import Foundation
import CoreData
import Combine

class GoalRepository: ObservableObject {
    private let context: NSManagedObjectContext

    @Published private(set) var goals: [Goal] = []

    init(context: NSManagedObjectContext = CoreDataStack.shared.viewContext) {
        self.context = context
        fetchGoals()
        setupNotificationObserver()
    }

    private func setupNotificationObserver() {
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(contextDidChange),
            name: .NSManagedObjectContextObjectsDidChange,
            object: context
        )
    }

    @objc private func contextDidChange(_ notification: Notification) {
        fetchGoals()
    }

    // MARK: - Fetch

    func fetchGoals(for account: Account? = nil) {
        context.perform { [weak self] in
            guard let self else { return }
            let request: NSFetchRequest<Goal> = Goal.fetchRequest()
            if let account = account {
                request.predicate = NSPredicate(format: "account == %@", account)
            }
            request.sortDescriptors = [
                NSSortDescriptor(keyPath: \Goal.createdAt, ascending: true)
            ]

            do {
                let fetched = try self.context.fetch(request)
                DispatchQueue.main.async {
                    self.goals = fetched
                }
            } catch {
                print("Failed to fetch goals: \(error)")
                DispatchQueue.main.async {
                    self.goals = []
                }
            }
        }
    }

    // MARK: - Create

    @discardableResult
    func createGoal(
        name: String,
        targetAmount: Decimal,
        targetDate: Date? = nil,
        account: Account?
    ) -> Goal {
        let goal = Goal(context: context)
        goal.name = name
        goal.targetAmount = NSDecimalNumber(decimal: targetAmount)
        goal.targetDate = targetDate
        goal.account = account
        save()
        return goal
    }

    // MARK: - Update

    func updateGoal(
        _ goal: Goal,
        name: String? = nil,
        targetAmount: Decimal? = nil,
        targetDate: Date? = nil,
        clearTargetDate: Bool = false,
        isActive: Bool? = nil
    ) {
        if let name = name {
            goal.name = name
        }
        if let targetAmount = targetAmount {
            goal.targetAmount = NSDecimalNumber(decimal: targetAmount)
        }
        if clearTargetDate {
            goal.targetDate = nil
        } else if let targetDate = targetDate {
            goal.targetDate = targetDate
        }
        if let isActive = isActive {
            goal.isActive = isActive
        }
        save()
    }

    func deleteGoal(_ goal: Goal) {
        context.delete(goal)
        save()
    }

    // MARK: - Save

    private func save() {
        guard context.hasChanges else { return }
        do {
            try context.save()
            fetchGoals()
        } catch {
            print("Failed to save goals: \(error)")
        }
    }
}