DataMapper.hpp

// SPDX-License-Identifier: Apache-2.0
#pragma once
 
#include "../SqlConnection.hpp"
#include "../SqlDataBinder.hpp"
#include "../SqlLogger.hpp"
#include "../SqlRealName.hpp"
#include "../SqlStatement.hpp"
#include "../Utils.hpp"
#include "BelongsTo.hpp"
#include "CollectDifferences.hpp"
#include "Field.hpp"
#include "HasMany.hpp"
#include "HasManyThrough.hpp"
#include "HasOneThrough.hpp"
#include "QueryBuilders.hpp"
#include "Record.hpp"
 
#include <reflection-cpp/reflection.hpp>
 
#include <cassert>
#include <concepts>
#include <tuple>
#include <type_traits>
#include <utility>
 
namespace Lightweight
{
 
/// @defgroup DataMapper Data Mapper
///
/// @brief The data mapper is a high level API for mapping records to and from the database using high level C++ syntax.
 
namespace detail
{
    // Converts a container of T to a container of std::shared_ptr<T>.
    template <template <typename> class Allocator, template <typename, typename> class Container, typename Object>
    auto ToSharedPtrList(Container<Object, Allocator<Object>> container)
    {
        using SharedPtrRecord = std::shared_ptr<Object>;
        auto sharedPtrContainer = Container<SharedPtrRecord, Allocator<SharedPtrRecord>> {};
        for (auto& object: container)
            sharedPtrContainer.emplace_back(std::make_shared<Object>(std::move(object)));
        return sharedPtrContainer;
    }
} // namespace detail
 
/// @brief Main API for mapping records to and from the database using high level C++ syntax.
///
/// A DataMapper instances operates on a single SQL connection and provides methods to
/// create, read, update and delete records in the database.
///
/// @see Field, BelongsTo, HasMany, HasManyThrough, HasOneThrough
/// @ingroup DataMapper
///
/// @code
/// struct Person
/// {
///    Field<SqlGuid, PrimaryKey::AutoAssign> id;
///    Field<SqlAnsiString<30>> name;
///    Field<SqlAnsiString<40>> email;
/// };
///
/// auto dm = DataMapper {};
///
/// // Create a new person record
/// auto person = Person { .id = SqlGuid::Create(), .name = "John Doe", .email = "johnt@doe.com" };
///
/// // Create the record in the database and set the primary key on the record
/// auto const personId = dm.Create(person);
///
/// // Query the person record from the database
/// auto const queriedPerson = dm.Query<Person>(personId)
///                              .Where(FieldNameOf<&Person::id>, "=", personId)
///                              .First();
///
/// if (queriedPerson.has_value())
///     std::println("Queried Person: {}", DataMapper::Inspect(queriedPerson.value()));
///
/// // Update the person record in the database
/// person.email = "alt@doe.com";
/// dm.Update(person);
///
/// // Delete the person record from the database
/// dm.Delete(person);
/// @endcode
class DataMapper
{
  public:
    /// Constructs a new data mapper, using the default connection.
    DataMapper():
        _connection {},
        _stmt { _connection }
    {
    }
 
    /// Constructs a new data mapper, using the given connection.
    explicit DataMapper(SqlConnection&& connection):
        _connection { std::move(connection) },
        _stmt { _connection }
    {
    }
 
    /// Constructs a new data mapper, using the given connection string.
    explicit DataMapper(SqlConnectionString connectionString):
        _connection { std::move(connectionString) },
        _stmt { _connection }
    {
    }
 
    DataMapper(DataMapper const&) = delete;
    DataMapper(DataMapper&&) noexcept = default;
    DataMapper& operator=(DataMapper const&) = delete;
    DataMapper& operator=(DataMapper&&) noexcept = default;
    ~DataMapper() = default;
 
    /// Returns the connection reference used by this data mapper.
    [[nodiscard]] SqlConnection const& Connection() const noexcept
    {
        return _connection;
    }
 
    /// Returns the mutable connection reference used by this data mapper.
    [[nodiscard]] SqlConnection& Connection() noexcept
    {
        return _connection;
    }
 
    /// Constructs a human readable string representation of the given record.
    template <typename Record>
    static std::string Inspect(Record const& record);
 
    /// Constructs a string list of SQL queries to create the table for the given record type.
    template <typename Record>
    std::vector<std::string> CreateTableString(SqlServerType serverType);
 
    /// Constructs a string list of SQL queries to create the tables for the given record types.
    template <typename FirstRecord, typename... MoreRecords>
    std::vector<std::string> CreateTablesString(SqlServerType serverType);
 
    /// Creates the table for the given record type.
    template <typename Record>
    void CreateTable();
 
    /// Creates the tables for the given record types.
    template <typename FirstRecord, typename... MoreRecords>
    void CreateTables();
 
    /// @brief Creates a new record in the database.
    ///
    /// The record is inserted into the database and the primary key is set on this record.
    ///
    /// @return The primary key of the newly created record.
    template <typename Record>
    RecordPrimaryKeyType<Record> Create(Record& record);
 
    /// @brief Creates a new record in the database.
    ///
    /// @note This is a variation of the Create() method and does not update the record's primary key.
    ///
    /// @return The primary key of the newly created record.
    template <typename Record>
    RecordPrimaryKeyType<Record> CreateExplicit(Record const& record);
 
    /// @brief Queries a single record (based on primary key) from the database.
    ///
    /// The primary key(s) are used to identify the record to load.
    /// If the record is not found, std::nullopt is returned.
    template <typename Record, typename... PrimaryKeyTypes>
    std::optional<Record> QuerySingle(PrimaryKeyTypes&&... primaryKeys);
 
    /// @brief Queries a single record (based on primary key) from the database without auto-loading relations.
    ///
    /// The primary key(s) are used to identify the record to load.
    ///
    /// Main goal of this function is to load record without relationships to
    /// decrease compilation time and work around some limitations of template instantiation
    /// depth on MSVC compiler.
    template <typename Record, typename... PrimaryKeyTypes>
    std::optional<Record> QuerySingleWithoutRelationAutoLoading(PrimaryKeyTypes&&... primaryKeys);
 
    /// Queries multiple records from the database, based on the given query.
    template <typename Record, typename... InputParameters>
    std::vector<Record> Query(SqlSelectQueryBuilder::ComposedQuery const& selectQuery, InputParameters&&... inputParameters);
 
