refactor(router): include currency conversion utility functions as Currency methods (#1790)

crates/common_enums/src/enums.rs

@@ -1,3 +1,5 @@
+use std::num::TryFromIntError;
+
 use router_derive;
 use serde::{Deserialize, Serialize};
 use utoipa::ToSchema;
@@ -289,6 +291,40 @@ pub enum Currency {
 }
 
 impl Currency {
+    /// Convert the amount to its base denomination based on Currency and return String
+    pub fn to_currency_base_unit(&self, amount: i64) -> Result<String, TryFromIntError> {
+        let amount_f64 = self.to_currency_base_unit_asf64(amount)?;
+        Ok(format!("{amount_f64:.2}"))
+    }
+
+    /// Convert the amount to its base denomination based on Currency and return f64
+    pub fn to_currency_base_unit_asf64(&self, amount: i64) -> Result<f64, TryFromIntError> {
+        let amount_f64: f64 = u32::try_from(amount)?.into();
+        let amount = if self.is_zero_decimal_currency() {
+            amount_f64
+        } else if self.is_three_decimal_currency() {
+            amount_f64 / 1000.00
+        } else {
+            amount_f64 / 100.00
+        };
+        Ok(amount)
+    }
+
+    /// Convert the amount to its base denomination based on Currency and check for zero decimal currency and return String
+    /// Paypal Connector accepts Zero and Two decimal currency but not three decimal and it should be updated as required for 3 decimal currencies.
+    /// Paypal Ref - https://developer.paypal.com/docs/reports/reference/paypal-supported-currencies/
+    pub fn to_currency_base_unit_with_zero_decimal_check(
+        &self,
+        amount: i64,
+    ) -> Result<String, TryFromIntError> {
+        let amount_f64 = self.to_currency_base_unit_asf64(amount)?;
+        if self.is_zero_decimal_currency() {
+            Ok(amount_f64.to_string())
+        } else {
+            Ok(format!("{amount_f64:.2}"))
+        }
+    }
+
     pub fn iso_4217(&self) -> &'static str {
         match *self {
             Self::AED => "784",