const { WeakLRUCache } = require('weak-lru-cache')
let getLastVersion
const mapGet = Map.prototype.get
exports.CachingStore = Store => class extends Store {
	constructor(dbName, options) {
		super(dbName, options)
		if (!this.env.cacheCommitter) {
			this.env.cacheCommitter = true
			this.on('aftercommit', ({ operations, results }) => {
				results = results || []
				let activeCache
				for (let i = 0, l = operations.length; i < l; i++) {
					let operation = operations[i]
					if (typeof operation[1] === 'object') {
						if (activeCache) {
							if (results[i] === 0) {
								let expirationPriority = ((operation[1] || 0).length || 0) >> 10
								let entry = mapGet.call(activeCache, operation[0])
								if (entry)
									activeCache.used(entry, expirationPriority) // this will enter it into the LRFU
							} else
								activeCache.delete(operation[0]) // just delete it from the map
						}
					} else if (operation && operation.length === undefined) {
						activeCache = operation.cachingDb && operation.cachingDb.cache
					}
				}
			})
		}
		this.db.cachingDb = this
		this.cache = new WeakLRUCache(options.cache)
	}
	get(id, cacheMode) {
		let value = this.cache.getValue(id)
		if (value !== undefined)
			return value
		value = super.get(id)
		if (value && typeof value === 'object' && !cacheMode && typeof id !== 'object') {
			let entry = this.cache.setValue(id, value, this.lastSize >> 10)
			if (this.useVersions) {
				entry.version = getLastVersion()
			}
		}
		return value
	}
	getEntry(id, cacheMode) {
		let entry = this.cache.get(id)
		if (entry)
			return entry
		let value = super.get(id)
		if (value === undefined)
			return
		if (value && typeof value === 'object' && !cacheMode && typeof id !== 'object') {
			entry = this.cache.setValue(id, value, this.lastSize >> 10)
		} else {
			entry = { value }
		}
		if (this.useVersions) {
			entry.version = getLastVersion()
		}
		return entry
	}
	putEntry(id, entry, ifVersion) {
		let result = super.put(id, entry.value, entry.version, ifVersion)
		if (typeof id === 'object')
			return result
		if (result && result.then)
			this.cache.setManually(id, entry) // set manually so we can keep it pinned in memory until it is committed
		else // sync operation, immediately add to cache
			this.cache.set(id, entry)
	}
	put(id, value, version, ifVersion) {
		// if (this.cache.get(id)) // if there is a cache entry, remove it from scheduledEntries and 
		let result = super.put(id, value, version, ifVersion)
		if (typeof id !== 'object') {
			// sync operation, immediately add to cache, otherwise keep it pinned in memory until it is committed
			let entry = this.cache.setValue(id, value, result.isSync ? 0 : -1)
			if (version !== undefined)
				entry.version = version
		}
		return result
	}
	putSync(id, value, version, ifVersion) {
		if (id !== 'object') {
			// sync operation, immediately add to cache, otherwise keep it pinned in memory until it is committed
			if (value && typeof value === 'object') {
				let entry = this.cache.setValue(id, value)
				if (version !== undefined)
					entry.version = version
			} else // it is possible that  a value used to exist here
				this.cache.delete(id)
		}
		return super.putSync(id, value, version, ifVersion)
	}
	remove(id, ifVersion) {
		this.cache.delete(id)
		return super.remove(id, ifVersion)
	}
	removeSync(id, ifVersion) {
		this.cache.delete(id)
		return super.removeSync(id, ifVersion)
	}
	clear() {
		this.cache.clear()
		super.clear()
	}
	childTransaction(execute) {
		throw new Error('Child transactions are not supported in caching stores')
	}
}
exports.setGetLastVersion = (get) => {
	getLastVersion = get
}