    /// Queries multiple records and returns them as a vector of std::tuple of the given record types.
    /// This can be used to query multiple record types in a single query.
    ///
    /// example:
    /// @code
    /// struct Person
    /// {
    ///   int id;
    ///   std::string name;
    ///   std::string email;
    ///   std::string phone;
    /// };
    /// struct Address
    /// {
    ///   int id;
    ///   std::string address;
    ///   std::string city;
    ///   std::string country;
    /// };
    /// void example(DataMapper& dm)
    /// {
    ///   auto const sqlQueryString = R"(SELECT p.*, a.* FROM "Person" p INNER JOIN "Address" a ON p.id = a.id WHERE p.city =
    ///   Berlin AND a.country = Germany)";
    ///   auto const records = dm.QueryToTuple<Person, Address>(sqlQueryString);
    ///   for (auto const& [person, address] : records)
    ///   {
    ///     std::println("Person: {}", DataMapper::Inspect(person));
    ///     std::println("Address: {}", DataMapper::Inspect(address));
    ///   }
    /// }
    /// @endcode
    template <typename... Records>
        requires DataMapperRecords<Records...>
    std::vector<std::tuple<Records...>> QueryToTuple(SqlSelectQueryBuilder::ComposedQuery const& selectQuery);
 
    /// Queries multiple records from the database, based on the given query.
    ///
    /// @param sqlQueryString The SQL query string to execute.
    /// @param inputParameters The input parameters for the query to be bound before executing.
    /// @return A vector of records of the given type that were found via the query.
    ///
    /// example:
    /// @code
    /// struct Person
    /// {
    ///     int id;
    ///     std::string name;
    ///     std::string email;
    ///     std::string phone;
    ///     std::string address;
    ///     std::string city;
    ///     std::string country;
    /// };
    ///
    /// void example(DataMapper& dm)
    /// {
    ///     auto const sqlQueryString = R"(SELECT * FROM "Person" WHERE "city" = ? AND "country" = ?)";
    ///     auto const records = dm.Query<Person>(sqlQueryString, "Berlin", "Germany");
    ///     for (auto const& record: records)
    ///     {
    ///         std::println("Person: {}", DataMapper::Inspect(record));
    ///     }
    /// }
    /// @endcode
    template <typename Record, typename... InputParameters>
    std::vector<Record> Query(std::string_view sqlQueryString, InputParameters&&... inputParameters);
 
    /// Queries records from the database, based on the given query and can be used to retrieve only part of the record
    /// by specifying the ElementMask.
    ///
    /// example:
    /// @code
    ///
    /// struct Person
    /// {
    ///    int id;
    ///    std::string name;
    ///    std::string email;
    ///    std::string phone;
    ///    std::string address;
    ///    std::string city;
    ///    std::string country;
    /// };
    ///
    /// auto infos = dm.Query<SqlElements<1,5>(RecordTableName<Person>.Fields({"name"sv, "city"sv}));
    ///
    /// for(auto const& info : infos)
    /// {
    ///    // only info.name and info.city are loaded
    /// }
    /// @endcode
    template <typename ElementMask, typename Record, typename... InputParameters>
    std::vector<Record> Query(SqlSelectQueryBuilder::ComposedQuery const& selectQuery, InputParameters&&... inputParameters);
 
    /// Queries records of different types from the database, based on the given query.
    /// User can constructed query that selects columns from the multiple tables
    /// this function is uset to get result of the
    ///
    /// example:
    /// @code
    ///
    /// struct JointA{};
    /// struct JointB{};
    /// struct JointC{};
    ///
    /// // the following query will construct statement to fetch all elements of JointA and JointC types
    /// auto dm = DataMapper {};
    /// auto const query = dm.FromTable(RecordTableName<JoinTestA>)
    ///             .Select()
    ///             .Fields<JointA, JointC>()
    ///             .InnerJoin<&JointB::a_id, &JointA::id>()
    ///             .InnerJoin<&JointC::id, &JointB::c_id>()
    ///             .All();
    /// auto const records = dm.Query<JointA, JointC>(query);
    /// for(const auto [elementA, elementC] : records)
    /// {
    ///   // do something with elementA and elementC
    /// }
    template <typename FirstRecord, typename NextRecord, typename... InputParameters>
        requires DataMapperRecord<FirstRecord> && DataMapperRecord<NextRecord>
    // TODO : need more generic one and we also have queryToTuple
    std::vector<std::tuple<FirstRecord, NextRecord>> Query(SqlSelectQueryBuilder::ComposedQuery const& selectQuery,
                                                           InputParameters&&... inputParameters);
 
    /// Queries records of different types from the database, based on the given query.
    template <typename FirstRecord, typename NextRecord>
        requires DataMapperRecord<FirstRecord> && DataMapperRecord<NextRecord>
    // TODO : need more generic one and we also have queryToTuple
    SqlAllFieldsQueryBuilder<std::tuple<FirstRecord, NextRecord>> Query()
    {
        std::string fields;
 
        auto const emplaceRecordsFrom = [&fields]<typename Record>() {
            Reflection::EnumerateMembers<Record>([&fields]<size_t I, typename Field>() {
                if (!fields.empty())
                    fields += ", ";
                fields += std::format(R"("{}"."{}")", RecordTableName<Record>, FieldNameAt<I, Record>);
            });
        };
 
        emplaceRecordsFrom.template operator()<FirstRecord>();
        emplaceRecordsFrom.template operator()<NextRecord>();
 
        return SqlAllFieldsQueryBuilder<std::tuple<FirstRecord, NextRecord>>(_stmt, std::move(fields));
    }
 
    /// Queries records of given Record type.
    ///
    /// The query builder can be used to further refine the query.
    /// The query builder will execute the query when a method like All(), First(n), etc. is called.
    ///
    /// @returns A query builder for the given Record type.
    ///
    /// @code
    /// auto const records = dm.Query<Person>()
    ///                        .Where(FieldNameOf<&Person::is_active>, "=", true)
    ///                        .All();
    /// @endcode
    template <typename Record>
    SqlAllFieldsQueryBuilder<Record> Query()
    {
        std::string fields;
        Reflection::EnumerateMembers<Record>([&fields]<size_t I, typename Field>() {
            if (!fields.empty())
                fields += ", ";
            fields += '"';
            fields += RecordTableName<Record>;
            fields += "\".\"";
            fields += FieldNameAt<I, Record>;
            fields += '"';
        });
        return SqlAllFieldsQueryBuilder<Record>(_stmt, std::move(fields));
    }
 
    /// Updates the record in the database.
    template <typename Record>
    void Update(Record& record);
 
    /// Deletes the record from the database.
    template <typename Record>
    std::size_t Delete(Record const& record);
 
    /// Constructs an SQL query builder for the given table name.
    SqlQueryBuilder FromTable(std::string_view tableName)
    {
        return _connection.Query(tableName);
    }
 
    /// Checks if the record has any modified fields.
    template <typename Record>
    bool IsModified(Record const& record) const noexcept;
 
    /// Clears the modified state of the record.
    template <typename Record>
    void ClearModifiedState(Record& record) noexcept;
 
    /// Loads all direct relations to this record.
    template <typename Record>
    void LoadRelations(Record& record);
 
