Implemented phase 1 for the POC prototype in the Website service.

Services/Website/Sources/Library/Internal/Extensions/Int+Euros.swift

@@ -0,0 +1,14 @@
+import Foundation
+
+extension Int {
+
+    // MARK: Computed
+
+    /// The amount of euro cents as a price: whole euros bare (`€240`), anything else to the cent (`€12.50`).
+    var euros: String {
+        isMultiple(of: 100)
+            ? "€\(self / 100)"
+            : String(format: "€%d.%02d", self / 100, self % 100)
+    }
+
+}

Services/Website/Sources/Library/Internal/Extensions/Listing+Display.swift

@@ -0,0 +1,89 @@
+import Foundation
+import Persistence
+
+extension Listing {
+
+    // MARK: Computed
+
+    /// The chip stating the copy's grade or condition.
+    ///
+    /// A slab reads `CGC 9.8` — good from 9.0 up, a warning below 7.0 — a raw issue `Raw · NM`, and a collected edition its condition.
+    var chip: (label: String, tone: Chip.Tone, isCertified: Bool) {
+        guard let grader, let grade else {
+            return (
+                kind == .singleIssues ? "Raw · \(condition)" : condition,
+                .neutral,
+                false
+            )
+        }
+
+        return (
+            "\(grader) \(grade.gradeLabel)",
+            grade >= 9 ? .good : grade < 7 ? .warn : .neutral,
+            true
+        )
+    }
+
+    /// The format the listing is published in, or `nil` when its token names none.
+    var kind: Format? {
+        .init(rawValue: format)
+    }
+
+    /// The path of the listing's detail screen.
+    var path: String {
+        .Route.listing(slug)
+    }
+
+    /// The line under a card's title: the publisher, year, and printing, led by the format for a collected edition.
+    var summary: String {
+        let lead = kind == .singleIssues ? nil : kind?.singular
+
+        return [lead, publisher, String(year), printing]
+            .compactMap(\.self)
+            .joined(separator: " · ")
+    }
+
+}
+
+extension Shop {
+
+    // MARK: Computed
+
+    /// The shop's location, e.g. `Amsterdam, NL`.
+    var location: String {
+        "\(city), \(country)"
+    }
+
+    /// The uppercased initials of the first two words of the shop's name that start with a letter.
+    var monogram: String {
+        name
+            .split(separator: " ")
+            .filter { $0.first?.isLetter == true }
+            .prefix(2)
+            .compactMap(\.first)
+            .map { String($0).uppercased() }
+            .joined()
+    }
+
+    /// The path of the shop's public screen.
+    var path: String {
+        .Route.shop(slug)
+    }
+
+    /// The shop's standing in a line: where it is, since when, and how it is rated.
+    var standing: String {
+        "\(location) · selling on CCN since \(sinceYear) · \(String(format: "%.1f", rating)) from \(ratedSales) rated sales"
+    }
+
+}
+
+extension Double {
+
+    // MARK: Computed
+
+    /// The grade to one decimal place, e.g. `9.8`.
+    var gradeLabel: String {
+        String(format: "%.1f", self)
+    }
+
+}

Services/Website/Sources/Library/Internal/Extensions/String+Routes.swift

@@ -1,3 +1,5 @@
+import Foundation
+
 extension String {
     /// A namespace for the paths of the site's screens.
     ///
@@ -35,5 +37,36 @@ extension String {
         static let terms = "/terms"
         /// The want list.
         static let wants = "/wants"
+
+        /// The path of a listing's detail screen.
+        /// - Parameter slug: the listing's URL slug.
+        static func listing(
+            _ slug: String
+        ) -> String {
+            "/listing/\(slug)"
+        }
+
+        /// The path of a shop's public screen.
+        /// - Parameter slug: the shop's URL slug.
+        static func shop(
+            _ slug: String
+        ) -> String {
+            "/shop/\(slug)"
+        }
+
+        /// The path of the sign-in screen, returning to the given path afterwards.
+        /// - Parameter path: the path the visitor's gated action started from.
+        static func signIn(
+            returningTo path: String
+        ) -> String {
+            "\(signIn)?return=\(path.addingPercentEncoding(withAllowedCharacters: .urlQueryValueAllowed) ?? "")"
+        }
     }
 }
+
+// MARK: - Constants
+
+private extension CharacterSet {
+    /// The characters a query value carries unescaped.
+    static let urlQueryValueAllowed = CharacterSet.urlQueryAllowed.subtracting(.init(charactersIn: "&=+?#"))
+}