// SPDX-FileCopyrightText: 2021 Carl Schwan <carlschwan@kde.org>
//
// SPDX-License-Identifier: LGPL-2.1-or-later

#include "qolmaccount.h"

#include "connection.h"
#include "e2ee/qolmsession.h"
#include "e2ee/qolmutility.h"
#include "e2ee/qolmutils.h"

#include "csapi/keys.h"

#include <QtCore/QRandomGenerator>

#include <olm/olm.h>

using namespace Quotient;

QHash<QString, QString> OneTimeKeys::curve25519() const
{
    return keys[Curve25519Key];
}

//std::optional<QHash<QString, QString>> OneTimeKeys::get(QString keyType) const
//{
//    if (!keys.contains(keyType)) {
//        return std::nullopt;
//    }
//    return keys[keyType];
//}

// Convert olm error to enum
QOlmError lastError(OlmAccount *account) {
    return fromString(olm_account_last_error(account));
}

QOlmAccount::QOlmAccount(const QString& userId, const QString& deviceId,
                         QObject* parent)
    : QObject(parent)
    , m_userId(userId)
    , m_deviceId(deviceId)
{}

QOlmAccount::~QOlmAccount()
{
    olm_clear_account(m_account);
    delete[](reinterpret_cast<uint8_t *>(m_account));
}

void QOlmAccount::createNewAccount()
{
    m_account = olm_account(new uint8_t[olm_account_size()]);
    size_t randomSize = olm_create_account_random_length(m_account);
    QByteArray randomData = getRandom(randomSize);
    const auto error = olm_create_account(m_account, randomData.data(), randomSize);
    if (error == olm_error()) {
        throw lastError(m_account);
    }
    emit needsSave();
}

void QOlmAccount::unpickle(QByteArray &pickled, const PicklingMode &mode)
{
    m_account = olm_account(new uint8_t[olm_account_size()]);
    const QByteArray key = toKey(mode);
    const auto error = olm_unpickle_account(m_account, key.data(), key.length(), pickled.data(), pickled.size());
    if (error == olm_error()) {
        qCWarning(E2EE) << "Failed to unpickle olm account";
        //TODO: Do something that is not dying
        // Probably log the user out since we have no way of getting to the keys
        //throw lastError(m_account);
    }
}

std::variant<QByteArray, QOlmError> QOlmAccount::pickle(const PicklingMode &mode)
{
    const QByteArray key = toKey(mode);
    const size_t pickleLength = olm_pickle_account_length(m_account);
    QByteArray pickleBuffer(pickleLength, '0');
    const auto error = olm_pickle_account(m_account, key.data(),
                key.length(), pickleBuffer.data(), pickleLength);
    if (error == olm_error()) {
        return lastError(m_account);
    }
    return pickleBuffer;
}

IdentityKeys QOlmAccount::identityKeys() const
{
    const size_t keyLength = olm_account_identity_keys_length(m_account);
    QByteArray keyBuffer(keyLength, '0');
    const auto error = olm_account_identity_keys(m_account, keyBuffer.data(), keyLength);
    if (error == olm_error()) {
        throw lastError(m_account);
    }
    const QJsonObject key = QJsonDocument::fromJson(keyBuffer).object();
    return IdentityKeys {
        key.value(QStringLiteral("curve25519")).toString().toUtf8(),
        key.value(QStringLiteral("ed25519")).toString().toUtf8()
    };
}

QByteArray QOlmAccount::sign(const QByteArray &message) const
{
    QByteArray signatureBuffer(olm_account_signature_length(m_account), '0');

    const auto error = olm_account_sign(m_account, message.data(), message.length(),
            signatureBuffer.data(), signatureBuffer.length());

    if (error == olm_error()) {
        throw lastError(m_account);
    }
    return signatureBuffer;
}

QByteArray QOlmAccount::sign(const QJsonObject &message) const
{
    return sign(QJsonDocument(message).toJson(QJsonDocument::Compact));
}

QByteArray QOlmAccount::signIdentityKeys() const
{
    const auto keys = identityKeys();
    QJsonObject body
    {
        {"algorithms", QJsonArray{"m.olm.v1.curve25519-aes-sha2", "m.megolm.v1.aes-sha2"}},
        {"user_id", m_userId},
        {"device_id", m_deviceId},
        {"keys",
            QJsonObject{
                {QStringLiteral("curve25519:") + m_deviceId, QString::fromUtf8(keys.curve25519)},
                {QStringLiteral("ed25519:") + m_deviceId, QString::fromUtf8(keys.ed25519)}
            }
        }
    };
    return sign(QJsonDocument(body).toJson(QJsonDocument::Compact));

}

size_t QOlmAccount::maxNumberOfOneTimeKeys() const
{
    return olm_account_max_number_of_one_time_keys(m_account);
}

size_t QOlmAccount::generateOneTimeKeys(size_t numberOfKeys)
{
    const size_t randomLength = olm_account_generate_one_time_keys_random_length(m_account, numberOfKeys);
    QByteArray randomBuffer = getRandom(randomLength);
    const auto error = olm_account_generate_one_time_keys(m_account, numberOfKeys, randomBuffer.data(), randomLength);

    if (error == olm_error()) {
        throw lastError(m_account);
    }
    emit needsSave();
    return error;
}

