import Foundation
import UIKit

@MainActor
struct DeviceContext: Sendable {
    let languageCode: String
    let osName: String
    let osVersion: String
    let deviceModel: String
    let deviceId: String
    let appName: String
    let appVersion: String
    let channel: String
    let screenScale: String

    static let shared: DeviceContext = {
        // 仅在主线程读取一次 UIKit/Bundle 信息
        let language = Locale.current.language.languageCode?.identifier ?? "en"
        let osName = "iOS"
        let osVersion = UIDevice.current.systemVersion
        let deviceModel = UIDevice.current.model
        let deviceId = UIDevice.current.identifierForVendor?.uuidString ?? UUID().uuidString
        let appName = Bundle.main.infoDictionary?["CFBundleName"] as? String ?? "eparty"
        let appVersion = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "1.0.0"
        #if DEBUG
        let channel = "molistar_enterprise"
        #else
        let channel = "appstore"
        #endif
        let scale = String(format: "%.2f", Double(UIScreen.main.scale))

        return DeviceContext(
            languageCode: language,
            osName: osName,
            osVersion: osVersion,
            deviceModel: deviceModel,
            deviceId: deviceId,
            appName: appName,
            appVersion: appVersion,
            channel: channel,
            screenScale: scale
        )
    }()
}

enum UserAgentProvider {
    @MainActor
    static func userAgent() -> String {
        let ctx = DeviceContext.shared
        return "\(ctx.appName)/\(ctx.appVersion) (\(ctx.deviceModel); \(ctx.osName) \(ctx.osVersion); Scale/\(ctx.screenScale))"
    }
}