// See the License for the specific language governing permissions and
// limitations under the License.

// Provides utility methods to generate X.509 certificates with different
// options. This implementation is Largely inspired from
// https://golang.org/src/crypto/tls/generate_cert.go.

package util

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"

	"istio.io/istio/pkg/config/resource"
)

var (
	// InternalError defines a diag.MessageType for message "InternalError".
	// Description: There was an internal error in the toolchain. This is almost always a bug in the implementation.
	InternalError = diag.NewMessageType(diag.Error, "IST0001", "Internal error: %v")

	// Deprecated defines a diag.MessageType for message "Deprecated".

| HOST_PROBE_SNAT_IPV6 | "fd16:9254:7127:1337:ffff:ffff:ffff:ffff" | IPv6 link local ranges are designed to be collision-resistant by default, and so this probably never needs to be overridden |

## Sidecar Mode Implementation Details

Istio CNI injection is currently based on the same Pod annotations used in init-container/inject mode.

### Selection API

- plugin config "exclude namespaces" applies first
- ambient is enabled if:

func NewCollection[I, O any](c Collection[I], hf TransformationSingle[I, O], opts ...CollectionOption) Collection[O] {
	// For implementation simplicity, represent TransformationSingle as a TransformationMulti so we can share an implementation.
	hm := func(ctx HandlerContext, i I) []O {
		res := hf(ctx, i)
		if res == nil {
			return nil
		}
		return []O{*res}
	}

)

// DeploymentController implements a controller that materializes a Gateway into an in cluster gateway proxy
// to serve requests from. This is implemented with a Deployment and Service today.
// The implementation makes a few non-obvious choices - namely using Server Side Apply from go templates
// and not using controller-runtime.
//
// controller-runtime has a number of constraints that make it inappropriate for usage here, despite this

	// DisableAutomountSAToken indicates to opt out of auto mounting ServiceAccount's API credentials
	DisableAutomountSAToken bool

	// Ports for this application. Port numbers may or may not be used, depending
	// on the implementation.
	Ports Ports

	// ServiceAnnotations is annotations on service object.
	ServiceAnnotations map[string]string

	// ServiceLabels is the labels on service object.
	ServiceLabels map[string]string

    Default implementations exist for Kubernetes objects, Istio `config.Config` objects, and `ResourceName() string` implementations.
* `Equals(k K) bool` may be implemented to provide custom implementations to compare objects. Comparison is done to detect if changes were made.
  Default implementations are available for Kubernetes and protobuf objects, and will fallback to `reflect.DeepEqual`.

	}
}

type adsStream interface {
	Send(*discovery.DiscoveryResponse) error
	Recv() (*discovery.DiscoveryRequest, error)
	Context() context.Context
}

// StreamAggregatedResources is an implementation of XDS API used for proxying between Istiod and Envoy.
// Every time envoy makes a fresh connection to the agent, we reestablish a new connection to the upstream xds

	requestDuration.Record(time.Since(start).Seconds())
	log.Debugf("upstream response for hostname %q : %v", hostname, response)
	return response
}

// ServeDNS is the implementation of DNS interface
func (h *LocalDNSServer) ServeDNS(proxy *dnsProxy, w dns.ResponseWriter, req *dns.Msg) {
	requests.Increment()
	var response *dns.Msg

	pre = append(pre, authzBuilder.BuildHTTP(cls)...)
	// TODO: these feel like the wrong place to insert, but this retains backwards compatibility with the original implementation
	post = extension.PopAppendHTTP(post, wasm, extensions.PluginPhase_STATS)
	post = extension.PopAppendHTTP(post, wasm, extensions.PluginPhase_UNSPECIFIED_PHASE)
	post = append(post, xdsfilters.WaypointUpstreamMetadataFilter)