/*
Copyright 2020 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 generate

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/golang/glog"
	"github.com/pkg/errors"
	"github.com/spf13/cobra"
	"github.com/spf13/cobra/doc"
	"k8s.io/minikube/pkg/minikube/out"
)

// Docs generates docs for minikube command
func Docs(root *cobra.Command, path string) error {
	cmds := root.Commands()
	for _, c := range cmds {
		if c.Hidden {
			glog.Infof("Skipping generating doc for %s as it's a hidden command", c.Name())
			continue
		}
		contents, err := DocForCommand(c)
		if err != nil {
			return errors.Wrapf(err, "generating doc for %s", c.Name())
		}
		if err := saveDocForCommand(c, []byte(contents), path); err != nil {
			return errors.Wrapf(err, "saving doc for %s", c.Name())
		}
	}
	return nil
}

// DocForCommand returns the specific doc for that command
func DocForCommand(command *cobra.Command) (string, error) {
	buf := bytes.NewBuffer([]byte{})
	if err := generateTitle(command, buf); err != nil {
		return "", errors.Wrap(err, "generating title")
	}
	if err := rewriteFlags(command); err != nil {
		return "", errors.Wrap(err, "rewriting flags")
	}
	if err := writeSubcommands(command, buf); err != nil {
		return "", errors.Wrap(err, "writing subcommands")
	}
	return removeHelpText(buf), nil
}

// after every command, cobra automatically appends
// ### SEE ALSO

// * [minikube addons](minikube_addons.md)	 - Modify minikube's Kubernetes addons

// ###### Auto generated by spf13/cobra on 1-Apr-2020
// help text which is unnecessary info after every subcommand
// This function removes that text.
func removeHelpText(buffer *bytes.Buffer) string {
	beginningHelpText := "### SEE ALSO"
	endHelpText := "###### Auto generated by spf13/cobra"
	scanner := bufio.NewScanner(buffer)
	includeLine := true

	final := bytes.NewBuffer([]byte{})
	for scanner.Scan() {
		line := scanner.Text()
		if strings.Contains(line, beginningHelpText) {
			includeLine = false
			continue
		}
		if strings.Contains(line, endHelpText) {
			includeLine = true
			continue
		}
		if !includeLine {
			continue
		}
		// scanner strips the ending newline
		if _, err := final.WriteString(line + "\n"); err != nil {
			glog.Warningf("error removing help text: %v", err)
			break
		}
	}
	return final.String()
}

// writeSubcommands recursively appends all subcommands to the doc
func writeSubcommands(command *cobra.Command, w io.Writer) error {
	if err := doc.GenMarkdown(command, w); err != nil {
		return errors.Wrapf(err, "getting markdown custom")
	}
	if !command.HasSubCommands() {
		return nil
	}
	subCommands := command.Commands()
	for _, sc := range subCommands {
		if err := writeSubcommands(sc, w); err != nil {
			return err
		}
	}
	return nil
}

func generateTitle(command *cobra.Command, w io.Writer) error {
	date := time.Now().Format("2006-01-02")
	title := out.ApplyTemplateFormatting(9999, false, title, out.V{"Command": command.Name(), "Description": command.Short, "Date": date})
	_, err := w.Write([]byte(title))
	return err
}

func saveDocForCommand(command *cobra.Command, contents []byte, path string) error {
	fp := filepath.Join(path, fmt.Sprintf("%s.md", command.Name()))
	if err := os.Remove(fp); err != nil {
		glog.Warningf("error removing %s", fp)
	}
	return ioutil.WriteFile(fp, contents, 0644)
}