/*
Copyright 2019 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 apply

import (
	"encoding/json"
	"fmt"
	"io"
	"time"

	"github.com/jonboulle/clockwork"
	"k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/jsonmergepatch"
	"k8s.io/apimachinery/pkg/util/mergepatch"
	"k8s.io/apimachinery/pkg/util/strategicpatch"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/cli-runtime/pkg/resource"
	oapi "k8s.io/kube-openapi/pkg/util/proto"
	cmdutil "k8s.io/kubectl/pkg/cmd/util"
	"k8s.io/kubectl/pkg/scheme"
	"k8s.io/kubectl/pkg/util"
	"k8s.io/kubectl/pkg/util/openapi"
)

const (
	// maxPatchRetry is the maximum number of conflicts retry for during a patch operation before returning failure
	maxPatchRetry = 5
	// backOffPeriod is the period to back off when apply patch results in error.
	backOffPeriod = 1 * time.Second
	// how many times we can retry before back off
	triesBeforeBackOff = 1
)

// Patcher defines options to patch OpenAPI objects.
type Patcher struct {
	Mapping *meta.RESTMapping
	Helper  *resource.Helper

	Overwrite bool
	BackOff   clockwork.Clock

	Force             bool
	CascadingStrategy metav1.DeletionPropagation
	Timeout           time.Duration
	GracePeriod       int

	// If set, forces the patch against a specific resourceVersion
	ResourceVersion *string

	// Number of retries to make if the patch fails with conflict
	Retries int

	OpenapiSchema openapi.Resources
}

func newPatcher(o *ApplyOptions, info *resource.Info, helper *resource.Helper) (*Patcher, error) {
	var openapiSchema openapi.Resources
	if o.OpenAPIPatch {
		openapiSchema = o.OpenAPISchema
	}

	return &Patcher{
		Mapping:           info.Mapping,
		Helper:            helper,
		Overwrite:         o.Overwrite,
		BackOff:           clockwork.NewRealClock(),
		Force:             o.DeleteOptions.ForceDeletion,
		CascadingStrategy: o.DeleteOptions.CascadingStrategy,
		Timeout:           o.DeleteOptions.Timeout,
		GracePeriod:       o.DeleteOptions.GracePeriod,
		OpenapiSchema:     openapiSchema,
		Retries:           maxPatchRetry,
	}, nil
}

func (p *Patcher) delete(namespace, name string) error {
	options := asDeleteOptions(p.CascadingStrategy, p.GracePeriod)
	_, err := p.Helper.DeleteWithOptions(namespace, name, &options)
	return err
}

func (p *Patcher) patchSimple(obj runtime.Object, modified []byte, source, namespace, name string, errOut io.Writer) ([]byte, runtime.Object, error) {
	// Serialize the current configuration of the object from the server.
	current, err := runtime.Encode(unstructured.UnstructuredJSONScheme, obj)
	if err != nil {
		return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf("serializing current configuration from:\n%v\nfor:", obj), source, err)
	}

	// Retrieve the original configuration of the object from the annotation.
	original, err := util.GetOriginalConfiguration(obj)
	if err != nil {
		return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf("retrieving original configuration from:\n%v\nfor:", obj), source, err)
	}

	var patchType types.PatchType
	var patch []byte
	var lookupPatchMeta strategicpatch.LookupPatchMeta
	var schema oapi.Schema
	createPatchErrFormat := "creating patch with:\noriginal:\n%s\nmodified:\n%s\ncurrent:\n%s\nfor:"

	// Create the versioned struct from the type defined in the restmapping
	// (which is the API version we'll be submitting the patch to)
	versionedObject, err := scheme.Scheme.New(p.Mapping.GroupVersionKind)
	switch {
	case runtime.IsNotRegisteredError(err):
		// fall back to generic JSON merge patch
		patchType = types.MergePatchType
		preconditions := []mergepatch.PreconditionFunc{mergepatch.RequireKeyUnchanged("apiVersion"),
			mergepatch.RequireKeyUnchanged("kind"), mergepatch.RequireMetadataKeyUnchanged("name")}
		patch, err = jsonmergepatch.CreateThreeWayJSONMergePatch(original, modified, current, preconditions...)
		if err != nil {
			if mergepatch.IsPreconditionFailed(err) {
				return nil, nil, fmt.Errorf("%s", "At least one of apiVersion, kind and name was changed")
			}
			return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf(createPatchErrFormat, original, modified, current), source, err)
		}
	case err != nil:
		return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf("getting instance of versioned object for %v:", p.Mapping.GroupVersionKind), source, err)
	case err == nil:
		// Compute a three way strategic merge patch to send to server.
		patchType = types.StrategicMergePatchType

