/*
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 alicloud

import (
	"sync"
	"time"

	"k8s.io/apimachinery/pkg/util/wait"
	klog "k8s.io/klog/v2"
)

type autoScalingGroups struct {
	registeredAsgs           []*asgInformation
	instanceToAsg            map[string]*Asg
	cacheMutex               sync.Mutex
	instancesNotInManagedAsg map[string]struct{}
	service                  *autoScalingWrapper
}

func newAutoScalingGroups(service *autoScalingWrapper) *autoScalingGroups {
	registry := &autoScalingGroups{
		registeredAsgs:           make([]*asgInformation, 0),
		service:                  service,
		instanceToAsg:            make(map[string]*Asg),
		instancesNotInManagedAsg: make(map[string]struct{}),
	}

	go wait.Forever(func() {
		registry.cacheMutex.Lock()
		defer registry.cacheMutex.Unlock()
		if err := registry.regenerateCache(); err != nil {
			klog.Errorf("failed to do regenerating ASG cache,because of %s", err.Error())
		}
	}, time.Hour)

	return registry
}

// Register registers asg in AliCloud Manager.
func (m *autoScalingGroups) Register(asg *Asg) {
	m.cacheMutex.Lock()
	defer m.cacheMutex.Unlock()

	m.registeredAsgs = append(m.registeredAsgs, &asgInformation{
		config: asg,
	})
}

// FindForInstance returns AsgConfig of the given Instance
func (m *autoScalingGroups) FindForInstance(instanceId string) (*Asg, error) {
	m.cacheMutex.Lock()
	defer m.cacheMutex.Unlock()
	if config, found := m.instanceToAsg[instanceId]; found {
		return config, nil
	}
	if _, found := m.instancesNotInManagedAsg[instanceId]; found {
		// The instance is already known to not belong to any configured ASG
		// Skip regenerateCache so that we won't unnecessarily call DescribeAutoScalingGroups
		// See https://github.com/kubernetes/contrib/issues/2541
		return nil, nil
	}
	if err := m.regenerateCache(); err != nil {
		return nil, err
	}
	if config, found := m.instanceToAsg[instanceId]; found {
		return config, nil
	}
	// instance does not belong to any configured ASG
	m.instancesNotInManagedAsg[instanceId] = struct{}{}
	return nil, nil
}

func (m *autoScalingGroups) regenerateCache() error {
	newCache := make(map[string]*Asg)

	for _, asg := range m.registeredAsgs {
		instances, err := m.service.getScalingInstancesByGroup(asg.config.id)
		if err != nil {
			return err
		}
		for _, instance := range instances {
			newCache[instance.InstanceId] = asg.config
		}
	}

	m.instanceToAsg = newCache
	return nil
}