/*
Copyright 2018 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package validating

import (
	"context"
	"fmt"
	"sync"
	"time"

	v1 "k8s.io/api/admissionregistration/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/runtime/schema"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apiserver/pkg/admission"
	admissionmetrics "k8s.io/apiserver/pkg/admission/metrics"
	"k8s.io/apiserver/pkg/admission/plugin/webhook"
	webhookerrors "k8s.io/apiserver/pkg/admission/plugin/webhook/errors"
	"k8s.io/apiserver/pkg/admission/plugin/webhook/generic"
	webhookrequest "k8s.io/apiserver/pkg/admission/plugin/webhook/request"
	webhookutil "k8s.io/apiserver/pkg/util/webhook"
	"k8s.io/apiserver/pkg/warning"
	"k8s.io/klog/v2"
	utiltrace "k8s.io/utils/trace"
)

const (
	// ValidatingAuditAnnotationPrefix is a prefix for keeping noteworthy
	// validating audit annotations.
	ValidatingAuditAnnotationPrefix = "validating.webhook.admission.k8s.io/"
	// ValidatingAuditAnnotationFailedOpenKeyPrefix in an annotation indicates
	// the validating webhook failed open when the webhook backend connection
	// failed or returned an internal server error.
	ValidatingAuditAnnotationFailedOpenKeyPrefix = "failed-open." + ValidatingAuditAnnotationPrefix
)

type validatingDispatcher struct {
	cm     *webhookutil.ClientManager
	plugin *Plugin
}

func newValidatingDispatcher(p *Plugin) func(cm *webhookutil.ClientManager) generic.Dispatcher {
	return func(cm *webhookutil.ClientManager) generic.Dispatcher {
		return &validatingDispatcher{cm, p}
	}
}

var _ generic.Dispatcher = &validatingDispatcher{}

func (d *validatingDispatcher) Dispatch(ctx context.Context, attr admission.Attributes, o admission.ObjectInterfaces, hooks []webhook.WebhookAccessor) error {
	var relevantHooks []*generic.WebhookInvocation
	// Construct all the versions we need to call our webhooks
	versionedAttrs := map[schema.GroupVersionKind]*generic.VersionedAttributes{}
	for _, hook := range hooks {
		invocation, statusError := d.plugin.ShouldCallHook(hook, attr, o)
		if statusError != nil {
			return statusError
		}
		if invocation == nil {
			continue
		}
		relevantHooks = append(relevantHooks, invocation)
		// If we already have this version, continue
		if _, ok := versionedAttrs[invocation.Kind]; ok {
			continue
		}
		versionedAttr, err := generic.NewVersionedAttributes(attr, invocation.Kind, o)
		if err != nil {
			return apierrors.NewInternalError(err)
		}
		versionedAttrs[invocation.Kind] = versionedAttr
	}

	if len(relevantHooks) == 0 {
		// no matching hooks
		return nil
	}

	// Check if the request has already timed out before spawning remote calls
	select {
	case <-ctx.Done():
		// parent context is canceled or timed out, no point in continuing
		return apierrors.NewTimeoutError("request did not complete within requested timeout", 0)
	default:
	}

	wg := sync.WaitGroup{}
	errCh := make(chan error, len(relevantHooks))
	wg.Add(len(relevantHooks))
	for i := range relevantHooks {
		go func(invocation *generic.WebhookInvocation, idx int) {
			defer wg.Done()
			hook, ok := invocation.Webhook.GetValidatingWebhook()
			if !ok {
				utilruntime.HandleError(fmt.Errorf("validating webhook dispatch requires v1.ValidatingWebhook, but got %T", hook))
				return
			}
			versionedAttr := versionedAttrs[invocation.Kind]
			t := time.Now()
			err := d.callHook(ctx, hook, invocation, versionedAttr)
			ignoreClientCallFailures := hook.FailurePolicy != nil && *hook.FailurePolicy == v1.Ignore
			rejected := false
			if err != nil {
				switch err := err.(type) {
				case *webhookutil.ErrCallingWebhook:
					if !ignoreClientCallFailures {
						rejected = true
						admissionmetrics.Metrics.ObserveWebhookRejection(ctx, hook.Name, "validating", string(versionedAttr.Attributes.GetOperation()), admissionmetrics.WebhookRejectionCallingWebhookError, 0)
					}
				case *webhookutil.ErrWebhookRejection:
					rejected = true
					admissionmetrics.Metrics.ObserveWebhookRejection(ctx, hook.Name, "validating", string(versionedAttr.Attributes.GetOperation()), admissionmetrics.WebhookRejectionNoError, int(err.Status.ErrStatus.Code))
				default:
					rejected = true
					admissionmetrics.Metrics.ObserveWebhookRejection(ctx, hook.Name, "validating", string(versionedAttr.Attributes.GetOperation()), admissionmetrics.WebhookRejectionAPIServerInternalError, 0)
				}
			}
			admissionmetrics.Metrics.ObserveWebhook(ctx, time.Since(t), rejected, versionedAttr.Attributes, "validating", hook.Name)
			if err == nil {
				return
			}

