Woocommerce - Can I intercept the Line Price (Cart) calculation? - wordpress

Question

So for example, I have a product which costs £2/item if you buy singles or £1/item if you buy it in packs of 6.
Customers enter their quantity required, let's say 7, and then add it to the basket.
The total cost should be £8. £6 (1 pack) + £2 (1 single). But if I add it to the basket currently the price will come out as £7 as you'd expect (it just does 7 x the price set which is £1).
I need to intercept/filter the line price so that it calculates the number of packs, and the number of singles, and then returns the right amount. I can design the function and the math, I just need to know where to hook into.
i.e. is there a filter like woocommerce_get_cart or something similar? And if so, how do I alter the line price?
(p.s. I know I could achieve the with variable products for instance but that's not an option for stock control reasons).

Answer 1

public function calculate_totals() {
$this->reset();
$this->coupons = $this->get_coupons();
do_action( 'woocommerce_before_calculate_totals', $this );
if ( $this->is_empty() ) {
$this->set_session();
return;
}
$tax_rates = array();
$shop_tax_rates = array();
/**
* Calculate subtotals for items. This is done first so that discount logic can use the values.
*/
foreach ( $this->get_cart() as $cart_item_key => $values ) {
$_product = $values['data'];
// Count items + weight
$this->cart_contents_weight += $_product->get_weight() * $values['quantity'];
$this->cart_contents_count += $values['quantity'];
// Prices
$line_price = $_product->get_price() * $values['quantity'];
$line_subtotal = 0;
$line_subtotal_tax = 0;
/**
* No tax to calculate
*/
if ( ! $_product->is_taxable() ) {
// Subtotal is the undiscounted price
$this->subtotal += $line_price;
$this->subtotal_ex_tax += $line_price;
/**
* Prices include tax
*
* To prevent rounding issues we need to work with the inclusive price where possible
* otherwise we'll see errors such as when working with a 9.99 inc price, 20% VAT which would
* be 8.325 leading to totals being 1p off
*
* Pre tax coupons come off the price the customer thinks they are paying - tax is calculated
* afterwards.
*
* e.g. $100 bike with $10 coupon = customer pays $90 and tax worked backwards from that
*/
} elseif ( $this->prices_include_tax ) {
// Get base tax rates
if ( empty( $shop_tax_rates[ $_product->tax_class ] ) ) {
$shop_tax_rates[ $_product->tax_class ] = WC_Tax::get_base_tax_rates( $_product->tax_class );
}
// Get item tax rates
if ( empty( $tax_rates[ $_product->get_tax_class() ] ) ) {
$tax_rates[ $_product->get_tax_class() ] = WC_Tax::get_rates( $_product->get_tax_class() );
}
$base_tax_rates = $shop_tax_rates[ $_product->tax_class ];
$item_tax_rates = $tax_rates[ $_product->get_tax_class() ];
/**
* ADJUST TAX - Calculations when base tax is not equal to the item tax
*/
if ( $item_tax_rates !== $base_tax_rates ) {
// Work out a new base price without the shop's base tax
$taxes = WC_Tax::calc_tax( $line_price, $base_tax_rates, true, true );
// Now we have a new item price (excluding TAX)
$line_subtotal = $line_price - array_sum( $taxes );
// Now add modified taxes
$tax_result = WC_Tax::calc_tax( $line_subtotal, $item_tax_rates );
$line_subtotal_tax = array_sum( $tax_result );
/**
* Regular tax calculation (customer inside base and the tax class is unmodified
*/
} else {
// Calc tax normally
$taxes = WC_Tax::calc_tax( $line_price, $item_tax_rates, true );
$line_subtotal_tax = array_sum( $taxes );
$line_subtotal = $line_price - array_sum( $taxes );
}
/**
* Prices exclude tax
*
* This calculation is simpler - work with the base, untaxed price.
