feat: first commit

backend/internal/adapter/rediscache/cache.go

@@ -0,0 +1,58 @@
+// Package rediscache implements the LinkCache port on Redis. This is the layer
+// that keeps the redirect hot path off Postgres.
+package rediscache
+
+import (
+	"context"
+	"encoding/json"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+
+	"github.com/snip/backend/internal/port"
+)
+
+type Cache struct {
+	rdb    *redis.Client
+	prefix string
+}
+
+func New(ctx context.Context, addr, password string, db int) (*Cache, error) {
+	rdb := redis.NewClient(&redis.Options{Addr: addr, Password: password, DB: db})
+	if err := rdb.Ping(ctx).Err(); err != nil {
+		_ = rdb.Close()
+		return nil, err
+	}
+	return &Cache{rdb: rdb, prefix: "code:"}, nil
+}
+
+func (c *Cache) key(code string) string { return c.prefix + code }
+
+func (c *Cache) GetResolution(ctx context.Context, code string) (port.Resolution, bool, error) {
+	b, err := c.rdb.Get(ctx, c.key(code)).Bytes()
+	if err == redis.Nil {
+		return port.Resolution{}, false, nil
+	}
+	if err != nil {
+		return port.Resolution{}, false, err
+	}
+	var r port.Resolution
+	if err := json.Unmarshal(b, &r); err != nil {
+		return port.Resolution{}, false, err
+	}
+	return r, true, nil
+}
+
+func (c *Cache) SetResolution(ctx context.Context, code string, r port.Resolution, ttl time.Duration) error {
+	b, err := json.Marshal(r)
+	if err != nil {
+		return err
+	}
+	return c.rdb.Set(ctx, c.key(code), b, ttl).Err()
+}
+
+func (c *Cache) Invalidate(ctx context.Context, code string) error {
+	return c.rdb.Del(ctx, c.key(code)).Err()
+}
+
+func (c *Cache) Close() error { return c.rdb.Close() }