public function calculateData(): array
    {
        //Listenpreis
        self::calculateAddPercentage(self::$buying_price, self::$discount, 'discount');
        //Bareinkaufspreis
        self::calculateSubPercentage($this->calculated_cash_discount, self::$procurement_cost, 'procurement_cost');
        //Zieleinkaufspreis
        self::calculateAddPercentage($this->calculated_discount, self::$cash_discount, 'cash_discount');
        //Bezugs- oder Einstandpreis
        self::calculateSubPercentage($this->calculated_procurement_cost, self::$cost, 'cost');
        //Selbstkostenpreis
        self::calculateSubPercentage($this->calculated_cost, self::$profit, 'profit');
        //Barverkaufspreis
        self::calculateSubPercentage($this->calculated_profit, self::$customer_card_discount, 'customer_card_discount');
        //Zielverkaufspreis
        self::calculateSubPercentage($this->calculated_customer_card_discount, self::$discount_two, 'discount_two');
        //Listenverkaufspreis
        self::calculateSubPercentage($this->calculated_value_added_tax, self::$calculated_loss, 'calculated_loss');
        //Mehrwersteuer
        self::calculateSubPercentage($this->calculated_discount_two, self::$value_added_tax, 'value_added_tax');

        // difference as number between selling price and result
        $difference_displayed  = $this->calculated_calculated_loss - self::$selling_price;
        $difference_calculated = $this->calculated_calculated_loss - self::$selling_price;

        $difference_displayed_plus  = strpos($difference_displayed, '-') ? '+' : '-';
        $difference_calculated_plus = strpos($difference_calculated, '-') ? '+' : '-';

        $plus_minus = '';
        switch(true)
        {
            case $difference_displayed_plus == '+':
            case $difference_calculated_plus == '+':
                $plus_minus = '+';
            break;
            case $difference_displayed_plus == '-':
            case $difference_calculated_plus == '-':
                $plus_minus            = '-';
                $difference_displayed  = str_replace('-', '', $difference_displayed);
                $difference_calculated = str_replace('-', '', $difference_calculated);
        }

        $difference_displayed  = $plus_minus.self::numberFormat($difference_displayed, 'de_DE', 2);
        $difference_calculated = $plus_minus.self::numberFormat($difference_calculated, 'de_DE', 4);

        // percentage difference between selling price and buying price displayed ( 2 digits)
        $lost_percentage_displayed = ($this->displayed_calculated_loss - self::$selling_price) / $this->displayed_calculated_loss * 100;

        // percentage difference between selling price and buying price calculated (4 digits)
        $lost_percentage_calculated = ($this->calculated_calculated_loss - self::$selling_price) / $this->calculated_calculated_loss * 100;

        $lost_percentage_displayed  = round($lost_percentage_displayed, self::$displayed_digits);
        $lost_percentage_calculated = round($lost_percentage_calculated, self::$calculated_digits);

        $lost_percentage_displayed  = str_replace('--', '-', $plus_minus.self::dotToComma($lost_percentage_displayed)).'%';
        $lost_percentage_calculated = str_replace('--', '-', $plus_minus.self::dotToComma($lost_percentage_calculated)).'%';

        $factor_displayed  = round($this->displayed_calculated_loss / self::$buying_price, 2);
        $factor_calculated = round($this->calculated_calculated_loss / self::$buying_price, 4);
        // get factor for the calculation
        $factor_currency_displayed  = self::dotToComma($factor_displayed);
        $factor_currency_calculated = self::dotToComma($factor_calculated);