		// Try to use openapi first if the openapi spec is available and can successfully calculate the patch.
		// Otherwise, fall back to baked-in types.
		if p.OpenapiSchema != nil {
			if schema = p.OpenapiSchema.LookupResource(p.Mapping.GroupVersionKind); schema != nil {
				lookupPatchMeta = strategicpatch.PatchMetaFromOpenAPI{Schema: schema}
				if openapiPatch, err := strategicpatch.CreateThreeWayMergePatch(original, modified, current, lookupPatchMeta, p.Overwrite); err != nil {
					fmt.Fprintf(errOut, "warning: error calculating patch from openapi spec: %v\n", err)
				} else {
					patchType = types.StrategicMergePatchType
					patch = openapiPatch
				}
			}
		}

		if patch == nil {
			lookupPatchMeta, err = strategicpatch.NewPatchMetaFromStruct(versionedObject)
			if err != nil {
				return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf(createPatchErrFormat, original, modified, current), source, err)
			}
			patch, err = strategicpatch.CreateThreeWayMergePatch(original, modified, current, lookupPatchMeta, p.Overwrite)
			if err != nil {
				return nil, nil, cmdutil.AddSourceToErr(fmt.Sprintf(createPatchErrFormat, original, modified, current), source, err)
			}
		}
	}

	if string(patch) == "{}" {
		return patch, obj, nil
	}

	if p.ResourceVersion != nil {
		patch, err = addResourceVersion(patch, *p.ResourceVersion)
		if err != nil {
			return nil, nil, cmdutil.AddSourceToErr("Failed to insert resourceVersion in patch", source, err)
		}
	}

	patchedObj, err := p.Helper.Patch(namespace, name, patchType, patch, nil)
	return patch, patchedObj, err
}

// Patch tries to patch an OpenAPI resource. On success, returns the merge patch as well
// the final patched object. On failure, returns an error.
func (p *Patcher) Patch(current runtime.Object, modified []byte, source, namespace, name string, errOut io.Writer) ([]byte, runtime.Object, error) {
	var getErr error
	patchBytes, patchObject, err := p.patchSimple(current, modified, source, namespace, name, errOut)
	if p.Retries == 0 {
		p.Retries = maxPatchRetry
	}
	for i := 1; i <= p.Retries && errors.IsConflict(err); i++ {
		if i > triesBeforeBackOff {
			p.BackOff.Sleep(backOffPeriod)
		}
		current, getErr = p.Helper.Get(namespace, name)
		if getErr != nil {
			return nil, nil, getErr
		}
		patchBytes, patchObject, err = p.patchSimple(current, modified, source, namespace, name, errOut)
	}
	if err != nil && (errors.IsConflict(err) || errors.IsInvalid(err)) && p.Force {
		patchBytes, patchObject, err = p.deleteAndCreate(current, modified, namespace, name)
	}
	return patchBytes, patchObject, err
}

func (p *Patcher) deleteAndCreate(original runtime.Object, modified []byte, namespace, name string) ([]byte, runtime.Object, error) {
	if err := p.delete(namespace, name); err != nil {
		return modified, nil, err
	}
	// TODO: use wait
	if err := wait.PollImmediate(1*time.Second, p.Timeout, func() (bool, error) {
		if _, err := p.Helper.Get(namespace, name); !errors.IsNotFound(err) {
			return false, err
		}
		return true, nil
	}); err != nil {
		return modified, nil, err
	}
	versionedObject, _, err := unstructured.UnstructuredJSONScheme.Decode(modified, nil, nil)
	if err != nil {
		return modified, nil, err
	}
	createdObject, err := p.Helper.Create(namespace, true, versionedObject)
	if err != nil {
		// restore the original object if we fail to create the new one
		// but still propagate and advertise error to user
		recreated, recreateErr := p.Helper.Create(namespace, true, original)
		if recreateErr != nil {
			err = fmt.Errorf("An error occurred force-replacing the existing object with the newly provided one:\n\n%v.\n\nAdditionally, an error occurred attempting to restore the original object:\n\n%v", err, recreateErr)
		} else {
			createdObject = recreated
		}
	}
	return modified, createdObject, err
}

func addResourceVersion(patch []byte, rv string) ([]byte, error) {
	var patchMap map[string]interface{}
	err := json.Unmarshal(patch, &patchMap)
	if err != nil {
		return nil, err
	}
	u := unstructured.Unstructured{Object: patchMap}
	a, err := meta.Accessor(&u)
	if err != nil {
		return nil, err
	}
	a.SetResourceVersion(rv)

	return json.Marshal(patchMap)
}