#include <cassert>
#include <string>
#include <tuple>
#include <type_traits>
#include <vector>

#include <sqlite3.h> 

template<size_t I>
struct builder_impl
{
    template<typename T, typename G>
    static void set_value(T& tup, size_t idx, G& val)
    {
        if (idx == I - 1)
        {
            std::get<I - 1>(tup) = val;
        }
        else 
        {
            builder_impl<I - 1>::set_value(tup, idx, val);
        }
    }
};
 
template <>
struct builder_impl<0>
{
    template<typename T, typename G>
    static void set_value(T& tup, size_t idx, G& val) 
    { 
        assert(false); 
    }
};

template <typename G, typename... Ts>
void set_value_at(std::tuple<Ts...>& tup, size_t idx, G const& val)
{
    builder_impl<sizeof...(Ts)>::set_value(tup, idx, val);
} 
 
template <typename G, typename... Ts>
void set_value_at(std::tuple<Ts...>& tup, size_t idx, G& val)
{
    builder_impl<sizeof...(Ts)>::set_value(tup, idx, val);
}



class DBManager
{
    public:
        
        // Constructor
        DBManager(const std::string& db_path);
        
        // Destructor
        ~DBManager();
        
        // execute query
        template<typename... T>
        std::vector<std::tuple<T...>*>* execute_query(
            const std::string& sql_statement,
            int& return_code)
        {
            sqlite3_stmt* sqlite_statement;
        
            // Prepare the sqlite statement
            return_code = sqlite3_prepare_v2(db, sql_statement.c_str(), -1, 
                                             &sqlite_statement, nullptr);
            if (return_code != SQLITE_OK)
            {
                return nullptr;
            } 
            
            auto output_vector = new std::vector<std::tuple<T...>*>();            
            
            // Iterate until we've collected all the output
            int step_return = 0;
            while ((step_return = sqlite3_step(sqlite_statement)) != SQLITE_DONE)
            {
                // Create a new result row to be populated below
                auto result_row = new std::tuple<T...>();
                
                // Iterate over the columns in the row
                int num_cols = sqlite3_data_count(sqlite_statement);
                for (int col_idx = 0; col_idx < num_cols; col_idx++)
                {
                    switch(sqlite3_column_type(sqlite_statement, col_idx))
                    {
                        case SQLITE_INTEGER:                        
                            set_value_at(*result_row, col_idx, 
                                         sqlite3_column_int64(sqlite_statement, 
                                                              col_idx));
                            break;
                            
                        case SQLITE_FLOAT:
                            set_value_at(*result_row, col_idx, 
                                         sqlite3_column_double(sqlite_statement, 
                                                                col_idx));
                            break;
                            
                        case SQLITE_TEXT:
                            //~ set_value_at(*result_row, col_idx, 
                                         //~ std::string(reinterpret_cast<const char*>(sqlite3_column_text(sqlite_statement, col_idx))));
                            break;
                            
                        case SQLITE_BLOB:
                            break;
                            
                        case SQLITE_NULL:
                            //~ set_value_at(*result_row, col_idx, std::string(""));
                            break;
                    }
                }
                
                output_vector->push_back(result_row);
            }
            
            return output_vector;
        }
        
    private:
    
        sqlite3 *db;
};