//
//  LocalData.swift
//  Reader
//
//  Created by Shadowfacts on 11/25/21.
//

import Foundation
import Fervor
import CryptoKit

struct LocalData {
    
    private init() {}
    
    private static let encoder = JSONEncoder()
    private static let decoder = JSONDecoder()
    
    private static var defaults = UserDefaults(suiteName: "group.net.shadowfacts.Reader")!
    
    static var accounts: [Account] {
        get {
            guard let data = defaults.data(forKey: "accounts"),
                  let accounts = try? decoder.decode([Account].self, from: data) else {
                return []
            }
            return accounts
        }
        set {
            let data = try! encoder.encode(newValue)
            defaults.set(data, forKey: "accounts")
        }
    }
    
    static var mostRecentAccountID: Data? {
        get {
            return defaults.data(forKey: "mostRecentAccountID")
        }
        set {
            defaults.set(newValue, forKey: "mostRecentAccountID")
        }
    }
    
    static func mostRecentAccount() -> Account? {
        guard let id = mostRecentAccountID else {
            return nil
        }
        return account(with: id)
    }
    
    static func account(with id: Data) -> Account? {
        return accounts.first(where: { $0.id == id })
    }
    
    static func migrateIfNecessary() {
        if let accounts = UserDefaults.standard.object(forKey: "accounts") {
            UserDefaults.standard.removeObject(forKey: "accounts")
            defaults.set(accounts, forKey: "accounts")
        }
        if let mostRecentAccountID = UserDefaults.standard.object(forKey: "mostRecentAccountID") {
            UserDefaults.standard.removeObject(forKey: "mostRecentAccountID")
            defaults.set(mostRecentAccountID, forKey: "mostRecentAccountID")
        }
    }
    
    struct Account: Codable {
        let id: Data
        let instanceURL: URL
        let clientID: String
        let clientSecret: String
        let token: Token
        
        init(instanceURL: URL, clientID: String, clientSecret: String, token: Token) {
            // we use a hash of instance host and account id rather than random ids so that
            // user activites can uniquely identify accounts across devices
            var hasher = SHA256()
            hasher.update(data: instanceURL.host!.data(using: .utf8)!)
            hasher.update(data: token.owner!.data(using: .utf8)!)
            self.id = Data(hasher.finalize())
            
            self.instanceURL = instanceURL
            self.clientID = clientID
            self.clientSecret = clientSecret
            self.token = token
        }
    }
    
}