import Foundation

/// Authentifizierter HTTP-Transport. Setzt automatisch den `Authorization: Bearer`-
/// Header, refreshed bei `401` einmal proaktiv und wiederholt den Request.
///
/// Eine Instanz pro App-Backend (z.B. memoro-api, cards-api). Beim Init
/// die Basis-URL des jeweiligen App-Servers übergeben, nicht die mana-auth-URL.
public actor AuthenticatedTransport {
    private let baseURL: URL
    private let session: URLSession
    private let auth: AuthClient

    public init(baseURL: URL, auth: AuthClient, session: URLSession = .shared) {
        self.baseURL = baseURL
        self.session = session
        self.auth = auth
    }

    /// Führt einen authentifizierten Request aus. Bei `401` wird der
    /// Access-Token einmal refreshed und der Call wiederholt.
    public func request(
        path: String,
        method: String = "GET",
        body: Data? = nil,
        contentType: String = "application/json"
    ) async throws -> (Data, HTTPURLResponse) {
        let token = try await auth.freshAccessToken()
        let response = try await send(path: path, method: method, body: body, contentType: contentType, token: token)
        if response.1.statusCode == 401 {
            let refreshed = try await auth.refreshAccessToken()
            return try await send(path: path, method: method, body: body, contentType: contentType, token: refreshed)
        }
        return response
    }

    private func send(
        path: String,
        method: String,
        body: Data?,
        contentType: String,
        token: String
    ) async throws -> (Data, HTTPURLResponse) {
        var request = URLRequest(url: baseURL.appending(path: path))
        request.httpMethod = method
        request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        if let body {
            request.httpBody = body
            request.setValue(contentType, forHTTPHeaderField: "Content-Type")
        }

        do {
            let (data, response) = try await session.data(for: request)
            guard let http = response as? HTTPURLResponse else {
                throw AuthError.networkFailure("Keine HTTP-Antwort")
            }
            return (data, http)
        } catch let error as URLError {
            throw AuthError.networkFailure(error.localizedDescription)
        }
    }
}