import Foundation

/// Whisper sometimes answers a vocabulary prompt with the prompt itself when there is little speech.
public enum PromptEcho {
    static func normalize(_ text: String) -> String {
        String(text.lowercased().map { $0.isLetter || $0.isNumber ? $0 : " " })
            .split(separator: " ")
            .joined(separator: " ")
    }

    /// True when `text` is nothing but the first k ≥ 2 terms of the prompt.
    /// A single term on its own is valid speech ("Anthropic").
    public static func isEcho(_ text: String, vocabulary: [String]) -> Bool {
        guard vocabulary.count >= 2 else { return false }
        let normalized = normalize(text)
        guard !normalized.isEmpty else { return false }
        return (2...vocabulary.count).contains { k in
            normalize(vocabulary.prefix(k).joined(separator: " ")) == normalized
        }
    }
}