feat: first commit

backend/internal/adapter/memory/cache.go

@@ -0,0 +1,48 @@
+package memory
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/snip/backend/internal/port"
+)
+
+type cacheEntry struct {
+	res     port.Resolution
+	expires time.Time
+}
+
+// Cache is a TTL map standing in for Redis.
+type Cache struct {
+	mu sync.RWMutex
+	m  map[string]cacheEntry
+}
+
+func NewCache() *Cache {
+	return &Cache{m: make(map[string]cacheEntry)}
+}
+
+func (c *Cache) GetResolution(_ context.Context, code string) (port.Resolution, bool, error) {
+	c.mu.RLock()
+	e, ok := c.m[code]
+	c.mu.RUnlock()
+	if !ok || time.Now().After(e.expires) {
+		return port.Resolution{}, false, nil
+	}
+	return e.res, true, nil
+}
+
+func (c *Cache) SetResolution(_ context.Context, code string, r port.Resolution, ttl time.Duration) error {
+	c.mu.Lock()
+	c.m[code] = cacheEntry{res: r, expires: time.Now().Add(ttl)}
+	c.mu.Unlock()
+	return nil
+}
+
+func (c *Cache) Invalidate(_ context.Context, code string) error {
+	c.mu.Lock()
+	delete(c.m, code)
+	c.mu.Unlock()
+	return nil
+}