/*
Copyright 2016 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 resources

import (
	"fmt"
	"sync"
	"time"

	"github.com/golang/glog"
	"k8s.io/kops/pkg/apis/kops"
	"k8s.io/kops/upup/pkg/fi"
)

type ResourceTracker struct {
	Name string
	Type string
	ID   string

	// If true, this resource is not owned by the cluster
	Shared bool

	blocks  []string
	blocked []string
	done    bool

	deleter      func(cloud fi.Cloud, tracker *ResourceTracker) error
	groupKey     string
	groupDeleter func(cloud fi.Cloud, trackers []*ResourceTracker) error

	Dumper func(r *ResourceTracker) (interface{}, error)

	obj interface{}
}

var _ Resources = &ClusterResources{}

// Resources is a representation of a cluster with abilities to ListResources and DeleteResources
type Resources interface {
	ListResources() (map[string]*ResourceTracker, error)
	DeleteResources(resources map[string]*ResourceTracker) error
}

// ClusterResources is an implementation of Resources
// The algorithm is pretty simple: it discovers all the resources it can (primary using tags)
// There are a few tweaks to that approach, like choosing a default ordering, but it is not much smarter.
// Some dependencies are invisible (e.g. ELB dependencies).
type ClusterResources struct {
	ClusterName string
	Cloud       fi.Cloud
	Region      string
}

func (c *ClusterResources) ListResources() (map[string]*ResourceTracker, error) {
	switch c.Cloud.ProviderID() {
	case kops.CloudProviderAWS:
		return c.listResourcesAWS()
	case kops.CloudProviderGCE:
		return c.listResourcesGCE()
	case kops.CloudProviderVSphere:
		return c.listResourcesVSphere()
	default:
		return nil, fmt.Errorf("Delete on clusters on %q not (yet) supported", c.Cloud.ProviderID())
	}
}

func (c *ClusterResources) DeleteResources(resources map[string]*ResourceTracker) error {
	depMap := make(map[string][]string)

	done := make(map[string]*ResourceTracker)

	var mutex sync.Mutex

	for k, t := range resources {
		for _, block := range t.blocks {
			depMap[block] = append(depMap[block], k)
		}

		for _, blocked := range t.blocked {
			depMap[k] = append(depMap[k], blocked)
		}

		if t.done {
			done[k] = t
		}
	}

	glog.V(2).Infof("Dependencies")
	for k, v := range depMap {
		glog.V(2).Infof("\t%s\t%v", k, v)
	}

	iterationsWithNoProgress := 0
	for {
		// TODO: Some form of default ordering based on types?

		failed := make(map[string]*ResourceTracker)

		for {
			phase := make(map[string]*ResourceTracker)

			for k, r := range resources {
				if _, d := done[k]; d {
					continue
				}

				if _, d := failed[k]; d {
					// Only attempt each resource once per pass
					continue
				}

				ready := true
				for _, dep := range depMap[k] {
					if _, d := done[dep]; !d {
						glog.V(4).Infof("dependency %q of %q not deleted; skipping", dep, k)
						ready = false
					}
				}
				if !ready {
					continue
				}

				phase[k] = r
			}

			if len(phase) == 0 {
				break
			}

			groups := make(map[string][]*ResourceTracker)
			for k, t := range phase {
				groupKey := t.groupKey
				if groupKey == "" {
					groupKey = "_" + k
				}
				groups[groupKey] = append(groups[groupKey], t)
			}

			var wg sync.WaitGroup
			for _, trackers := range groups {
				wg.Add(1)

				go func(trackers []*ResourceTracker) {
					mutex.Lock()
					for _, t := range trackers {
						k := t.Type + ":" + t.ID
						failed[k] = t
					}
					mutex.Unlock()

					defer wg.Done()

					human := trackers[0].Type + ":" + trackers[0].ID

					var err error
					if trackers[0].groupDeleter != nil {
						err = trackers[0].groupDeleter(c.Cloud, trackers)
					} else {
						if len(trackers) != 1 {
							glog.Fatalf("found group without groupKey")
						}
						err = trackers[0].deleter(c.Cloud, trackers[0])
					}
					if err != nil {
						mutex.Lock()
						if IsDependencyViolation(err) {
							fmt.Printf("%s\tstill has dependencies, will retry\n", human)
							glog.V(4).Infof("API call made when had dependency: %s", human)
						} else {
							fmt.Printf("%s\terror deleting resource, will retry: %v\n", human, err)
						}
						for _, t := range trackers {
							k := t.Type + ":" + t.ID
							failed[k] = t
						}
						mutex.Unlock()
					} else {
						mutex.Lock()
						fmt.Printf("%s\tok\n", human)

						iterationsWithNoProgress = 0
						for _, t := range trackers {
							k := t.Type + ":" + t.ID
							delete(failed, k)
							done[k] = t
						}
						mutex.Unlock()
					}
				}(trackers)
			}
			wg.Wait()
		}

		if len(resources) == len(done) {
			return nil
		}

		fmt.Printf("Not all resources deleted; waiting before reattempting deletion\n")
		for k := range resources {
			if _, d := done[k]; d {
				continue
			}

			fmt.Printf("\t%s\n", k)
		}

		iterationsWithNoProgress++
		if iterationsWithNoProgress > 42 {
			return fmt.Errorf("Not making progress deleting resources; giving up")
		}

		time.Sleep(10 * time.Second)
	}
}