//Copyright 2015 Red Hat Inc. 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 clidoc

import (
	"bytes"
	"fmt"
	"html"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"github.com/ory/x/cmdx"

	"github.com/spf13/cobra"
)

func printOptions(buf *bytes.Buffer, cmd *cobra.Command, name string) error {
	flags := cmd.NonInheritedFlags()
	flags.SetOutput(buf)
	if flags.HasAvailableFlags() {
		buf.WriteString("### Options\n\n```\n")
		flags.PrintDefaults()
		buf.WriteString("```\n\n")
	}

	parentFlags := cmd.InheritedFlags()
	parentFlags.SetOutput(buf)
	if parentFlags.HasAvailableFlags() {
		buf.WriteString("### Options inherited from parent commands\n\n```\n")
		parentFlags.PrintDefaults()
		buf.WriteString("```\n\n")
	}
	return nil
}

// GenMarkdown creates markdown output.
func GenMarkdown(cmd *cobra.Command, w io.Writer) error {
	return GenMarkdownCustom(cmd, w, func(s string) string { return s })
}

// GenMarkdownCustom creates custom markdown output.
func GenMarkdownCustom(cmd *cobra.Command, w io.Writer, linkHandler func(string) string) error {
	cmd.InitDefaultHelpCmd()
	cmd.InitDefaultHelpFlag()

	buf := new(bytes.Buffer)
	name := cmd.CommandPath()

	buf.WriteString("## " + html.EscapeString(name) + "\n\n")
	buf.WriteString(fenceIndentedBlocks(cmd.Short) + "\n\n")
	if len(cmd.Long) > 0 {
		buf.WriteString("### Synopsis\n\n")
		long, err := cmdx.TemplateCommandField(cmd, cmd.Long)
		if err != nil {
			buf.WriteString(fmt.Sprintf("<!-- Error rendering cmd.Long: %s -->\n\n", err.Error()))
			long = cmd.Long
		}
		buf.WriteString(fenceIndentedBlocks(long) + "\n\n")
	}

	if cmd.Runnable() {
		buf.WriteString(fmt.Sprintf("```\n%s\n```\n\n", cmd.UseLine()))
	}

	if len(cmd.Example) > 0 {
		buf.WriteString("### Examples\n\n")
		example, err := cmdx.TemplateCommandField(cmd, cmd.Example)
		if err != nil {
			buf.WriteString(fmt.Sprintf("<!-- Error rendering cmd.Example: %s -->\n\n", err.Error()))
			example = cmd.Example
		}
		buf.WriteString(fmt.Sprintf("```\n%s\n```\n\n", example))
	}

	if err := printOptions(buf, cmd, name); err != nil {
		return err
	}
	if hasSeeAlso(cmd) {
		buf.WriteString("### See also\n\n")
		if cmd.HasParent() {
			parent := cmd.Parent()
			pname := parent.CommandPath()
			link := pname + ".md"
			link = strings.Replace(link, " ", "_", -1)
			short := parent.Short
			if short != "" {
				short = fmt.Sprintf(" %s", short)
			}
			buf.WriteString(fmt.Sprintf("* [%s](%s)%s\n", pname, linkHandler(link), short))
			cmd.VisitParents(func(c *cobra.Command) {
				if c.DisableAutoGenTag {
					cmd.DisableAutoGenTag = c.DisableAutoGenTag
				}
			})
		}

		children := cmd.Commands()
		sort.Sort(byName(children))

		for _, child := range children {
			if !child.IsAvailableCommand() || child.IsAdditionalHelpTopicCommand() {
				continue
			}
			cname := name + " " + child.Name()
			link := cname + ".md"
			link = strings.Replace(link, " ", "_", -1)
			short := child.Short
			if short != "" {
				short = fmt.Sprintf(" - %s", short)
			}
			buf.WriteString(fmt.Sprintf("* [%s](%s)\t%s\n", cname, linkHandler(link), short))
		}
		buf.WriteString("\n")
	}

	_, err := buf.WriteTo(w)
	return err
}

// GenMarkdownTree will generate a markdown page for this command and all
// descendants in the directory given. The header may be nil.
// This function may not work correctly if your command names have `-` in them.
// If you have `cmd` with two subcmds, `sub` and `sub-third`,
// and `sub` has a subcommand called `third`, it is undefined which
// help output will be in the file `cmd-sub-third.1`.
func GenMarkdownTree(cmd *cobra.Command, dir string) error {
	identity := func(s string) string { return s }
	emptyStr := func(s string) string { return "" }
	return GenMarkdownTreeCustom(cmd, dir, emptyStr, identity)
}

// GenMarkdownTreeCustom is the the same as GenMarkdownTree, but
// with custom filePrepender and linkHandler.
func GenMarkdownTreeCustom(cmd *cobra.Command, dir string, filePrepender, linkHandler func(string) string) error {
	for _, c := range cmd.Commands() {
		if !c.IsAvailableCommand() || c.IsAdditionalHelpTopicCommand() {
			continue
		}
		if err := GenMarkdownTreeCustom(c, dir, filePrepender, linkHandler); err != nil {
			return err
		}
	}

	basename := strings.Replace(cmd.CommandPath(), " ", "_", -1) + ".md"
	filename := filepath.Join(dir, basename)
	f, err := os.Create(filename) //#nosec:G304) //#nosec:G304
	if err != nil {
		return err
	}
	defer (func() { _ = f.Close() })()

	if _, err := io.WriteString(f, filePrepender(filename)); err != nil {
		return err
	}
	if err := GenMarkdownCustom(cmd, f, linkHandler); err != nil {
		return err
	}
	return nil
}

var indentedBlock = regexp.MustCompile(`(?m)^(?: {4}|\t).*(?:\n(?: {4}|\t).*)*`)

func fenceIndentedBlocks(s string) string {
	return indentedBlock.ReplaceAllStringFunc(s, func(block string) string {
		// trim trailing newline to keep fence tidy
		block = strings.TrimRight(block, "\n")

		// de-indent exactly one level for nicer fenced output
		lines := strings.Split(block, "\n")
		for i, ln := range lines {
			switch {
			case strings.HasPrefix(ln, "    "):
				lines[i] = ln[4:]
			case strings.HasPrefix(ln, "\t"):
				lines[i] = ln[1:]
			}
		}
		b := strings.Join(lines, "\n")

		// guard against already fenced content
		if strings.HasPrefix(strings.TrimSpace(b), "```") {
			return block
		}
		return "```\n" + b + "\n```"
	})
}