//
//  SpotifyNowPlayingMonitor.swift
//  iris
//
//  Polling monitor for Spotify currently playing track.
//

import Foundation
import os

@available(iOS 16.0, *)
struct SpotifyNowPlaying: Equatable, Sendable {
    let itemId: String
    let title: String
    let artist: String?
    let album: String?
    let isPlaying: Bool

    func asFeedItem(baseGeneratedAt: Int, now: Int) -> FeedItem {
        let desiredLifetimeSec = 30
        let ttl = max(1, (now - baseGeneratedAt) + desiredLifetimeSec)

        let subtitleParts = [artist, album]
            .compactMap { $0?.trimmingCharacters(in: .whitespacesAndNewlines) }
            .filter { !$0.isEmpty }
        let subtitle = subtitleParts.isEmpty ? "Spotify" : subtitleParts.joined(separator: " • ")

        return FeedItem(
            id: "spotify:now:\(itemId)",
            type: .nowPlaying,
            title: title.truncated(maxLength: TextConstraints.titleMax),
            subtitle: subtitle.truncated(maxLength: TextConstraints.subtitleMax),
            priority: isPlaying ? 0.35 : 0.2,
            ttlSec: ttl,
            condition: nil,
            startsAt: nil,
            bucket: .fyi,
            actions: ["DISMISS"]
        )
    }
}

@available(iOS 16.0, *)
@MainActor
final class SpotifyNowPlayingMonitor {
    struct Update: Sendable {
        let isConnected: Bool
        let snapshot: SpotifyNowPlaying?
    }

    var onUpdate: ((Update) -> Void)? = nil

    private let authManager: SpotifyAuthManager
    private let apiClient: SpotifyAPIClient
    private let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "iris", category: "SpotifyNowPlaying")

    private var pollTimer: DispatchSourceTimer?
    private var isRunning = false
    private var lastSnapshot: SpotifyNowPlaying? = nil

    init(authManager: SpotifyAuthManager) {
        self.authManager = authManager
        self.apiClient = SpotifyAPIClient(authManager: authManager)
    }

    func start() {
        guard !isRunning else { return }
        isRunning = true
        logger.info("Spotify monitor started")
        startPolling()

        Task { @MainActor in
            await refresh(reason: "start")
        }
    }

    func stop() {
        guard isRunning else { return }
        isRunning = false
        logger.info("Spotify monitor stopped")

        pollTimer?.cancel()
        pollTimer = nil
    }

    private func startPolling() {
        guard pollTimer == nil else { return }
        let timer = DispatchSource.makeTimerSource(queue: .main)
        timer.schedule(deadline: .now() + 4, repeating: 4)
        timer.setEventHandler { [weak self] in
            guard let self else { return }
            Task { @MainActor in
                await self.refresh(reason: "poll")
            }
        }
        timer.resume()
        pollTimer = timer
    }

    private func refresh(reason: String) async {
        guard authManager.isConnected else {
            if lastSnapshot != nil {
                lastSnapshot = nil
                onUpdate?(Update(isConnected: false, snapshot: nil))
            }
            return
        }

        do {
            let playback = try await apiClient.getCurrentPlayback()

            guard let track = playback?.item, playback?.isPlaying == true else {
                if lastSnapshot != nil {
                    lastSnapshot = nil
                    onUpdate?(Update(isConnected: true, snapshot: nil))
                }
                return
            }

            let artistName = track.artists.first?.name
            let snapshot = SpotifyNowPlaying(
                itemId: track.id,
                title: track.name,
                artist: artistName,
                album: track.album.name,
                isPlaying: playback?.isPlaying ?? false
            )

            guard snapshot != lastSnapshot else { return }
            lastSnapshot = snapshot
            onUpdate?(Update(isConnected: true, snapshot: snapshot))
            logger.debug("Spotify now playing: \(snapshot.title)")

        } catch SpotifyAPIClient.SpotifyAPIError.notAuthenticated {
            if lastSnapshot != nil {
                lastSnapshot = nil
                onUpdate?(Update(isConnected: false, snapshot: nil))
            }
        } catch SpotifyAPIClient.SpotifyAPIError.rateLimited {
            logger.warning("Spotify rate limited, skipping this poll")
        } catch {
            logger.error("Spotify fetch error: \(error.localizedDescription)")
        }
    }
}