//
//  SpotifyAPIClient.swift
//  iris
//
//  Spotify Web API client for fetching currently playing track.
//

import Foundation
import os

@available(iOS 16.0, *)
@MainActor
final class SpotifyAPIClient {
    private let authManager: SpotifyAuthManager
    private let logger = Logger(subsystem: Bundle.main.bundleIdentifier ?? "iris", category: "SpotifyAPI")
    private let baseUrl = "https://api.spotify.com/v1"

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

    func getCurrentPlayback() async throws -> SpotifyPlaybackState? {
        try await getCurrentPlayback(isRetry: false)
    }

    private func getCurrentPlayback(isRetry: Bool) async throws -> SpotifyPlaybackState? {
        let refreshed = await authManager.refreshTokenIfNeeded()
        guard refreshed else {
            throw SpotifyAPIError.notAuthenticated
        }

        guard let token = authManager.accessToken else {
            throw SpotifyAPIError.notAuthenticated
        }

        var request = URLRequest(url: URL(string: "\(baseUrl)/me/player/currently-playing")!)
        request.httpMethod = "GET"
        request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")

        let (data, response) = try await URLSession.shared.data(for: request)

        guard let httpResponse = response as? HTTPURLResponse else {
            throw SpotifyAPIError.invalidResponse
        }

        switch httpResponse.statusCode {
        case 200:
            return try JSONDecoder().decode(SpotifyPlaybackState.self, from: data)
        case 204:
            return nil
        case 401:
            guard !isRetry else {
                throw SpotifyAPIError.tokenExpired
            }
            let refreshed = await authManager.refreshTokenIfNeeded()
            if refreshed {
                return try await getCurrentPlayback(isRetry: true)
            }
            throw SpotifyAPIError.tokenExpired
        case 429:
            let retryAfter = httpResponse.value(forHTTPHeaderField: "Retry-After")
            logger.warning("Rate limited, retry after: \(retryAfter ?? "unknown")")
            throw SpotifyAPIError.rateLimited
        default:
            logger.error("API error: \(httpResponse.statusCode)")
            throw SpotifyAPIError.apiError(httpResponse.statusCode)
        }
    }

    enum SpotifyAPIError: Error {
        case notAuthenticated
        case tokenExpired
        case invalidResponse
        case rateLimited
        case apiError(Int)
    }
}