import Foundation

protocol LoginUseCase: Sendable {
    func execute(salesCode: String) async throws -> LoginSession
}

/// Shared by the use case and the form so that both enforce the same rule.
enum SalesCodeValidator {
    static func normalized(_ input: String) -> String {
        input.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
    }

    static func isValid(_ input: String) -> Bool {
        normalized(input).count >= 3
    }
}

struct DefaultLoginUseCase: LoginUseCase {
    let authenticationService: any AuthenticationService

    func execute(salesCode: String) async throws -> LoginSession {
        guard SalesCodeValidator.isValid(salesCode) else {
            throw LoginError.invalidSalesCode
        }
        try Task.checkCancellation()
        return try await authenticationService.signIn(
            salesCode: SalesCodeValidator.normalized(salesCode)
        )
    }
}