//
//  DataProvider.swift
//  SportsTime
//

import Foundation
import Combine

/// Protocol defining data operations for teams, stadiums, and games
protocol DataProvider: Sendable {
    func fetchTeams(for sport: Sport) async throws -> [Team]
    func fetchAllTeams() async throws -> [Team]
    func fetchStadiums() async throws -> [Stadium]
    func fetchGames(sports: Set<Sport>, startDate: Date, endDate: Date) async throws -> [Game]
    func fetchGame(by id: UUID) async throws -> Game?

    // Resolved data (with team/stadium references)
    func fetchRichGames(sports: Set<Sport>, startDate: Date, endDate: Date) async throws -> [RichGame]
}

/// Environment-aware data provider that switches between stub and CloudKit
@MainActor
final class AppDataProvider: ObservableObject {
    static let shared = AppDataProvider()

    private let provider: any DataProvider

    @Published private(set) var teams: [Team] = []
    @Published private(set) var stadiums: [Stadium] = []
    @Published private(set) var isLoading = false
    @Published private(set) var error: Error?
    @Published private(set) var errorMessage: String?
    @Published private(set) var isUsingStubData: Bool

    private var teamsById: [UUID: Team] = [:]
    private var stadiumsById: [UUID: Stadium] = [:]

    private init() {
        #if targetEnvironment(simulator)
        self.provider = StubDataProvider()
        self.isUsingStubData = true
        #else
        self.provider = CloudKitDataProvider()
        self.isUsingStubData = false
        #endif
    }

    // MARK: - Data Loading

    func loadInitialData() async {
        isLoading = true
        error = nil
        errorMessage = nil

        do {
            async let teamsTask = provider.fetchAllTeams()
            async let stadiumsTask = provider.fetchStadiums()

            let (loadedTeams, loadedStadiums) = try await (teamsTask, stadiumsTask)

            self.teams = loadedTeams
            self.stadiums = loadedStadiums

            // Build lookup dictionaries
            self.teamsById = Dictionary(uniqueKeysWithValues: loadedTeams.map { ($0.id, $0) })
            self.stadiumsById = Dictionary(uniqueKeysWithValues: loadedStadiums.map { ($0.id, $0) })
        } catch let cloudKitError as CloudKitError {
            self.error = cloudKitError
            self.errorMessage = cloudKitError.errorDescription
        } catch {
            self.error = error
            self.errorMessage = error.localizedDescription
        }

        isLoading = false
    }

    func clearError() {
        error = nil
        errorMessage = nil
    }

    func retry() async {
        await loadInitialData()
    }

    // MARK: - Data Access

    func team(for id: UUID) -> Team? {
        teamsById[id]
    }

    func stadium(for id: UUID) -> Stadium? {
        stadiumsById[id]
    }

    func teams(for sport: Sport) -> [Team] {
        teams.filter { $0.sport == sport }
    }

    func fetchGames(sports: Set<Sport>, startDate: Date, endDate: Date) async throws -> [Game] {
        try await provider.fetchGames(sports: sports, startDate: startDate, endDate: endDate)
    }

    func fetchRichGames(sports: Set<Sport>, startDate: Date, endDate: Date) async throws -> [RichGame] {
        let games = try await provider.fetchGames(sports: sports, startDate: startDate, endDate: endDate)

        return games.compactMap { game in
            guard let homeTeam = teamsById[game.homeTeamId],
                  let awayTeam = teamsById[game.awayTeamId],
                  let stadium = stadiumsById[game.stadiumId] else {
                return nil
            }
            return RichGame(game: game, homeTeam: homeTeam, awayTeam: awayTeam, stadium: stadium)
        }
    }

    func richGame(from game: Game) -> RichGame? {
        guard let homeTeam = teamsById[game.homeTeamId],
              let awayTeam = teamsById[game.awayTeamId],
              let stadium = stadiumsById[game.stadiumId] else {
            return nil
        }
        return RichGame(game: game, homeTeam: homeTeam, awayTeam: awayTeam, stadium: stadium)
    }
}