/*
    Copyright 2016 Amebis

    This file is part of Updater.

    Updater is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    Updater is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Updater. If not, see <http://www.gnu.org/licenses/>.
*/

#include "stdafx.h"


///
/// Module initializer
///
class wxUpdCheckInitializer : public wxInitializer
{
protected:
    FILE *m_pLogFile;

public:
    wxConfig m_config;
    wxString m_path;
    wxLocale m_locale;

public:
    wxUpdCheckInitializer();
    virtual ~wxUpdCheckInitializer();
};


wxUpdCheckInitializer::wxUpdCheckInitializer() :
    m_pLogFile(NULL),
    m_config(wxT(UPDATER_CFG_APPLICATION) wxT("\\Updater"), wxT(UPDATER_CFG_VENDOR)),
    wxInitializer()
{
    if (wxInitializer::IsOk()) {
        // Set desired locale.
        wxLanguage language = (wxLanguage)m_config.Read(wxT("Language"), wxLANGUAGE_DEFAULT);
        if (wxLocale::IsAvailable(language))
            wxVERIFY(m_locale.Init(language));

        if (!m_config.Read(wxT("CachePath"), &m_path))
            m_path = wxFileName::GetTempDir();
        if (!wxEndsWithPathSeparator(m_path))
            m_path += wxFILE_SEP_PATH;

        if (!wxDirExists(m_path))
            wxMkdir(m_path);

        m_pLogFile = fopen(m_path + wxT(UPDATER_LOG_FILE), "w+");
        if (m_pLogFile)
            delete wxLog::SetActiveTarget(new wxLogStderr(m_pLogFile));
    } else
        m_pLogFile = NULL;
}


wxUpdCheckInitializer::~wxUpdCheckInitializer()
{
    if (m_pLogFile != NULL) {
        delete wxLog::SetActiveTarget(NULL);
        fclose(m_pLogFile);
    }
}


///
/// Main function
///
int CALLBACK WinMain(_In_ HINSTANCE hInstance, _In_ HINSTANCE hPrevInstance, _In_ LPSTR lpCmdLine, _In_ int nCmdShow)
{
    wxApp::CheckBuildOptions(WX_BUILD_OPTIONS_SIGNATURE, "program");

    // Initialize wxWidgets.
    wxUpdCheckInitializer initializer;
    if (!initializer.IsOk())
        return -1;

    // Create RSA AES cryptographic context.
    wxCryptoSessionRSAAES cs;
    if (!cs.IsOk())
        return -1;

    // Import public key.
    wxCryptoKey ck;
    {
        HRSRC res = ::FindResource(NULL, MAKEINTRESOURCE(IDR_KEY_PUBLIC), RT_RCDATA);
        wxASSERT_MSG(res, wxT("public key not found"));
        HGLOBAL res_handle = ::LoadResource(NULL, res);
        wxASSERT_MSG(res_handle, wxT("loading resource failed"));

        if (!ck.ImportPublic(cs, ::LockResource(res_handle), ::SizeofResource(NULL, res)))
            return -1;
    }

    long val;
    wxDateTime last_checked = initializer.m_config.Read(wxT("LastChecked"), &val) ? wxDateTime((time_t)val) : wxInvalidDateTime;

    for (const wxChar *server = wxT(UPDATER_HTTP_SERVER); server[0]; server += wcslen(server) + 1) {
        wxXmlDocument doc;

        wxLogStatus(wxT("Contacting repository at %s..."), server);

        // Load repository database.
        wxHTTP http;
        if (last_checked.IsValid())
            http.SetHeader(wxS("If-Modified-Since"), last_checked.Format(wxS("%a, %d %b %Y %H:%M:%S %z")));
        if (!http.Connect(server, UPDATER_HTTP_PORT)) {
            wxLogWarning(wxT("Error resolving %s server name."), server);
            continue;
        }
        wxInputStream *httpStream = http.GetInputStream(wxS(UPDATER_HTTP_PATH));
        if (!httpStream) {
            if (http.GetResponse() == 304) {
                wxLogStatus(wxT("Repository did not change since the last time..."));
                return 0;
            }

            wxLogWarning(wxT("Error response received from server %s (port %u) requesting %s."), server, UPDATER_HTTP_PORT, UPDATER_HTTP_PATH);
            continue;
        }
        wxLogStatus(wxT("Loading repository catalogue..."));
        if (!doc.Load(*httpStream, "UTF-8", wxXMLDOC_KEEP_WHITESPACE_NODES)) {
            wxLogWarning(wxT("Error loading repository catalogue."));
            wxDELETE(httpStream);
            http.Close();
            continue;
        }
        wxDELETE(httpStream);
        http.Close();

        wxLogStatus(wxT("Verifying repository catalogue signature..."));

        // Find the (first) signature.
        wxXmlNode *document = doc.GetDocumentNode();
        std::vector<BYTE> sig;
        for (wxXmlNode *prolog = document->GetChildren(); prolog; prolog = prolog->GetNext()) {
            if (prolog->GetType() == wxXML_COMMENT_NODE) {
                wxString content = prolog->GetContent();
                size_t content_len = content.length();
                if (content_len >= _countof(wxS(UPDATER_SIGNATURE_MARK)) - 1 &&
                    memcmp((const wxStringCharType*)content, wxS(UPDATER_SIGNATURE_MARK), sizeof(wxStringCharType)*(_countof(wxS(UPDATER_SIGNATURE_MARK)) - 1)) == 0)
                {
                    // Read the signature.
                    size_t signature_len = content_len - (_countof(wxS(UPDATER_SIGNATURE_MARK)) - 1);
                    sig.resize(wxBase64DecodedSize(signature_len));
                    size_t res = wxBase64Decode(sig.data(), sig.capacity(), content.Right(signature_len), wxBase64DecodeMode_SkipWS);
                    if (res != wxCONV_FAILED) {
                        sig.resize(res);

