Add: The class to handle Vietnam Currency Issues

2 features:
- Change the currency symbol "đ" to anything, e.g: VND, VNĐ, đồng
- Change the stupid zeros in VND to the more "human" display.

inc/class-wooviet-currency.php

@@ -0,0 +1,92 @@
+<?php
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * The class to handle Vietnam Currency Issues
+ *
+ * @author   htdat
+ * @since    1.0
+ *
+ */
+class WooViet_Currency {
+
+	/**
+	 * The new symbol of the VND currency
+	 * @var string
+	 * @use change_currency_symbol()
+	 */
+	protected $new_symbol;
+	/**
+	 * @var string
+	 * @use convert_price_thousand_to_k()
+	 */
+	protected $thousand_text;
+
+	/**
+	 * Change the currency symbol "đ" to anything, e.g: VND, VNĐ, đồng
+	 *
+	 * @param string $new_symbol - Allow HTML tags like "<span style="color: red;"> đồng</span>"
+	 */
+	public function change_currency_symbol( $new_symbol = ' đ ' ) {
+		$this->new_symbol = $new_symbol;
+		add_filter( 'woocommerce_currency_symbol', array( $this, 'filter_woocommerce_currency_symbol' ), 10, 2 );
+	}
+
+	/**
+	 * @see https://docs.woocommerce.com/document/change-a-currency-symbol/
+	 *
+	 * @use change_currency_symbol()
+	 *
+	 * @param $currency_symbol
+	 * @param $currency
+	 *
+	 * @return mixed
+	 */
+	public function filter_woocommerce_currency_symbol( $currency_symbol, $currency ) {
+		switch ( $currency ) {
+			case 'VND':
+				$currency_symbol = $this->new_symbol;
+				break;
+		}
+
+		return $currency_symbol;
+	}
+
+	/**
+	 * Change the stupid zeros in VND to the more "human" display.
+	 * E.g: 50000 (VND) will be 50K (VND), or 50 thousands (VND)
+	 *
+	 * @param string $thousand_text - Allow HTML tags like "<span style="color: green;"> K</span>"
+	 *
+	 */
+	public function convert_price_thousand_to_k( $thousand_text = ' K' ) {
+		$this->thousand_text = $thousand_text;
+		add_filter( 'formatted_woocommerce_price', array( $this, 'filter_formatted_woocommerce_price' ), 10, 5 );
+	}
+
+	/**
+	 * @use convert_price_thousand_to_k()
+	 *
+	 * @param string $formatted_price
+	 * @param float $price
+	 * @param $decimals
+	 * @param $decimal_separator
+	 * @param $thousand_separator
+	 *
+	 * @return string
+	 */
+	public function filter_formatted_woocommerce_price( $formatted_price, $price, $decimals, $decimal_separator, $thousand_separator ) {
+
+		if ( $price < 1000 ) {
+			return $formatted_price;
+		} else {
+			$new_formatted_price = number_format( $price / 1000, $decimals, $decimal_separator, $thousand_separator ) . $this->thousand_text;
+
+			return $new_formatted_price;
+		}
+
+	}
+}