//
//  TimlineState.swift
//  Tusker
//
//  Created by Shadowfacts on 12/13/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import Foundation
import CoreData
import Pachyderm

@objc(TimelineState)
public final class TimelineState: NSManagedObject {
    
    @nonobjc public class func fetchRequest(timeline: Timeline) -> NSFetchRequest<TimelineState> {
        let req = NSFetchRequest<TimelineState>(entityName: "TimelineState")
        req.predicate = NSPredicate(format: "timelineKind = %@", toTimelineKind(timeline))
        return req
    }
    
    @NSManaged private var timelineKind: String
    @NSManaged public var centerStatusID: String?
    @NSManaged private var statuses: NSOrderedSet
    
    var timeline: Timeline {
        get { fromTimelineKind(timelineKind) }
        set { timelineKind = toTimelineKind(newValue) }
    }
    
    var statusMOs: [StatusMO] {
        statuses.array as! [StatusMO]
    }
    
    convenience init(timeline: Timeline, context: NSManagedObjectContext) {
        self.init(context: context)
        self.timeline = timeline
    }
    
    func setStatuses(_ statusIDs: [String]) {
        let context = managedObjectContext!
        // todo: this feels really inefficient, but I'm not sure if it's better or worse than doing a single "id IN %@" fetch and sorting after
        let mos = statusIDs.compactMap { try? context.fetch(StatusMO.fetchRequest(id: $0)).first }
        self.statuses = NSOrderedSet(array: mos)
    }
    
}

// blergh, this is the simplest way of getting the Timeline into a format that A) CoreData can handle and B) is usable in the predicate
private func toTimelineKind(_ timeline: Timeline) -> String {
    switch timeline {
    case .home:
        return "home"
    case .public(local: true):
        return "local"
    case .public(local: false):
        return "federated"
    case .direct:
        return "direct"
    case .tag(hashtag: let name):
        return "hashtag:\(name)"
    case .list(id: let id):
        return "list:\(id)"
    }
}

private func fromTimelineKind(_ kind: String) -> Timeline {
    if kind == "home" {
        return .home
    } else if kind == "local" {
        return .public(local: true)
    } else if kind == "federated" {
        return .public(local: false)
    } else if kind == "direct" {
        return .direct
    } else if kind.starts(with: "hashtag:") {
        return .tag(hashtag: String(trimmingPrefix("hashtag:", of: kind)))
    } else if kind.starts(with: "list:") {
        return .list(id: String(trimmingPrefix("list:", of: kind)))
    } else {
        fatalError("invalid timeline kind \(kind)")
    }
}

// replace with Collection.trimmingPrefix
@available(iOS, obsoleted: 16.0)
private func trimmingPrefix(_ prefix: String, of str: String) -> Substring {
    return str[str.index(str.startIndex, offsetBy: prefix.count)...]
}