    /// Configures the auto loading of relations for the given record.
    ///
    /// This means, that no explicit loading of relations is required.
    /// The relations are automatically loaded when accessed.
    template <typename Record>
    void ConfigureRelationAutoLoading(Record& record);
 
  private:
    /// @brief Queries a single record from the database based on the given query.
    ///
    /// @param selectQuery The SQL select query to execute.
    /// @param args The input parameters for the query.
    ///
    /// @return The record if found, otherwise std::nullopt.
    template <typename Record, typename... Args>
    std::optional<Record> QuerySingle(SqlSelectQueryBuilder selectQuery, Args&&... args);
 
    template <typename Record, typename ValueType>
    void SetId(Record& record, ValueType&& id);
 
    template <typename Record, size_t InitialOffset = 1>
    Record& BindOutputColumns(Record& record);
 
    template <typename Record, size_t InitialOffset = 1>
    Record& BindOutputColumns(Record& record, SqlStatement* stmt);
 
    template <typename ElementMask, typename Record, size_t InitialOffset = 1>
    Record& BindOutputColumns(Record& record);
 
    template <typename ElementMask, typename Record, size_t InitialOffset = 1>
    Record& BindOutputColumns(Record& record, SqlStatement* stmt);
 
    template <typename FieldType>
    std::optional<typename FieldType::ReferencedRecord> LoadBelongsTo(typename FieldType::ValueType value);
 
    template <size_t FieldIndex, typename Record, typename OtherRecord>
    void LoadHasMany(Record& record, HasMany<OtherRecord>& field);
 
    template <typename ReferencedRecord, typename ThroughRecord, typename Record>
    void LoadHasOneThrough(Record& record, HasOneThrough<ReferencedRecord, ThroughRecord>& field);
 
    template <typename ReferencedRecord, typename ThroughRecord, typename Record>
    void LoadHasManyThrough(Record& record, HasManyThrough<ReferencedRecord, ThroughRecord>& field);
 
    template <size_t FieldIndex, typename Record, typename OtherRecord, typename Callable>
    void CallOnHasMany(Record& record, Callable const& callback);
 
    template <typename ReferencedRecord, typename ThroughRecord, typename Record, typename Callable>
    void CallOnHasManyThrough(Record& record, Callable const& callback);
 
    SqlConnection _connection;
    SqlStatement _stmt;
};
 
// ------------------------------------------------------------------------------------------------
 
template <typename Record>
std::string DataMapper::Inspect(Record const& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    std::string str;
    Reflection::CallOnMembers(record, [&str]<typename Name, typename Value>(Name const& name, Value const& value) {
        if (!str.empty())
            str += '\n';
 
        if constexpr (FieldWithStorage<Value>)
        {
            if constexpr (Value::IsOptional)
            {
                if (!value.Value().has_value())
                {
                    str += std::format("{} {} := <nullopt>", Reflection::TypeNameOf<Value>, name);
                }
                else
                {
                    str += std::format("{} {} := {}", Reflection::TypeNameOf<Value>, name, value.Value().value());
                }
            }
            else if constexpr (IsBelongsTo<Value>)
            {
                str += std::format("{} {} := {}", Reflection::TypeNameOf<Value>, name, value.Value());
            }
            else if constexpr (std::same_as<typename Value::ValueType, char>)
            {
            }
            else
            {
                str += std::format("{} {} := {}", Reflection::TypeNameOf<Value>, name, value.InspectValue());
            }
        }
        else if constexpr (!IsHasMany<Value> && !IsHasManyThrough<Value> && !IsHasOneThrough<Value> && !IsBelongsTo<Value>)
            str += std::format("{} {} := {}", Reflection::TypeNameOf<Value>, name, value);
    });
    return "{\n" + std::move(str) + "\n}";
}
 
template <typename Record>
std::vector<std::string> DataMapper::CreateTableString(SqlServerType serverType)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto migration = SqlQueryBuilder(*SqlQueryFormatter::Get(serverType)).Migration();
    auto createTable = migration.CreateTable(RecordTableName<Record>);
 
    Reflection::EnumerateMembers<Record>([&]<size_t I, typename FieldType>() {
        if constexpr (FieldWithStorage<FieldType>)
        {
            if constexpr (IsAutoIncrementPrimaryKey<FieldType>)
                createTable.PrimaryKeyWithAutoIncrement(std::string(FieldNameAt<I, Record>),
                                                        SqlColumnTypeDefinitionOf<typename FieldType::ValueType>);
            else if constexpr (FieldType::IsPrimaryKey)
                createTable.PrimaryKey(std::string(FieldNameAt<I, Record>),
                                       SqlColumnTypeDefinitionOf<typename FieldType::ValueType>);
            else if constexpr (IsBelongsTo<FieldType>)
            {
                constexpr size_t referencedFieldIndex = []() constexpr -> size_t {
                    auto index = size_t(-1);
                    Reflection::EnumerateMembers<typename FieldType::ReferencedRecord>(
                        [&index]<size_t J, typename ReferencedFieldType>() constexpr -> void {
                            if constexpr (IsField<ReferencedFieldType>)
                                if constexpr (ReferencedFieldType::IsPrimaryKey)
                                    index = J;
                        });
                    return index;
                }();
                createTable.ForeignKey(
                    std::string(FieldNameAt<I, Record>),
                    SqlColumnTypeDefinitionOf<typename FieldType::ValueType>,
                    SqlForeignKeyReferenceDefinition {
                        .tableName = std::string { RecordTableName<typename FieldType::ReferencedRecord> },
                        .columnName =
                            std::string { FieldNameAt<referencedFieldIndex, typename FieldType::ReferencedRecord> } });
            }
            else if constexpr (FieldType::IsMandatory)
                createTable.RequiredColumn(std::string(FieldNameAt<I, Record>),
                                           SqlColumnTypeDefinitionOf<typename FieldType::ValueType>);
            else
                createTable.Column(std::string(FieldNameAt<I, Record>),
                                   SqlColumnTypeDefinitionOf<typename FieldType::ValueType>);
        }
    });
 
    return migration.GetPlan().ToSql();
}
 
template <typename FirstRecord, typename... MoreRecords>
std::vector<std::string> DataMapper::CreateTablesString(SqlServerType serverType)
{
    std::vector<std::string> output;
    auto const append = [&output](auto const& sql) {
        output.insert(output.end(), sql.begin(), sql.end());
    };
    append(CreateTableString<FirstRecord>(serverType));
    (append(CreateTableString<MoreRecords>(serverType)), ...);
    return output;
}
 
template <typename Record>
void DataMapper::CreateTable()
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto const sqlQueryStrings = CreateTableString<Record>(_connection.ServerType());
    for (auto const& sqlQueryString: sqlQueryStrings)
        _stmt.ExecuteDirect(sqlQueryString);
}
 
template <typename FirstRecord, typename... MoreRecords>
void DataMapper::CreateTables()
{
    CreateTable<FirstRecord>();
    (CreateTable<MoreRecords>(), ...);
}
 
template <typename Record>
RecordPrimaryKeyType<Record> DataMapper::CreateExplicit(Record const& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto query = _connection.Query(RecordTableName<Record>).Insert(nullptr);
 
