/*
Copyright 2015 The Kubernetes Authors All rights reserved.

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 cmd

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"os"
	gruntime "runtime"
	"strings"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/errors"
	"k8s.io/kubernetes/pkg/api/unversioned"
	"k8s.io/kubernetes/pkg/kubectl"
	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
	"k8s.io/kubernetes/pkg/kubectl/cmd/util/editor"
	"k8s.io/kubernetes/pkg/kubectl/cmd/util/jsonmerge"
	"k8s.io/kubernetes/pkg/kubectl/resource"
	"k8s.io/kubernetes/pkg/runtime"
	"k8s.io/kubernetes/pkg/util"
	"k8s.io/kubernetes/pkg/util/strategicpatch"
	"k8s.io/kubernetes/pkg/util/yaml"

	"github.com/golang/glog"
	"github.com/spf13/cobra"
)

const (
	editLong = `Edit a resource from the default editor.

The edit command allows you to directly edit any API resource you can retrieve via the
command line tools. It will open the editor defined by your KUBE_EDITOR, or EDITOR
environment variables, or fall back to 'vi' for Linux or 'notepad' for Windows.
You can edit multiple objects, although changes are applied one at a time. The command
accepts filenames as well as command line arguments, although the files you point to must
be previously saved versions of resources.

The files to edit will be output in the default API version, or a version specified
by --output-version. The default format is YAML - if you would like to edit in JSON
pass -o json. The flag --windows-line-endings can be used to force Windows line endings,
otherwise the default for your operating system will be used.

In the event an error occurs while updating, a temporary file will be created on disk
that contains your unapplied changes. The most common error when updating a resource
is another editor changing the resource on the server. When this occurs, you will have
to apply your changes to the newer version of the resource, or update your temporary
saved copy to include the latest resource version.`

	editExample = `  # Edit the service named 'docker-registry':
  $ kubectl edit svc/docker-registry

  # Use an alternative editor
  $ KUBE_EDITOR="nano" kubectl edit svc/docker-registry

  # Edit the service 'docker-registry' in JSON using the v1 API format:
  $ kubectl edit svc/docker-registry --output-version=v1 -o json`
)

var errExit = fmt.Errorf("exit directly")

func NewCmdEdit(f *cmdutil.Factory, out io.Writer) *cobra.Command {
	filenames := []string{}
	cmd := &cobra.Command{
		Use:     "edit (RESOURCE/NAME | -f FILENAME)",
		Short:   "Edit a resource on the server",
		Long:    editLong,
		Example: fmt.Sprintf(editExample),
		Run: func(cmd *cobra.Command, args []string) {
			err := RunEdit(f, out, cmd, args, filenames)
			if err == errExit {
				os.Exit(1)
			}
			cmdutil.CheckErr(err)
		},
	}
	usage := "Filename, directory, or URL to file to use to edit the resource"
	kubectl.AddJsonFilenameFlag(cmd, &filenames, usage)
	cmd.Flags().StringP("output", "o", "yaml", "Output format. One of: yaml|json.")
	cmd.Flags().String("output-version", "", "Output the formatted object with the given version (default api-version).")
	cmd.Flags().Bool("windows-line-endings", gruntime.GOOS == "windows", "Use Windows line-endings (default Unix line-endings)")
	cmdutil.AddApplyAnnotationFlags(cmd)
	cmdutil.AddRecordFlag(cmd)
	return cmd
}

func RunEdit(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, args []string, filenames []string) error {
	var printer kubectl.ResourcePrinter
	var ext string
	switch format := cmdutil.GetFlagString(cmd, "output"); format {
	case "json":
		printer = &kubectl.JSONPrinter{}
		ext = ".json"
	case "yaml":
		printer = &kubectl.YAMLPrinter{}
		ext = ".yaml"
	default:
		return cmdutil.UsageError(cmd, "The flag 'output' must be one of yaml|json")
	}

	cmdNamespace, enforceNamespace, err := f.DefaultNamespace()
	if err != nil {
		return err
	}

	mapper, typer := f.Object()
	resourceMapper := &resource.Mapper{
		ObjectTyper:  typer,
		RESTMapper:   mapper,
		ClientMapper: resource.ClientMapperFunc(f.ClientForMapping),
		Decoder:      f.Decoder(true),
	}

	r := resource.NewBuilder(mapper, typer, resource.ClientMapperFunc(f.ClientForMapping), f.Decoder(true)).
		NamespaceParam(cmdNamespace).DefaultNamespace().
		FilenameParam(enforceNamespace, filenames...).
		ResourceTypeOrNameArgs(true, args...).
		Latest().
		Flatten().
		Do()
	err = r.Err()
	if err != nil {
		return err
	}

	infos, err := r.Infos()
	if err != nil {
		return err
	}

	clientConfig, err := f.ClientConfig()
	if err != nil {
		return err
	}

	encoder := f.JSONEncoder()
	defaultVersion, err := cmdutil.OutputVersion(cmd, clientConfig.GroupVersion)
	if err != nil {
		return err
	}
	objs, err := resource.AsVersionedObjects(infos, defaultVersion.String(), encoder)
	if err != nil {
		return err
	}

