[#XX] ape: Introduce single-run chain router

* The single-run chain router created from APE overrides
  set in Bearer token.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

pkg/ape/router/single_pass.go

@@ -0,0 +1,55 @@
+package router
+
+import (
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/ape"
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/bearer"
+	cidSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
+	apechain "git.frostfs.info/TrueCloudLab/policy-engine/pkg/chain"
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/engine"
+	"git.frostfs.info/TrueCloudLab/policy-engine/pkg/engine/inmemory"
+)
+
+func newTarget(ct ape.ChainTarget) (engine.Target, error) {
+	var target engine.Target
+	switch ct.TargetType {
+	case ape.TargetTypeContainer:
+		var cid cidSDK.ID
+		err := cid.DecodeString(ct.Name)
+		if err != nil {
+			return target, fmt.Errorf("invalid cid format: %s", target.Name)
+		}
+		target.Type = engine.Container
+	case ape.TargetTypeGroup:
+		target.Type = engine.Group
+	case ape.TargetTypeNamespace:
+		target.Type = engine.Namespace
+	case ape.TargetTypeUser:
+		target.Type = engine.User
+	default:
+		return target, fmt.Errorf("unsupported target type: %v", ct.TargetType)
+	}
+	target.Name = ct.Name
+	return target, nil
+}
+
+// SingleUseRouterWithBearerTokenChains creates chain router with inmemory storage implementation and
+// fed with APE chains defined in Bearer token.
+func SingleUseRouterWithBearerTokenChains(overrides []*bearer.APEOverride) (engine.ChainRouter, error) {
+	storage := inmemory.NewInmemoryMorphRuleChainStorage()
+	for _, override := range overrides {
+		target, err := newTarget(override.Target)
+		if err != nil {
+			return nil, err
+		}
+		for i := range override.Chains {
+			chain := new(apechain.Chain)
+			if err := chain.DecodeBytes(override.Chains[i].Raw); err != nil {
+				return nil, fmt.Errorf("invalid ape chain: %w", err)
+			}
+			storage.AddMorphRuleChain(apechain.Ingress, target, chain)
+		}
+	}
+	return engine.NewDefaultChainRouter(storage), nil
+}