/*
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 admission

import (
	"context"
	"fmt"
	"sync"

	auditinternal "k8s.io/apiserver/pkg/apis/audit"
	"k8s.io/apiserver/pkg/audit"
)

// auditHandler logs annotations set by other admission handlers
type auditHandler struct {
	Interface
	// TODO: move the lock near the Annotations field of the audit event so it is always protected from concurrent access.
	// to protect the 'Annotations' map of the audit event from concurrent writes
	mutex sync.Mutex
	ae    *auditinternal.Event
}

var _ Interface = &auditHandler{}
var _ MutationInterface = &auditHandler{}
var _ ValidationInterface = &auditHandler{}

// WithAudit is a decorator for a admission phase. It saves annotations
// of attribute into the audit event. Attributes passed to the Admit and
// Validate function must be instance of privateAnnotationsGetter or
// AnnotationsGetter, otherwise an error is returned.
func WithAudit(i Interface, ae *auditinternal.Event) Interface {
	if i == nil {
		return i
	}
	return &auditHandler{Interface: i, ae: ae}
}

func (handler *auditHandler) Admit(ctx context.Context, a Attributes, o ObjectInterfaces) error {
	if !handler.Interface.Handles(a.GetOperation()) {
		return nil
	}
	if err := ensureAnnotationGetter(a); err != nil {
		return err
	}
	var err error
	if mutator, ok := handler.Interface.(MutationInterface); ok {
		err = mutator.Admit(ctx, a, o)
		handler.logAnnotations(a)
	}
	return err
}

func (handler *auditHandler) Validate(ctx context.Context, a Attributes, o ObjectInterfaces) error {
	if !handler.Interface.Handles(a.GetOperation()) {
		return nil
	}
	if err := ensureAnnotationGetter(a); err != nil {
		return err
	}
	var err error
	if validator, ok := handler.Interface.(ValidationInterface); ok {
		err = validator.Validate(ctx, a, o)
		handler.logAnnotations(a)
	}
	return err
}

func ensureAnnotationGetter(a Attributes) error {
	_, okPrivate := a.(privateAnnotationsGetter)
	_, okPublic := a.(AnnotationsGetter)
	if okPrivate || okPublic {
		return nil
	}
	return fmt.Errorf("attributes must be an instance of privateAnnotationsGetter or AnnotationsGetter")
}

func (handler *auditHandler) logAnnotations(a Attributes) {
	if handler.ae == nil {
		return
	}
	handler.mutex.Lock()
	defer handler.mutex.Unlock()

	switch a := a.(type) {
	case privateAnnotationsGetter:
		for key, value := range a.getAnnotations(handler.ae.Level) {
			audit.LogAnnotation(handler.ae, key, value)
		}
	case AnnotationsGetter:
		for key, value := range a.GetAnnotations(handler.ae.Level) {
			audit.LogAnnotation(handler.ae, key, value)
		}
	default:
		// this will never happen, because we have already checked it in ensureAnnotationGetter
	}
}