			if callErr, ok := err.(*webhookutil.ErrCallingWebhook); ok {
				if ignoreClientCallFailures {
					klog.Warningf("Failed calling webhook, failing open %v: %v", hook.Name, callErr)

					key := fmt.Sprintf("%sround_0_index_%d", ValidatingAuditAnnotationFailedOpenKeyPrefix, idx)
					value := hook.Name
					if err := versionedAttr.Attributes.AddAnnotation(key, value); err != nil {
						klog.Warningf("Failed to set admission audit annotation %s to %s for validating webhook %s: %v", key, value, hook.Name, err)
					}
					utilruntime.HandleError(callErr)
					return
				}

				klog.Warningf("Failed calling webhook, failing closed %v: %v", hook.Name, err)
				errCh <- apierrors.NewInternalError(err)
				return
			}

			if rejectionErr, ok := err.(*webhookutil.ErrWebhookRejection); ok {
				err = rejectionErr.Status
			}
			klog.Warningf("rejected by webhook %q: %#v", hook.Name, err)
			errCh <- err
		}(relevantHooks[i], i)
	}
	wg.Wait()
	close(errCh)

	var errs []error
	for e := range errCh {
		errs = append(errs, e)
	}
	if len(errs) == 0 {
		return nil
	}
	if len(errs) > 1 {
		for i := 1; i < len(errs); i++ {
			// TODO: merge status errors; until then, just return the first one.
			utilruntime.HandleError(errs[i])
		}
	}
	return errs[0]
}

func (d *validatingDispatcher) callHook(ctx context.Context, h *v1.ValidatingWebhook, invocation *generic.WebhookInvocation, attr *generic.VersionedAttributes) error {
	if attr.Attributes.IsDryRun() {
		if h.SideEffects == nil {
			return &webhookutil.ErrCallingWebhook{WebhookName: h.Name, Reason: fmt.Errorf("Webhook SideEffects is nil")}
		}
		if !(*h.SideEffects == v1.SideEffectClassNone || *h.SideEffects == v1.SideEffectClassNoneOnDryRun) {
			return webhookerrors.NewDryRunUnsupportedErr(h.Name)
		}
	}

	uid, request, response, err := webhookrequest.CreateAdmissionObjects(attr, invocation)
	if err != nil {
		return &webhookutil.ErrCallingWebhook{WebhookName: h.Name, Reason: err}
	}
	// Make the webhook request
	client, err := invocation.Webhook.GetRESTClient(d.cm)
	if err != nil {
		return &webhookutil.ErrCallingWebhook{WebhookName: h.Name, Reason: err}
	}
	trace := utiltrace.New("Call validating webhook",
		utiltrace.Field{"configuration", invocation.Webhook.GetConfigurationName()},
		utiltrace.Field{"webhook", h.Name},
		utiltrace.Field{"resource", attr.GetResource()},
		utiltrace.Field{"subresource", attr.GetSubresource()},
		utiltrace.Field{"operation", attr.GetOperation()},
		utiltrace.Field{"UID", uid})
	defer trace.LogIfLong(500 * time.Millisecond)

	// if the webhook has a specific timeout, wrap the context to apply it
	if h.TimeoutSeconds != nil {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, time.Duration(*h.TimeoutSeconds)*time.Second)
		defer cancel()
	}

	r := client.Post().Body(request)

	// if the context has a deadline, set it as a parameter to inform the backend
	if deadline, hasDeadline := ctx.Deadline(); hasDeadline {
		// compute the timeout
		if timeout := time.Until(deadline); timeout > 0 {
			// if it's not an even number of seconds, round up to the nearest second
			if truncated := timeout.Truncate(time.Second); truncated != timeout {
				timeout = truncated + time.Second
			}
			// set the timeout
			r.Timeout(timeout)
		}
	}

	if err := r.Do(ctx).Into(response); err != nil {
		return &webhookutil.ErrCallingWebhook{WebhookName: h.Name, Reason: err}
	}
	trace.Step("Request completed")

	result, err := webhookrequest.VerifyAdmissionResponse(uid, false, response)
	if err != nil {
		return &webhookutil.ErrCallingWebhook{WebhookName: h.Name, Reason: err}
	}

	for k, v := range result.AuditAnnotations {
		key := h.Name + "/" + k
		if err := attr.Attributes.AddAnnotation(key, v); err != nil {
			klog.Warningf("Failed to set admission audit annotation %s to %s for validating webhook %s: %v", key, v, h.Name, err)
		}
	}
	for _, w := range result.Warnings {
		warning.AddWarning(ctx, "", w)
	}
	if result.Allowed {
		return nil
	}
	return &webhookutil.ErrWebhookRejection{Status: webhookerrors.ToStatusErr(h.Name, result.Result)}
}
