pkg/common/cmd/templates/markdown.go

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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 templates

//These codes copy from kubectl pkg/templates/markdown.go

import (
	"fmt"
	"io"
	"strings"

	"github.com/russross/blackfriday/v2"
)

const linebreak = "\n"

// ASCIIRenderer implements blackfriday.Renderer
var _ blackfriday.Renderer = &ASCIIRenderer{}

// ASCIIRenderer is a blackfriday.Renderer intended for rendering markdown
// documents as plain text, well suited for human reading on terminals.
type ASCIIRenderer struct {
	Indentation string

	listItemCount uint
	listLevel     uint
}

// render markdown to text
func (r *ASCIIRenderer) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
	switch node.Type {
	case blackfriday.Text:
		raw := string(node.Literal)
		lines := strings.Split(raw, linebreak)
		for _, line := range lines {
			trimmed := strings.Trim(line, " \n\t")
			if len(trimmed) > 0 && trimmed[0] != '_' {
				w.Write([]byte(" "))
			}
			w.Write([]byte(trimmed))
		}
	case blackfriday.HorizontalRule, blackfriday.Hardbreak:
		w.Write([]byte(linebreak + "----------" + linebreak))
	case blackfriday.Code, blackfriday.CodeBlock:
		w.Write([]byte(linebreak))
		lines := []string{}
		for _, line := range strings.Split(string(node.Literal), linebreak) {
			trimmed := strings.Trim(line, " \t")
			// Adding 4 times of indentation will let blackfriday to accept
			// this literal as Code or CodeBlock again in next invocation
			indented := strings.Repeat(r.Indentation, 4) + trimmed
			lines = append(lines, indented)
		}
		w.Write([]byte(strings.Join(lines, linebreak)))
	case blackfriday.Image:
		w.Write(node.LinkData.Destination)
	case blackfriday.Link:
		w.Write([]byte(" "))
		w.Write(node.LinkData.Destination)
	case blackfriday.Paragraph:
		if r.listLevel == 0 {
			w.Write([]byte(linebreak))
		}
	case blackfriday.List:
		if entering {
			w.Write([]byte(linebreak))
			r.listLevel++
		} else {
			r.listLevel--
			r.listItemCount = 0
		}
	case blackfriday.Item:
		if entering {
			r.listItemCount++
			for i := 0; uint(i) < r.listLevel; i++ {
				w.Write([]byte(r.Indentation))
			}
			if node.ListFlags&blackfriday.ListTypeOrdered != 0 {
				w.Write([]byte(fmt.Sprintf("%d. ", r.listItemCount)))
			} else {
				w.Write([]byte("* "))
			}
		} else {
			w.Write([]byte(linebreak))
		}
	default:
		normalText(w, node.Literal)
	}
	return blackfriday.GoToNext
}

func normalText(w io.Writer, text []byte) {
	w.Write([]byte(strings.Trim(string(text), " \n\t")))
}

// RenderHeader writes document preamble and TOC if requested.
func (r *ASCIIRenderer) RenderHeader(w io.Writer, ast *blackfriday.Node) {

}

// RenderFooter writes document footer.
func (r *ASCIIRenderer) RenderFooter(w io.Writer, ast *blackfriday.Node) {
	io.WriteString(w, "\n")
}