/*
Copyright 2019 The KubeSphere 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 cache

import (
	"regexp"
	"strings"
	"time"

	"kubesphere.io/kubesphere/pkg/server/options"

	"github.com/mitchellh/mapstructure"
	"k8s.io/apimachinery/pkg/util/wait"

	"kubesphere.io/kubesphere/pkg/server/errors"
)

var ErrNoSuchKey = errors.New("no such key")

const (
	TypeInMemoryCache    = "InMemoryCache"
	defaultCleanupPeriod = 2 * time.Hour
)

type simpleObject struct {
	value       string
	neverExpire bool
	expiredAt   time.Time
}

func (so *simpleObject) IsExpired() bool {
	if so.neverExpire {
		return false
	}
	if time.Now().After(so.expiredAt) {
		return true
	}
	return false
}

// InMemoryCacheOptions used to create inMemoryCache in memory.
// CleanupPeriod specifies cleans up expired token every period.
// Note the SimpleCache cannot be used in multi-replicas apiserver,
// which will lead to data inconsistency.
type InMemoryCacheOptions struct {
	CleanupPeriod time.Duration `json:"cleanupPeriod" yaml:"cleanupPeriod" mapstructure:"cleanupperiod"`
}

// imMemoryCache implements cache.Interface use memory objects, it should be used only for testing
type inMemoryCache struct {
	store map[string]simpleObject
}

func NewInMemoryCache(options *InMemoryCacheOptions, stopCh <-chan struct{}) (Interface, error) {
	var cleanupPeriod time.Duration
	cache := &inMemoryCache{
		store: make(map[string]simpleObject),
	}

	if options == nil || options.CleanupPeriod == 0 {
		cleanupPeriod = defaultCleanupPeriod
	} else {
		cleanupPeriod = options.CleanupPeriod
	}
	go wait.Until(cache.cleanInvalidToken, cleanupPeriod, stopCh)

	return cache, nil
}

func (s *inMemoryCache) cleanInvalidToken() {
	for k, v := range s.store {
		if v.IsExpired() {
			delete(s.store, k)
		}
	}
}

func (s *inMemoryCache) Keys(pattern string) ([]string, error) {
	// There is a little difference between go regexp and redis key pattern
	// In redis, * means any character, while in go . means match everything.
	pattern = strings.Replace(pattern, "*", ".", -1)

	re, err := regexp.Compile(pattern)
	if err != nil {
		return nil, err
	}
	var keys []string
	for k := range s.store {
		if re.MatchString(k) {
			keys = append(keys, k)
		}
	}

	return keys, nil
}

func (s *inMemoryCache) Set(key string, value string, duration time.Duration) error {
	sobject := simpleObject{
		value:       value,
		neverExpire: false,
		expiredAt:   time.Now().Add(duration),
	}

	if duration == NeverExpire {
		sobject.neverExpire = true
	}

	s.store[key] = sobject
	return nil
}

func (s *inMemoryCache) Del(keys ...string) error {
	for _, key := range keys {
		delete(s.store, key)
	}
	return nil
}

func (s *inMemoryCache) Get(key string) (string, error) {
	if sobject, ok := s.store[key]; ok {
		if sobject.neverExpire || time.Now().Before(sobject.expiredAt) {
			return sobject.value, nil
		}
	}

	return "", ErrNoSuchKey
}

func (s *inMemoryCache) Exists(keys ...string) (bool, error) {
	for _, key := range keys {
		if _, ok := s.store[key]; !ok {
			return false, nil
		}
	}

	return true, nil
}

func (s *inMemoryCache) Expire(key string, duration time.Duration) error {
	value, err := s.Get(key)
	if err != nil {
		return err
	}

	sobject := simpleObject{
		value:       value,
		neverExpire: false,
		expiredAt:   time.Now().Add(duration),
	}

	if duration == NeverExpire {
		sobject.neverExpire = true
	}

	s.store[key] = sobject
	return nil
}

type inMemoryCacheFactory struct {
}

func (sf *inMemoryCacheFactory) Type() string {
	return TypeInMemoryCache
}

func (sf *inMemoryCacheFactory) Create(options options.DynamicOptions, stopCh <-chan struct{}) (Interface, error) {
	var sOptions InMemoryCacheOptions
	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
		WeaklyTypedInput: true,
		Result:           &sOptions,
	})
	if err != nil {
		return nil, err
	}
	if err := decoder.Decode(options); err != nil {
		return nil, err
	}

	return NewInMemoryCache(&sOptions, stopCh)
}

func init() {
	RegisterCacheFactory(&inMemoryCacheFactory{})
}