SHA-256 hash of the object
  hashId: string // Legacy field for backward compatibility
  index: number // Index for duplicates
  event: Event
  parsed: unknown // Parsed object (AuthorPresentationArticle, Series, etc.)
  version: number
  hidden: boolean
  createdAt: number
  cachedAt: number
}

const DB_PREFIX = 'nostr_objects_'
const DB_VERSION = 2 // Incremented to add id, hash, index fields

class ObjectCacheService {
  private dbs: Map<ObjectType, IDBDatabase> = new Map()

  private async initDB(objectType: ObjectType): Promise<IDBDatabase> {
    if (this.dbs.has(objectType)) {
      return this.dbs.get(objectType)!
    }

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

      const dbName = `${DB_PREFIX}${objectType}`
      const request = indexedDB.open(dbName, DB_VERSION)

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

      request.onsuccess = (): void => {
        const db = request.result
        this.dbs.set(objectType, db)
        resolve(db)
      }

      request.onupgradeneeded = (event: IDBVersionChangeEvent): void => {
        const db = (event.target as IDBOpenDBRequest).result
        if (!db.objectStoreNames.contains('objects')) {
          const store = db.createObjectStore('objects', { keyPath: 'id' })
          store.createIndex('hash', 'hash', { unique: false })
          store.createIndex('hashId', 'hashId', { unique: false }) // Legacy index
          store.createIndex('version', 'version', { unique: false })
          store.createIndex('index', 'index', { unique: false })
          store.createIndex('hidden', 'hidden', { unique: false })
          store.createIndex('cachedAt', 'cachedAt', { unique: false })
        } else {
          // Migration: add new indexes if they don't exist
          const {transaction} = (event.target as IDBOpenDBRequest)
          if (transaction) {
            const store = transaction.objectStore('objects')
            if (!store.indexNames.contains('hash')) {
              store.createIndex('hash', 'hash', { unique: false })
            }
            if (!store.indexNames.contains('index')) {
              store.createIndex('index', 'index', { unique: false })
            }
          }
        }
      }
    })
  }

  /**
   * Count objects with the same hash to determine the index
   */
  private async countObjectsWithHash(objectType: ObjectType, hash: string): Promise<number> {
    try {
      const db = await this.initDB(objectType)
      const transaction = db.transaction(['objects'], 'readonly')
      const store = transaction.objectStore('objects')
      const index = store.index('hash')

      return new Promise((resolve, reject) => {
        const request = index.count(IDBKeyRange.only(hash))
        request.onsuccess = (): void => {
          resolve(request.result)
        }
        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error(`Error counting objects with hash ${hash}:`, error)
      return 0
    }
  }

  /**
   * Store an object in cache
   * Verifies and sets the index before insertion
   */
  async set(
    objectType: ObjectType,
    hash: string,
    event: Event,
    parsed: unknown,
    version: number,
    hidden: boolean,
    index?: number
  ): Promise<void> {
    try {
      const db = await this.initDB(objectType)

      // If index is not provided, calculate it by counting objects with the same hash
      let finalIndex = index
      if (finalIndex === undefined) {
        const count = await this.countObjectsWithHash(objectType, hash)
        finalIndex = count
      }

      const id = buildObjectId(hash, finalIndex, version)

      const transaction = db.transaction(['objects'], 'readwrite')
      const store = transaction.objectStore('objects')

      const cached: CachedObject = {
        id,
        hash,
        hashId: hash, // Legacy field for backward compatibility
        index: finalIndex,
        event,
        parsed,
        version,
        hidden,
        createdAt: event.created_at,
        cachedAt: Date.now(),
      }

      await new Promise<void>((resolve, reject) => {
        const request = store.put(cached)
        request.onsuccess = (): void => {
          resolve()
        }
        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error(`Error caching ${objectType} object:`, error)
    }
  }

  /**
   * Get an object from cache by hash
   * Returns the latest non-hidden version
   */
  async get(objectType: ObjectType, hash: string): Promise<unknown | null> {
    try {
      const db = await this.initDB(objectType)
      const transaction = db.transaction(['objects'], 'readonly')
      const store = transaction.objectStore('objects')
      const hashIndex = store.index('hash')

      return new Promise<unknown | null>((resolve, reject) => {
        const request = hashIndex.openCursor(IDBKeyRange.only(hash))
        const objects: CachedObject[] = []

        request.onsuccess = (event: Event): void => {
          const cursor = (event.target as IDBRequest<IDBCursorWithValue>).result
          if (cursor) {
            const obj = cursor.value as CachedObject
            if (obj?.hash === hash && !obj.hidden) {
              objects.push(obj)
            }
            cursor.continue()
          } else {
            // Sort by version descending and return the latest
            if (objects.length > 0) {
              objects.sort((a, b) => b.version - a.version)
              resolve(objects[0]?.parsed ?? null)
            } else {
              resolve(null)
            }
          }
        }

        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error(`Error retrieving ${objectType} object from cache:`, error)
      return null
    }
  }

  /**
   * Get an object from cache by ID
   */
  async getById(objectType: ObjectType, id: string): Promise<unknown | null> {
    try {
      const db = await this.initDB(objectType)
      const transaction = db.transaction(['objects'], 'readonly')
      const store = transaction.objectStore('objects')

      return new Promise<unknown | null>((resolve, reject) => {
        const request = store.get(id)
        request.onsuccess = (): void => {
          const obj = request.result as CachedObject | undefined
          if (obj && !obj.hidden) {
            resolve(obj.parsed)
          } else {
            resolve(null)
          }
        }
        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error(`Error retrieving ${objectType} object by ID from cache:`, error)
      return null
    }
  }

  /**
   * Get an author presentation by pubkey (searches all cached authors)
   */
  async getAuthorByPubkey(pubkey: string): Promise<AuthorPresentationArticle | null> {
    try {
      const db = await this.initDB('author')
      const transaction = db.transaction(['objects'], 'readonly')
      const store = transaction.objectStore('objects')

      return new Promise((resolve, reject) => {
        const request = store.openCursor()
        const objects: CachedObject[] = []

        request.onsuccess = (event: Event): void => {
          const cursor = (event.target as IDBRequest<IDBCursorWithValue>).result
          if (cursor) {
            const obj = cursor.value as CachedObject
            if (obj?.event.pubkey === pubkey && !obj.hidden) {
              objects.push(obj)
            }
            cursor.continue()
          } else {
            // Sort by version descending and return the latest
            if (objects.length > 0) {
              objects.sort((a, b) => b.version - a.version)
              resolve((objects[0]?.parsed ?? null) as AuthorPresentationArticle | null)
            } else {
              resolve(null)
            }
          }
        }

        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error('Error retrieving author from cache by pubkey:', error)
      return null
    }
  }

  /**
   * Clear cache for an object type
   */
  async clear(objectType: ObjectType): Promise<void> {
    try {
      const db = await this.initDB(objectType)
      const transaction = db.transaction(['objects'], 'readwrite')
      const store = transaction.objectStore('objects')
      await new Promise<void>((resolve, reject) => {
        const request = store.clear()
        request.onsuccess = (): void => {
          resolve()
        }
        request.onerror = (): void => {
          reject(request.error)
        }
      })
    } catch (error) {
      console.error(`Error clearing ${objectType} cache:`, error)
    }
  }
}

export const objectCache = new ObjectCacheService()