import Elementary
import Foundation
import Infrastructure
import Localization

/// The website's landing page, with its text localized to a given locale.
struct IndexPage {

    // MARK: Properties

    /// The analytics tracker embedded as a deferred script in the document head, or `nil` to omit it.
    let analytics: Analytics?

    /// The version token appended to the page's asset URLs, or `nil` to leave them unversioned.
    let assetVersion: String?

    /// The locale the page content is localized to.
    let locale: Locale

    /// The public origin the page derives its canonical URL and language alternates from, or `nil` to omit them.
    let siteOrigin: String?

    /// Resolves the page's text from the bundled String Catalog for the page's ``locale``.
    private let localize: Localize

    // MARK: Initializers

    /// Creates a landing page localized to the given locale.
    /// - Parameters:
    ///   - locale: the locale the page content is localized to.
    ///   - assetVersion: the version token appended to the page's asset URLs, or `nil` (the default) to leave them unversioned.
    ///   - siteOrigin: the public origin the page derives its canonical URL and language alternates from, or `nil` (the default) to omit them.
    ///   - analytics: the analytics tracker embedded in the document head, or `nil` (the default) to omit it.
    init(
        locale: Locale,
        assetVersion: String? = nil,
        siteOrigin: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.locale = locale
        self.siteOrigin = siteOrigin
        self.localize = .init(bundle: .module)
    }

}

// MARK: - Page

extension IndexPage: Page {

    // MARK: Constants

    /// The path the page is served at; ``RootController`` registers its route against it, and the page builds its canonical URL from it.
    static let path = "/"

    // MARK: Computed

    /// The canonical URL of the page's edition in its language, or `nil` when the origin is unknown.
    ///
    /// The origin alone for the default language, since canonical URLs carry no trailing slash — `TrailingSlashRedirectMiddleware` enforces
    /// that on every path but the root, which has nothing to strip.
    var canonicalURL: String? {
        siteOrigin.map {
            Language(of: locale).url(
                origin: $0,
                path: Self.path
            )
        }
    }

    /// The site-wide metadata, preceded by the `hreflang` alternates tying the page's language editions together.
    @HTMLBuilder
    var metadata: some HTML {
        languageAlternates(
            origin: siteOrigin,
            path: Self.path
        )
        siteMetadata
    }

    // MARK: Properties

    var content: some HTML {
        p {
            localize("index.greeting", locale: locale)
        }
    }

    var scripts: [any Asset] {
        [StaticFile.index, StaticFile.shared]
    }

    var stylesheets: [any Asset] {
        [StaticFile.shared, StaticFile.index]
    }

    var title: String {
        localize("index.title", locale: locale)
    }

}