                        // Remove the signature as it is not a part of the validation check.
                        document->RemoveChild(prolog);
                        wxDELETE(prolog);
                        break;
                    } else
                        sig.clear();
                }
            }
        }

        if (sig.empty()) {
            wxLogWarning(wxT("Signature not found in the repository catalogue."));
            continue;
        }

        // Hash the content.
        wxCryptoHashSHA1 ch(cs);
        if (!wxXmlHashNode(ch, document))
            continue;

        // We have the hash, we have the signature, we have the public key. Now verify.
        if (!wxCryptoVerifySignature(ch, sig.data(), sig.size(), ck)) {
            wxLogWarning(wxT("Repository catalogue signature does not match its content, or signature verification failed."));
            continue;
        }

        // The signature is correct. Now parse the file.
        wxLogStatus(wxT("Parsing repository catalogue..."));

        // Start processing the XML file.
        wxXmlNode *elRoot = doc.GetRoot();
        const wxString &nameRoot = elRoot->GetName();
        if (nameRoot != wxT("Packages")) {
            wxLogWarning(wxT("Invalid root element in repository catalogue (actual: %s, expected %s)."), nameRoot.c_str(), wxT("Packages"));
            continue;
        }

        // Iterate over packages.
        wxUint32 versionMax = 0;
        wxString versionStrMax;
        wxString urlMax;
        std::vector<BYTE> sigMax;
        for (wxXmlNode *elPackage = elRoot->GetChildren(); elPackage; elPackage = elPackage->GetNext()) {
            if (elPackage->GetType() == wxXML_ELEMENT_NODE && elPackage->GetName() == wxT("Package")) {
                // Get package version.
                wxUint32 version = 0;
                wxString versionStr;
                for (wxXmlNode *elVersion = elPackage->GetChildren(); elVersion; elVersion = elVersion->GetNext()) {
                    if (elVersion->GetType() == wxXML_ELEMENT_NODE && elVersion->GetName() == wxT("Version")) {
                        for (wxXmlNode *elVersionNote = elVersion->GetChildren(); elVersionNote; elVersionNote = elVersionNote->GetNext()) {
                            if (elVersionNote->GetType() == wxXML_ELEMENT_NODE) {
                                const wxString &name = elVersionNote->GetName();
                                if (name == wxT("hex"))
                                    version = _tcstoul(elVersionNote->GetNodeContent(), NULL, 16);
                                else if (name == wxT("desc"))
                                    versionStr = elVersionNote->GetNodeContent();
                            }
                        }
                    }
                }
                if (version <= UPDATER_PRODUCT_VERSION || version < versionMax) {
                    // This package is older than currently installed product or the superseeded package found.
                    continue;
                }

                // Get package download URL for our platform and language.
                wxString platformId;
#if defined(__WINDOWS__)
                platformId += wxT("win");
#endif
#if defined(_WIN64)
                platformId += wxT("-amd64");
#else
                platformId += wxT("-x86");
#endif
                wxString languageId(initializer.m_locale.GetCanonicalName());
                wxString url;
                std::vector<BYTE> sig;
                for (wxXmlNode *elDownloads = elPackage->GetChildren(); elDownloads; elDownloads = elDownloads->GetNext()) {
                    if (elDownloads->GetType() == wxXML_ELEMENT_NODE && elDownloads->GetName() == wxT("Downloads")) {
                        for (wxXmlNode *elPlatform = elDownloads->GetChildren(); elPlatform; elPlatform = elPlatform->GetNext()) {
                            if (elPlatform->GetType() == wxXML_ELEMENT_NODE) {
                                if (elPlatform->GetName() == wxT("Platform") && elPlatform->GetAttribute(wxT("id")) == platformId) {
                                    // Get language.
                                    for (wxXmlNode *elLocale = elPlatform->GetChildren(); elLocale; elLocale = elLocale->GetNext()) {
                                        if (elLocale->GetType() == wxXML_ELEMENT_NODE && elLocale->GetName() == wxT("Localization") && elLocale->GetAttribute(wxT("lang")) == languageId) {
                                            for (wxXmlNode *elLocaleNote = elLocale->GetChildren(); elLocaleNote; elLocaleNote = elLocaleNote->GetNext()) {
                                                if (elLocaleNote->GetType() == wxXML_ELEMENT_NODE) {
                                                    const wxString &name = elLocaleNote->GetName();
                                                    if (name == wxT("url"))
                                                        url = elLocaleNote->GetNodeContent();
                                                    else if (name == wxT("signature")) {
                                                        // Read the signature.
                                                        wxString content(elLocaleNote->GetNodeContent());
                                                        sig.resize(wxBase64DecodedSize(content.length()));
                                                        size_t res = wxBase64Decode(sig.data(), sig.capacity(), content, wxBase64DecodeMode_SkipWS);
                                                        if (res != wxCONV_FAILED)
                                                            sig.resize(res);
                                                        else
                                                            sig.clear();
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                if (url.IsEmpty() || sig.empty()) {
                    // This package is for different architecture and/or language.
                    // ... or missing URL and/or signature.
                    continue;
                }

                versionMax = version;
                versionStrMax = versionStr;
                urlMax = url;
                sigMax = sig;
            }
        }

        if (versionMax) {
            wxLogMessage(wxT("Update package found (version: %s, URL: %s)."), versionStrMax.c_str(), urlMax.c_str());


        } else
            wxLogStatus(wxT("Update check complete. Your package is up to date."));

        // Save the last check date.
        initializer.m_config.Write(wxT("LastChecked"), (long)wxDateTime::GetTimeNow());

        return 0;
    }

    // No success.
    return 1;
}