Meta Event Match Quality Is Low

function propulse_normalise_and_hash( $value, $type = 'text' ) {
	if ( empty( $value ) ) {
		return '';
	}

	$value = trim( (string) $value );

	switch ( $type ) {
		case 'email':
			$value = strtolower( $value );
			break;

		case 'phone':
			// Digits only. Country code included, no leading zeros.
			$value = preg_replace( '/[^0-9]/', '', $value );
			$value = ltrim( $value, '0' );
			break;

		case 'name':
		case 'city':
			$value = strtolower( $value );
			$value = preg_replace( '/[^a-z\x{00C0}-\x{024F}]/u', '', $value );
			break;

		case 'postcode':
			$value = strtolower( preg_replace( '/\s+/', '', $value ) );
			break;

		case 'country':
		case 'state':
			$value = strtolower( substr( preg_replace( '/[^a-zA-Z]/', '', $value ), 0, 2 ) );
			break;

		default:
			$value = strtolower( $value );
	}

	if ( '' === $value ) {
		return '';
	}

	return hash( 'sha256', $value );
}

function propulse_capi_user_data( WC_Order $order ) {
	$data = array(
		'em'          => propulse_normalise_and_hash( $order->get_billing_email(), 'email' ),
		'ph'          => propulse_normalise_and_hash( $order->get_billing_phone(), 'phone' ),
		'fn'          => propulse_normalise_and_hash( $order->get_billing_first_name(), 'name' ),
		'ln'          => propulse_normalise_and_hash( $order->get_billing_last_name(), 'name' ),
		'ct'          => propulse_normalise_and_hash( $order->get_billing_city(), 'city' ),
		'st'          => propulse_normalise_and_hash( $order->get_billing_state(), 'state' ),
		'zp'          => propulse_normalise_and_hash( $order->get_billing_postcode(), 'postcode' ),
		'country'     => propulse_normalise_and_hash( $order->get_billing_country(), 'country' ),
		'external_id' => propulse_normalise_and_hash( propulse_stable_external_id( $order ), 'text' ),
	);

	// Sent in plain text — hashing these makes them unusable.
	$fbc = $order->get_meta( '_propulse_fbc' );
	$fbp = $order->get_meta( '_propulse_fbp' );

	if ( $fbc ) {
		$data['fbc'] = $fbc;
	}
	if ( $fbp ) {
		$data['fbp'] = $fbp;
	}

	$data['client_ip_address'] = $order->get_customer_ip_address();
	$data['client_user_agent'] = $order->get_customer_user_agent();

	// Meta rejects empty strings — remove rather than send blank.
	return array_filter( $data, function ( $v ) {
		return '' !== $v && null !== $v;
	} );
}

function propulse_stable_external_id( WC_Order $order ) {
	$user_id = $order->get_user_id();

	if ( $user_id ) {
		return 'uid_' . $user_id;
	}

	// Guest checkout — derive from email so the same person matches across orders.
	return 'em_' . strtolower( trim( $order->get_billing_email() ) );
}