import Hummingbird
import NIOCore

/// Serves the website's health-check route.
///
/// The controller exposes its routes as a `RouteCollection` so they can be added to a router
/// (or a sub-group) by the application that composes it:
///
/// ```swift
/// router.addRoutes(HealthController<AppRequestContext>().routes)
/// ```
///
/// - Note: `Context` is the request context the routes are resolved against, and must match the
///   context of the router the routes are added to.
public struct HealthController<Context: RequestContext>: Sendable {
    
    // MARK: Properties
    
    /// The JSON payload returned for every health check.
    private let payload: String

    // MARK: Initializers

    /// Creates a health controller.
    public init() {
        self.payload = #"{"status":"ok"}"#
    }

    // MARK: Computed

    /// The routes served by the controller.
    ///
    /// Serves a `GET` request for the health path (`/health`) with a static JSON status payload.
    public var routes: RouteCollection<Context> {
        let routes = RouteCollection(context: Context.self)

        routes.get(
            .Health.check,
            use: check
        )

        return routes
    }

}

// MARK: - Helpers

private extension HealthController {

    // MARK: Methods

    /// Handles a request for the health check.
    ///
    /// Returns a constant JSON body built directly per request — the payload is a tiny literal with no
    /// rendering step, so there is nothing to pre-render or cache.
    /// - Parameters:
    ///   - request: the incoming request.
    ///   - context: the context the request is resolved against.
    /// - Returns: a `200 OK` response carrying the static JSON status payload.
    @Sendable
    func check(
        request: Request,
        context: some RequestContext
    ) -> Response {
        Response(
            status: .ok,
            headers: [.contentType: "application/json"],
            body: .init(byteBuffer: .init(string: payload))
        )
    }

}

// MARK: - Constants

private extension RouterPath {
    /// A namespace for the ``HealthController`` route paths.
    enum Health {
        /// The path of the health-check endpoint.
        static let check: RouterPath = "/health"
    }
}