import Foundation
import NaturalLanguage

/// Uses Apple's bundled sentence embeddings when the language asset exists.
/// Distances are converted to a stable 0...1 ranking signal only within one
/// query; callers must not compare values across embedding revisions.
public struct RDAINaturalLanguageSemanticScorer: RDAISemanticScoring {
    public init() {}

    public func score(query: String, text: String, languageCode: String?) async -> Double? {
        await Task.detached(priority: .utility) {
            let language = languageCode.flatMap(NLLanguage.init(rawValue:)) ?? .english
            guard let embedding = NLEmbedding.sentenceEmbedding(for: language) else { return nil }
            let distance = embedding.distance(between: query, and: text)
            guard distance.isFinite else { return nil }
            return 1 / (1 + Double(distance))
        }.value
    }
}