[#259] Support contract based policies

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/cache/policy.go

@@ -0,0 +1,72 @@
+package cache
+
+import (
+	"fmt"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/engine"
+	"github.com/bluele/gcache"
+	"go.uber.org/zap"
+)
+
+// MorphPolicyCache provides lru cache for listing policies stored in policy contract.
+type MorphPolicyCache struct {
+	cache  gcache.Cache
+	logger *zap.Logger
+}
+
+type MorphPolicyCacheKey struct {
+	Target engine.Target
+	Name   chain.Name
+}
+
+const (
+	// DefaultMorphPolicyCacheSize is a default maximum number of entries in cache.
+	DefaultMorphPolicyCacheSize = 1e4
+	// DefaultMorphPolicyCacheLifetime is a default lifetime of entries in cache.
+	DefaultMorphPolicyCacheLifetime = time.Minute
+)
+
+// DefaultMorphPolicyConfig returns new default cache expiration values.
+func DefaultMorphPolicyConfig(logger *zap.Logger) *Config {
+	return &Config{
+		Size:     DefaultMorphPolicyCacheSize,
+		Lifetime: DefaultMorphPolicyCacheLifetime,
+		Logger:   logger,
+	}
+}
+
+// NewMorphPolicyCache creates an object of MorphPolicyCache.
+func NewMorphPolicyCache(config *Config) *MorphPolicyCache {
+	gc := gcache.New(config.Size).LRU().Expiration(config.Lifetime).Build()
+	return &MorphPolicyCache{cache: gc, logger: config.Logger}
+}
+
+// Get returns a cached object. Returns nil if value is missing.
+func (o *MorphPolicyCache) Get(key MorphPolicyCacheKey) []*chain.Chain {
+	entry, err := o.cache.Get(key)
+	if err != nil {
+		return nil
+	}
+
+	result, ok := entry.([]*chain.Chain)
+	if !ok {
+		o.logger.Warn(logs.InvalidCacheEntryType, zap.String("actual", fmt.Sprintf("%T", entry)),
+			zap.String("expected", fmt.Sprintf("%T", result)))
+		return nil
+	}
+
+	return result
+}
+
+// Put puts an object to cache.
+func (o *MorphPolicyCache) Put(key MorphPolicyCacheKey, list []*chain.Chain) error {
+	return o.cache.Set(key, list)
+}
+
+// Delete deletes an object from cache.
+func (o *MorphPolicyCache) Delete(key MorphPolicyCacheKey) bool {
+	return o.cache.Remove(key)
+}