//
//  FeedlySetStarredArticlesOperation.swift
//  Account
//
//  Created by Kiel Gillard on 14/10/19.
//  Copyright © 2019 Ranchero Software, LLC. All rights reserved.
//

import Foundation
import os.log

protocol FeedlyStarredEntryIdProviding {
	var entryIds: Set<String> { get }
}

/// Single responsibility is to associate a starred status for ingested and remote
/// articles identfied by the provided identifiers *for the entire account.*
final class FeedlySetStarredArticlesOperation: FeedlyOperation {
	private let account: Account
	private let allStarredEntryIdsProvider: FeedlyStarredEntryIdProviding
	private let log: OSLog
	
	init(account: Account, allStarredEntryIdsProvider: FeedlyStarredEntryIdProviding, log: OSLog) {
		self.account = account
		self.allStarredEntryIdsProvider = allStarredEntryIdsProvider
		self.log = log
	}
	
	override func main() {
		guard !isCancelled else {
			didFinish()
			return
		}
		
		let group = DispatchGroup()
		
		let remoteStarredArticleIds = allStarredEntryIdsProvider.entryIds
		account.fetchStarredArticleIDs { localStarredArticleIDs in
			// Mark articles as starred
			let deltaStarredArticleIDs = remoteStarredArticleIds.subtracting(localStarredArticleIDs)
			let markStarredArticles = self.account.fetchArticles(.articleIDs(deltaStarredArticleIDs))
			self.account.update(markStarredArticles, statusKey: .starred, flag: true)

			// Save any starred statuses for articles we haven't yet received
			let markStarredArticleIDs = Set(markStarredArticles.map { $0.articleID })
			let missingStarredArticleIDs = deltaStarredArticleIDs.subtracting(markStarredArticleIDs)
			group.enter()
			self.account.ensureStatuses(missingStarredArticleIDs, true, .starred, true) {
				group.leave()
			}

			// Mark articles as unstarred
			let deltaUnstarredArticleIDs = localStarredArticleIDs.subtracting(remoteStarredArticleIds)
			let markUnstarredArticles = self.account.fetchArticles(.articleIDs(deltaUnstarredArticleIDs))
			self.account.update(markUnstarredArticles, statusKey: .starred, flag: false)

			// Save any unstarred statuses for articles we haven't yet received
			let markUnstarredArticleIDs = Set(markUnstarredArticles.map { $0.articleID })
			let missingUnstarredArticleIDs = deltaUnstarredArticleIDs.subtracting(markUnstarredArticleIDs)
			group.enter()
			self.account.ensureStatuses(missingUnstarredArticleIDs, true, .starred, false) {
				group.leave()
			}

			group.notify(queue: .main) {
				self.didFinish()
			}
		}
	}
}