    Reflection::EnumerateMembers(record, [&query]<auto I, typename FieldType>(FieldType const& /*field*/) {
        if constexpr (SqlInputParameterBinder<FieldType> && !IsAutoIncrementPrimaryKey<FieldType>)
            query.Set(FieldNameAt<I, Record>, SqlWildcard);
    });
 
    _stmt.Prepare(query);
 
    Reflection::CallOnMembers(
        record,
        [this, i = SQLSMALLINT { 1 }]<typename Name, typename FieldType>(Name const& name, FieldType const& field) mutable {
            if constexpr (SqlInputParameterBinder<FieldType> && !IsAutoIncrementPrimaryKey<FieldType>)
                _stmt.BindInputParameter(i++, field, name);
        });
 
    _stmt.Execute();
 
    if constexpr (HasAutoIncrementPrimaryKey<Record>)
        return { _stmt.LastInsertId(RecordTableName<Record>) };
    else if constexpr (HasPrimaryKey<Record>)
    {
        RecordPrimaryKeyType<Record> const* primaryKey = nullptr;
        Reflection::EnumerateMembers(record, [&]<size_t I, typename FieldType>(FieldType& field) {
            if constexpr (IsField<FieldType>)
            {
                if constexpr (FieldType::IsPrimaryKey)
                {
                    primaryKey = &field.Value();
                }
            }
        });
        return *primaryKey;
    }
}
 
template <typename Record>
RecordPrimaryKeyType<Record> DataMapper::Create(Record& record)
{
    static_assert(!std::is_const_v<Record>);
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    // If the primary key is not an auto-increment field and the primary key is not set, we need to set it.
    CallOnPrimaryKey(record, [&]<size_t PrimaryKeyIndex, typename PrimaryKeyType>(PrimaryKeyType& primaryKeyField) {
        if constexpr (PrimaryKeyType::IsAutoAssignPrimaryKey)
        {
            if (!primaryKeyField.IsModified())
            {
                using ValueType = typename PrimaryKeyType::ValueType;
                if constexpr (std::same_as<ValueType, SqlGuid>)
                {
                    primaryKeyField = SqlGuid::Create();
                }
                else if constexpr (requires { ValueType {} + 1; })
                {
                    auto maxId = SqlStatement { _connection }.ExecuteDirectScalar<ValueType>(
                        std::format(R"sql(SELECT MAX("{}") FROM "{}")sql",
                                    FieldNameAt<PrimaryKeyIndex, Record>,
                                    RecordTableName<Record>));
                    primaryKeyField = maxId.value_or(ValueType {}) + 1;
                }
            }
        }
    });
 
    CreateExplicit(record);
 
    if constexpr (HasAutoIncrementPrimaryKey<Record>)
        SetId(record, _stmt.LastInsertId(RecordTableName<Record>));
 
    ClearModifiedState(record);
    ConfigureRelationAutoLoading(record);
 
    if constexpr (HasPrimaryKey<Record>)
        return GetPrimaryKeyField(record);
}
 
template <typename Record>
bool DataMapper::IsModified(Record const& record) const noexcept
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    bool modified = false;
 
    Reflection::CallOnMembers(record, [&modified](auto const& /*name*/, auto const& field) {
        if constexpr (requires { field.IsModified(); })
        {
            modified = modified || field.IsModified();
        }
    });
 
    return modified;
}
 
template <typename Record>
void DataMapper::Update(Record& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto query = _connection.Query(RecordTableName<Record>).Update();
 
    Reflection::CallOnMembersWithoutName(record, [&query]<size_t I, typename FieldType>(FieldType const& field) {
        if (field.IsModified())
            query.Set(FieldNameAt<I, Record>, SqlWildcard);
        // for some reason compiler do not want to properly deduce FieldType, so here we
        // directly infer the type from the Record type and index
        if constexpr (IsPrimaryKey<Reflection::MemberTypeOf<I, Record>>)
            std::ignore = query.Where(FieldNameAt<I, Record>, SqlWildcard);
    });
 
    _stmt.Prepare(query);
 
    // Bind the SET clause
    SQLSMALLINT i = 1;
    Reflection::CallOnMembers(
        record, [this, &i]<typename Name, typename FieldType>(Name const& name, FieldType const& field) mutable {
            if (field.IsModified())
                _stmt.BindInputParameter(i++, field.Value(), name);
        });
 
    // Bind the WHERE clause
    Reflection::CallOnMembers(
        record, [this, &i]<typename Name, typename FieldType>(Name const& name, FieldType const& field) mutable {
            if constexpr (FieldType::IsPrimaryKey)
                _stmt.BindInputParameter(i++, field.Value(), name);
        });
 
    _stmt.Execute();
 
    ClearModifiedState(record);
}
 
template <typename Record>
std::size_t DataMapper::Delete(Record const& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto query = _connection.Query(RecordTableName<Record>).Delete();
 
    Reflection::CallOnMembers(record,
                              [&query]<typename Name, typename FieldType>(Name const& name, FieldType const& /*field*/) {
                                  if constexpr (FieldType::IsPrimaryKey)
                                      std::ignore = query.Where(name, SqlWildcard);
                              });
 
    _stmt.Prepare(query);
 
    // Bind the WHERE clause
    Reflection::CallOnMembers(
        record,
        [this, i = SQLSMALLINT { 1 }]<typename Name, typename FieldType>(Name const& name, FieldType const& field) mutable {
            if constexpr (FieldType::IsPrimaryKey)
                _stmt.BindInputParameter(i++, field.Value(), name);
        });
 
    _stmt.Execute();
 
    return _stmt.NumRowsAffected();
}
 
template <typename Record, typename... PrimaryKeyTypes>
std::optional<Record> DataMapper::QuerySingleWithoutRelationAutoLoading(PrimaryKeyTypes&&... primaryKeys)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    auto queryBuilder = _connection.Query(RecordTableName<Record>).Select();
 
    Reflection::EnumerateMembers<Record>([&]<size_t I, typename FieldType>() {
        if constexpr (FieldWithStorage<FieldType>)
        {
            queryBuilder.Field(FieldNameAt<I, Record>);
 
            if constexpr (FieldType::IsPrimaryKey)
                std::ignore = queryBuilder.Where(FieldNameAt<I, Record>, SqlWildcard);
        }
    });
 
