Fixed issue with deleting old rates from rates cache

paul-shuvo · Aug 2, 2022 · cc1387a · cc1387a
1 parent e121673
commit cc1387a
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Showing 2 changed files with 29 additions and 13 deletions.
diff --git a/index.js b/index.js
@@ -249,9 +249,9 @@ class CurrencyConverter {
         this.isRatesCaching = ratesCacheOptions.isRatesCaching;
 
         if (ratesCacheOptions.ratesCacheDuration === undefined)
-            this.ratesCacheDuration = 3600000; // Defaults to 3600 seconds (1 hour)
+            this.ratesCacheDuration = 3600; // Defaults to 3600 seconds (1 hour)
         else
-            this.ratesCacheDuration = ratesCacheOptions.ratesCacheDuration * 1000;
+            this.ratesCacheDuration = ratesCacheOptions.ratesCacheDuration;
 
         return this
     }
@@ -261,9 +261,10 @@ class CurrencyConverter {
             return new Promise((resolve, _) => {resolve(1) })
         } else {
             let currencyPair = this.currencyFrom.toUpperCase() + this.currencyTo.toUpperCase();
-            if (currencyPair in this.ratesCache) {
+            let now = new Date();
+            if (currencyPair in this.ratesCache && now < this.ratesCache[currencyPair].expiryDate) {
                 return new Promise((resolve, _) => {
-                    resolve(this.ratesCache[currencyPair]);
+                    resolve(this.ratesCache[currencyPair].rate);
                 });
             } else {
                 return got(`https://www.google.co.in/search?q=${this.currencyFrom}+to+${this.currencyTo}+&hl=en`)
@@ -282,8 +283,7 @@ class CurrencyConverter {
                                 rates = this.replaceAll(rates, ",", "")
                         }
                         if (this.isRatesCaching) {
-                            this.ratesCache[currencyPair] = parseFloat(rates);
-                            this.removeCurrencyPairFromRatesCache(currencyPair);
+                            this.addRateToRatesCache(currencyPair, parseFloat(rates));
                         }
                         return parseFloat(rates)
                 })
@@ -321,11 +321,25 @@ class CurrencyConverter {
         return this.currencies[currencyCode_]
     }
 
-    removeCurrencyPairFromRatesCache(currencyPair) {
-        // Deletes cached currencyPair rate an hour later
-        setTimeout(function() {
-            delete this.ratesCache[currencyPair];
-        }, this.ratesCacheDuration);
+    addRateToRatesCache(currencyPair, rate_) {
+        let now = new Date();
+        if (currencyPair in this.ratesCache) {
+            if (now > this.ratesCache[currencyPair].expiryDate) {
+                let newExpiry = new Date();
+                newExpiry.setSeconds(newExpiry.getSeconds() + this.ratesCacheDuration);
+                this.ratesCache[currencyPair] = {
+                    rate: rate_,
+                    expiryDate: newExpiry
+                };
+            }
+        } else {
+            let newExpiry = new Date();
+            newExpiry.setSeconds(newExpiry.getSeconds() + this.ratesCacheDuration);
+            this.ratesCache[currencyPair] = {
+                rate: rate_,
+                expiryDate: newExpiry
+            };
+        }
     }
   }
 

diff --git a/readme.md b/readme.md
@@ -75,7 +75,9 @@ currencyConverter.rates().then((response) => {
 })
 ```
 
-Rates can be cached. To implement rate caching, instantiate an object of CurrencyConverter only once in your project, in a CurrencyConverter file, and setup rates caching then import the instance of CurrencyConverter from the CurrencyConverter file in your project across the rest of your project. Use chaining to convert currencies when caching is implemented. Below is an example of a CurrencyConverter file.
+Rates can be cached for currency pairs. To implement rate caching, instantiate an object of CurrencyConverter only once in your project, in a CurrencyConverter file, and setup rates caching then import the instance of CurrencyConverter from the CurrencyConverter file in your project across the rest of your project. Use chaining to convert currencies when caching is implemented. Below is an example of a CurrencyConverter file.
+
+Note: Rates are not actually deleted after the ratesCacheDuration. The rate remains in the rates cache of the CurrencyConverter object until a request is made for the same currency pair at which point, the old rate is overwritten.
 
 ```javascript
 const CC = require('currency-converter-lt')
@@ -84,7 +86,7 @@ let currencyConverter = new CC()
 
 let ratesCacheOptions = {
     isRatesCaching: true, // Set this boolean to true to implement rate caching
-    ratesCacheDuration: 3600 // Set this to a positive number to set the number of seconds you want your rates to be cached. Defaults to 3600 seconds (1 hour)
+    ratesCacheDuration: 3600 // Set this to a positive number to set the number of seconds you want the rates to be cached. Defaults to 3600 seconds (1 hour)
 }
 
 currencyConverter = currencyConverter.setupRatesCache(ratesCacheOptions)