        $result = [
            'buying_price'              => self::numberFormat(self::$buying_price, 'de_DE', 2),
            'selling_price'             => self::numberFormat(self::$selling_price, 'de_DE', 2),
            'currency'                  => self::$currency,
            'displayed'                 => [
                'discount'               => $this->displayed_discount,
                'cash_discount'          => $this->displayed_cash_discount,
                'procurement_cost'       => $this->displayed_procurement_cost,
                'cost'                   => $this->displayed_cost,
                'profit'                 => $this->displayed_profit,
                'customer_card_discount' => $this->displayed_customer_card_discount,
                'discount_two'           => $this->displayed_discount_two,
                'value_added_tax'        => $this->displayed_value_added_tax,
                'calculated_loss'        => $this->displayed_calculated_loss,
                'final_value'            => $this->displayed_calculated_loss,
                'lost_percentage'        => $lost_percentage_displayed,
                'lost_value'             => $difference_displayed,
                'factor'                 => $factor_displayed,
                'positive_negative'      => ($plus_minus == '+' ? 'positive' : 'negative')
            ],
            'displayed_currency'        => [
                'discount'               => $this->displayed_currency_discount,
                'cash_discount'          => $this->displayed_currency_cash_discount,
                'procurement_cost'       => $this->displayed_currency_procurement_cost,
                'cost'                   => $this->displayed_currency_cost,
                'profit'                 => $this->displayed_currency_profit,
                'customer_card_discount' => $this->displayed_currency_customer_card_discount,
                'discount_two'           => $this->displayed_currency_discount_two,
                'value_added_tax'        => $this->displayed_currency_value_added_tax,
                'calculated_loss'        => $this->displayed_currency_calculated_loss,
                'final_value'            => $this->displayed_currency_calculated_loss,
                'lost_percentage'        => $lost_percentage_displayed,
                'lost_value'             => $difference_displayed,
                'factor'                 => $factor_currency_displayed,
                'positive_negative'      => ($plus_minus == '+' ? 'positive' : 'negative')

            ],
            'calculated'                => [
                'discount'               => $this->calculated_discount,
                'cash_discount'          => $this->calculated_cash_discount,
                'procurement_cost'       => $this->calculated_procurement_cost,
                'cost'                   => $this->calculated_cost,
                'profit'                 => $this->calculated_profit,
                'customer_card_discount' => $this->calculated_customer_card_discount,
                'discount_two'           => $this->calculated_discount_two,
                'value_added_tax'        => $this->calculated_value_added_tax,
                'calculated_loss'        => $this->calculated_calculated_loss,
                'final_value'            => $this->calculated_calculated_loss,
                'lost_percentage'        => $lost_percentage_calculated,
                'lost_value'             => $difference_calculated,
                'factor'                 => $factor_calculated,
                'positive_negative'      => ($plus_minus == '+' ? 'positive' : 'negative')

            ],
            'calculated_currency'       => [
                'discount'               => $this->calculated_currency_discount,
                'cash_discount'          => $this->calculated_currency_cash_discount,
                'procurement_cost'       => $this->calculated_currency_procurement_cost,
                'cost'                   => $this->calculated_currency_cost,
                'profit'                 => $this->calculated_currency_profit,
                'customer_card_discount' => $this->calculated_currency_customer_card_discount,
                'discount_two'           => $this->calculated_currency_discount_two,
                'value_added_tax'        => $this->calculated_currency_value_added_tax,
                'calculated_loss'        => $this->calculated_currency_calculated_loss,
                'final_value'            => $this->calculated_currency_calculated_loss,
                'lost_percentage'        => $lost_percentage_calculated,
                'lost_value'             => $difference_calculated,
                'factor'                 => $factor_currency_calculated,
                'positive_negative'      => ($plus_minus == '+' ? 'positive' : 'negative')

            ],
            'calculated_base'           => [
                'discount'               => self::$discount,
                'cash_discount'          => self::$cash_discount,
                'procurement_cost'       => self::$procurement_cost,
                'cost'                   => self::$cost,
                'profit'                 => self::$profit,
                'customer_card_discount' => self::$customer_card_discount,
                'discount_two'           => self::$discount_two,
                'value_added_tax'        => self::$value_added_tax,
                'calculated_loss'        => self::$calculated_loss,
            ],
            'calculated_base_displayed' => [
                'discount'               => self::dotToComma(self::$discount),
                'cash_discount'          => self::dotToComma(self::$cash_discount),
                'procurement_cost'       => self::dotToComma(self::$procurement_cost),
                'cost'                   => self::dotToComma(self::$cost),
                'profit'                 => self::dotToComma(self::$profit),
                'customer_card_discount' => self::dotToComma(self::$customer_card_discount),
                'discount_two'           => self::dotToComma(self::$discount_two),
                'value_added_tax'        => self::dotToComma(self::$value_added_tax),
                'calculated_loss'        => self::dotToComma(self::$calculated_loss),
            ]
        ];

        $_SESSION['calculated_data'] = $result;

        return $result;
    }