import Foundation
import CryptoKit

/// spec, раздел "Мнемоника и seed → Каноническая wordlist".
/// 2048 lowercase ASCII слов, sorted lexicographically.
/// Binding fingerprint: SHA-256(canonical_bytes) =
///   2f5eed53a4727b4bf8880d8f3f199efc90e58503646d9ff8eff3a2ed3b24dbda
enum Wordlist {
    static let canonical: [String] = {
        guard let url = Bundle.main.url(forResource: "wordlist", withExtension: "txt"),
              let raw = try? String(contentsOf: url, encoding: .ascii)
        else {
            fatalError("Resources/wordlist.txt отсутствует или повреждён")
        }
        let words = raw.split(separator: "\n").map { String($0) }
        precondition(words.count == 2048, "wordlist должен содержать ровно 2048 слов, получено \(words.count)")
        return words
    }()

    /// Binary search index слова в canonical wordlist.
    static func index(of word: String) -> UInt16? {
        var lo = 0
        var hi = canonical.count
        while lo < hi {
            let mid = (lo + hi) / 2
            if canonical[mid] < word {
                lo = mid + 1
            } else if canonical[mid] > word {
                hi = mid
            } else {
                return UInt16(mid)
            }
        }
        return nil
    }

    /// Verify binding fingerprint при старте приложения (spec обязательное правило).
    static func verifyBindingFingerprint() -> Bool {
        let canonicalBytes = canonical.map { $0 + "\n" }.joined().data(using: .ascii)!
        let hash = SHA256.hash(data: canonicalBytes)
        let hex = hash.map { String(format: "%02x", $0) }.joined()
        return hex == "2f5eed53a4727b4bf8880d8f3f199efc90e58503646d9ff8eff3a2ed3b24dbda"
    }
}