import Foundation
import Hummingbird
import Infrastructure

/// Serves the website's root routes.
///
/// The controller exposes its routes through its `RouterController` conformance, so the application that composes it registers them declaratively:
///
/// ```swift
/// router.addController {
///     RootController<AppRequestContext>()
/// }
/// ```
///
/// - 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 RootController<Context: LocalizedRequestContext> {

    // MARK: Properties

    /// The landing page, rendered once per supported language and reused for every request.
    private let responses: LocalizedHTMLCollectionResponse

    // MARK: Initializers

    /// Creates a root controller.
    /// - Parameter assetVersion: the version token appended to the page's asset URLs, or `nil` (the default) to leave them unversioned.
    public init(
        assetVersion: String? = nil
    ) {
        self.responses = .init(bundle: .module) {
            IndexPage(
                locale: $0,
                assetVersion: assetVersion
            )
        }
    }

}

// MARK: - RouteController

extension RootController: RouterController {

    // MARK: Properties

    public var routes: RouteCollection<Context> {
        let routes = RouteCollection(context: Context.self)

        routes.get(
            .Root.index,
            use: index
        )

        return routes
    }

}

// MARK: - Helpers

private extension RootController {

    // MARK: Methods

    /// Handles a request for the landing page.
    ///
    /// Renders the ``IndexPage`` in the language stored on the context by ``LocalizationMiddleware``, falling back to the default language.
    /// - Parameters:
    ///   - request: the incoming request.
    ///   - context: the context the request is resolved against.
    /// - Returns: the cached ``IndexPage`` response for the context's language.
    @Sendable
    func index(
        request: Request,
        context: Context
    ) -> Response {
        responses.response(
            for: context.language,
            request: request
        )
    }

}

// MARK: - Constants

private extension RouterPath {
    /// A namespace for the ``RootController`` route paths.
    enum Root {
        /// The path of the landing page.
        static let index: RouterPath = "/"
    }
}