//
// MainService.swift
// IceGlass
//
// Copyright 2026 Rouslan Zenetl. All Rights Reserved.
//

import Foundation

class MainService: @unchecked Sendable {
    private let logger = IceGlassLogger(
        subsystem: Bundle.main.bundleIdentifier ?? "dev.rzen.indie.IceGlass",
        category: "MainService"
    )

    static let shared = MainService()

    private lazy var menuManager = MenuManager.shared
    private lazy var statusItemManager = StatusItemManager.shared
    private lazy var settings = AppSettings.shared
    private lazy var notificationManager = NotificationManager.shared

    private var pollingTimer: Timer?
    private var scoreboardApi: ApiService?

    /// All game days from the API (full window: yesterday/today/tomorrow)
    private var allGamesByDate: [Scoreboard.GameDay] = []

    /// Previous game snapshots for detecting state/score changes (keyed by game ID)
    private var previousGameStates: [Int: GameSnapshot] = [:]

    /// Whether this is the first fetch (suppress notifications on initial load)
    private var isFirstFetch = true

    struct GameSnapshot {
        let gameState: String
        let awayScore: Int?
        let homeScore: Int?
    }

    /// Game days filtered by display option
    var gamesByDate: [Scoreboard.GameDay] {
        let includedDates = settings.displayOption.includedDates()
        return allGamesByDate.filter { includedDates.contains($0.date) }
    }

    /// Whether any game across all days is currently live
    var anyGameLive: Bool {
        allGamesByDate.flatMap(\.games).contains { game in
            game.parsedGameState.isLive
        }
    }

    /// Whether any game is in pre-game state
    var anyGamePre: Bool {
        allGamesByDate.flatMap(\.games).contains { game in
            game.parsedGameState == .pre
        }
    }

    /// Whether any game today is scheduled (future)
    var anyGameToday: Bool {
        let today = Date.todayET
        return allGamesByDate.contains { gd in
            gd.date == today && !gd.games.isEmpty
        }
    }

    /// The best polling interval based on current game states
    var bestPollingInterval: PollingInterval {
        if anyGameLive { return .liveGame }
        if anyGamePre { return .preGame }
        if anyGameToday { return .gameDay }
        return .idle
    }

    private init() {
        logger.debug("Initializing")
        DispatchQueue.main.async { [weak self] in
            guard let self = self else {
                AppTerminator.terminate()
                return
            }

            Task { @MainActor in
                self.initApis()
                self.reschedulePollingTimer(.bootstrap)
                await self.fetchScoreboard()
            }
        }
    }

    private func initApis() {
        scoreboardApi = ApiService(
            url: URL(string: "https://api-web.nhle.com/v1/scoreboard/now")
        ) { [weak self] data, _ in
            guard let self = self else { return }

            do {
                let scoreboard = try JSONDecoder().decode(Scoreboard.self, from: data)

                // Filter to yesterday/today/tomorrow window
                let yesterday = Date.yesterdayET
                let today = Date.todayET
                let tomorrow = Date.tomorrowET
                let windowDates = Set([yesterday, today, tomorrow])

                let filtered = scoreboard.gamesByDate.filter { gd in
                    windowDates.contains(gd.date)
                }

                // Detect state and score changes before updating
                if !self.isFirstFetch {
                    self.detectChanges(in: filtered)
                }

                self.allGamesByDate = filtered

                // Update snapshots for next comparison
                self.updateSnapshots(from: filtered)

                if self.isFirstFetch {
                    self.isFirstFetch = false
                }

                self.logger.info("Scoreboard updated: \(filtered.map { "\($0.date): \($0.games.count) games" }.joined(separator: ", "))")

                // Adjust polling based on game states
                let interval = self.bestPollingInterval
                Task { @MainActor in
                    self.reschedulePollingTimer(interval)
                }

                self.statusItemManager.updateGameCounts(self.gamesByDate)
                self.menuManager.scoreboardChanged()
            } catch {
                self.logger.error("Failed to decode scoreboard: \(error.localizedDescription)")
            }
        }
    }

    // MARK: - Change Detection

    private func detectChanges(in gameDays: [Scoreboard.GameDay]) {
        for gameDay in gameDays {
            for game in gameDay.games {
                guard let previous = previousGameStates[game.id] else { continue }

                let previousState = GameState(rawValue: previous.gameState)
                let currentState = game.parsedGameState

                // Game started: FUT/PRE → LIVE
                if let prevState = previousState, prevState.isFuture, currentState.isLive {
                    logger.info("Game \(game.id) started: \(game.awayTeam.abbrev) @ \(game.homeTeam.abbrev)")
                    notificationManager.notifyGameStarted(game)
                }

                // Goal scored: score increased on either team
                if let prevAway = previous.awayScore, let prevHome = previous.homeScore,
                   let curAway = game.awayTeam.score, let curHome = game.homeTeam.score {

                    if curAway > prevAway {
                        logger.info("Goal! \(game.awayTeam.abbrev) scored in game \(game.id): \(curAway):\(curHome)")
                        notificationManager.notifyGoalScored(game, scoringTeam: game.awayTeam)
                    }
                    if curHome > prevHome {
                        logger.info("Goal! \(game.homeTeam.abbrev) scored in game \(game.id): \(curAway):\(curHome)")
                        notificationManager.notifyGoalScored(game, scoringTeam: game.homeTeam)
                    }
                }
            }
        }
    }

    private func updateSnapshots(from gameDays: [Scoreboard.GameDay]) {
        for gameDay in gameDays {
            for game in gameDay.games {
                previousGameStates[game.id] = GameSnapshot(
                    gameState: game.gameState,
                    awayScore: game.awayTeam.score,
                    homeScore: game.homeTeam.score
                )
            }
        }
    }

    // MARK: - Polling

    private func reschedulePollingTimer(_ pollingInterval: PollingInterval) {
        if !Thread.isMainThread {
            logger.warning("reschedulePollingTimer called not on main thread")
            return
        }

        let rescheduleTolerance: TimeInterval = 3
        var needsRescheduling = false

        if self.pollingTimer == nil {
            needsRescheduling = true
        } else if !self.pollingTimer!.isValid {
            needsRescheduling = true
        } else if abs(self.pollingTimer!.fireDate.timeIntervalSinceNow - pollingInterval.rawValue) > rescheduleTolerance {
            needsRescheduling = true
        }

        if needsRescheduling {
            self.logger.debug("Rescheduling polling timer to \(pollingInterval.rawValue)s")
            self.pollingTimer = Timer.startTimer(
                timer: self.pollingTimer,
                interval: pollingInterval.rawValue
            ) { [weak self] _ in
                Task { @MainActor in
                    await self?.fetchScoreboard()
                }
            }
        }
    }

    private func fetchScoreboard() async {
        await scoreboardApi?.fetch()
    }

    func fetchAll() async {
        await fetchScoreboard()
    }
}