import SwiftUI
import SwiftData

@MainActor
@Observable
final class GamesHistoryViewModel {
    private let modelContext: ModelContext

    var allVisits: [StadiumVisit] = []
    var selectedSports: Set<Sport> = [] {
        didSet { recomputeFilteredData() }
    }
    var isLoading = false
    var error: String?

    // Pre-computed stored properties (updated via recomputeFilteredData)
    private(set) var filteredVisits: [StadiumVisit] = []
    private(set) var visitsByYear: [Int: [StadiumVisit]] = [:]
    private(set) var sortedYears: [Int] = []
    private(set) var totalGamesCount: Int = 0

    init(modelContext: ModelContext) {
        self.modelContext = modelContext
    }

    func loadGames() async {
        isLoading = true
        defer { isLoading = false }

        let descriptor = FetchDescriptor<StadiumVisit>(
            sortBy: [SortDescriptor(\.visitDate, order: .reverse)]
        )

        do {
            allVisits = try modelContext.fetch(descriptor)
        } catch {
            self.error = "Failed to load games: \(error.localizedDescription)"
            allVisits = []
        }

        recomputeFilteredData()
    }

    func toggleSport(_ sport: Sport) {
        if selectedSports.contains(sport) {
            selectedSports.remove(sport)
        } else {
            selectedSports.insert(sport)
        }
    }

    func clearFilters() {
        selectedSports.removeAll()
    }

    private func recomputeFilteredData() {
        if selectedSports.isEmpty {
            filteredVisits = allVisits
        } else {
            filteredVisits = allVisits.filter { visit in
                guard let stadium = AppDataProvider.shared.stadium(for: visit.stadiumId) else {
                    return false
                }
                return selectedSports.contains(stadium.sport)
            }
        }

        let calendar = Calendar.current
        visitsByYear = Dictionary(grouping: filteredVisits) { visit in
            calendar.component(.year, from: visit.visitDate)
        }
        sortedYears = visitsByYear.keys.sorted(by: >)
        totalGamesCount = filteredVisits.count
    }
}