Siri: cheapest [fuel] near me intent + App Shortcuts (cached-first, freshness label)

FuelBoardTests/Sources/FuelBoardShared/SiriCheapestLookup.swift

@@ -0,0 +1 @@
+../../../Shared/SiriCheapestLookup.swift

FuelBoardTests/Tests/FuelBoardSharedTests/FuelBoardTests.swift

@@ -406,3 +406,73 @@ final class DistanceLabelTests: XCTestCase {
         XCTAssertEqual(DistanceUnit.kilometers.displayMiles(15), 24) // 15 mi = 24.1 km
     }
 }
+
+final class SiriCheapestLookupTests: XCTestCase {
+    private func station(_ id: String, lat: Double, lng: Double, _ prices: [FuelType: Double]) -> FuelStation {
+        FuelStation(id: id, name: id, brand: "X", address: "", postcode: "", lat: lat, lng: lng, prices: prices, priceUpdated: nil)
+    }
+
+    func testCheapestPicksLowestPriceNotNearest() {
+        // Near station is pricier; far station is cheaper — price must win.
+        let stations = [
+            station("near", lat: 53.0, lng: -1.0, [.e10: 145.9]),
+            station("far", lat: 53.5, lng: -1.5, [.e10: 139.9]),
+        ]
+        let result = SiriCheapestLookup.cheapest(in: stations, fuel: .e10, fromLat: 53.01, lng: -1.01)
+        XCTAssertEqual(result?.id, "far", "cheapest by price, not by distance")
+    }
+
+    func testCheapestTieBreaksByDistance() {
+        let stations = [
+            station("near", lat: 53.0, lng: -1.0, [.e10: 140.0]),
+            station("far", lat: 53.9, lng: -1.9, [.e10: 140.0]),
+        ]
+        let result = SiriCheapestLookup.cheapest(in: stations, fuel: .e10, fromLat: 53.01, lng: -1.01)
+        XCTAssertEqual(result?.id, "near", "equal prices resolve to the nearest station")
+    }
+
+    func testCheapestSkipsStationsWithoutThatFuel() {
+        let stations = [
+            station("noDiesel", lat: 53.0, lng: -1.0, [.e10: 139.9]),
+            station("sellsDiesel", lat: 53.5, lng: -1.5, [.diesel: 149.9]),
+        ]
+        let result = SiriCheapestLookup.cheapest(in: stations, fuel: .diesel, fromLat: 53.01, lng: -1.01)
+        XCTAssertEqual(result?.id, "sellsDiesel", "stations without the fuel are skipped")
+    }
+
+    func testCheapestReturnsNilWhenNoStationSellsFuel() {
+        let stations = [station("a", lat: 53.0, lng: -1.0, [.e10: 139.9])]
+        XCTAssertNil(SiriCheapestLookup.cheapest(in: stations, fuel: .diesel, fromLat: 53.0, lng: -1.0))
+    }
+
+    func testCheapestReturnsNilForEmptyInput() {
+        XCTAssertNil(SiriCheapestLookup.cheapest(in: [], fuel: .e10, fromLat: 53.0, lng: -1.0))
+    }
+
+    func testFreshnessLabelUsesDataUpdatedStamp() {
+        let label = SiriCheapestLookup.freshnessLabel(
+            updated: "2026-08-14T10:31:36.000Z",
+            lastRefresh: nil
+        )
+        XCTAssertTrue(label.hasPrefix("as of "), "stamp must be prefixed for the dialog")
+        XCTAssertFalse(label.contains("10:31"), "stamp is converted to the user's local time, not raw UTC")
+    }
+
+    func testFreshnessLabelFallsBackToLastRefresh() {
+        let label = SiriCheapestLookup.freshnessLabel(updated: nil, lastRefresh: Date(timeIntervalSince1970: 0))
+        XCTAssertTrue(label.hasPrefix("as of "), "local refresh date is used when no GOV.UK stamp exists")
+    }
+
+    func testFreshnessLabelEmptyWithoutAnyDate() {
+        XCTAssertEqual(SiriCheapestLookup.freshnessLabel(updated: nil, lastRefresh: nil), "")
+    }
+
+    func testFreshnessLabelToleratesPlainISODate() {
+        // Some relays emit no fractional seconds.
+        let label = SiriCheapestLookup.freshnessLabel(
+            updated: "2026-08-14T10:31:36Z",
+            lastRefresh: nil
+        )
+        XCTAssertTrue(label.hasPrefix("as of "), "plain ISO 8601 still parses")
+    }
+}