import XCTest
#if SWIFT_PACKAGE
@testable import FuelBoardShared
#endif

/// The Best Value gate's option list.
///
/// This one array is the figure behind two user-facing things — the BEST VALUE
/// badge on a station row and the proximity alert — so its granularity is a
/// setting, not an implementation detail. It was four coarse values (50p, £1,
/// £2, £5); these tests pin the 50p step and the £5 ceiling so a later edit
/// cannot quietly coarsen it back.
final class FuelStoreBestValueThresholdTests: XCTestCase {
    func testOptionsStepByFiftyPenceUpToFivePounds() {
        let options = FuelStore.bestValueAlertThresholdOptionsGBP
        XCTAssertEqual(options, [0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0])
        XCTAssertEqual(options.count, 10)
        XCTAssertEqual(options.first, 0.5, "the floor is the cheapest worth-the-drive saving offered")
        XCTAssertEqual(options.last, 5.0, "£5 is the ceiling")
    }

    /// The store writes the threshold as a string and, on load, rejects any
    /// value that is not one of these options — falling back to the £1 default.
    /// So an option that does not survive `String` → `Double` exactly would
    /// silently discard the user's choice. Multiples of 0.5 are exactly
    /// representable in binary, and this keeps them that way.
    func testEveryOptionSurvivesTheStoresStringRoundTrip() {
        for option in FuelStore.bestValueAlertThresholdOptionsGBP {
            XCTAssertEqual(Double(String(option)), option,
                           "£\(option) does not round-trip through the store's string encoding")
        }
    }
}