ccn/Services/Website/Sources/Library/Internal/Protocols/Page.swift

import Elementary
import Foundation
import Localization

/// A page of the website: an HTML document with the shared scaffolding assembled around the page's content.
///
/// A conforming page supplies its locale, its localized title, the stylesheets and scripts it needs, and its content; the protocol assembles the rest of the
/// document around them: the metadata, stylesheet, icon, and manifest links in the head, the content followed by the script tags in the body, and the
/// document language derived from the locale.
protocol Page: HTMLDocument, Sendable {

    // MARK: Associated types

    /// The type of the page's markup.
    associatedtype Content: HTML

    // MARK: Properties

    /// The page's markup, rendered before the ``scripts``.
    @HTMLBuilder
    var content: Content { get }

    /// The locale the page content is localized to.
    var locale: Locale { get }

    /// The scripts loaded at the end of the document body, in order.
    var scripts: [StaticFile] { get }

    /// The stylesheets linked in the document head, in order.
    var stylesheets: [StaticFile] { get }

}

// MARK: - Implementations

extension Page {

    // MARK: Computed

    /// The page ``content`` followed by its ``scripts``.
    @HTMLBuilder
    var body: some HTML {
        content
        for file in scripts {
            script(.src(file.urlPath(for: .js))) {}
        }
    }

    /// The metadata, ``stylesheets``, icon, and manifest links placed in the document head.
    ///
    /// The charset declaration is omitted: Elementary's `HTMLDocument` scaffolding already
    /// emits `<meta charset="UTF-8">` before this markup, and HTML5 allows only one.
    @HTMLBuilder
    var head: some HTML {
        meta(
            .name(.viewport),
            .content("width=device-width, initial-scale=1")
        )
        for file in stylesheets {
            link(
                .rel(.stylesheet),
                .href(file.urlPath(for: .css))
            )
        }
        link(
            .rel(.icon),
            .href(StaticFile.favicon.urlPath(for: .ico)),
            .custom(
                name: "sizes",
                value: "any"
            )
        )
        link(
            .rel(.icon),
            .href(StaticFile.icon.urlPath(for: .svg)),
            .custom(
                name: "type",
                value: "image/svg+xml"
            )
        )
        link(
            .rel("apple-touch-icon"),
            .href(StaticFile.appleTouchIcon.urlPath(for: .png))
        )
        link(
            .rel("manifest"),
            .href(StaticFile.site.urlPath(for: .webmanifest))
        )
        meta(
            .name("theme-color"),
            .content("#fafafa")
        )
        meta(
            .name("theme-color"),
            .content("#0c0710"),
            .custom(
                name: "media",
                value: "(prefers-color-scheme: dark)"
            )
        )
    }

    /// The document language, derived from the page's locale and falling back to the default language.
    var lang: String {
        locale.language.languageCode?.identifier
            ?? LanguageList(bundle: .module).default
    }

}