From f34056f241c744d20595e4eb2a32235a0399e7e5 Mon Sep 17 00:00:00 2001
From: Adora Laura Kalb <adora@lila.network>
Date: Fri, 19 Apr 2024 09:02:33 +0200
Subject: [PATCH] add cache file and a unit test

---
 cache/cache.go      | 92 +++++++++++++++++++++++++++++++++++++++++++++
 cache/cache_test.go | 34 +++++++++++++++++
 2 files changed, 126 insertions(+)
 create mode 100644 cache/cache.go
 create mode 100644 cache/cache_test.go

diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 0000000..96cde8b
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,92 @@
+/*
+Copyright 2024 Adora Laura Kalb <adora@lila.network>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cache
+
+import (
+	"net/netip"
+	"sync"
+	"time"
+)
+
+var (
+	GlobalScoreCache  *ScoreCache
+	cacheExpiredAfter = 5 * time.Minute
+)
+
+type ServerScore struct {
+	expiresAt time.Time
+	Score     float64
+}
+
+type ScoreCache struct {
+	stop chan struct{}
+
+	mu sync.RWMutex
+
+	scores map[netip.Addr]ServerScore
+}
+
+type CacheMissError struct{}
+
+func (m *CacheMissError) Error() string {
+	return "User is not in cache!"
+}
+
+func newCacheMissError() *CacheMissError {
+	return &CacheMissError{}
+}
+
+func NewLocalCache() *ScoreCache {
+	lc := &ScoreCache{
+		scores: make(map[netip.Addr]ServerScore),
+		stop:   make(chan struct{}),
+	}
+
+	return lc
+}
+
+func (sc *ScoreCache) Add(score float64, ip netip.Addr, ts time.Time) {
+	ssc := ServerScore{Score: score, expiresAt: ts.Add(cacheExpiredAfter)}
+	sc.mu.Lock()
+	sc.scores[ip] = ssc
+	sc.mu.Unlock()
+}
+
+func (lc *ScoreCache) Get(ip netip.Addr) (ServerScore, error) {
+	now := time.Now()
+	lc.mu.RLock()
+	defer lc.mu.RUnlock()
+
+	cachedScore, ok := lc.scores[ip]
+	if !ok {
+		return ServerScore{}, newCacheMissError()
+	}
+
+	if now.After(cachedScore.expiresAt) {
+		lc.delete(ip)
+		return ServerScore{}, newCacheMissError()
+	}
+
+	return cachedScore, nil
+}
+
+func (lc *ScoreCache) delete(ip netip.Addr) {
+	lc.mu.Lock()
+
+	delete(lc.scores, ip)
+	lc.mu.Unlock()
+}
diff --git a/cache/cache_test.go b/cache/cache_test.go
new file mode 100644
index 0000000..38be9a9
--- /dev/null
+++ b/cache/cache_test.go
@@ -0,0 +1,34 @@
+/*
+Copyright 2024 Adora Laura Kalb <adora@lila.network>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cache
+
+import (
+	"net/netip"
+	"testing"
+	"time"
+)
+
+func TestCacheGet(t *testing.T) {
+	const testFloat = 1.23456
+	cache := NewLocalCache()
+	cache.Add(testFloat, netip.MustParseAddr("1.2.3.4"), time.Now().Add(5*time.Minute))
+
+	score, _ := cache.Get(netip.MustParseAddr("1.2.3.4"))
+	if score.Score != testFloat {
+		t.Fatalf("cache.Get(\"1.2.3.4\") = %f, want %f", score.Score, testFloat)
+	}
+}