B2B Bulk Discount Matrix Table

<?php
/**
 * B2B Bulk Discount Matrix Table
 * ----------------------------------------
 * Outputs a semantic wholesale-pricing-tier table on single product pages
 * for products that belong to a configurable category (default: "wholesale").
 *
 * Drop this into your child theme's functions.php OR save as
 *   /wp-content/mu-plugins/bulk-discount-matrix.php
 *
 */

defined( 'ABSPATH' ) || exit;

/**
 * Category slug (or array of slugs) that triggers the matrix.
 * Override via the `bdm_target_categories` filter.
 */
function bdm_get_target_categories() {
	return apply_filters( 'bdm_target_categories', array( 'wholesale' ) );
}

/**
 * Resolve the active tier set for a given product.
 *
 * @param int $product_id
 * @return array
 */
function bdm_get_discount_tiers( $product_id ) {
	$default_tiers = array(
		array( 'min_qty' => 10,  'max_qty' => 49,  'discount' => 10 ),
		array( 'min_qty' => 50,  'max_qty' => 99,  'discount' => 20 ),
		array( 'min_qty' => 100, 'max_qty' => 0,   'discount' => 30 ),
	);

	$product_tiers = get_post_meta( $product_id, '_bulk_discount_tiers', true );

	$tiers = ( is_array( $product_tiers ) && ! empty( $product_tiers ) )
		? $product_tiers
		: $default_tiers;

	return apply_filters( 'bdm_discount_tiers', $tiers, $product_id );
}

/**
 * Get the base unit price we apply the discount to.
 * Falls back gracefully for variable products.
 *
 * @param WC_Product $product
 * @return float
 */
function bdm_get_base_price( $product ) {
	$price = (float) $product->get_regular_price();

	if ( ! $price && $product->is_type( 'variable' ) ) {
		$price = (float) $product->get_variation_regular_price( 'min' );
	}

	return $price;
}

/**
 * Render the bulk discount matrix on the single product page.
 */
function bdm_render_discount_table() {
	global $product;

	if ( ! $product instanceof WC_Product ) {
		return;
	}

	$product_id      = $product->get_id();
	$target_cats     = bdm_get_target_categories();

	if ( ! has_term( $target_cats, 'product_cat', $product_id ) ) {
		return;
	}

	$tiers = bdm_get_discount_tiers( $product_id );
	if ( empty( $tiers ) ) {
		return;
	}

	$base_price = bdm_get_base_price( $product );
	if ( $base_price <= 0 ) {
		return;
	}

	// Sort tiers by min_qty ascending for clean output.
	usort( $tiers, function ( $a, $b ) {
		return (int) $a['min_qty'] <=> (int) $b['min_qty'];
	} );

	?>
	<section class="bdm-bulk-discount-matrix" aria-labelledby="bdm-heading-<?php echo esc_attr( $product_id ); ?>">
		<h3 id="bdm-heading-<?php echo esc_attr( $product_id ); ?>" class="bdm-title">
			<?php esc_html_e( 'Wholesale Pricing Tiers', 'bdm' ); ?>
		</h3>

		<table class="bdm-table">
			<caption class="screen-reader-text">
				<?php esc_html_e( 'Volume discount pricing by quantity', 'bdm' ); ?>
			</caption>
			<thead>
				<tr>
					<th scope="col"><?php esc_html_e( 'Quantity', 'bdm' ); ?></th>
					<th scope="col"><?php esc_html_e( 'Discount', 'bdm' ); ?></th>
					<th scope="col"><?php esc_html_e( 'Unit Price', 'bdm' ); ?></th>
					<th scope="col"><?php esc_html_e( 'You Save / Unit', 'bdm' ); ?></th>
				</tr>
			</thead>
			<tbody>
				<?php foreach ( $tiers as $tier ) :
					$min      = isset( $tier['min_qty'] )  ? (int) $tier['min_qty']  : 0;
					$max      = isset( $tier['max_qty'] )  ? (int) $tier['max_qty']  : 0;
					$discount = isset( $tier['discount'] ) ? (float) $tier['discount'] : 0;

					if ( $min <= 0 || $discount <= 0 ) {
						continue;
					}

					$qty_label  = $max > 0
						? sprintf( '%d – %d', $min, $max )
						: sprintf( /* translators: %d: minimum quantity */ esc_html__( '%d+', 'bdm' ), $min );

					$tier_price = $base_price * ( 1 - ( $discount / 100 ) );
					$savings    = $base_price - $tier_price;
				?>
					<tr>
						<th scope="row" class="bdm-qty"><?php echo wp_kses_post( $qty_label ); ?></th>
						<td class="bdm-discount"><?php echo esc_html( rtrim( rtrim( number_format( $discount, 2 ), '0' ), '.' ) ); ?>%</td>
						<td class="bdm-price"><?php echo wp_kses_post( wc_price( $tier_price ) ); ?></td>
						<td class="bdm-savings"><?php echo wp_kses_post( wc_price( $savings ) ); ?></td>
					</tr>
				<?php endforeach; ?>
			</tbody>
		</table>

		<p class="bdm-note">
			<small><?php esc_html_e( 'Discounts are applied automatically at checkout based on cart quantity.', 'bdm' ); ?></small>
		</p>
	</section>
	<?php
}
add_action( 'woocommerce_single_product_summary', 'bdm_render_discount_table', 25 );

/**
 * Lightweight inline styles.
 */
function bdm_inline_styles() {
	if ( ! function_exists( 'is_product' ) || ! is_product() ) {
		return;
	}
	?>
	<style id="bdm-inline-css">
		.bdm-bulk-discount-matrix {
			margin: 1.5rem 0;
			padding: 1rem 1.25rem;
			border: 1px solid #e5e7eb;
			border-radius: 8px;
			background: #f9fafb;
		}
		.bdm-bulk-discount-matrix .bdm-title {
			margin: 0 0 .75rem;
			font-size: 1.05rem;
			font-weight: 700;
			letter-spacing: .01em;
		}
		.bdm-table {
			width: 100%;
			border-collapse: collapse;
			font-size: .95rem;
		}
		.bdm-table th,
		.bdm-table td {
			padding: .65rem .85rem;
			text-align: left;
			border-bottom: 1px solid #e5e7eb;
		}
		.bdm-table thead th {
			background: #111827;
			color: #fff;
			font-weight: 600;
			font-size: .85rem;
			text-transform: uppercase;
			letter-spacing: .03em;
		}
		.bdm-table tbody tr:nth-child(even) { background: #ffffff; }
		.bdm-table tbody tr:hover { background: #eef2ff; }
		.bdm-table tbody th.bdm-qty { font-weight: 600; }
		.bdm-table .bdm-discount,
		.bdm-table .bdm-price,
		.bdm-table .bdm-savings { font-variant-numeric: tabular-nums; }
		.bdm-bulk-discount-matrix .bdm-note { margin: .75rem 0 0; color: #6b7280; }

		@media (max-width: 480px) {
			.bdm-table th,
			.bdm-table td { padding: .5rem .55rem; font-size: .9rem; }
		}
	</style>
	<?php
}
add_action( 'wp_head', 'bdm_inline_styles' );