import AppIntents
import SwiftUI

/// Siri / Shortcuts surface for "cheapest [fuel] near me".
///
/// Design (see skill reference `siri-app-intents-scope.md`):
/// - App Intents (iOS 16+), no entitlements/capabilities/Info.plist keys.
/// - Cached-data-first: answers from the full-UK dump saved in the app-group
///   defaults by the normal app fetch. The dialog ALWAYS labels data age
///   ("as of 6:30 AM") — silent stale answers are a trust killer for fuel
///   prices. The fresh-data path (relay baseURL is LAN-only) is a P0
///   dependency; until it lands, off-LAN answers use whatever the phone
///   last fetched at home.
/// - Location: last-known location fallback (background CoreLocation from a
///   Siri-launched process is slow/unreliable).
/// - Phrases stay literal/boring for App Store review; `\.applicationName`
///   appears in one phrase per the review guidance.

// MARK: - Fuel parameter

extension FuelType: AppEnum {
    static var typeDisplayRepresentation: TypeDisplayRepresentation = "Fuel"

    static var caseDisplayRepresentations: [FuelType: DisplayRepresentation] = [
        .e10: "Unleaded",
        .e5: "Premium",
        .diesel: "Diesel",
    ]
}

// MARK: - Intent

struct CheapestFuelIntent: AppIntent {
    static var title: LocalizedStringResource = "Cheapest Fuel Near Me"
    static var description = IntentDescription(
        "Finds the cheapest station selling a fuel near you, using the latest cached prices."
    )

    @Parameter(title: "Fuel")
    var fuel: FuelType

    func perform() async throws -> some IntentResult & ProvidesDialog & ShowsSnippetView & ReturnsValue<String> {
        let stations = FuelStore.loadStations()

        guard !stations.isEmpty else {
            let dialog = "I don't have any price data yet. Open FuelBoard once to download the latest prices, then ask me again."
            return .result(
                value: "No price data yet",
                dialog: IntentDialog(stringLiteral: dialog),
                view: CheapestFuelMessage(text: "No price data yet — open FuelBoard to download prices.")
            )
        }

        guard let coordinate = FuelStore.loadLocationWithDate()?.coordinate else {
            let dialog = "I don't know your location yet. Open FuelBoard and allow location access, then ask me again."
            return .result(
                value: "Location unavailable",
                dialog: IntentDialog(stringLiteral: dialog),
                view: CheapestFuelMessage(text: "Location unavailable — open FuelBoard to share your location.")
            )
        }

        guard let station = SiriCheapestLookup.cheapest(
            in: stations,
            fuel: fuel,
            fromLat: coordinate.lat,
            lng: coordinate.lng
        ), let price = station.prices[fuel] else {
            let fuelName = fuel.displayName.lowercased()
            return .result(
                value: "No \(fuelName) stations found",
                dialog: IntentDialog(stringLiteral: "I couldn't find any station selling \(fuelName) near you."),
                view: CheapestFuelMessage(text: "No \(fuelName) stations found.")
            )
        }

        let distanceKM = station.distanceKM(to: coordinate.lat, lng2: coordinate.lng)
        let distanceText = FuelStore.loadDistanceUnit().format(distanceKM)
        let priceText = String(format: "£%.3f", price / 100)
        let freshness = SiriCheapestLookup.freshnessLabel(
            updated: FuelStore.loadDataUpdated(),
            lastRefresh: FuelStore.loadLastRefresh()
        )
        let summary = "\(station.name): \(priceText), \(distanceText)"
        let freshnessClause = freshness.isEmpty ? "" : " — prices \(freshness)"
        let dialog = "The cheapest \(fuel.displayName.lowercased()) near you is \(station.name) at \(priceText), \(distanceText) away\(freshnessClause)."

        return .result(
            value: summary,
            dialog: IntentDialog(stringLiteral: dialog),
            view: CheapestFuelCard(
                stationName: station.name,
                fuelName: fuel.displayName,
                price: priceText,
                distance: distanceText,
                freshness: freshness
            )
        )
    }
}

// MARK: - Snippets

/// Price card shown in Shortcuts / Siri results.
struct CheapestFuelCard: View {
    let stationName: String
    let fuelName: String
    let price: String
    let distance: String
    let freshness: String

    var body: some View {
        HStack(spacing: 14) {
            Image(systemName: "fuelpump.fill")
                .font(.title2)
                .foregroundStyle(.tint)
            VStack(alignment: .leading, spacing: 2) {
                Text(stationName)
                    .font(.headline)
                    .lineLimit(1)
                Text("\(fuelName) · \(distance)")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                if !freshness.isEmpty {
                    Text(freshness)
                        .font(.caption)
                        .foregroundStyle(.tertiary)
                }
            }
            Spacer(minLength: 8)
            Text(price)
                .font(.title2.bold())
                .monospacedDigit()
        }
        .padding(12)
    }
}

/// Fallback message card for the no-data / no-location / no-station cases.
struct CheapestFuelMessage: View {
    let text: String

    var body: some View {
        HStack(spacing: 10) {
            Image(systemName: "info.circle")
                .foregroundStyle(.secondary)
            Text(text)
                .font(.subheadline)
        }
        .padding(12)
    }
}

// MARK: - App Shortcuts

struct FuelBoardShortcuts: AppShortcutsProvider {
    static var appShortcuts: [AppShortcut] {
        AppShortcut(
            intent: CheapestFuelIntent(),
            phrases: [
                "Ask \(.applicationName) what's the cheapest \(\.$fuel) near me",
                "Find the cheapest \(\.$fuel) near me \(.applicationName)",
                "Cheapest \(\.$fuel) near me \(.applicationName)",
            ],
            shortTitle: "Cheapest Fuel",
            systemImageName: "fuelpump"
        )
    }
}