Function.h

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/*
 * SPDX-License-Identifier: GPL-2.0-or-later
 * SPDX-FileName: Function.h
 * SPDX-FileContributor: Dmitry Vedenko
 */
 
#pragma once
 
#include <functional>
#include <string>
#include <string_view>
#include <tuple>
#include <type_traits>
 
struct sqlite3;
struct sqlite3_value;
struct sqlite3_context;
 
namespace audacity::sqlite
{
namespace details
{
using SQLiteFunctorWithArgs =
   std::function<void(sqlite3_context*, int, sqlite3_value**)>;
 
using SQLiteFunctor= std::function<void(sqlite3_context*)>;
 
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, bool& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, int& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, unsigned int& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, long& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, unsigned long& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, long long& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, unsigned long long& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, double& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, float& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, std::string& result);
SQLITE_HELPERS_API void FromSQLiteValue(sqlite3_value& value, std::string_view& result);
 
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, bool value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, int value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, unsigned int value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, long value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, unsigned long value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, long long value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, unsigned long long value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, double value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, float value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, const std::string& value);
SQLITE_HELPERS_API void SetSQLiteFunctionResult(sqlite3_context* context, const std::string_view& value);
 
SQLITE_HELPERS_API void
SetSQLiteFunctionError(sqlite3_context* context, const std::string_view& error);
 
template<typename T>
std::decay_t<T> FromSQLiteValue(sqlite3_value& value)
{
   std::decay_t<T> result;
   FromSQLiteValue(value, result);
   return result;
}
 
template<typename... Args, std::size_t... Is>
auto SQLiteValuesToTuple(sqlite3_value** values, std::index_sequence<Is...>)
{
   return std::make_tuple(FromSQLiteValue<Args>(*values[Is])...);
}
 
template <typename CallbackType>
struct SQLiteFunction {};
 
template<typename R, typename... Args>
struct SQLiteFunction<std::function<R(Args...)>>
{
   static constexpr std::size_t Arity = sizeof...(Args);
 
   static SQLiteFunctorWithArgs ToSQLiteFunctorWithArgs(std::function<R(Args...)> callback)
   {
      return [function = std::move(callback)](
                sqlite3_context* context, int argc, sqlite3_value** argv)
      {
         if (argc != sizeof...(Args))
         {
            SetSQLiteFunctionError(context, "Invalid number of arguments");
            return;
         }
 
         if constexpr (std::is_same_v<R, void>)
         {
            std::apply(
               function, SQLiteValuesToTuple<Args...>(
                            argv, std::make_index_sequence<sizeof...(Args)>()));
         }
         else
         {
            SetSQLiteFunctionResult(
               context,
               std::apply(
                  function,
                  SQLiteValuesToTuple<Args...>(
                     argv, std::make_index_sequence<sizeof...(Args)>())));
         }
      };
   }
};
 
template <typename R> struct SQLiteFunction<std::function<R()>>
{
   static SQLiteFunctor ToSQLiteFunctor(std::function<R()> callback)
   {
      return [function = std::move(callback)](sqlite3_context* context)
      {
         if constexpr (std::is_same_v<R, void>)
            function();
         else
            SetSQLiteFunctionResult(context, function());
      };
   }
};
 
template<typename CallbackType>
auto MakeSQLiteFunctorWithArgs(CallbackType callback)
{
   using FunctionType = decltype(std::function { callback });
   return SQLiteFunction<FunctionType>::ToSQLiteFunctorWithArgs(
      std::move(callback));
}
 
template<typename CallbackType>
constexpr std::size_t GetFunctionArity()
{
   using FunctionType = decltype(std::function { std::declval<CallbackType>() });
   return SQLiteFunction<FunctionType>::Arity;
}
 
template <typename CallbackType>
auto MakeSQLiteFunctor(CallbackType callback)
{
   using FunctionType = decltype(std::function { callback });
   return SQLiteFunction<FunctionType>::ToSQLiteFunctor(
      std::move(callback));
}
 
} // namespace details
 
class SQLITE_HELPERS_API ScalarFunction final
{
   template<typename ScalarFunctionType>
   ScalarFunction(
      sqlite3* connection, std::string name, ScalarFunctionType function)
       : mConnection { connection }
       , mName { std::move(name) }
       , mFunctor { details::MakeSQLiteFunctorWithArgs(std::move(function)) }
   {
      Register(details::GetFunctionArity<ScalarFunctionType>());
   }
 
public:
   ScalarFunction() = default;
   ScalarFunction(const ScalarFunction&) = delete;
   ScalarFunction(ScalarFunction&&) noexcept;
   ScalarFunction& operator=(const ScalarFunction&) = delete;
   ScalarFunction& operator=(ScalarFunction&&) noexcept;
 
   ~ScalarFunction();
 
private:
   void Register(std::size_t arity);
 
   static void CallFunction(sqlite3_context* context, int argc, sqlite3_value** argv);
 
   sqlite3* mConnection { nullptr };
   std::string mName;
   details::SQLiteFunctorWithArgs mFunctor;
   friend class Connection;
};
 
class SQLITE_HELPERS_API AggregateFunction final
{
   template<typename StepFunctionType, typename FinalFunctionType>
   AggregateFunction(
      sqlite3* connection, std::string name, StepFunctionType stepFunction,
      FinalFunctionType finalFunction)
       : mConnection { connection }
       , mName { std::move(name) }
       , mStepFunctor { details::MakeSQLiteFunctorWithArgs(
            std::move(stepFunction)) }
       , mFinalFunctor { details::MakeSQLiteFunctor(std::move(finalFunction)) }
   {
      Register(details::GetFunctionArity<StepFunctionType>());
   }
 
public:
 
   AggregateFunction() = default;
   AggregateFunction(const AggregateFunction&) = delete;
   AggregateFunction(AggregateFunction&&) noexcept;
   AggregateFunction& operator=(const AggregateFunction&) = delete;
   AggregateFunction& operator=(AggregateFunction&&) noexcept;
 
   ~AggregateFunction();
 
private:
   void Register(std::size_t arity);
 
   static void CallStepFunction (
      sqlite3_context* context, int argc, sqlite3_value** argv);
 
   static void CallFinalFunction(sqlite3_context* context);
 
   sqlite3* mConnection { nullptr };
   std::string mName;
   details::SQLiteFunctorWithArgs mStepFunctor;
   details::SQLiteFunctor mFinalFunctor;
   friend class Connection;
};
 
} // namespace audacity::sqlite