    _stmt.Prepare(queryBuilder.First());
    _stmt.Execute(std::forward<PrimaryKeyTypes>(primaryKeys)...);
 
    auto resultRecord = std::optional<Record> { Record {} };
    auto reader = _stmt.GetResultCursor();
    if (!detail::ReadSingleResult(_stmt.Connection().ServerType(), reader, *resultRecord))
        return std::nullopt;
 
    return resultRecord;
}
 
template <typename Record, typename... PrimaryKeyTypes>
std::optional<Record> DataMapper::QuerySingle(PrimaryKeyTypes&&... primaryKeys)
{
    auto record = QuerySingleWithoutRelationAutoLoading<Record>(std::forward<PrimaryKeyTypes>(primaryKeys)...);
    if (record)
        ConfigureRelationAutoLoading(*record);
    return record;
}
 
template <typename Record, typename... Args>
std::optional<Record> DataMapper::QuerySingle(SqlSelectQueryBuilder selectQuery, Args&&... args)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers<Record>([&]<size_t I, typename FieldType>() {
        if constexpr (FieldWithStorage<FieldType>)
            selectQuery.Field(SqlQualifiedTableColumnName { RecordTableName<Record>, FieldNameAt<I, Record> });
    });
    _stmt.Prepare(selectQuery.First().ToSql());
    _stmt.Execute(std::forward<Args>(args)...);
 
    auto resultRecord = std::optional<Record> { Record {} };
    auto reader = _stmt.GetResultCursor();
    if (!detail::ReadSingleResult(_stmt.Connection().ServerType(), reader, *resultRecord))
        return std::nullopt;
    return resultRecord;
}
 
// TODO: Provide Query(QueryBuilder, ...) method variant
 
template <typename Record, typename... InputParameters>
inline LIGHTWEIGHT_FORCE_INLINE std::vector<Record> DataMapper::Query(
    SqlSelectQueryBuilder::ComposedQuery const& selectQuery, InputParameters&&... inputParameters)
{
    static_assert(DataMapperRecord<Record> || std::same_as<Record, SqlVariantRow>, "Record must satisfy DataMapperRecord");
 
    return Query<Record>(selectQuery.ToSql(), std::forward<InputParameters>(inputParameters)...);
}
 
template <typename Record, typename... InputParameters>
std::vector<Record> DataMapper::Query(std::string_view sqlQueryString, InputParameters&&... inputParameters)
{
    auto result = std::vector<Record> {};
 
    if constexpr (std::same_as<Record, SqlVariantRow>)
    {
        _stmt.Prepare(sqlQueryString);
        _stmt.Execute(std::forward<InputParameters>(inputParameters)...);
        size_t const numResultColumns = _stmt.NumColumnsAffected();
        while (_stmt.FetchRow())
        {
            auto& record = result.emplace_back();
            record.reserve(numResultColumns);
            for (auto const i: std::views::iota(1U, numResultColumns + 1))
                record.emplace_back(_stmt.GetColumn<SqlVariant>(static_cast<SQLUSMALLINT>(i)));
        }
    }
    else
    {
        static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
        bool const canSafelyBindOutputColumns = detail::CanSafelyBindOutputColumns<Record>(_stmt.Connection().ServerType());
 
        _stmt.Prepare(sqlQueryString);
        _stmt.Execute(std::forward<InputParameters>(inputParameters)...);
 
        auto reader = _stmt.GetResultCursor();
 
        for (;;)
        {
            auto& record = result.emplace_back();
 
            if (canSafelyBindOutputColumns)
                BindOutputColumns(record);
 
            if (!reader.FetchRow())
                break;
 
            if (!canSafelyBindOutputColumns)
                detail::GetAllColumns(reader, record);
        }
 
        // Drop the last record, which we failed to fetch (End of result set).
        result.pop_back();
 
        for (auto& record: result)
            ConfigureRelationAutoLoading(record);
    }
 
    return result;
}
 
template <typename... Records>
    requires DataMapperRecords<Records...>
std::vector<std::tuple<Records...>> DataMapper::QueryToTuple(SqlSelectQueryBuilder::ComposedQuery const& selectQuery)
{
    using value_type = std::tuple<Records...>;
    auto result = std::vector<value_type> {};
 
    _stmt.Prepare(selectQuery.ToSql());
    _stmt.Execute();
    auto reader = _stmt.GetResultCursor();
 
    constexpr auto calculateOffset = []<size_t I, typename Tuple>() {
        size_t offset = 1;
 
        if constexpr (I > 0)
        {
            [&]<size_t... Indices>(std::index_sequence<Indices...>) {
                ((Indices < I ? (offset += Reflection::CountMembers<std::tuple_element_t<Indices, Tuple>>) : 0), ...);
            }(std::make_index_sequence<I> {});
        }
        return offset;
    };
 
    auto const BindElements = [&](auto& record) {
        Reflection::template_for<0, std::tuple_size_v<value_type>>([&]<auto I>() {
            using TupleElement = std::decay_t<std::tuple_element_t<I, value_type>>;
            auto& element = std::get<I>(record);
            constexpr size_t offset = calculateOffset.template operator()<I, value_type>();
            this->BindOutputColumns<TupleElement, offset>(element);
        });
    };
 
    auto const GetElements = [&](auto& record) {
        Reflection::template_for<0, std::tuple_size_v<value_type>>([&]<auto I>() {
            auto& element = std::get<I>(record);
            constexpr size_t offset = calculateOffset.template operator()<I, value_type>();
            detail::GetAllColumns(reader, element, offset - 1);
        });
    };
 
    bool const canSafelyBindOutputColumns = [&]() {
        bool result = true;
        Reflection::template_for<0, std::tuple_size_v<value_type>>([&]<auto I>() {
            using TupleElement = std::decay_t<std::tuple_element_t<I, value_type>>;
            result &= detail::CanSafelyBindOutputColumns<TupleElement>(_stmt.Connection().ServerType());
        });
        return result;
    }();
 
    for (;;)
    {
        auto& record = result.emplace_back();
 
        if (canSafelyBindOutputColumns)
            BindElements(record);
 
        if (!reader.FetchRow())
            break;
 
        if (!canSafelyBindOutputColumns)
            GetElements(record);
    }
 
    // Drop the last record, which we failed to fetch (End of result set).
    result.pop_back();
 
    for (auto& record: result)
    {
        Reflection::template_for<0, std::tuple_size_v<value_type>>([&]<auto I>() {
            auto& element = std::get<I>(record);
            ConfigureRelationAutoLoading(element);
        });
    }
 
    return result;
}
 
template <typename FirstRecord, typename SecondRecord, typename... InputParameters>
    requires DataMapperRecord<FirstRecord> && DataMapperRecord<SecondRecord>
std::vector<std::tuple<FirstRecord, SecondRecord>> DataMapper::Query(SqlSelectQueryBuilder::ComposedQuery const& selectQuery,
                                                                     InputParameters&&... inputParameters)
{
    auto result = std::vector<std::tuple<FirstRecord, SecondRecord>> {};
 
