// Copyright 2019 The Kubernetes Authors.
// SPDX-License-Identifier: Apache-2.0

// package kubectlcobra contains cobra commands from kubectl
package kubectlcobra

import (
	"fmt"
	"io"
	"strings"

	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/cli-runtime/pkg/printers"
	"k8s.io/cli-runtime/pkg/resource"
	"k8s.io/client-go/dynamic"
	"k8s.io/kubectl/pkg/cmd/apply"
	"k8s.io/kubectl/pkg/cmd/util"
	"k8s.io/kubectl/pkg/validation"
)

// PruneOptions encapsulates the necessary information to
// implement the prune functionality.
type PruneOptions struct {
	client    dynamic.Interface
	builder   *resource.Builder
	mapper    meta.RESTMapper
	namespace string
	// The currently applied objects (as Infos), including the
	// current grouping object. These objects are used to
	// calculate the prune set after retreiving the previous
	// grouping objects.
	currentGroupingObject *resource.Info
	// The set of retrieved grouping objects (as Infos) selected
	// by the grouping label. This set should also include the
	// current grouping object. Stored here to make testing
	// easier by manually setting the retrieved grouping infos.
	pastGroupingObjects      []*resource.Info
	retrievedGroupingObjects bool

	toPrinter func(string) (printers.ResourcePrinter, error)
	out       io.Writer

	validator validation.Schema

	// TODO: DeleteOptions--cascade?
}

// NewPruneOptions returns a struct (PruneOptions) encapsulating the necessary
// information to run the prune. Returns an error if an error occurs
// gathering this information.
// TODO: Add dry-run options.
func NewPruneOptions(f util.Factory, ao *apply.ApplyOptions) (*PruneOptions, error) {

	po := &PruneOptions{}
	var err error
	// Fields copied from ApplyOptions.
	po.namespace = ao.Namespace
	po.toPrinter = ao.ToPrinter
	po.out = ao.Out
	// Client/Builder fields from the Factory.
	po.client, err = f.DynamicClient()
	if err != nil {
		return nil, err
	}
	po.builder = f.NewBuilder()
	po.mapper, err = f.ToRESTMapper()
	if err != nil {
		return nil, err
	}
	po.validator, err = f.Validator(false)
	if err != nil {
		return nil, err
	}
	// Retrieve/store the grouping object for current apply.
	currentObjects, err := ao.GetObjects()
	if err != nil {
		return nil, err
	}
	currentGroupingObject, found := findGroupingObject(currentObjects)
	if !found {
		return nil, fmt.Errorf("Current grouping object not found during prune.")
	}
	po.currentGroupingObject = currentGroupingObject
	// Initialize past grouping objects as empty.
	po.pastGroupingObjects = []*resource.Info{}
	po.retrievedGroupingObjects = false

	return po, nil
}

// getPreviousGroupingObjects returns the set of grouping objects
// that have the same label as the current grouping object. Removes
// the current grouping object from this set. Returns an error
// if there is a problem retrieving the grouping objects.
func (po *PruneOptions) getPreviousGroupingObjects() ([]*resource.Info, error) {

	// Ensures the "pastGroupingObjects" is set.
	if !po.retrievedGroupingObjects {
		if err := po.retrievePreviousGroupingObjects(); err != nil {
			return nil, err
		}
	}

	// Remove the current grouping info from the previous grouping infos.
	currentInventory, err := infoToInventory(po.currentGroupingObject)
	if err != nil {
		return nil, err
	}
	pastGroupInfos := []*resource.Info{}
	for _, pastInfo := range po.pastGroupingObjects {
		pastInventory, err := infoToInventory(pastInfo)
		if err != nil {
			return nil, err
		}
		if !currentInventory.Equals(pastInventory) {
			pastGroupInfos = append(pastGroupInfos, pastInfo)
		}
	}
	return pastGroupInfos, nil
}

