//
//  AuthenticationMiddleware.swift
//
//  Copyright 2026 Brendan Szymanski <hello@bscubed.dev>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
//  SPDX-License-Identifier: GPL-3.0-or-later
//

import Foundation
import HTTPTypes
import OpenAPIRuntime

/// Stamps Jellyfin's `Authorization` header onto every outgoing request.
///
/// Jellyfin does not use a bare bearer token. It expects a `MediaBrowser` scheme carrying the
/// client identity alongside the token:
///
/// ```
/// Authorization: MediaBrowser Client="Luminate", Device="workstation",
///                DeviceId="...", Version="0.1.0", Token="..."
/// ```
///
/// The server keys a session by `DeviceId`, so that value must stay stable across launches. Before
/// sign-in the token is sent as an empty string, which is what the pre-auth endpoints expect.
///
/// This middleware is the only place that header is built; no call site assembles it by hand.
package struct AuthenticationMiddleware: ClientMiddleware {
    /// The application name reported to the server.
    package let clientName: String
    /// The human-readable device name shown in the server's active-devices list.
    package let deviceName: String
    /// The stable per-machine device identifier the server keys its session by.
    package let deviceID: String
    /// The application version reported to the server.
    package let version: String
    /// The access token, or `nil` before sign-in.
    package let token: String?

    /// Creates a middleware for one client identity.
    ///
    /// - Parameters:
    ///   - clientName: The application name reported to the server.
    ///   - deviceName: The human-readable device name.
    ///   - deviceID: The stable per-machine device identifier.
    ///   - version: The application version.
    ///   - token: The access token, or `nil` before sign-in.
    package init(clientName: String, deviceName: String, deviceID: String, version: String, token: String?) {
        self.clientName = clientName
        self.deviceName = deviceName
        self.deviceID = deviceID
        self.version = version
        self.token = token
    }

    /// Adds the `Authorization` header and forwards the request down the chain.
    ///
    /// - Parameters:
    ///   - request: The request as assembled by the generated client.
    ///   - body: The request body, if any.
    ///   - baseURL: The server URL the request is bound for.
    ///   - operationID: The Jellyfin operation identifier, unused here.
    ///   - next: The next step in the middleware chain.
    /// - Returns: Whatever `next` returns, unmodified.
    /// - Throws: Whatever `next` throws.
    package func intercept(
        _ request: HTTPRequest,
        body: HTTPBody?,
        baseURL: URL,
        operationID: String,
        next: @Sendable (HTTPRequest, HTTPBody?, URL) async throws -> (HTTPResponse, HTTPBody?)
    ) async throws -> (HTTPResponse, HTTPBody?) {
        var request = request
        request.headerFields[.authorization] = authorizationValue
        return try await next(request, body, baseURL)
    }

    /// The `MediaBrowser` credential string, with an empty token when unauthenticated.
    private var authorizationValue: String {
        """
        MediaBrowser Client="\(clientName)", Device="\(deviceName)", DeviceId="\(deviceID)", \
        Version="\(version)", Token="\(token ?? "")"
        """
    }
}