#include "sshclient.h"

#include <QEventLoop>
#include <QtConcurrent>

#include <fstream>

#ifdef Q_OS_WINDOWS
const uint32_t S_IRWXU = 0644;
#endif

namespace libssh {
    const QString libsshTimeoutError = "Timeout connecting to";

    std::function<QString()> Client::m_passphraseCallback;

    Client::Client(QObject *parent) : QObject(parent)
    { }

    Client::~Client()
    { }

    int Client::callback(const char *prompt, char *buf, size_t len, int echo, int verify, void *userdata)
    {
        auto passphrase = m_passphraseCallback();
        passphrase.toStdString().copy(buf, passphrase.size() + 1);
        return 0;
    }

    ErrorCode Client::connectToHost(const ServerCredentials &credentials)
    {
        if (m_session == nullptr) {
            m_session = ssh_new();

            if (m_session == nullptr) {
                qDebug() << "Failed to create ssh session";
                return ErrorCode::InternalError;
            }

            int port = credentials.port;
            int logVerbosity = SSH_LOG_NOLOG;
            std::string hostIp = credentials.hostName.toStdString();
            std::string hostUsername = credentials.userName.toStdString() + "@" + hostIp;

            ssh_options_set(m_session, SSH_OPTIONS_HOST, hostIp.c_str());
            ssh_options_set(m_session, SSH_OPTIONS_PORT, &port);
            ssh_options_set(m_session, SSH_OPTIONS_USER, hostUsername.c_str());
            ssh_options_set(m_session, SSH_OPTIONS_LOG_VERBOSITY, &logVerbosity);

            QFutureWatcher<int> watcher;
            QFuture<int> future = QtConcurrent::run([this]() {
                return ssh_connect(m_session);
            });

            QEventLoop wait;
            connect(&watcher, &QFutureWatcher<ErrorCode>::finished, &wait, &QEventLoop::quit);
            watcher.setFuture(future);
            wait.exec();

            int connectionResult = watcher.result();

            if (connectionResult != SSH_OK) {
                return fromLibsshErrorCode();
            }

            std::string authUsername = credentials.userName.toStdString();

            int authResult = SSH_ERROR;
            if (credentials.secretData.contains("BEGIN") && credentials.secretData.contains("PRIVATE KEY")) {
                ssh_key privateKey = nullptr;
                ssh_key publicKey = nullptr;
                authResult = ssh_pki_import_privkey_base64(credentials.secretData.toStdString().c_str(), nullptr, callback, nullptr, &privateKey);
                if (authResult == SSH_OK) {
                    authResult = ssh_pki_export_privkey_to_pubkey(privateKey, &publicKey);
                }

                if (authResult == SSH_OK) {
                    authResult = ssh_userauth_try_publickey(m_session, authUsername.c_str(), publicKey);
                }

                if (authResult == SSH_OK) {
                    authResult = ssh_userauth_publickey(m_session, authUsername.c_str(), privateKey);
                }

                if (publicKey) {
                    ssh_key_free(publicKey);
                }
                if (privateKey) {
                    ssh_key_free(privateKey);
                }
                if (authResult != SSH_OK) {
                    qCritical() << ssh_get_error(m_session);
                    ErrorCode errorCode = fromLibsshErrorCode();
                    if (errorCode == ErrorCode::NoError) {
                        errorCode = ErrorCode::SshPrivateKeyFormatError;
                    }
                    return errorCode;
                }
            } else {
                authResult = ssh_userauth_password(m_session, authUsername.c_str(), credentials.secretData.toStdString().c_str());
                if (authResult != SSH_OK) {
                    return fromLibsshErrorCode();
                }
            }
        }
        return ErrorCode::NoError;
    }

    void Client::disconnectFromHost()
    {
        if (m_session != nullptr) {
            if (ssh_is_connected(m_session)) {
                ssh_disconnect(m_session);
            }
            ssh_free(m_session);
            m_session = nullptr;
        }
    }

    ErrorCode Client::executeCommand(const QString &data,
                                        const std::function<ErrorCode (const QString &, Client &)> &cbReadStdOut,
                                        const std::function<ErrorCode (const QString &, Client &)> &cbReadStdErr)
    {
        m_channel = ssh_channel_new(m_session);

        if (m_channel == nullptr) {
            return closeChannel();
        }

        int result = ssh_channel_open_session(m_channel);

        if (result == SSH_OK && ssh_channel_is_open(m_channel)) {
            qDebug() << "SSH chanel opened";
        } else {
            return closeChannel();
        }

        QFutureWatcher<ErrorCode> watcher;
        connect(&watcher, &QFutureWatcher<ErrorCode>::finished, this, &Client::writeToChannelFinished);

