fuelprice-exporter/cache/cache.go

/*
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 NewScoreCache() *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()

	cachedScore, ok := lc.scores[ip]
	if !ok {
		lc.mu.RUnlock()
		return ServerScore{}, newCacheMissError()
	}
	lc.mu.RUnlock()

	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()
}