//
//  ItemListType.swift
//  Reader
//
//  Created by Shadowfacts on 3/13/22.
//

import Foundation
import CoreData
import Persistence

enum ItemListType: Hashable, Equatable {
    case unread
    case all
    case group(Group)
    case feed(Feed)
    
    var title: String {
        switch self {
        case .unread:
            return "Unread Articles"
        case .all:
            return "All Articles"
        case let .group(group):
            return group.title
        case let .feed(feed):
            return feed.title ?? feed.url?.host() ?? "Unknown Feed"
        }
    }
    
    var idFetchRequest: NSFetchRequest<NSManagedObjectID> {
        let req = NSFetchRequest<NSManagedObjectID>(entityName: "Item")
        req.resultType = .managedObjectIDResultType
        switch self {
        case .unread:
            req.predicate = NSPredicate(format: "read = NO")
        case .all:
            break
        case .group(let group):
            req.predicate = NSPredicate(format: "feed in %@", group.feeds!)
        case .feed(let feed):
            req.predicate = NSPredicate(format: "feed = %@", feed)
        }
        return req
    }
    
    var countFetchRequest: NSFetchRequest<Item>? {
        let req = Item.fetchRequest()
        switch self {
        case .unread:
            req.predicate = NSPredicate(format: "read = NO")
        case .all:
            return nil
        case .group(let group):
            // use the feed ids, because passing the NSSet of feeds into the predicate results in a multithreading violation if the request is used on a different context
            let feedIDs = group.feeds!.map { ($0 as! Feed).objectID }
            req.predicate = NSPredicate(format: "read = NO AND feed in %@", feedIDs)
        case .feed(let feed):
            req.predicate = NSPredicate(format: "read = NO AND feed = %@", feed)
        }
        return req
    }
}