*/
} else {
// Get item tax rates
if ( empty( $tax_rates[ $_product->get_tax_class() ] ) ) {
$tax_rates[ $_product->get_tax_class() ] = WC_Tax::get_rates( $_product->get_tax_class() );
}
$item_tax_rates = $tax_rates[ $_product->get_tax_class() ];
// Base tax for line before discount - we will store this in the order data
$taxes = WC_Tax::calc_tax( $line_price, $item_tax_rates );
$line_subtotal_tax = array_sum( $taxes );
$line_subtotal = $line_price;
}
// Add to main subtotal
$this->subtotal += $line_subtotal + $line_subtotal_tax;
$this->subtotal_ex_tax += $line_subtotal;
}
/**
* Calculate totals for items
*/
foreach ( $this->get_cart() as $cart_item_key => $values ) {
$_product = $values['data'];
// Prices
$base_price = $_product->get_price();
$line_price = $_product->get_price() * $values['quantity'];
// Tax data
$taxes = array();
$discounted_taxes = array();
/**
* No tax to calculate
*/
if ( ! $_product->is_taxable() ) {
// Discounted Price (price with any pre-tax discounts applied)
$discounted_price = $this->get_discounted_price( $values, $base_price, true );
$line_subtotal_tax = 0;
$line_subtotal = $line_price;
$line_tax = 0;
$line_total = WC_Tax::round( $discounted_price * $values['quantity'] );
/**
* Prices include tax
*/
} elseif ( $this->prices_include_tax ) {
$base_tax_rates = $shop_tax_rates[ $_product->tax_class ];
$item_tax_rates = $tax_rates[ $_product->get_tax_class() ];
/**
* ADJUST TAX - Calculations when base tax is not equal to the item tax
*/
if ( $item_tax_rates !== $base_tax_rates ) {
// Work out a new base price without the shop's base tax
$taxes = WC_Tax::calc_tax( $line_price, $base_tax_rates, true, true );
// Now we have a new item price (excluding TAX)
$line_subtotal = round( $line_price - array_sum( $taxes ), WC_ROUNDING_PRECISION );
$taxes = WC_Tax::calc_tax( $line_subtotal, $item_tax_rates );
$line_subtotal_tax = array_sum( $taxes );
// Adjusted price (this is the price including the new tax rate)
$adjusted_price = ( $line_subtotal + $line_subtotal_tax ) / $values['quantity'];
// Apply discounts
$discounted_price = $this->get_discounted_price( $values, $adjusted_price, true );
$discounted_taxes = WC_Tax::calc_tax( $discounted_price * $values['quantity'], $item_tax_rates, true );
$line_tax = array_sum( $discounted_taxes );
$line_total = ( $discounted_price * $values['quantity'] ) - $line_tax;
/**
* Regular tax calculation (customer inside base and the tax class is unmodified
*/
} else {
// Work out a new base price without the item tax
$taxes = WC_Tax::calc_tax( $line_price, $item_tax_rates, true );
// Now we have a new item price (excluding TAX)
$line_subtotal = $line_price - array_sum( $taxes );
$line_subtotal_tax = array_sum( $taxes );
// Calc prices and tax (discounted)
$discounted_price = $this->get_discounted_price( $values, $base_price, true );
$discounted_taxes = WC_Tax::calc_tax( $discounted_price * $values['quantity'], $item_tax_rates, true );
$line_tax = array_sum( $discounted_taxes );
$line_total = ( $discounted_price * $values['quantity'] ) - $line_tax;
}
// Tax rows - merge the totals we just got
foreach ( array_keys( $this->taxes + $discounted_taxes ) as $key ) {
$this->taxes[ $key ] = ( isset( $discounted_taxes[ $key ] ) ? $discounted_taxes[ $key ] : 0 ) + ( isset( $this->taxes[ $key ] ) ? $this->taxes[ $key ] : 0 );
}
/**
* Prices exclude tax
*/
} else {
$item_tax_rates = $tax_rates[ $_product->get_tax_class() ];
// Work out a new base price without the shop's base tax
$taxes = WC_Tax::calc_tax( $line_price, $item_tax_rates );
// Now we have the item price (excluding TAX)