    _stmt.Prepare(selectQuery.ToSql());
    _stmt.Execute(std::forward<InputParameters>(inputParameters)...);
 
    auto const ConfigureFetchAndBind = [this](auto& record) {
        auto& [recordFirst, recordSecond] = record;
        // clang-cl gives false possitive error that *this*
        // is not used in the lambda, to avoid the warning,
        // use it here explicitly
        this->BindOutputColumns<FirstRecord, 1>(recordFirst);
        this->BindOutputColumns<SecondRecord, Reflection::CountMembers<FirstRecord> + 1>(recordSecond);
        this->ConfigureRelationAutoLoading(recordFirst);
        this->ConfigureRelationAutoLoading(recordSecond);
    };
 
    ConfigureFetchAndBind(result.emplace_back());
    while (_stmt.FetchRow())
        ConfigureFetchAndBind(result.emplace_back());
 
    // remove the last empty record
    if (!result.empty())
        result.pop_back();
 
    return result;
}
 
template <typename ElementMask, typename Record, typename... InputParameters>
std::vector<Record> DataMapper::Query(SqlSelectQueryBuilder::ComposedQuery const& selectQuery,
                                      InputParameters&&... inputParameters)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    _stmt.Prepare(selectQuery.ToSql());
    _stmt.Execute(std::forward<InputParameters>(inputParameters)...);
 
    auto records = std::vector<Record> {};
 
    // TODO: We could optimize this further by only considering ElementMask fields in Record.
    bool const canSafelyBindOutputColumns = detail::CanSafelyBindOutputColumns<Record>(_stmt.Connection().ServerType());
 
    auto reader = _stmt.GetResultCursor();
 
    for (;;)
    {
        auto& record = records.emplace_back();
 
        if (canSafelyBindOutputColumns)
            BindOutputColumns<ElementMask>(record);
 
        if (!reader.FetchRow())
            break;
 
        if (!canSafelyBindOutputColumns)
            detail::GetAllColumns<ElementMask>(reader, record);
    }
 
    // Drop the last record, which we failed to fetch (End of result set).
    records.pop_back();
 
    for (auto& record: records)
        ConfigureRelationAutoLoading(record);
 
    return records;
}
 
template <typename Record>
void DataMapper::ClearModifiedState(Record& record) noexcept
{
    static_assert(!std::is_const_v<Record>);
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers(record, []<size_t I, typename FieldType>(FieldType& field) {
        if constexpr (requires { field.SetModified(false); })
        {
            field.SetModified(false);
        }
    });
}
 
template <typename Record, typename Callable>
inline LIGHTWEIGHT_FORCE_INLINE void CallOnPrimaryKey(Record& record, Callable const& callable)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers(record, [&]<size_t I, typename FieldType>(FieldType& field) {
        if constexpr (IsField<FieldType>)
        {
            if constexpr (FieldType::IsPrimaryKey)
            {
                return callable.template operator()<I, FieldType>(field);
            }
        }
    });
}
 
template <typename Record, typename Callable>
inline LIGHTWEIGHT_FORCE_INLINE void CallOnPrimaryKey(Callable const& callable)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers<Record>([&]<size_t I, typename FieldType>() {
        if constexpr (IsField<FieldType>)
        {
            if constexpr (FieldType::IsPrimaryKey)
            {
                return callable.template operator()<I, FieldType>();
            }
        }
    });
}
 
template <typename Record, typename Callable>
inline LIGHTWEIGHT_FORCE_INLINE void CallOnBelongsTo(Callable const& callable)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers<Record>([&]<size_t I, typename FieldType>() {
        if constexpr (IsBelongsTo<FieldType>)
        {
            return callable.template operator()<I, FieldType>();
        }
    });
}
 
template <typename FieldType>
std::optional<typename FieldType::ReferencedRecord> DataMapper::LoadBelongsTo(typename FieldType::ValueType value)
{
    using ReferencedRecord = typename FieldType::ReferencedRecord;
 
    std::optional<ReferencedRecord> record { std::nullopt };
    CallOnPrimaryKey<ReferencedRecord>([&]<size_t PrimaryKeyIndex, typename PrimaryKeyType>() {
        if (auto result = QuerySingle<ReferencedRecord>(value); result)
            record = std::move(result);
        else
            SqlLogger::GetLogger().OnWarning(
                std::format("Loading BelongsTo failed for {}", RecordTableName<ReferencedRecord>));
    });
    return record;
}
 
template <size_t FieldIndex, typename Record, typename OtherRecord, typename Callable>
void DataMapper::CallOnHasMany(Record& record, Callable const& callback)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    static_assert(DataMapperRecord<OtherRecord>, "OtherRecord must satisfy DataMapperRecord");
 
    using FieldType = HasMany<OtherRecord>;
    using ReferencedRecord = typename FieldType::ReferencedRecord;
 
    CallOnPrimaryKey(record, [&]<size_t PrimaryKeyIndex, typename PrimaryKeyType>(PrimaryKeyType const& primaryKeyField) {
        auto query = _connection.Query(RecordTableName<ReferencedRecord>)
                         .Select()
                         .Build([&](auto& query) {
                             Reflection::EnumerateMembers<ReferencedRecord>(
                                 [&]<size_t ReferencedFieldIndex, typename ReferencedFieldType>() {
                                     if constexpr (FieldWithStorage<ReferencedFieldType>)
                                     {
                                         query.Field(FieldNameAt<ReferencedFieldIndex, ReferencedRecord>);
                                     }
                                 });
                         })
                         .Where(FieldNameAt<FieldIndex, ReferencedRecord>, SqlWildcard);
        callback(query, primaryKeyField);
    });
}
 
template <size_t FieldIndex, typename Record, typename OtherRecord>
void DataMapper::LoadHasMany(Record& record, HasMany<OtherRecord>& field)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    static_assert(DataMapperRecord<OtherRecord>, "OtherRecord must satisfy DataMapperRecord");
 
    CallOnHasMany<FieldIndex, Record, OtherRecord>(record, [&](SqlSelectQueryBuilder selectQuery, auto& primaryKeyField) {
        field.Emplace(detail::ToSharedPtrList(Query<OtherRecord>(selectQuery.All(), primaryKeyField.Value())));
    });
}
 
template <typename ReferencedRecord, typename ThroughRecord, typename Record>
void DataMapper::LoadHasOneThrough(Record& record, HasOneThrough<ReferencedRecord, ThroughRecord>& field)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    static_assert(DataMapperRecord<ThroughRecord>, "ThroughRecord must satisfy DataMapperRecord");
 