        QFuture<ErrorCode> future = QtConcurrent::run([this, &data, &cbReadStdOut, &cbReadStdErr]() {
            const size_t bufferSize = 2048;

            int bytesRead = 0;
            char buffer[bufferSize];

            int result = ssh_channel_request_exec(m_channel, data.toUtf8());
            if (result == SSH_OK) {
                std::string output;
                auto readOutput = [&](bool isStdErr) {
                    bytesRead = ssh_channel_read(m_channel, buffer, sizeof(buffer), isStdErr);
                    while (bytesRead > 0)
                    {
                        output = std::string(buffer, bytesRead);
                        if (!output.empty()) {
                            if (cbReadStdOut && !isStdErr){
                                auto error = cbReadStdOut(output.c_str(), *this);
                                if (error != ErrorCode::NoError) {
                                    return error;
                                }
                            }
                            if (cbReadStdErr && isStdErr){
                                auto error = cbReadStdErr(output.c_str(), *this);
                                if (error != ErrorCode::NoError) {
                                    return error;
                                }
                            }
                        }
                        bytesRead = ssh_channel_read(m_channel, buffer, sizeof(buffer), isStdErr);
                    }
                    return ErrorCode::NoError;
                };

                auto error = readOutput(false);
                if (error != ErrorCode::NoError) {
                    return error;
                }
                error = readOutput(true);
                if (error != ErrorCode::NoError) {
                    return error;
                }
            } else {
                return closeChannel();
            }
            return closeChannel();
        });
        watcher.setFuture(future);

        QEventLoop wait;
        QObject::connect(this, &Client::writeToChannelFinished, &wait, &QEventLoop::quit);
        wait.exec();

        return watcher.result();
    }

    ErrorCode Client::writeResponse(const QString &data)
    {
        if (m_channel == nullptr) {
            qCritical() << "ssh channel not initialized";
            return fromLibsshErrorCode();
        }

        int bytesWritten = ssh_channel_write(m_channel, data.toUtf8(), (uint32_t)data.size());
        if (bytesWritten == data.size() && ssh_channel_write(m_channel, "\n", 1)) {
            return fromLibsshErrorCode();
        }
        return fromLibsshErrorCode();
    }

    ErrorCode Client::closeChannel()
    {
        if (m_channel != nullptr) {
            if (ssh_channel_is_eof(m_channel)) {
                ssh_channel_send_eof(m_channel);
            }
            if (ssh_channel_is_open(m_channel)) {
                ssh_channel_close(m_channel);
            }
            ssh_channel_free(m_channel);
            m_channel = nullptr;
        }
        return fromLibsshErrorCode();
    }

    ErrorCode Client::sftpFileCopy(const SftpOverwriteMode overwriteMode, const std::string& localPath, const std::string& remotePath, const std::string& fileDesc)
    {
        m_sftpSession = sftp_new(m_session);

        if (m_sftpSession == nullptr) {
            return closeSftpSession();
        }

        int result = sftp_init(m_sftpSession);

        if (result != SSH_OK) {
            return closeSftpSession();
        }

        QFutureWatcher<ErrorCode> watcher;
        connect(&watcher, &QFutureWatcher<ErrorCode>::finished, this, &Client::sftpFileCopyFinished);

        QFuture<ErrorCode> future = QtConcurrent::run([this, overwriteMode, &localPath, &remotePath, &fileDesc]() {
            int accessType = O_WRONLY | O_CREAT | overwriteMode;
            sftp_file file;
            const size_t bufferSize = 16384;
            char buffer[bufferSize];

            file = sftp_open(m_sftpSession, remotePath.c_str(), accessType, S_IRWXU);

            if (file == nullptr) {
                return closeSftpSession();
            }

            int localFileSize = std::filesystem::file_size(localPath);
            int chunksCount = localFileSize / (bufferSize);

            std::ifstream fin(localPath, std::ios::binary | std::ios::in);

            if (fin.is_open()) {
                for (int currentChunkId = 0; currentChunkId < chunksCount; currentChunkId++) {
                    fin.read(buffer, bufferSize);

                    int bytesWritten = sftp_write(file, buffer, bufferSize);

                    std::string chunk(buffer, bufferSize);

                    if (bytesWritten != bufferSize) {
                        fin.close();
                        sftp_close(file);
                        return closeSftpSession();
                    }
                }

                int lastChunkSize = localFileSize % (bufferSize);

                if (lastChunkSize != 0) {
                    fin.read(buffer, lastChunkSize);

                    std::string chunk(buffer, lastChunkSize);

                    int bytesWritten = sftp_write(file, buffer, lastChunkSize);

                    if (bytesWritten != lastChunkSize) {
                        fin.close();
                        sftp_close(file);
                        return closeSftpSession();
                    }
                }
            } else {
                sftp_close(file);
                return closeSftpSession();
            }

            fin.close();

            int result = sftp_close(file);
            if (result != SSH_OK) {
                return closeSftpSession();
            }

            return closeSftpSession();
        });
        watcher.setFuture(future);

