import Foundation

public protocol SunoOutputValidating: Sendable {
    func validate(_ output: CompiledSunoOutput) throws
}

public enum SunoOutputValidationError: Error, Equatable, LocalizedError, Sendable {
    case missingContent

    public var errorDescription: String? {
        switch self {
        case .missingContent:
            return "Add lyrics or a style prompt before finalizing the song output."
        }
    }
}

public struct CompiledSunoOutputValidator: SunoOutputValidating {
    public init() {}

    public func validate(_ output: CompiledSunoOutput) throws {
        let lyrics = output.lyricsText.trimmingCharacters(in: .whitespacesAndNewlines)
        let style = output.stylePrompt.trimmingCharacters(in: .whitespacesAndNewlines)

        guard !lyrics.isEmpty || !style.isEmpty else {
            throw SunoOutputValidationError.missingContent
        }
    }
}