From a5f5cd24cd13f5845ccc9b695582e61c2619de0f Mon Sep 17 00:00:00 2001
From: Asim Aslam <asim@aslam.me>
Date: Tue, 15 Jun 2021 21:05:38 +0100
Subject: [PATCH] add 5 minute cache

---
 currency/handler/currency.go | 28 +++++++++++++++++++++++++++-
 currency/main.go             |  9 ++++++---
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/currency/handler/currency.go b/currency/handler/currency.go
index a34913d..378ae5d 100644
--- a/currency/handler/currency.go
+++ b/currency/handler/currency.go
@@ -10,10 +10,12 @@ import (
 	"github.com/micro/micro/v3/service/errors"
 	"github.com/micro/micro/v3/service/logger"
 	pb "github.com/micro/services/currency/proto"
+	"github.com/patrickmn/go-cache"
 )
 
 type Currency struct {
-	Api string
+	Api   string
+	Cache *cache.Cache
 }
 
 func (c *Currency) Rates(ctx context.Context, req *pb.RatesRequest, rsp *pb.RatesResponse) error {
@@ -24,6 +26,13 @@ func (c *Currency) Rates(ctx context.Context, req *pb.RatesRequest, rsp *pb.Rate
 		return errors.BadRequest("currency.rates", "code is invalid")
 	}
 
+	// try the cache
+	if rates, ok := c.Cache.Get("rates:" + req.Code); ok {
+		rsp.Code = req.Code
+		rsp.Rates = rates.(map[string]float64)
+		return nil
+	}
+
 	resp, err := http.Get(c.Api + "/latest/" + req.Code)
 	if err != nil {
 		logger.Errorf("Failed to get rates: %v\n", err)
@@ -58,6 +67,9 @@ func (c *Currency) Rates(ctx context.Context, req *pb.RatesRequest, rsp *pb.Rate
 		rsp.Rates[code], _ = rate.(float64)
 	}
 
+	// set for a period of time
+	c.Cache.Set("rates:"+req.Code, rsp.Rates, cache.DefaultExpiration)
+
 	return nil
 }
 
@@ -71,6 +83,17 @@ func (c *Currency) Convert(ctx context.Context, req *pb.ConvertRequest, rsp *pb.
 
 	uri := fmt.Sprintf("%s/pair/%s/%s", c.Api, req.From, req.To)
 
+	// try the cache
+	if req.Amount == 0 {
+		rate, ok := c.Cache.Get("pair:" + req.From + req.To)
+		if ok {
+			rsp.From = req.From
+			rsp.To = req.To
+			rsp.Rate = rate.(float64)
+			return nil
+		}
+	}
+
 	if req.Amount > 0.0 {
 		uri = fmt.Sprintf("%s/%v", uri, req.Amount)
 	}
@@ -101,5 +124,8 @@ func (c *Currency) Convert(ctx context.Context, req *pb.ConvertRequest, rsp *pb.
 	rsp.Rate, _ = respBody["conversion_rate"].(float64)
 	rsp.Amount, _ = respBody["conversion_result"].(float64)
 
+	// save for a period of time
+	c.Cache.Set("pair:"+req.From+req.To, rsp.Rate, cache.DefaultExpiration)
+
 	return nil
 }
diff --git a/currency/main.go b/currency/main.go
index c541792..1dadf24 100644
--- a/currency/main.go
+++ b/currency/main.go
@@ -1,12 +1,14 @@
 package main
 
 import (
-	"github.com/micro/services/currency/handler"
-	pb "github.com/micro/services/currency/proto"
+	"time"
 
 	"github.com/micro/micro/v3/service"
 	"github.com/micro/micro/v3/service/config"
 	"github.com/micro/micro/v3/service/logger"
+	"github.com/micro/services/currency/handler"
+	pb "github.com/micro/services/currency/proto"
+	"github.com/patrickmn/go-cache"
 )
 
 func main() {
@@ -35,7 +37,8 @@ func main() {
 
 	// Register handler
 	pb.RegisterCurrencyHandler(srv.Server(), &handler.Currency{
-		Api: api + key,
+		Api:   api + key,
+		Cache: cache.New(5*time.Minute, 10*time.Minute),
 	})
 
 	// Run service