OneTimeKeys QOlmAccount::oneTimeKeys() const
{
    const size_t oneTimeKeyLength = olm_account_one_time_keys_length(m_account);
    QByteArray oneTimeKeysBuffer(oneTimeKeyLength, '0');

    const auto error = olm_account_one_time_keys(m_account, oneTimeKeysBuffer.data(), oneTimeKeyLength);
    if (error == olm_error()) {
        throw lastError(m_account);
    }
    const auto json = QJsonDocument::fromJson(oneTimeKeysBuffer).object();
    OneTimeKeys oneTimeKeys;
    fromJson(json, oneTimeKeys.keys);
    return oneTimeKeys;
}

QHash<QString, SignedOneTimeKey> QOlmAccount::signOneTimeKeys(const OneTimeKeys &keys) const
{
    QHash<QString, SignedOneTimeKey> signedOneTimeKeys;
    for (const auto &keyid : keys.curve25519().keys()) {
        const auto oneTimeKey = keys.curve25519()[keyid];
        QByteArray sign = signOneTimeKey(oneTimeKey);
        signedOneTimeKeys["signed_curve25519:" + keyid] = signedOneTimeKey(oneTimeKey.toUtf8(), sign);
    }
    return signedOneTimeKeys;
}

SignedOneTimeKey QOlmAccount::signedOneTimeKey(const QByteArray &key, const QString &signature) const
{
    SignedOneTimeKey sign{};
    sign.key = key;
    sign.signatures = {{m_userId, {{"ed25519:" + m_deviceId, signature}}}};
    return sign;
}

QByteArray QOlmAccount::signOneTimeKey(const QString &key) const
{
    QJsonDocument j(QJsonObject{{"key", key}});
    return sign(j.toJson(QJsonDocument::Compact));
}

std::optional<QOlmError> QOlmAccount::removeOneTimeKeys(
    const QOlmSessionPtr& session)
{
    const auto error = olm_remove_one_time_keys(m_account, session->raw());

    if (error == olm_error()) {
        return lastError(m_account);
    }
    emit needsSave();
    return std::nullopt;
}

OlmAccount* QOlmAccount::data() { return m_account; }

DeviceKeys QOlmAccount::deviceKeys() const
{
    DeviceKeys deviceKeys;
    deviceKeys.userId = m_userId;
    deviceKeys.deviceId = m_deviceId;
    deviceKeys.algorithms = QStringList {"m.olm.v1.curve25519-aes-sha2", "m.megolm.v1.aes-sha2"};

    const auto idKeys = identityKeys();
    deviceKeys.keys["curve25519:" + m_deviceId] = idKeys.curve25519;
    deviceKeys.keys["ed25519:" + m_deviceId] = idKeys.ed25519;

    const auto sign = signIdentityKeys();
    deviceKeys.signatures[m_userId]["ed25519:" + m_deviceId] = sign;

    return deviceKeys;
}

UploadKeysJob *QOlmAccount::createUploadKeyRequest(const OneTimeKeys &oneTimeKeys)
{
    auto keys = deviceKeys();

    if (oneTimeKeys.curve25519().isEmpty()) {
        return new UploadKeysJob(keys);
    }

    // Sign & append the one time keys.
    auto temp = signOneTimeKeys(oneTimeKeys);
    QHash<QString, QVariant> oneTimeKeysSigned;
    for (const auto &[keyId, key] : asKeyValueRange(temp)) {
        oneTimeKeysSigned[keyId] = QVariant::fromValue(toJson(key));
    }

    return new UploadKeysJob(keys, oneTimeKeysSigned);
}

std::variant<QOlmSessionPtr, QOlmError> QOlmAccount::createInboundSession(const QOlmMessage &preKeyMessage)
{
    Q_ASSERT(preKeyMessage.type() == QOlmMessage::PreKey);
    return QOlmSession::createInboundSession(this, preKeyMessage);
}

std::variant<QOlmSessionPtr, QOlmError> QOlmAccount::createInboundSessionFrom(const QByteArray &theirIdentityKey, const QOlmMessage &preKeyMessage)
{
    Q_ASSERT(preKeyMessage.type() == QOlmMessage::PreKey);
    return QOlmSession::createInboundSessionFrom(this, theirIdentityKey, preKeyMessage);
}

std::variant<QOlmSessionPtr, QOlmError> QOlmAccount::createOutboundSession(const QByteArray &theirIdentityKey, const QByteArray &theirOneTimeKey)
{
    return QOlmSession::createOutboundSession(this, theirIdentityKey, theirOneTimeKey);
}

void QOlmAccount::markKeysAsPublished()
{
    olm_account_mark_keys_as_published(m_account);
    emit needsSave();
}

bool Quotient::verifyIdentitySignature(const DeviceKeys& deviceKeys,
                                       const QString& deviceId,
                                       const QString& userId)
{
    const auto signKeyId = "ed25519:" + deviceId;
    const auto signingKey = deviceKeys.keys[signKeyId];
    const auto signature = deviceKeys.signatures[userId][signKeyId];

    return ed25519VerifySignature(signingKey, toJson(deviceKeys), signature);
}

bool Quotient::ed25519VerifySignature(const QString& signingKey,
                                      const QJsonObject& obj,
                                      const QString& signature)
{
    if (signature.isEmpty())
        return false;

    QJsonObject obj1 = obj;

    obj1.remove("unsigned");
    obj1.remove("signatures");

    auto canonicalJson = QJsonDocument(obj1).toJson(QJsonDocument::Compact);

    QByteArray signingKeyBuf = signingKey.toUtf8();
    QOlmUtility utility;
    auto signatureBuf = signature.toUtf8();
    auto result = utility.ed25519Verify(signingKeyBuf, canonicalJson, signatureBuf);
    if (std::holds_alternative<QOlmError>(result)) {
        return false;
    }

    return std::get<bool>(result);
}