    // Find the PK of Record
    CallOnPrimaryKey(record, [&]<size_t PrimaryKeyIndex, typename PrimaryKeyType>(PrimaryKeyType const& primaryKeyField) {
        // Find the BelongsTo of ThroughRecord pointing to the PK of Record
        CallOnBelongsTo<ThroughRecord>([&]<size_t ThroughBelongsToIndex, typename ThroughBelongsToType>() {
            // Find the PK of ThroughRecord
            CallOnPrimaryKey<ThroughRecord>([&]<size_t ThroughPrimaryKeyIndex, typename ThroughPrimaryKeyType>() {
                // Find the BelongsTo of ReferencedRecord pointing to the PK of ThroughRecord
                CallOnBelongsTo<ReferencedRecord>([&]<size_t ReferencedKeyIndex, typename ReferencedKeyType>() {
                    // Query the ReferencedRecord where:
                    // - the BelongsTo of ReferencedRecord points to the PK of ThroughRecord,
                    // - and the BelongsTo of ThroughRecord points to the PK of Record
                    auto query =
                        _connection.Query(RecordTableName<ReferencedRecord>)
                            .Select()
                            .Build([&](auto& query) {
                                Reflection::EnumerateMembers<ReferencedRecord>(
                                    [&]<size_t ReferencedFieldIndex, typename ReferencedFieldType>() {
                                        if constexpr (FieldWithStorage<ReferencedFieldType>)
                                        {
                                            query.Field(SqlQualifiedTableColumnName {
                                                RecordTableName<ReferencedRecord>,
                                                FieldNameAt<ReferencedFieldIndex, ReferencedRecord> });
                                        }
                                    });
                            })
                            .InnerJoin(RecordTableName<ThroughRecord>,
                                       FieldNameAt<ThroughPrimaryKeyIndex, ThroughRecord>,
                                       FieldNameAt<ReferencedKeyIndex, ReferencedRecord>)
                            .InnerJoin(RecordTableName<Record>,
                                       FieldNameAt<PrimaryKeyIndex, Record>,
                                       SqlQualifiedTableColumnName { RecordTableName<ThroughRecord>,
                                                                     FieldNameAt<ThroughBelongsToIndex, ThroughRecord> })
                            .Where(
                                SqlQualifiedTableColumnName {
                                    RecordTableName<Record>,
                                    FieldNameAt<PrimaryKeyIndex, ThroughRecord>,
                                },
                                SqlWildcard);
                    if (auto link = QuerySingle<ReferencedRecord>(std::move(query), primaryKeyField.Value()); link)
                    {
                        field.EmplaceRecord(std::make_shared<ReferencedRecord>(std::move(*link)));
                    }
                });
            });
        });
    });
}
 
template <typename ReferencedRecord, typename ThroughRecord, typename Record, typename Callable>
void DataMapper::CallOnHasManyThrough(Record& record, Callable const& callback)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    // Find the PK of Record
    CallOnPrimaryKey(record, [&]<size_t PrimaryKeyIndex, typename PrimaryKeyType>(PrimaryKeyType const& primaryKeyField) {
        // Find the BelongsTo of ThroughRecord pointing to the PK of Record
        CallOnBelongsTo<ThroughRecord>([&]<size_t ThroughBelongsToRecordIndex, typename ThroughBelongsToRecordType>() {
            using ThroughBelongsToRecordFieldType = Reflection::MemberTypeOf<ThroughBelongsToRecordIndex, ThroughRecord>;
            if constexpr (std::is_same_v<typename ThroughBelongsToRecordFieldType::ReferencedRecord, Record>)
            {
                // Find the BelongsTo of ThroughRecord pointing to the PK of ReferencedRecord
                CallOnBelongsTo<ThroughRecord>(
                    [&]<size_t ThroughBelongsToReferenceRecordIndex, typename ThroughBelongsToReferenceRecordType>() {
                        using ThroughBelongsToReferenceRecordFieldType =
                            Reflection::MemberTypeOf<ThroughBelongsToReferenceRecordIndex, ThroughRecord>;
                        if constexpr (std::is_same_v<typename ThroughBelongsToReferenceRecordFieldType::ReferencedRecord,
                                                     ReferencedRecord>)
                        {
                            auto query = _connection.Query(RecordTableName<ReferencedRecord>)
                                             .Select()
                                             .Build([&](auto& query) {
                                                 Reflection::EnumerateMembers<ReferencedRecord>(
                                                     [&]<size_t ReferencedFieldIndex, typename ReferencedFieldType>() {
                                                         if constexpr (FieldWithStorage<ReferencedFieldType>)
                                                         {
                                                             query.Field(SqlQualifiedTableColumnName {
                                                                 RecordTableName<ReferencedRecord>,
                                                                 FieldNameAt<ReferencedFieldIndex, ReferencedRecord> });
                                                         }
                                                     });
                                             })
                                             .InnerJoin(RecordTableName<ThroughRecord>,
                                                        FieldNameAt<ThroughBelongsToReferenceRecordIndex, ThroughRecord>,
                                                        SqlQualifiedTableColumnName { RecordTableName<ReferencedRecord>,
                                                                                      FieldNameAt<PrimaryKeyIndex, Record> })
                                             .Where(
                                                 SqlQualifiedTableColumnName {
                                                     RecordTableName<ThroughRecord>,
                                                     FieldNameAt<ThroughBelongsToRecordIndex, ThroughRecord>,
                                                 },
                                                 SqlWildcard);
                            callback(query, primaryKeyField);
                        }
                    });
            }
        });
    });
}
 
template <typename ReferencedRecord, typename ThroughRecord, typename Record>
void DataMapper::LoadHasManyThrough(Record& record, HasManyThrough<ReferencedRecord, ThroughRecord>& field)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    CallOnHasManyThrough<ReferencedRecord, ThroughRecord>(
        record, [&](SqlSelectQueryBuilder& selectQuery, auto& primaryKeyField) {
            field.Emplace(detail::ToSharedPtrList(Query<ReferencedRecord>(selectQuery.All(), primaryKeyField.Value())));
        });
}
 
template <typename Record>
void DataMapper::LoadRelations(Record& record)
{
    static_assert(!std::is_const_v<Record>);
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers(record, [&]<size_t FieldIndex, typename FieldType>(FieldType& field) {
        if constexpr (IsBelongsTo<FieldType>)
        {
            field = LoadBelongsTo<FieldType>(field.Value());
        }
        else if constexpr (IsHasMany<FieldType>)
        {
            LoadHasMany<FieldIndex>(record, field);
        }
        else if constexpr (IsHasOneThrough<FieldType>)
        {
            LoadHasOneThrough(record, field);
        }
        else if constexpr (IsHasManyThrough<FieldType>)
        {
            LoadHasManyThrough(record, field);
        }
    });
}
 
template <typename Record, typename ValueType>
inline LIGHTWEIGHT_FORCE_INLINE void DataMapper::SetId(Record& record, ValueType&& id)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    // static_assert(HasPrimaryKey<Record>);
 
