import Foundation
import SwiftUI

/// Минимальный держатель identity для первой итерации.
/// Полные derived keys (ML-DSA + ML-KEM) — Phase 2 (FFI к Rust).
struct Identity: Equatable {
    let masterSeed: Data
    let accountIdHex: String
    let mnemonic: String?
}

@MainActor
final class IdentityManager: ObservableObject {
    @Published private(set) var identity: Identity?

    private let storageKey = "MontanaIdentity_v1"

    init() {}

    /// Загрузить existing identity из Keychain (если есть).
    func loadIfPresent() {
        guard let data = KeychainStore.read(key: storageKey),
              let stored = try? JSONDecoder().decode(StoredIdentity.self, from: data) else {
            return
        }
        identity = Identity(
            masterSeed: stored.masterSeed,
            accountIdHex: stored.accountIdHex,
            mnemonic: nil
        )
    }

    /// Создать новую identity из случайной мнемоники.
    func createNew() throws -> String {
        let mnemonic = Mnemonic.generate()
        try install(mnemonic: mnemonic)
        return mnemonic
    }

    /// Восстановить identity из существующей мнемоники.
    func restore(from mnemonic: String) throws {
        try install(mnemonic: mnemonic)
    }

    /// Стереть identity локально (для тестов / переустановки).
    func wipe() {
        KeychainStore.delete(key: storageKey)
        identity = nil
    }

    private func install(mnemonic: String) throws {
        let masterSeed = try Mnemonic.decodeAndDerive(mnemonic: mnemonic)
        // Placeholder account_id = SHA-256("mt-account-placeholder" || masterSeed[0..16])
        // Реальный account_id = SHA-256("mt-account" || pubkey_suite || ml_dsa_pubkey) — Phase 2
        let accountIdHex = HashUtil.sha256Hex(prefix: "mt-account-placeholder", body: masterSeed.prefix(16))

        let stored = StoredIdentity(masterSeed: masterSeed, accountIdHex: accountIdHex)
        let data = try JSONEncoder().encode(stored)
        KeychainStore.write(key: storageKey, value: data)

        identity = Identity(masterSeed: masterSeed, accountIdHex: accountIdHex, mnemonic: mnemonic)
    }
}

private struct StoredIdentity: Codable {
    let masterSeed: Data
    let accountIdHex: String
}