	var (
		windowsLineEndings = cmdutil.GetFlagBool(cmd, "windows-line-endings")
		edit               = editor.NewDefaultEditor(f.EditorEnvs())
		results            = editResults{}
		original           = []byte{}
		edited             = []byte{}
		file               string
	)

outter:
	for i := range objs {
		obj := objs[i]
		// some bookkeeping
		results.header.flush()
		containsError := false

		for {
			// generate the file to edit
			buf := &bytes.Buffer{}
			var w io.Writer = buf
			if windowsLineEndings {
				w = util.NewCRLFWriter(w)
			}
			if err := results.header.writeTo(w); err != nil {
				return preservedFile(err, results.file, out)
			}
			if !containsError {
				if err := printer.PrintObj(obj, w); err != nil {
					return preservedFile(err, results.file, out)
				}
				original = buf.Bytes()
			} else {
				// In case of an error, preserve the edited file.
				// Remove the comments (header) from it since we already
				// have included the latest header in the buffer above.
				buf.Write(manualStrip(edited))
			}

			// launch the editor
			editedDiff := edited
			edited, file, err = edit.LaunchTempFile(fmt.Sprintf("%s-edit-", os.Args[0]), ext, buf)
			if err != nil {
				return preservedFile(err, results.file, out)
			}
			if bytes.Equal(stripComments(editedDiff), stripComments(edited)) {
				// Ugly hack right here. We will hit this either (1) when we try to
				// save the same changes we tried to save in the previous iteration
				// which means our changes are invalid or (2) when we exit the second
				// time. The second case is more usual so we can probably live with it.
				// TODO: A less hacky fix would be welcome :)
				fmt.Fprintln(out, "Edit cancelled, no valid changes were saved.")
				continue outter
			}

			// cleanup any file from the previous pass
			if len(results.file) > 0 {
				os.Remove(results.file)
			}
			glog.V(4).Infof("User edited:\n%s", string(edited))

			// Compare content without comments
			if bytes.Equal(stripComments(original), stripComments(edited)) {
				os.Remove(file)
				fmt.Fprintln(out, "Edit cancelled, no changes made.")
				continue outter
			}
			lines, err := hasLines(bytes.NewBuffer(edited))
			if err != nil {
				return preservedFile(err, file, out)
			}
			if !lines {
				os.Remove(file)
				fmt.Fprintln(out, "Edit cancelled, saved file was empty.")
				continue outter
			}

			results = editResults{
				file: file,
			}

			// parse the edited file
			updates, err := resourceMapper.InfoForData(edited, "edited-file")
			if err != nil {
				// syntax error
				containsError = true
				results.header.reasons = append(results.header.reasons, editReason{head: fmt.Sprintf("The edited file had a syntax error: %v", err)})
				continue
			}
			// not a syntax error as it turns out...
			containsError = false

			// put configuration annotation in "updates"
			if err := kubectl.CreateOrUpdateAnnotation(cmdutil.GetFlagBool(cmd, cmdutil.ApplyAnnotationsFlag), updates, encoder); err != nil {
				return preservedFile(err, file, out)
			}
			if cmdutil.ShouldRecord(cmd, updates) {
				err = cmdutil.RecordChangeCause(updates.Object, f.Command())
				if err != nil {
					return err
				}
			}
			editedCopy := edited
			if editedCopy, err = runtime.Encode(encoder, updates.Object); err != nil {
				return preservedFile(err, file, out)
			}

			visitor := resource.NewFlattenListVisitor(updates, resourceMapper)

			// need to make sure the original namespace wasn't changed while editing
			if err = visitor.Visit(resource.RequireNamespace(cmdNamespace)); err != nil {
				return preservedFile(err, file, out)
			}

			// use strategic merge to create a patch
			originalJS, err := yaml.ToJSON(original)
			if err != nil {
				return preservedFile(err, file, out)
			}
			editedJS, err := yaml.ToJSON(editedCopy)
			if err != nil {
				return preservedFile(err, file, out)
			}
			patch, err := strategicpatch.CreateStrategicMergePatch(originalJS, editedJS, obj)
			// TODO: change all jsonmerge to strategicpatch
			// for checking preconditions
			preconditions := []jsonmerge.PreconditionFunc{}
			if err != nil {
				glog.V(4).Infof("Unable to calculate diff, no merge is possible: %v", err)
				return preservedFile(err, file, out)
			} else {
				preconditions = append(preconditions, jsonmerge.RequireKeyUnchanged("apiVersion"))
				preconditions = append(preconditions, jsonmerge.RequireKeyUnchanged("kind"))
				preconditions = append(preconditions, jsonmerge.RequireMetadataKeyUnchanged("name"))
				results.version = defaultVersion
			}

			if hold, msg := jsonmerge.TestPreconditionsHold(patch, preconditions); !hold {
				fmt.Fprintf(out, "error: %s", msg)
				return preservedFile(nil, file, out)
			}

