//
//  TimelinePosition.swift
//  Tusker
//
//  Created by Shadowfacts on 12/23/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import Foundation
import CoreData
import Pachyderm
import UserAccounts

@objc(TimelinePosition)
public final class TimelinePosition: NSManagedObject {
    
    @nonobjc class func fetchRequest(timeline: Timeline, account: UserAccountInfo) -> NSFetchRequest<TimelinePosition> {
        let req = NSFetchRequest<TimelinePosition>(entityName: "TimelinePosition")
        req.predicate = NSPredicate(format: "accountID = %@ AND timelineKind = %@", account.id, toTimelineKind(timeline))
        req.sortDescriptors = [NSSortDescriptor(key: "createdAt", ascending: true)]
        return req
    }
    
    @NSManaged public var accountID: String
    @NSManaged public var createdAt: Date
    @NSManaged private var timelineKind: String
    @NSManaged public var centerStatusID: String?
    @NSManaged private var statusIDsData: Data?
    
    @LazilyDecoding(arrayFrom: \TimelinePosition.statusIDsData)
    var statusIDs: [String]
    
    var timeline: Timeline {
        get { fromTimelineKind(timelineKind) }
        set { timelineKind = toTimelineKind(newValue) }
    }
    
    convenience init(timeline: Timeline, account: UserAccountInfo, context: NSManagedObjectContext) {
        self.init(context: context)
        self.timeline = timeline
        self.accountID = account.id
        self.createdAt = Date()
    }
    
    func changedRemotely() {
        _statusIDs.removeCachedValue()
    }
    
}

// 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
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)"
    }
}

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)
@available(visionOS 1.0, *)
private func trimmingPrefix(_ prefix: String, of str: String) -> Substring {
    return str[str.index(str.startIndex, offsetBy: prefix.count)...]
}