migrate.h

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/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/
 
#pragma once
 
#include "util/db/oral/oral.h"
#include <util/sll/qtutil.h>
 
namespace LC::Util::oral
{
    namespace detail
    {
        bool MatchesSchema (const QString& baseName, const QString& schema, QSqlDatabase& db)
        {
            auto result = Util::RunTextQuery (db,
                    "SELECT sql FROM sqlite_master WHERE type = 'table' AND name = '%1'"_qs
                            .arg (baseName));
            if (!result.next ())
                return true;
 
            const auto& existingDDL = result.value (0).toString ();
 
            auto figureOutFields = [] (const QString& str)
            {
                auto firstOpen = str.indexOf ('(');
                auto lastClose = str.lastIndexOf (')');
                return QStringView { str }.mid (firstOpen, lastClose - firstOpen);
            };
            auto existing = figureOutFields (existingDDL);
            auto suggested = figureOutFields (schema);
            return existing == suggested;
        }
    }
 
    template<typename Record, typename ImplFactory = SQLiteImplFactory>
    void Migrate (QSqlDatabase& db)
    {
        constexpr auto baseName = Record::ClassName;
        constexpr auto thisName = "copy" + baseName;
        const auto& schema = ToString<detail::AdaptCreateTableNamed<thisName, ImplFactory, Record> ()> ();
 
        const auto& baseNameStr = ToString<baseName> ();
        const auto& thisNameStr = ToString<thisName> ();
        if (detail::MatchesSchema (baseNameStr, schema, db))
        {
            qDebug () << Q_FUNC_INFO
                    << "not migrating"
                    << db.connectionName ();
            return;
        }
 
        qDebug () << Q_FUNC_INFO
                << "migrating"
                << db.connectionName ();
 
        Util::DBLock lock { db };
        lock.Init ();
 
        Util::RunTextQuery (db, schema);
 
        constexpr auto fields = JoinTup (detail::FieldNames<Record>, ", ");
 
        Util::RunTextQuery (db,
                "INSERT INTO %2 (%1) SELECT %1 FROM %3;"_qs
                        .arg (ToString<fields> (), thisNameStr, baseNameStr));
 
        Util::RunTextQuery (db,
                "DROP TABLE %1;"_qs
                        .arg (baseNameStr));
        Util::RunTextQuery (db,
                "ALTER TABLE %1 RENAME TO %2;"_qs
                        .arg (thisNameStr, baseNameStr));
 
        lock.Good ();
    }
}