//
//  StatusesTable.swift
//  Evergreen
//
//  Created by Brent Simmons on 5/8/16.
//  Copyright © 2016 Ranchero Software, LLC. All rights reserved.
//

import Foundation
import RSCore
import RSDatabase
import Data

// Article->ArticleStatus is a to-one relationship.
//
// CREATE TABLE if not EXISTS statuses (articleID TEXT NOT NULL PRIMARY KEY, read BOOL NOT NULL DEFAULT 0, starred BOOL NOT NULL DEFAULT 0, userDeleted BOOL NOT NULL DEFAULT 0, dateArrived DATE NOT NULL DEFAULT 0, accountInfo BLOB);

final class StatusesTable: DatabaseTable {

	let name: String
	let queue: RSDatabaseQueue
	private let cache = ObjectCache<ArticleStatus>(keyPathForID: \ArticleStatus.articleID)

	init(name: String, queue: RSDatabaseQueue) {

		self.name = name
		self.queue = queue
	}

	func markArticles(_ articles: Set<Article>, statusKey: String, flag: Bool) {

		// Main thread.

		assertNoMissingStatuses(articles)
		let statuses = Set(articles.flatMap { $0.status })
		markArticleStatuses(statuses, statusKey: statusKey, flag: flag)
	}

	func attachStatuses(_ articles: Set<Article>, _ database: FMDatabase) {

		// Look in cache first.
		attachCachedStatuses(articles)
		let articlesNeedingStatuses = articlesMissingStatuses(articles)
		if articlesNeedingStatuses.isEmpty {
			return
		}

		// Fetch from database.
		fetchAndCacheStatusesForArticles(articlesNeedingStatuses, database)
		attachCachedStatuses(articlesNeedingStatuses)

		// Create new statuses, and cache and save them in the database.
		// It shouldn’t happen that an Article in the database has no corresponding ArticleStatus,
		// but the case should be handled anyway.

		let articlesNeedingStatusesCreated = articlesMissingStatuses(articlesNeedingStatuses)
		if articlesNeedingStatusesCreated.isEmpty {
			return
		}
		createAndSaveStatusesForArticles(articlesNeedingStatusesCreated, database)

		assertNoMissingStatuses(articles)
	}


//	func ensureStatusesForParsedArticles(_ parsedArticles: [ParsedItem], _ callback: @escaping RSVoidCompletionBlock) {
//
//		// 1. Check cache for statuses
//		// 2. Fetch statuses not found in cache
//		// 3. Create, save, and cache statuses not found in database
//
//		var articleIDs = Set(parsedArticles.map { $0.articleID })
//		articleIDs = articleIDsMissingStatuses(articleIDs)
//		if articleIDs.isEmpty {
//			callback()
//			return
//		}
//
//		queue.fetch { (database: FMDatabase!) -> Void in
//
//			let statuses = self.fetchStatusesForArticleIDs(articleIDs, database: database)
//
//			DispatchQueue.main.async {
//
//				self.cache.addObjectsNotCached(Array(statuses))
//
//				let newArticleIDs = self.articleIDsMissingStatuses(articleIDs)
//				if !newArticleIDs.isEmpty {
//					self.createAndSaveStatusesForArticleIDs(newArticleIDs)
//				}
//
//				callback()
//			}
//		}
//	}
}

private extension StatusesTable {
	
	func attachCachedStatuses(_ articles: Set<Article>) {

		articles.forEach { (oneArticle) in

			if let cachedStatus = cache[oneArticle.databaseID] {
				oneArticle.status = cachedStatus
			}
		}
	}

	func assertNoMissingStatuses(_ articles: Set<Article>) {

		for oneArticle in articles {
			if oneArticle.status == nil {
				assertionFailure("All articles must have a status at this point.")
				return
			}
		}
	}

	// MARK: Fetching

	func fetchAndCacheStatusesForArticles(_ articles: Set<Article>, _ database: FMDatabase) {

		fetchAndCacheStatusesForArticleIDs(articles.articleIDs(), database)
	}

	func fetchAndCacheStatusesForArticleIDs(_ articleIDs: Set<String>, _ database: FMDatabase) {

		if let statuses = fetchStatusesForArticleIDs(articleIDs, database) {
			cache.addObjectsNotCached(Array(statuses))
		}
	}

	func fetchStatusesForArticleIDs(_ articleIDs: Set<String>, _ database: FMDatabase) -> Set<ArticleStatus>? {
		
		guard let resultSet = selectRowsWhere(key: DatabaseKey.articleID, inValues: Array(articleIDs), in: database) else {
			return nil
		}
		return articleStatusesWithResultSet(resultSet)
	}

	func articleStatusesWithResultSet(_ resultSet: FMResultSet) -> Set<ArticleStatus> {

		return resultSet.mapToSet(articleStatusWithRow)
	}

	func articleStatusWithRow(_ row: FMResultSet) -> ArticleStatus? {

		guard let articleID = row.string(forColumn: DatabaseKey.articleID) else {
			return nil
		}
		if let cachedStatus = cache[articleID] {
			return cachedStatus
		}
		let status = ArticleStatus(articleID: articleID, row: row)
		cache[articleID] = status
		return status
	}
	
	// MARK: Updating
	
	func markArticleStatuses(_ statuses: Set<ArticleStatus>, statusKey: String, flag: Bool) {

		// Ignore the statuses where status.[statusKey] == flag. Update the remainder and save in database.

		var articleIDsToUpdate = Set<String>()

		statuses.forEach { (oneStatus) in

			if oneStatus.boolStatus(forKey: statusKey) == flag {
				return
			}

			oneStatus.setBoolStatus(flag, forKey: statusKey)
			articleIDsToUpdate.insert(oneStatus.articleID)
		}

		if !articleIDsToUpdate.isEmpty {
			updateArticleStatusesInDatabase(articleIDsToUpdate, statusKey: statusKey, flag: flag)
		}
	}

	private func updateArticleStatusesInDatabase(_ articleIDs: Set<String>, statusKey: String, flag: Bool) {

		updateRowsWithValue(NSNumber(value: flag), valueKey: statusKey, whereKey: DatabaseKey.articleID, matches: Array(articleIDs))
	}
	
	// MARK: Creating

	func saveStatuses(_ statuses: Set<ArticleStatus>, _ database: FMDatabase) {

		let statusArray = statuses.map { $0.databaseDictionary() }
		insertRows(statusArray, insertType: .orIgnore, in: database)
	}

	func createAndSaveStatusesForArticles(_ articles: Set<Article>, _ database: FMDatabase) {

		let articleIDs = Set(articles.map { $0.databaseID })
		createAndSaveStatusesForArticleIDs(articleIDs, database)
	}

	func createAndSaveStatusesForArticleIDs(_ articleIDs: Set<String>, _ database: FMDatabase) {

		let now = Date()
		let statuses = articleIDs.map { ArticleStatus(articleID: $0, dateArrived: now) }
		cache.addObjectsNotCached(statuses)

		saveStatuses(Set(statuses), database)
	}

	// MARK: Utilities

	func articleIDsMissingCachedStatuses(_ articleIDs: Set<String>) -> Set<String> {
		
		return Set(articleIDs.filter { !cache.objectWithIDIsCached($0) })
	}

	func articlesMissingStatuses(_ articles: Set<Article>) -> Set<Article> {

		return articles.withNilProperty(\Article.status)
	}
}

//extension ParsedItem {
//
//	var articleID: String {
//		get {
//			return "\(feedURL) \(uniqueID)" //Must be same as Article.articleID
//		}
//	}
//}