Implemented phase 2 for the POC prototype in the Website service.

Services/Website/Sources/Library/Internal/Pages/ShopPage.swift

@@ -27,6 +27,9 @@ struct ShopPage {
     /// The shop shown.
     let shop: Shop
 
+    /// The signed-in viewer, or `nil` when signed out.
+    let viewer: Viewer?
+
     // MARK: Initializers
 
     /// Creates the public screen of a shop.
@@ -35,6 +38,7 @@ struct ShopPage {
     ///   - inventory: every listing of the shop, counted per format on the tabs.
     ///   - matches: the shop's listings matching the parameters; the screen shows the page they ask for.
     ///   - parameters: the tab, quick filters, and sort order applied.
+    ///   - viewer: the signed-in viewer, or `nil` (the default) when signed out.
     ///   - assetVersion: the version token appended to the page's asset URLs, or `nil` (the default) to leave them unversioned.
     ///   - analytics: the analytics tracker embedded in the document head, or `nil` (the default) to omit it.
     init(
@@ -42,9 +46,11 @@ struct ShopPage {
         inventory: [Listing],
         matches: [Listing],
         parameters: SearchParameters,
+        viewer: Viewer? = nil,
         assetVersion: String? = nil,
         analytics: Analytics? = nil
     ) {
+        self.viewer = viewer
         let slice = Pagination.slice(
             matches,
             page: parameters.page,
@@ -78,7 +84,7 @@ extension ShopPage: Page {
     // MARK: Computed
 
     var content: some HTML {
-        SiteLayout {
+        SiteLayout(viewer: viewer) {
             div(.class("page shop")) {
                 section(.class("shop__head")) {
                     span(.class("monogram monogram--xl")) {
@@ -116,20 +122,24 @@ extension ShopPage: Page {
                     div(.class("shop__actions")) {
                         a(
                             .class("button button--primary"),
-                            .href(signIn)
+                            .href(.Route.gated(.Route.message(shop: shop.slug), from: shop.path, viewer: viewer))
                         ) {
                             Icon(.message, size: 16)
                             "Message shop"
                         }
-                        a(
-                            .class("button button--outline"),
-                            .href(signIn)
-                        ) {
-                            "Follow shop"
-                        }
-                        span(.class("type-small shop__gate")) {
-                            Icon(.key, size: 13)
-                            "Both need a passkey sign-in"
+                        if viewer == nil {
+                            a(
+                                .class("button button--outline"),
+                                .href(.Route.signIn(returningTo: shop.path))
+                            ) {
+                                "Follow shop"
+                            }
+                            span(.class("type-small shop__gate")) {
+                                Icon(.key, size: 13)
+                                "Both need a passkey sign-in"
+                            }
+                        } else {
+                            Unavailable("Follow shop", modifier: "button--outline")
                         }
                     }
                 }
@@ -286,11 +296,6 @@ private extension ShopPage {
 
     // MARK: Computed
 
-    /// The sign-in screen, returning to this shop.
-    var signIn: String {
-        .Route.signIn(returningTo: shop.path)
-    }
-
     var stats: [(value: String, label: String)] {
         [
             ("\(counts.values.reduce(0, +))", "listings"),