// retrievePreviousGroupingObjects requests the previous grouping objects
// using the grouping label from the current grouping object. Sets
// the field "pastGroupingObjects". Returns an error if the grouping
// label doesn't exist for the current currentGroupingObject does not
// exist or if the call to retrieve the past grouping objects fails.
func (po *PruneOptions) retrievePreviousGroupingObjects() error {
	// Get the grouping label for this grouping object, and create
	// a label selector from it.
	if po.currentGroupingObject == nil || po.currentGroupingObject.Object == nil {
		return fmt.Errorf("Missing current grouping object.\n")
	}
	groupingLabel, err := retrieveGroupingLabel(po.currentGroupingObject.Object)
	if err != nil {
		return err
	}
	labelSelector := fmt.Sprintf("%s=%s", GroupingLabel, groupingLabel)
	retrievedGroupingInfos, err := po.builder.
		Unstructured().
		// TODO: Check if this validator is necessary.
		Schema(po.validator).
		ContinueOnError().
		NamespaceParam(po.namespace).DefaultNamespace().
		ResourceTypes("configmap").
		LabelSelectorParam(labelSelector).
		Flatten().
		Do().
		Infos()
	if err != nil {
		return err
	}
	po.pastGroupingObjects = retrievedGroupingInfos
	po.retrievedGroupingObjects = true
	return nil
}

// infoToInventory transforms the object represented by the passed "info"
// into its Inventory representation. Returns error if the passed Info
// is nil, or the Object in the Info is empty.
func infoToInventory(info *resource.Info) (*Inventory, error) {
	if info == nil || info.Object == nil {
		return nil, fmt.Errorf("Empty resource.Info can not calculate as inventory.\n")
	}
	obj := info.Object
	gk := obj.GetObjectKind().GroupVersionKind().GroupKind()
	return createInventory(info.Namespace, info.Name, gk)
}

// unionPastInventory takes a set of grouping objects (infos), returning the
// union of the objects referenced by these grouping objects as an
// InventorySet. Returns an error if any of the passed objects are not
// grouping objects, or if unable to retrieve the inventory from any
// grouping object.
func unionPastInventory(infos []*resource.Info) (*InventorySet, error) {
	inventorySet := NewInventorySet([]*Inventory{})
	for _, info := range infos {
		inv, err := retrieveInventoryFromGroupingObj([]*resource.Info{info})
		if err != nil {
			return nil, err
		}
		inventorySet.AddItems(inv)
	}
	return inventorySet, nil
}

// calcPruneSet returns the InventorySet representing the objects to
// delete (prune). pastGroupInfos are the set of past applied grouping
// objects, storing the inventory of the objects applied at the same time.
// Calculates the prune set as:
//
//   prune set = (prev1 U prev2 U ... U prevN) - (curr1, curr2, ..., currN)
//
// Returns an error if we are unable to retrieve the set of previously
// applied objects, or if we are unable to get the currently applied objects
// from the current grouping object.
func (po *PruneOptions) calcPruneSet(pastGroupingInfos []*resource.Info) (*InventorySet, error) {
	pastInventory, err := unionPastInventory(pastGroupingInfos)
	if err != nil {
		return nil, err
	}
	// Current grouping object as inventory set.
	c := []*resource.Info{po.currentGroupingObject}
	currentInv, err := retrieveInventoryFromGroupingObj(c)
	if err != nil {
		return nil, err
	}
	return pastInventory.Subtract(NewInventorySet(currentInv))
}

// Prune deletes the set of resources which were previously applied
// (retrieved from previous grouping objects) but omitted in
// the current apply. Prune also delete all previous grouping
// objects. Returns an error if there was a problem.
func (po *PruneOptions) Prune() error {

	// Retrieve previous grouping objects, and calculate the
	// union of the previous applies as an inventory set.
	pastGroupingInfos, err := po.getPreviousGroupingObjects()
	if err != nil {
		return err
	}
	pruneSet, err := po.calcPruneSet(pastGroupingInfos)
	if err != nil {
		return err
	}

	// Delete the prune objects.
	for _, inv := range pruneSet.GetItems() {
		mapping, err := po.mapper.RESTMapping(inv.GroupKind)
		if err != nil {
			return err
		}
		err = po.client.Resource(mapping.Resource).Namespace(inv.Namespace).Delete(inv.Name, &metav1.DeleteOptions{})
		if err != nil {
			return err
		}
		fmt.Fprintf(po.out, "%s/%s deleted\n", strings.ToLower(inv.GroupKind.Kind), inv.Name)
	}
	// Delete previous grouping objects.
	for _, pastGroupInfo := range pastGroupingInfos {
		err = po.client.Resource(pastGroupInfo.Mapping.Resource).
			Namespace(pastGroupInfo.Namespace).
			Delete(pastGroupInfo.Name, &metav1.DeleteOptions{})
		if err != nil {
			return err
		}
		printer, err := po.toPrinter("deleted")
		if err != nil {
			return err
		}
		if err = printer.PrintObj(pastGroupInfo.Object, po.out); err != nil {
			return err
		}
	}

	return nil
}