/// A static file shipped with the website service.
///
/// Each case identifies a file stored under the static files root (the `Resources/Static`
/// directory) and served by Hummingbird's `FileMiddleware` middleware.
enum StaticFile: CaseIterable, Sendable {
    /// The `js/app.js` script.
    case appJS
    /// The `favicon.ico` icon.
    case faviconICO
    /// The `icon.png` icon.
    case iconPNG
    /// The `icon.svg` icon.
    case iconSVG
    /// The `robots.txt` crawler directives.
    case robotsTXT
    /// The `site.webmanifest` web application manifest.
    case siteWebmanifest
    /// The `css/style.css` stylesheet.
    case styleCSS
}

// MARK: - Enumerations

extension StaticFile {
    /// A file extension used by a ``StaticFile``.
    enum Extension: String, Sendable {
        /// A Cascading Style Sheets file.
        case css
        /// A JavaScript file.
        case js
        /// A Portable Network Graphics image.
        case png
        /// A Windows icon image.
        case ico
        /// A Scalable Vector Graphics image.
        case svg
        /// A plain text file.
        case txt
        /// A web application manifest file.
        case webmanifest
    }
}

// MARK: - Extensions

extension StaticFile {

    // MARK: Computed
    
    /// The file's content type.
    var contentType: String {
        switch fileExtension {
        case .css: "text/css"
        case .js: "text/javascript"
        case .png: "image/png"
        case .ico: "image/vnd.microsoft.icon"
        case .svg: "image/svg+xml"
        case .txt: "text/plain"
        case .webmanifest: "application/manifest+json"
        }
    }

    /// The file's extension.
    var fileExtension: Extension {
        switch self {
        case .styleCSS: .css
        case .appJS: .js
        case .faviconICO: .ico
        case .iconPNG: .png
        case .iconSVG: .svg
        case .robotsTXT: .txt
        case .siteWebmanifest: .webmanifest
        }
    }

    /// The file's name, without extension.
    var fileName: String {
        switch self {
        case .appJS: "app"
        case .faviconICO: "favicon"
        case .iconPNG,
             .iconSVG: "icon"
        case .robotsTXT: "robots"
        case .siteWebmanifest: "site"
        case .styleCSS: "style"
        }
    }

    /// The path relative to the static files root (e.g. `"css/style.css"`).
    ///
    /// This also matches the URL path the file is served at by `FileMiddleware`.
    var relativePath: String {
        let file = "\(fileName).\(fileExtension.rawValue)"

        return subdirectory
            .map { "\($0)/\(file)" } ?? file
    }

    // MARK: Methods

    /// Resolves the file's path against the given base directory.
    /// 
    /// - Parameter basePath: the directory the static files are served from.
    /// - Returns: the path to the file, relative to the `basePath` path.
    public func path(
        relativeTo basePath: String
    ) -> String {
        guard !basePath.isEmpty else {
            return relativePath
        }

        return "\(basePath)/\(relativePath)"
    }

}

// MARK: - Helpers

private extension StaticFile {

    // MARK: Computed

    /// The sub-directory within the static root that holds the file, if any.
    var subdirectory: String? {
        switch self {
        case .appJS: "js"
        case .styleCSS: "css"
        default: nil
        }
    }

}