struct UserRegistered: PrismEvent {
    let userId: Int
    let email: String
}

struct OrderPlaced: PrismEvent {
    let orderId: Int
    let total: Double
    let userId: Int
}

struct PaymentFailed: PrismEvent {
    let orderId: Int
    let reason: String
}

let bus = PrismEventBus()

// Subscribe to user registrations
await bus.on(UserRegistered.self) { event in
    print("New user: \(event.email)")
    // Send welcome email, create default settings, etc.
}

// Subscribe to orders
await bus.on(OrderPlaced.self) { event in
    print("Order #\(event.orderId) for $\(event.total)")
    // Update inventory, notify warehouse, etc.
}

await bus.once(PaymentFailed.self) { event in
    print("First payment failure: \(event.reason)")
    // Alert on-call, only triggers once
}

// From a route handler
await server.post("/users") { request in
    let user = try createUser(from: request)

    await bus.emit(UserRegistered(userId: user.id, email: user.email))

    return .json(["id": user.id], status: .created)
}

await server.post("/orders") { request in
    let order = try processOrder(from: request)

    await bus.emit(OrderPlaced(
        orderId: order.id,
        total: order.total,
        userId: order.userId
    ))

    return .json(["orderId": order.id], status: .created)
}

// Define audit events
struct AuditEvent: PrismEvent {
    let action: String
    let userId: Int?
    let resource: String
    let details: String
}

// Subscribe — writes to database
await bus.on(AuditEvent.self) { event in
    try? await db.execute(
        "INSERT INTO audit_log (action, user_id, resource, details, created_at) VALUES (?, ?, ?, ?, datetime('now'))",
        parameters: [
            .text(event.action),
            event.userId.map { .integer($0) } ?? .null,
            .text(event.resource),
            .text(event.details)
        ]
    )
}

// Emit from routes
await server.delete("/users/:id") { request in
    let id = Int(request.parameters["id"] ?? "")!
    try await db.execute("DELETE FROM users WHERE id = ?", parameters: [.integer(id)])

    await bus.emit(AuditEvent(
        action: "DELETE",
        userId: id,
        resource: "users",
        details: "User account deleted"
    ))

    return PrismHTTPResponse(status: .noContent)
}

// on() returns a listener ID
let listenerId = await bus.on(UserRegistered.self) { event in
    print(event.email)
}

// Remove specific listener
await bus.off(id: listenerId)

// Remove all listeners for an event type
await bus.removeAll(for: UserRegistered.self)

// Check listener count
let count = await bus.listenerCount(for: OrderPlaced.self)

await bus.on(PrismServerStarted.self) { event in
    print("Server running on \(event.host):\(event.port)")
}

await bus.on(PrismServerStopped.self) { _ in
    print("Server stopped")
}

await bus.on(PrismRequestCompleted.self) { event in
    print("\(event.method) \(event.path) → \(event.statusCode) (\(event.duration))")
}

await bus.on(PrismServerError.self) { event in
    print("Error: \(event.error) at \(event.path ?? "unknown")")
}