    Reflection::EnumerateMembers(record, [&]<size_t I, typename FieldType>(FieldType& field) {
        if constexpr (IsField<FieldType>)
        {
            if constexpr (FieldType::IsPrimaryKey)
            {
                field = std::forward<FieldType>(id);
            }
        }
    });
}
 
template <typename Record, size_t InitialOffset>
inline LIGHTWEIGHT_FORCE_INLINE Record& DataMapper::BindOutputColumns(Record& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    BindOutputColumns<Record, InitialOffset>(record, &_stmt);
    return record;
}
 
template <typename Record, size_t InitialOffset>
Record& DataMapper::BindOutputColumns(Record& record, SqlStatement* stmt)
{
    return BindOutputColumns<std::make_integer_sequence<size_t, Reflection::CountMembers<Record>>, Record, InitialOffset>(
        record, stmt);
}
 
template <typename ElementMask, typename Record, size_t InitialOffset>
inline LIGHTWEIGHT_FORCE_INLINE Record& DataMapper::BindOutputColumns(Record& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    return BindOutputColumns<ElementMask, Record, InitialOffset>(record, &_stmt);
}
 
template <typename ElementMask, typename Record, size_t InitialOffset>
Record& DataMapper::BindOutputColumns(Record& record, SqlStatement* stmt)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
    static_assert(!std::is_const_v<Record>);
    assert(stmt != nullptr);
 
    Reflection::EnumerateMembers<ElementMask>(
        record, [stmt, i = SQLSMALLINT { InitialOffset }]<size_t I, typename Field>(Field& field) mutable {
            if constexpr (IsField<Field>)
            {
                stmt->BindOutputColumn(i++, &field.MutableValue());
            }
            else if constexpr (SqlOutputColumnBinder<Field>)
            {
                stmt->BindOutputColumn(i++, &field);
            }
        });
 
    return record;
}
 
template <typename Record>
void DataMapper::ConfigureRelationAutoLoading(Record& record)
{
    static_assert(DataMapperRecord<Record>, "Record must satisfy DataMapperRecord");
 
    Reflection::EnumerateMembers(record, [&]<size_t FieldIndex, typename FieldType>(FieldType& field) {
        if constexpr (IsBelongsTo<FieldType>)
        {
            field.SetAutoLoader(typename FieldType::Loader {
                .loadReference = [this, value = field.Value()]() -> std::optional<typename FieldType::ReferencedRecord> {
                    return LoadBelongsTo<FieldType>(value);
                },
            });
        }
        else if constexpr (IsHasMany<FieldType>)
        {
            using ReferencedRecord = typename FieldType::ReferencedRecord;
            HasMany<ReferencedRecord>& hasMany = field;
            hasMany.SetAutoLoader(typename FieldType::Loader {
                .count = [this, &record]() -> size_t {
                    size_t count = 0;
                    CallOnHasMany<FieldIndex, Record, ReferencedRecord>(
                        record, [&](SqlSelectQueryBuilder selectQuery, auto const& primaryKeyField) {
                            _stmt.Prepare(selectQuery.Count());
                            _stmt.Execute(primaryKeyField.Value());
                            if (_stmt.FetchRow())
                                count = _stmt.GetColumn<size_t>(1);
                            _stmt.CloseCursor();
                        });
                    return count;
                },
                .all = [this, &record, &hasMany]() { LoadHasMany<FieldIndex>(record, hasMany); },
                .each =
                    [this, &record](auto const& each) {
                        CallOnHasMany<FieldIndex, Record, ReferencedRecord>(
                            record, [&](SqlSelectQueryBuilder selectQuery, auto const& primaryKeyField) {
                                auto stmt = SqlStatement { _connection };
                                stmt.Prepare(selectQuery.All());
                                stmt.Execute(primaryKeyField.Value());
 
                                auto referencedRecord = ReferencedRecord {};
                                BindOutputColumns(referencedRecord, &stmt);
                                ConfigureRelationAutoLoading(referencedRecord);
 
                                while (stmt.FetchRow())
                                {
                                    each(referencedRecord);
                                    BindOutputColumns(referencedRecord, &stmt);
                                }
                            });
                    },
            });
        }
        else if constexpr (IsHasOneThrough<FieldType>)
        {
            using ReferencedRecord = typename FieldType::ReferencedRecord;
            using ThroughRecord = typename FieldType::ThroughRecord;
            HasOneThrough<ReferencedRecord, ThroughRecord>& hasOneThrough = field;
            hasOneThrough.SetAutoLoader(typename FieldType::Loader {
                .loadReference =
                    [this, &record, &hasOneThrough]() {
                        LoadHasOneThrough<ReferencedRecord, ThroughRecord>(record, hasOneThrough);
                    },
            });
        }
        else if constexpr (IsHasManyThrough<FieldType>)
        {
            using ReferencedRecord = typename FieldType::ReferencedRecord;
            using ThroughRecord = typename FieldType::ThroughRecord;
            HasManyThrough<ReferencedRecord, ThroughRecord>& hasManyThrough = field;
            hasManyThrough.SetAutoLoader(typename FieldType::Loader {
                .count = [this, &record]() -> size_t {
                    // Load result for Count()
                    size_t count = 0;
                    CallOnHasManyThrough<ReferencedRecord, ThroughRecord>(
                        record, [&](SqlSelectQueryBuilder& selectQuery, auto& primaryKeyField) {
                            _stmt.Prepare(selectQuery.Count());
                            _stmt.Execute(primaryKeyField.Value());
                            if (_stmt.FetchRow())
                                count = _stmt.GetColumn<size_t>(1);
                            _stmt.CloseCursor();
                        });
                    return count;
                },
                .all =
                    [this, &record, &hasManyThrough]() {
                        // Load result for All()
                        LoadHasManyThrough(record, hasManyThrough);
                    },
                .each =
                    [this, &record](auto const& each) {
                        // Load result for Each()
                        CallOnHasManyThrough<ReferencedRecord, ThroughRecord>(
                            record, [&](SqlSelectQueryBuilder& selectQuery, auto& primaryKeyField) {
                                auto stmt = SqlStatement { _connection };
                                stmt.Prepare(selectQuery.All());
                                stmt.Execute(primaryKeyField.Value());
 
                                auto referencedRecord = ReferencedRecord {};
                                BindOutputColumns(referencedRecord, &stmt);
                                ConfigureRelationAutoLoading(referencedRecord);
 
                                while (stmt.FetchRow())
                                {
                                    each(referencedRecord);
                                    BindOutputColumns(referencedRecord, &stmt);
                                }
                            });
                    },
            });
        }
    });
}
 
} // namespace Lightweight