			err = visitor.Visit(func(info *resource.Info, err error) error {
				patched, err := resource.NewHelper(info.Client, info.Mapping).Patch(info.Namespace, info.Name, api.StrategicMergePatchType, patch)
				if err != nil {
					glog.V(4).Infof(results.addError(err, info))
					return err
				}
				info.Refresh(patched, true)
				cmdutil.PrintSuccess(mapper, false, out, info.Mapping.Resource, info.Name, "edited")
				return nil
			})
			if err == nil {
				os.Remove(file)
				continue outter
			}
			// Handle all possible errors
			//
			// 1. retryable: propose kubectl replace -f
			// 2. notfound: indicate the location of the saved configuration of the deleted resource
			// 3. invalid: retry those on the spot by looping ie. reloading the editor
			if results.retryable > 0 {
				fmt.Fprintf(out, "You can run `%s replace -f %s` to try this update again.\n", os.Args[0], file)
				continue outter
			}
			if results.notfound > 0 {
				fmt.Fprintf(out, "The edits you made on deleted resources have been saved to %q\n", file)
				continue outter
			}
			// validation error
			containsError = true
		}
	}
	return nil
}

// editReason preserves a message about the reason this file must be edited again
type editReason struct {
	head  string
	other []string
}

// editHeader includes a list of reasons the edit must be retried
type editHeader struct {
	reasons []editReason
}

// writeTo outputs the current header information into a stream
func (h *editHeader) writeTo(w io.Writer) error {
	fmt.Fprint(w, `# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
`)
	for _, r := range h.reasons {
		if len(r.other) > 0 {
			fmt.Fprintf(w, "# %s:\n", r.head)
		} else {
			fmt.Fprintf(w, "# %s\n", r.head)
		}
		for _, o := range r.other {
			fmt.Fprintf(w, "# * %s\n", o)
		}
		fmt.Fprintln(w, "#")
	}
	return nil
}

func (h *editHeader) flush() {
	h.reasons = []editReason{}
}

// editResults capture the result of an update
type editResults struct {
	header    editHeader
	retryable int
	notfound  int
	edit      []*resource.Info
	file      string

	version unversioned.GroupVersion
}

func (r *editResults) addError(err error, info *resource.Info) string {
	switch {
	case errors.IsInvalid(err):
		r.edit = append(r.edit, info)
		reason := editReason{
			head: fmt.Sprintf("%s %q was not valid", info.Mapping.Resource, info.Name),
		}
		if err, ok := err.(errors.APIStatus); ok {
			if details := err.Status().Details; details != nil {
				for _, cause := range details.Causes {
					reason.other = append(reason.other, fmt.Sprintf("%s: %s", cause.Field, cause.Message))
				}
			}
		}
		r.header.reasons = append(r.header.reasons, reason)
		return fmt.Sprintf("Error: %s %q is invalid", info.Mapping.Resource, info.Name)
	case errors.IsNotFound(err):
		r.notfound++
		return fmt.Sprintf("Error: %s %q could not be found on the server", info.Mapping.Resource, info.Name)
	default:
		r.retryable++
		return fmt.Sprintf("Error: %s %q could not be patched: %v", info.Mapping.Resource, info.Name, err)
	}
}

// preservedFile writes out a message about the provided file if it exists to the
// provided output stream when an error happens. Used to notify the user where
// their updates were preserved.
func preservedFile(err error, path string, out io.Writer) error {
	if len(path) > 0 {
		if _, err := os.Stat(path); !os.IsNotExist(err) {
			fmt.Fprintf(out, "A copy of your changes has been stored to %q\n", path)
		}
	}
	return err
}

// hasLines returns true if any line in the provided stream is non empty - has non-whitespace
// characters, or the first non-whitespace character is a '#' indicating a comment. Returns
// any errors encountered reading the stream.
func hasLines(r io.Reader) (bool, error) {
	// TODO: if any files we read have > 64KB lines, we'll need to switch to bytes.ReadLine
	// TODO: probably going to be secrets
	s := bufio.NewScanner(r)
	for s.Scan() {
		if line := strings.TrimSpace(s.Text()); len(line) > 0 && line[0] != '#' {
			return true, nil
		}
	}
	if err := s.Err(); err != nil && err != io.EOF {
		return false, err
	}
	return false, nil
}

// stripComments will transform a YAML file into JSON, thus dropping any comments
// in it. Note that if the given file has a syntax error, the transformation will
// fail and we will manually drop all comments from the file.
func stripComments(file []byte) []byte {
	stripped := file
	stripped, err := yaml.ToJSON(stripped)
	if err != nil {
		stripped = manualStrip(file)
	}
	return stripped
}

// manualStrip is used for dropping comments from a YAML file
func manualStrip(file []byte) []byte {
	stripped := []byte{}
	lines := bytes.Split(file, []byte("\n"))
	for i, line := range lines {
		if bytes.HasPrefix(bytes.TrimSpace(line), []byte("#")) {
			continue
		}
		stripped = append(stripped, line...)
		if i < len(lines)-1 {
			stripped = append(stripped, '\n')
		}
	}
	return stripped
}
