import Foundation
import Observation
import OrgSocialKit

@Observable @MainActor
final class NotificationsViewModel {

    var notifications: [OrgSocialNotification] = []
    var isLoading = false
    var errorMessage: String?

    private let client = RelayClient()

    var feedURL: URL? {
        guard let raw = UserDefaults.standard.string(forKey: "publicFeedURL"),
              let url = URL(string: raw),
              url.scheme?.hasPrefix("http") == true else { return nil }
        return url
    }

    var relayURL: URL {
        let raw = UserDefaults.standard.string(forKey: "relayURL") ?? "https://relay.org-social.org"
        return URL(string: raw) ?? URL(string: "https://relay.org-social.org")!
    }

    var useRelay: Bool {
        UserDefaults.standard.object(forKey: "useRelay") as? Bool ?? true
    }

    func load() async {
        guard !isLoading else { return }
        guard useRelay else {
            errorMessage = "Notifications require a relay. Enable Use Relay in Settings."
            notifications = []
            return
        }
        guard let feedURL else {
            errorMessage = "Configure your Public Feed URL in Settings."
            return
        }
        isLoading = true
        errorMessage = nil
        defer { isLoading = false }
        do {
            let fetched = try await client.fetchNotifications(for: feedURL, from: relayURL)
            // Deduplicate by ID to prevent ForEach from receiving duplicate keys,
            // which causes UICollectionView item-count mismatches and crashes.
            var seen = Set<String>()
            notifications = fetched.filter { seen.insert($0.id).inserted }
        } catch RelayError.httpError(let code) where code == 404 {
            try? await client.registerFeed(feedURL, with: relayURL)
            errorMessage = "Your feed isn't indexed by the relay yet. It will be available in a few minutes."
        } catch {
            errorMessage = error.localizedDescription
        }
    }
}