Added rates caching for currency pairs

index.js

@@ -160,14 +160,15 @@ class CurrencyConverter {
         this.currencyAmount = 1
         this.convertedValue = 0
         this.isDecimalComma = false
+        this.ratesCache = {};
 
         if(params != undefined){
             if(params["from"] !== undefined)
                 this.from(params["from"])
 
             if(params["to"] !== undefined)
                 this.to(params["to"])
-            
+
             if(params["amount"] !== undefined)
                 this.amount(params["amount"])
 
@@ -178,7 +179,7 @@ class CurrencyConverter {
     from (currencyFrom) {
         if(typeof currencyFrom !== "string")
             throw new TypeError("currency code should be a string")
-            
+
         if(!this.currencyCode.includes(currencyFrom.toUpperCase()))
             throw new Error(`${currencyFrom} is not a valid currency code`)
 
@@ -201,15 +202,15 @@ class CurrencyConverter {
 
         if(currencyAmount <= 0)
             throw new Error("amount should be a positive number")
-            
+
         this.currencyAmount = currencyAmount
         return this
     }
 
     setDecimalComma (isDecimalComma){
         if(typeof isDecimalComma !== "boolean")
             throw new TypeError("isDecimalComma should be a boolean")
-        
+
         this.isDecimalComma = isDecimalComma
         return this
     }
@@ -230,25 +231,30 @@ class CurrencyConverter {
     rates(){
         if(this.currencyFrom === this.currencyTo)
             return new Promise((resolve, _) => {resolve(this.currencyAmount) })
-        else    
-            return got(`https://www.google.co.in/search?q=${this.currencyAmount}+${this.currencyFrom}+to+${this.currencyTo}+&hl=en`)
-                .then((html) => {
-	                return cheerio.load(html.body)})
-                .then(($) => {return $(".iBp4i").text().split(" ")[0]})
-                .then((rates) => {
-                    if(this.isDecimalComma){
-                        if(rates.includes("."))
-                            rates = this.replaceAll(rates, ".", "")
-                        if(rates.includes(","))
-                            rates = this.replaceAll(rates, ",", ".")
-                    }
-                    else{
-                        if(rates.includes(","))
-                            rates = this.replaceAll(rates, ",", "")
-                    }
-
-                    return parseFloat(rates)
-            })
+        else
+            let currencyPair = this.currencyFrom.toUpperCase() + this.currencyTo.toUpperCase();
+            if (currencyPair in this.ratesCache)
+                return this.ratesCache[currencyPair];
+            else
+                return got(`https://www.google.co.in/search?q=${this.currencyFrom}+to+${this.currencyTo}+&hl=en`)
+                    .then((html) => {
+    	                return cheerio.load(html.body)})
+                    .then(($) => {return $(".iBp4i").text().split(" ")[0]})
+                    .then((rates) => {
+                        if(this.isDecimalComma){
+                            if(rates.includes("."))
+                                rates = this.replaceAll(rates, ".", "")
+                            if(rates.includes(","))
+                                rates = this.replaceAll(rates, ",", ".")
+                        }
+                        else{
+                            if(rates.includes(","))
+                                rates = this.replaceAll(rates, ",", "")
+                        }
+                        this.ratesCache[currencyPair] = parseFloat(rates);
+                        this.removeCurrencyPairFromRatesCache(currencyPair);
+                        return parseFloat(rates)
+                })
     }
 
     convert(currencyAmount){
@@ -266,25 +272,32 @@ class CurrencyConverter {
             throw new Error("currency amount should be a positive value")
 
         return this.rates().then((rates) =>{
-            // this.convertedValue = rates * this.currencyAmount
+            this.convertedValue = rates * this.currencyAmount
 
 	    // as the google result now sends the exact converted
-	    // currency, multiplying the rates with currencyAmount 
+	    // currency, multiplying the rates with currencyAmount
 	    // makes it redundant.
-	    this.convertedValue = rates * 1
+	    // this.convertedValue = rates * 1
             return this.convertedValue
         })
     }
 
     currencyName(currencyCode_){
         if(typeof currencyCode_ != "string")
             throw new TypeError("currency code should be a string")
-        
+
         if(!this.currencyCode.includes(currencyCode_.toUpperCase()))
             throw new Error(`${currencyCode_} is not a valid currency code`)
 
         return this.currencies[currencyCode_]
     }
+
+    removeCurrencyPairFromRatesCache(currencyPair) {
+        // Deletes cached currencyPair rate an hour later
+        setTimeout(function() {
+            delete this.ratesCache[currencyPair];
+        }, 3600000);
+    }
   }
 
 module.exports = CurrencyConverter