import Foundation

/// 网络错误。
public enum NetworkError: Error, Sendable {
    case invalidResponse
    case http(statusCode: Int)
    case decoding(String)
}

/// 通用 HTTP 客户端（对应 Android Retrofit 的最小抽象）。
public protocol APIClient: Sendable {
    func get<T: Decodable & Sendable>(_ url: URL) async throws -> T
}

/// 基于 URLSession 的 APIClient 实现。
public struct URLSessionAPIClient: APIClient {
    private let session: URLSession

    public init(session: URLSession = .shared) {
        self.session = session
    }

    public func get<T: Decodable & Sendable>(_ url: URL) async throws -> T {
        let (data, response) = try await session.data(from: url)
        guard let http = response as? HTTPURLResponse else {
            throw NetworkError.invalidResponse
        }
        guard (200..<300).contains(http.statusCode) else {
            throw NetworkError.http(statusCode: http.statusCode)
        }
        do {
            return try JSONDecoder().decode(T.self, from: data)
        } catch {
            throw NetworkError.decoding(error.localizedDescription)
        }
    }
}