        QEventLoop wait;
        QObject::connect(this, &Client::sftpFileCopyFinished, &wait, &QEventLoop::quit);
        wait.exec();

        return watcher.result();
    }

    ErrorCode Client::closeSftpSession()
    {
        auto errorCode = fromLibsshSftpErrorCode(sftp_get_error(m_sftpSession));
        if (m_sftpSession != nullptr) {
            sftp_free(m_sftpSession);
            m_sftpSession = nullptr;
        }
        qCritical() << ssh_get_error(m_session);
        return errorCode;
    }

    ErrorCode Client::fromLibsshErrorCode()
    {
        int errorCode = ssh_get_error_code(m_session);
        if (errorCode != SSH_NO_ERROR) {
            QString errorMessage = ssh_get_error(m_session);
            qCritical() << errorMessage;
            if (errorMessage.contains(libsshTimeoutError)) {
                return ErrorCode::SshTimeoutError;
            }
        }

        switch (errorCode) {
        case(SSH_NO_ERROR): return ErrorCode::NoError;
        case(SSH_REQUEST_DENIED): return ErrorCode::SshRequestDeniedError;
        case(SSH_EINTR): return ErrorCode::SshInterruptedError;
        case(SSH_FATAL): return ErrorCode::SshInternalError;
        default: return ErrorCode::SshInternalError;
        }
    }
    ErrorCode Client::fromLibsshSftpErrorCode(int errorCode)
    {
        switch (errorCode) {
        case(SSH_FX_OK): return ErrorCode::NoError;
        case(SSH_FX_EOF): return ErrorCode::SshSftpEofError;
        case(SSH_FX_NO_SUCH_FILE): return ErrorCode::SshSftpNoSuchFileError;
        case(SSH_FX_PERMISSION_DENIED): return ErrorCode::SshSftpPermissionDeniedError;
        case(SSH_FX_FAILURE): return ErrorCode::SshSftpFailureError;
        case(SSH_FX_BAD_MESSAGE): return ErrorCode::SshSftpBadMessageError;
        case(SSH_FX_NO_CONNECTION): return ErrorCode::SshSftpNoConnectionError;
        case(SSH_FX_CONNECTION_LOST): return ErrorCode::SshSftpConnectionLostError;
        case(SSH_FX_OP_UNSUPPORTED): return ErrorCode::SshSftpOpUnsupportedError;
        case(SSH_FX_INVALID_HANDLE): return ErrorCode::SshSftpInvalidHandleError;
        case(SSH_FX_NO_SUCH_PATH): return ErrorCode::SshSftpNoSuchPathError;
        case(SSH_FX_FILE_ALREADY_EXISTS): return ErrorCode::SshSftpFileAlreadyExistsError;
        case(SSH_FX_WRITE_PROTECT): return ErrorCode::SshSftpWriteProtectError;
        case(SSH_FX_NO_MEDIA): return ErrorCode::SshSftpNoMediaError;
        default: return ErrorCode::SshSftpFailureError;
        }
    }

    ErrorCode Client::getDecryptedPrivateKey(const ServerCredentials &credentials, QString &decryptedPrivateKey, const std::function<QString()> &passphraseCallback)
    {
        int authResult = SSH_ERROR;
        ErrorCode errorCode = ErrorCode::NoError;

        ssh_key privateKey = nullptr;
        m_passphraseCallback = passphraseCallback;
        authResult = ssh_pki_import_privkey_base64(credentials.secretData.toStdString().c_str(), nullptr, callback, nullptr, &privateKey);
        if (authResult == SSH_OK) {
            char *b64 = nullptr;

            authResult = ssh_pki_export_privkey_base64(privateKey, nullptr, nullptr, nullptr, &b64);
            decryptedPrivateKey = QString(b64);

            if (authResult != SSH_OK) {
                qDebug() << "failed to export private key";
                errorCode = ErrorCode::InternalError;
            }
            else {
                ssh_string_free_char(b64);
            }
        } else {
            errorCode = ErrorCode::SshPrivateKeyError;
        }

        if (privateKey) {
            ssh_key_free(privateKey);
        }
        return errorCode;
    }
}