// 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;

// 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);
    }
}

QOlmExpected<QByteArray> 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();
    return sign(QJsonObject {
        { "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) } } } });
}

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;
}

UnsignedOneTimeKeys 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();
    UnsignedOneTimeKeys oneTimeKeys;
    fromJson(json, oneTimeKeys.keys);
    return oneTimeKeys;
}

OneTimeKeys QOlmAccount::signOneTimeKeys(const UnsignedOneTimeKeys &keys) const
{
    OneTimeKeys signedOneTimeKeys;
    const auto& curveKeys = keys.curve25519();
    for (const auto& [keyId, key] : asKeyValueRange(curveKeys))
        signedOneTimeKeys["signed_curve25519:" % keyId] =
            signedOneTimeKey(key.toUtf8(), sign(QJsonObject{{"key", key}}));
    return signedOneTimeKeys;
}

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

std::optional<QOlmError> QOlmAccount::removeOneTimeKeys(
    const QOlmSession& 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 UnsignedOneTimeKeys& oneTimeKeys) const
{
    return new UploadKeysJob(deviceKeys(), signOneTimeKeys(oneTimeKeys));
}

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

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

QOlmExpected<QOlmSessionPtr> 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();
    return utility.ed25519Verify(signingKeyBuf, canonicalJson, signatureBuf)
        .value_or(false);
}