$line_subtotal = $line_price;
$line_subtotal_tax = array_sum( $taxes );
// Now calc product rates
$discounted_price = $this->get_discounted_price( $values, $base_price, true );
$discounted_taxes = WC_Tax::calc_tax( $discounted_price * $values['quantity'], $item_tax_rates );
$discounted_tax_amount = array_sum( $discounted_taxes );
$line_tax = $discounted_tax_amount;
$line_total = $discounted_price * $values['quantity'];
// Tax rows - merge the totals we just got
foreach ( array_keys( $this->taxes + $discounted_taxes ) as $key ) {
$this->taxes[ $key ] = ( isset( $discounted_taxes[ $key ] ) ? $discounted_taxes[ $key ] : 0 ) + ( isset( $this->taxes[ $key ] ) ? $this->taxes[ $key ] : 0 );
}
}
// Cart contents total is based on discounted prices and is used for the final total calculation
$this->cart_contents_total += $line_total;
// Store costs + taxes for lines
$this->cart_contents[ $cart_item_key ]['line_total'] = $line_total;
$this->cart_contents[ $cart_item_key ]['line_tax'] = $line_tax;
$this->cart_contents[ $cart_item_key ]['line_subtotal'] = $line_subtotal;
$this->cart_contents[ $cart_item_key ]['line_subtotal_tax'] = $line_subtotal_tax;
// Store rates ID and costs - Since 2.2
$this->cart_contents[ $cart_item_key ]['line_tax_data'] = array( 'total' => $discounted_taxes, 'subtotal' => $taxes );
}
// Only calculate the grand total + shipping if on the cart/checkout
if ( is_checkout() || is_cart() || defined('WOOCOMMERCE_CHECKOUT') || defined('WOOCOMMERCE_CART') ) {
// Calculate the Shipping
$this->calculate_shipping();
// Trigger the fees API where developers can add fees to the cart
$this->calculate_fees();
// Total up/round taxes and shipping taxes
if ( $this->round_at_subtotal ) {
$this->tax_total = WC_Tax::get_tax_total( $this->taxes );
$this->shipping_tax_total = WC_Tax::get_tax_total( $this->shipping_taxes );
$this->taxes = array_map( array( 'WC_Tax', 'round' ), $this->taxes );
$this->shipping_taxes = array_map( array( 'WC_Tax', 'round' ), $this->shipping_taxes );
} else {
$this->tax_total = array_sum( $this->taxes );
$this->shipping_tax_total = array_sum( $this->shipping_taxes );
}
// VAT exemption done at this point - so all totals are correct before exemption
if ( WC()->customer->is_vat_exempt() ) {
$this->remove_taxes();
}
// Allow plugins to hook and alter totals before final total is calculated
do_action( 'woocommerce_calculate_totals', $this );
// Grand Total - Discounted product prices, discounted tax, shipping cost + tax
$this->total = max( 0, apply_filters( 'woocommerce_calculated_total', round( $this->cart_contents_total + $this->tax_total + $this->shipping_tax_total + $this->shipping_total + $this->fee_total, $this->dp ), $this ) );
} else {
// Set tax total to sum of all tax rows
$this->tax_total = WC_Tax::get_tax_total( $this->taxes );
// VAT exemption done at this point - so all totals are correct before exemption
if ( WC()->customer->is_vat_exempt() ) {
$this->remove_taxes();
}
}
do_action( 'woocommerce_after_calculate_totals', $this );
$this->set_session();
}
this is the original total calculations on WooCommerce.
near the bottom you have:
// Allow plugins to hook and alter totals before final total is calculated
do_action( 'woocommerce_calculate_totals', $this );
of which I believe you can use to do something like this:
add_action('woocommerce_calculate_totals','my_woocommerce_calculate_totals');
function my_woocommerce_calculate_totals($cart) {
// get some hints from the code above and do something like foreach ( $cart->get_cart() as $cart_item_key => $values ) { }
// do your math, then set $cart->cart_contents_total
}