import Foundation

public struct DeviceService: Sendable {
    private let client: any SimAdminClientProtocol
    private let sessions: InstanceSessionStore
    private let credentials: (any CredentialStore)?

    public init(
        client: any SimAdminClientProtocol,
        sessions: InstanceSessionStore,
        credentials: (any CredentialStore)? = nil
    ) {
        self.client = client
        self.sessions = sessions
        self.credentials = credentials
    }

    public func snapshot(_ instance: Instance) async throws -> DeviceSnapshot {
        let routes: [(id: String, title: String, route: UpstreamRoute)] = [
            ("device", "设备", .device),
            ("sim", "SIM", .sim),
            ("network", "蜂窝网络", .network),
            ("stats", "系统资源", .stats),
            ("cpu", "CPU", .statsCpu),
            ("connectivity", "连接状态", .connectivity)
        ]

        var sections: [DeviceSection] = []
        var successful = 0
        var unauthorized = false
        for item in routes {
            do {
                let response = try await request(item.route, instance)
                let values = try Self.flatten(Self.dataObject(response.data))
                sections.append(DeviceSection(id: item.id, title: item.title, values: values))
                successful += 1
            } catch UpstreamError.unauthorized, UpstreamError.forbidden {
                unauthorized = true
                sections.append(DeviceSection(id: item.id, title: item.title, values: [:]))
            } catch {
                sections.append(DeviceSection(id: item.id, title: item.title, values: [:]))
            }
        }
        if successful == 0 {
            throw unauthorized ? DeviceServiceError.unauthorized : DeviceServiceError.invalidResponse
        }
        return DeviceSnapshot(sections: sections)
    }

    private func request(_ route: UpstreamRoute, _ instance: Instance) async throws -> UpstreamResponse {
        var cookie = await sessions.cookie(for: instance.id, origin: instance.origin)
        do {
            return try await client.send(route, baseURL: instance.origin, cookie: cookie)
        } catch UpstreamError.unauthorized, UpstreamError.forbidden {
            cookie = try await login(instance)
            return try await client.send(route, baseURL: instance.origin, cookie: cookie)
        }
    }

    private func login(_ instance: Instance) async throws -> String {
        guard let credentials,
              let password = try credentials.get(instanceID: instance.id),
              !password.isEmpty
        else {
            throw DeviceServiceError.unauthorized
        }
        let sessionService = InstanceSessionService(store: sessions, client: client)
        let result = try await sessionService.login(instance, password: password)
        guard result.authenticated,
              let cookie = await sessionService.cookie(for: instance)
        else {
            throw DeviceServiceError.unauthorized
        }
        return cookie
    }

    static func dataObject(_ data: Data) throws -> [String: Any] {
        guard let root = try JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            throw DeviceServiceError.invalidResponse
        }
        if let payload = root["data"] as? [String: Any] { return payload }
        if let response = root["response"] as? [String: Any],
           let payload = response["data"] as? [String: Any] {
            return payload
        }
        return root
    }

    static func flatten(_ source: [String: Any], maximum: Int = 40) -> [String: String] {
        var output: [String: String] = [:]
        flatten(source, prefix: "", into: &output, remaining: maximum)
        return output
    }

    private static func flatten(
        _ source: [String: Any],
        prefix: String,
        into output: inout [String: String],
        remaining: Int
    ) {
        for (key, value) in source.sorted(by: { $0.key < $1.key }) {
            guard output.count < remaining else { return }
            let fullKey = prefix.isEmpty ? key : "\(prefix)_\(key)"
            switch value {
            case let text as String:
                output[fullKey] = text
            case let flag as Bool:
                output[fullKey] = flag ? "是" : "否"
            case let number as Int:
                output[fullKey] = String(number)
            case let number as Double:
                output[fullKey] = String(format: "%.1f", number)
            case let array as [Any]:
                let text = array.compactMap { entry -> String? in
                    if let record = entry as? [String: Any] {
                        let preferred = ["name", "zone", "mount_point", "interface", "model_name"]
                            .compactMap { record[$0] as? String }
                            .first
                        if let preferred { return preferred }
                    }
                    return entry as? String
                }.joined(separator: "、")
                output[fullKey] = text
            case let nested as [String: Any]:
                flatten(nested, prefix: fullKey, into: &output, remaining: remaining - output.count)
            default:
                break
            }
        }
    }
}