import XCTest
import CryptoKit
@testable import Closer

final class CoupleEncryptionManagerTests: XCTestCase {
    func testWrapUnwrapRoundTrip() throws {
        let key = try CoupleEncryptionManager.generateCoupleKey()
        let phrase = try RecoveryKeyManager.generatePhrase()
        let wrapped = try CoupleEncryptionManager.wrap(key, with: phrase)
        XCTAssertEqual(wrapped.kdfParams, CoupleEncryptionManager.kdfParamsTag)
        XCTAssertEqual(wrapped.kdfSalt.count, CoupleEncryptionManager.saltBytes)
        // Ciphertext includes nonce (12) + at least 1 byte plaintext + tag (16).
        XCTAssertGreaterThanOrEqual(wrapped.ciphertext.count, 29)

        let unwrapped = try CoupleEncryptionManager.unwrap(wrapped, with: phrase)
        XCTAssertEqual(unwrapped.rawKey.bytes, key.rawKey.bytes)
    }

    func testBadPhraseRejects() throws {
        let key = try CoupleEncryptionManager.generateCoupleKey()
        let phrase = try RecoveryKeyManager.generatePhrase()
        let wrapped = try CoupleEncryptionManager.wrap(key, with: phrase)
        let wrongPhrase = RecoveryKeyManager.normalize(phrase) + " wrong"
        XCTAssertThrowsError(try CoupleEncryptionManager.unwrap(wrapped, with: wrongPhrase))
    }

    func testInvitePhraseEncryptionRoundTrip() throws {
        let phrase = try RecoveryKeyManager.generatePhrase()
        let inviteCode = "ABC123"
        let blob = try CoupleEncryptionManager.encryptRecoveryPhrase(phrase, with: inviteCode)
        let recovered = try CoupleEncryptionManager.decryptRecoveryPhrase(blob, with: inviteCode)
        XCTAssertEqual(recovered, phrase)
    }

    func testInvitePhraseBadCodeRejects() throws {
        let phrase = try RecoveryKeyManager.generatePhrase()
        let blob = try CoupleEncryptionManager.encryptRecoveryPhrase(phrase, with: "ABC123")
        XCTAssertThrowsError(try CoupleEncryptionManager.decryptRecoveryPhrase(blob, with: "ABC124"))
    }

    /// Loads the Argon2id canonical fixture and asserts libsodium output matches.
    ///
    /// The expected value is a TODO_ANDROID_RUN placeholder until a paired CI run fills it.
    func testArgon2idKnownVector() throws {
        let fixture = try loadArgon2idFixture()

        guard let salt = dataFromHex(fixture.saltHex) else {
            XCTFail("Invalid salt_hex in fixture")
            return
        }

        let kek = try CoupleEncryptionManager.unwrapKEK(phrase: fixture.passwordUTF8, salt: salt)
        let kekHex = kek.bytes.map { String(format: "%02x", $0) }.joined()

        if fixture.expectedOutputHex == "TODO_ANDROID_RUN" {
            XCTSkip("Argon2id fixture needs Android BouncyCastle output")
        } else {
            XCTAssertEqual(kekHex, fixture.expectedOutputHex, "Argon2id known vector mismatch")
        }
    }

    // MARK: - Fixture helpers

    private struct Argon2idFixture: Decodable {
        let name: String
        let passwordUTF8: String
        let saltHex: String
        let params: Argon2idParams
        let expectedOutputHex: String

        enum CodingKeys: String, CodingKey {
            case name
            case passwordUTF8 = "password_utf8"
            case saltHex = "salt_hex"
            case params
            case expectedOutputHex = "expected_output_hex"
        }
    }

    private struct Argon2idParams: Decodable {
        let mKib: Int
        let t: Int
        let p: Int
        let version: Int

        enum CodingKeys: String, CodingKey {
            case mKib = "m_kib"
            case t
            case p
            case version
        }
    }

    private func loadArgon2idFixture() throws -> Argon2idFixture {
        let bundle = Bundle(for: type(of: self))
        guard let url = bundle.url(
            forResource: "argon2id_canonical_fixtures",
            withExtension: "json"
        ) else {
            throw XCTSkip("argon2id_canonical_fixtures.json not found in test bundle")
        }
        let data = try Data(contentsOf: url)
        let fixtures = try JSONDecoder().decode([Argon2idFixture].self, from: data)
        guard let first = fixtures.first else {
            throw XCTSkip("No Argon2id fixtures found")
        }
        return first
    }

    private func dataFromHex(_ hex: String) -> Data? {
        guard hex.count % 2 == 0 else { return nil }
        var data = Data(capacity: hex.count / 2)
        for i in stride(from: 0, to: hex.count, by: 2) {
            let start = hex.index(hex.startIndex, offsetBy: i)
            let end = hex.index(start, offsetBy: 2)
            guard let byte = UInt8(hex[start..<end], radix: 16) else { return nil }
            data.append(byte)
        }
        return data
    }

    /// Known-vector test (iOS self-consistency).
    ///
    /// Uses the first 10 words of the bundled wordlist and a deterministic salt.
    /// The expected SHA-256 of the unwrapped key is a placeholder until the test
    /// can be executed on macOS/CI where libsodium Argon2id is available.
    ///
    /// TODO(Batch 3 follow-up): replace `expectedHash` with the real output from
    /// a Mac/CI run, then add a matching BouncyCastle vector from Android.
    func testKnownVectorUnwrapPlaceholder() throws {
        let words = try Wordlist.load()
        let phrase = words.prefix(10).joined(separator: " ")
        let salt = Data((0x00...0x0F).map { $0 })

        let key = CoupleKeyMaterial(rawBytes: Data(repeating: 0xCD, count: 32))
        let kek = try CoupleEncryptionManager.unwrapKEK(phrase: phrase, salt: salt)
        let wrappedCiphertext = try FieldEncryptor.encrypt(
            key.rawKey.bytes,
            key: kek,
            aad: CoupleEncryptionManager.coupleKeyAAD.data(using: .utf8)
        )
        let wrapped = WrappedCoupleKey(
            ciphertext: wrappedCiphertext,
            kdfSalt: salt,
            kdfParams: CoupleEncryptionManager.kdfParamsTag
        )

        let unwrapped = try CoupleEncryptionManager.unwrap(wrapped, with: phrase)
        let hash = SHA256.hash(data: unwrapped.rawKey.bytes)
        let hashHex = hash.compactMap { String(format: "%02x", $0) }.joined()

        // Placeholder: libsodium Argon2id cannot run in this Linux environment.
        // Replace with the real hash after a Mac/CI run.
        let placeholderHash = "0000000000000000000000000000000000000000000000000000000000000000"
        XCTAssertNotEqual(hashHex, placeholderHash, "Expected hash placeholder must be updated on macOS/CI")

        // The real assertion (commented out until the Mac/CI run provides the value):
        // let expectedHash = "REPLACE_WITH_MAC_CI_HASH"
        // XCTAssertEqual(hashHex, expectedHash)

        // Document cross-platform gap in the test output.
        XCTAssertTrue(
            hashHex.count == 64,
            "Hash must be 64 hex chars. Cross-platform BouncyCastle↔libsodium verification requires a paired CI run (Android emulator + iOS simulator + shared fixture)."
        )
    }
}