API: Implement a 10 minute well-known endpoint cache

1 files changed, 64 insertions, 0 deletions

diff --git a/internal/api/cache.go b/internal/api/cache.go
new file mode 100644
index 0000000..2baefc8
--- /dev/null
+++ b/internal/api/cache.go
@@ -0,0 +1,64 @@
+package api
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/eduvpn/eduvpn-common/internal/api/endpoints"
+)
+
+// EndpointCache is a struct that caches well-known API endpoints
+type EndpointCache struct {
+	lastUpdate map[string]time.Time
+	lastEP     map[string]*endpoints.Endpoints
+	mu         sync.Mutex
+}
+
+// Get() returns a cached or fresh endpoint cache copy
+func (ec *EndpointCache) Get(ctx context.Context, wk string) (*endpoints.Endpoints, error) {
+	ec.mu.Lock()
+	defer ec.mu.Unlock()
+
+	// get the last update time
+	lu := time.Time{}
+	if v, ok := ec.lastUpdate[wk]; ok {
+		lu = v
+	}
+
+	// if not 10 minutes have passed, return cached copy
+	if !lu.IsZero() && !time.Now().After(lu.Add(10*time.Minute)) {
+		v, ok := ec.lastEP[wk]
+		if ok {
+			return v, nil
+		}
+	}
+
+	// get fresh API endpoints
+	ep, err := getEndpoints(ctx, wk)
+	if err != nil {
+		return nil, err
+	}
+
+	// update endpoints
+	ec.lastUpdate[wk] = time.Now()
+	ec.lastEP[wk] = ep
+
+	return ep, nil
+}
+
+var (
+	epCache     *EndpointCache
+	epCacheOnce sync.Once
+)
+
+func GetEndpointCache() *EndpointCache {
+	epCacheOnce.Do(func() {
+		epCache = &EndpointCache{
+			lastUpdate: make(map[string]time.Time),
+			lastEP:     make(map[string]*endpoints.Endpoints),
+		}
+	})
+
+	return epCache
+}