SqlMigration.hpp

// SPDX-License-Identifier: Apache-2.0
 
#pragma once
 
#include "Api.hpp"
#include "DataMapper/DataMapper.hpp"
#include "SqlQuery.hpp"
#include "SqlTransaction.hpp"
 
#include <functional>
#include <list>
#include <optional>
 
class SqlConnection;
 
namespace SqlMigration
{
 
class MigrationBase;
 
struct MigrationTimestamp
{
    uint64_t value {};
 
    constexpr bool operator==(MigrationTimestamp const& other) const noexcept
    {
        return value == other.value;
    }
 
    constexpr bool operator!=(MigrationTimestamp const& other) const noexcept
    {
        return !(*this == other);
    }
};
 
// Interface to be implemented by the user to execute SQL migrations
class SqlMigrationExecutor
{
  public:
    virtual ~SqlMigrationExecutor() = default;
 
    virtual void OnCreateTable(SqlCreateTablePlan const& createTable) = 0;
    virtual void OnAlterTable(SqlAlterTablePlan const& alterTable) = 0;
 
    virtual void OnDropTable(std::string_view tableName) = 0;
};
 
// Main API to use for managing SQL migrations
class MigrationManager
{
  public:
    using MigrationList = std::list<MigrationBase const*>;
 
    LIGHTWEIGHT_API static MigrationManager& GetInstance()
    {
        static MigrationManager instance;
        return instance;
    }
 
    LIGHTWEIGHT_API void AddMigration(MigrationBase const* migration);
 
    [[nodiscard]] LIGHTWEIGHT_API MigrationList const& GetAllMigrations() const noexcept;
 
    [[nodiscard]] LIGHTWEIGHT_API MigrationBase const* GetMigration(MigrationTimestamp timestamp) const;
 
    LIGHTWEIGHT_API void RemoveAllMigrations();
 
    [[nodiscard]] LIGHTWEIGHT_API std::list<MigrationBase const*> GetPending() const noexcept;
 
    using ExecuteCallback = std::function<void(MigrationBase const& /*migration*/, size_t /*current*/, size_t /*total*/)>;
 
    LIGHTWEIGHT_API void ApplySingleMigration(MigrationTimestamp timestamp);
    LIGHTWEIGHT_API void ApplySingleMigration(MigrationBase const& migration);
    LIGHTWEIGHT_API size_t ApplyPendingMigrations(ExecuteCallback const& feedbackCallback = {});
 
    LIGHTWEIGHT_API void CreateMigrationHistory();
    [[nodiscard]] LIGHTWEIGHT_API std::vector<MigrationTimestamp> GetAppliedMigrationIds() const;
 
    [[nodiscard]] LIGHTWEIGHT_API DataMapper& GetDataMapper();
 
    [[nodiscard]] LIGHTWEIGHT_API DataMapper& GetDataMapper() const
    {
        return const_cast<MigrationManager*>(this)->GetDataMapper();
    }
 
    LIGHTWEIGHT_API void CloseDataMapper();
 
    LIGHTWEIGHT_API SqlTransaction Transaction();
 
  private:
    MigrationList _migrations;
    mutable std::optional<DataMapper> _mapper;
};
 
// Represents a single unique SQL migration
class MigrationBase
{
  public:
    MigrationBase(MigrationTimestamp timestamp, std::string_view title):
        _timestamp { timestamp },
        _title { title }
    {
        MigrationManager::GetInstance().AddMigration(this);
    }
 
    virtual ~MigrationBase() = default;
 
    virtual void Execute(SqlMigrationQueryBuilder& planer) const = 0;
 
    [[nodiscard]] MigrationTimestamp GetTimestamp() const noexcept
    {
        return _timestamp;
    }
 
    [[nodiscard]] std::string_view GetTitle() const noexcept
    {
        return _title;
    }
 
  private:
    MigrationTimestamp _timestamp;
    std::string_view _title;
};
 
class Migration: public MigrationBase
{
  public:
    Migration(MigrationTimestamp timestamp,
              std::string_view title,
              std::function<void(SqlMigrationQueryBuilder&)> const& plan):
        MigrationBase(timestamp, title),
        _plan { plan }
    {
    }
 
    void Execute(SqlMigrationQueryBuilder& planer) const override
    {
        _plan(planer);
    }
 
  private:
    std::function<void(SqlMigrationQueryBuilder&)> _plan;
};
 
} // namespace SqlMigration
 
#define LIGHTWEIGHT_CONCATENATE(s1, s2) s1##s2
 
#define LIGHTWEIGHT_MIGRATION_INSTANCE(timestamp) migration_##timestamp
 
// Example use:
//
// LIGHTWEIGHT_SQL_MIGRATION(std::chrono::system_clock(...), "Create table 'MyTable'")
// {
//     // ...
// }
#define LIGHTWEIGHT_SQL_MIGRATION(timestamp, description)                              \
    struct Migration_##timestamp: public SqlMigration::MigrationBase                   \
    {                                                                                  \
        explicit Migration_##timestamp():                                              \
            MigrationBase(SqlMigration::MigrationTimestamp { timestamp }, description) \
        {                                                                              \
        }                                                                              \
                                                                                       \
        void Execute(SqlMigrationQueryBuilder& planer) const override;                 \
    };                                                                                 \
                                                                                       \
    static Migration_##timestamp LIGHTWEIGHT_CONCATENATE(migration_, timestamp);       \
                                                                                       \
    void Migration_##timestamp::Execute(SqlMigrationQueryBuilder& plan) const