markdown.go

/*
Copyright 2016 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 templates

import (
	"bytes"
	"fmt"
	"io"
	"strings"

	"github.com/russross/blackfriday"
)

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
}

// NormalText gets a text chunk *after* the markdown syntax was already
// processed and does a final cleanup on things we don't expect here, like
// removing linebreaks on things that are not a paragraph break (auto unwrap).
func (r *ASCIIRenderer) NormalText(out *bytes.Buffer, text []byte) {
	raw := string(text)
	lines := strings.Split(raw, linebreak)
	for _, line := range lines {
		trimmed := strings.Trim(line, " \n\t")
		if len(trimmed) > 0 && trimmed[0] != '_' {
			out.WriteString(" ")
		}
		out.WriteString(trimmed)
	}
}

// List renders the start and end of a list.
func (r *ASCIIRenderer) List(out *bytes.Buffer, text func() bool, flags int) {
	r.listLevel++
	out.WriteString(linebreak)
	text()
	r.listLevel--
}

// ListItem renders list items and supports both ordered and unordered lists.
func (r *ASCIIRenderer) ListItem(out *bytes.Buffer, text []byte, flags int) {
	if flags&blackfriday.LIST_ITEM_BEGINNING_OF_LIST != 0 {
		r.listItemCount = 1
	} else {
		r.listItemCount++
	}
	indent := strings.Repeat(r.Indentation, int(r.listLevel))
	var bullet string
	if flags&blackfriday.LIST_TYPE_ORDERED != 0 {
		bullet += fmt.Sprintf("%d.", r.listItemCount)
	} else {
		bullet += "*"
	}
	out.WriteString(indent + bullet + " ")
	r.fw(out, text)
	out.WriteString(linebreak)
}

// Paragraph renders the start and end of a paragraph.
func (r *ASCIIRenderer) Paragraph(out *bytes.Buffer, text func() bool) {
	out.WriteString(linebreak)
	text()
	out.WriteString(linebreak)
}

// BlockCode renders a chunk of text that represents source code.
func (r *ASCIIRenderer) BlockCode(out *bytes.Buffer, text []byte, lang string) {
	out.WriteString(linebreak)
	lines := []string{}
	for _, line := range strings.Split(string(text), linebreak) {
		indented := r.Indentation + line
		lines = append(lines, indented)
	}
	out.WriteString(strings.Join(lines, linebreak))
}

// GetFlags always returns 0
func (r *ASCIIRenderer) GetFlags() int { return 0 }

// HRule returns horizontal line
func (r *ASCIIRenderer) HRule(out *bytes.Buffer) {
	out.WriteString(linebreak + "----------" + linebreak)
}

// LineBreak returns a line break
func (r *ASCIIRenderer) LineBreak(out *bytes.Buffer) { out.WriteString(linebreak) }

// TitleBlock writes title block
func (r *ASCIIRenderer) TitleBlock(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// Header writes header
func (r *ASCIIRenderer) Header(out *bytes.Buffer, text func() bool, level int, id string) { text() }

// BlockHtml writes htlm
func (r *ASCIIRenderer) BlockHtml(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// BlockQuote writes block
func (r *ASCIIRenderer) BlockQuote(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// TableRow writes table row
func (r *ASCIIRenderer) TableRow(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// TableHeaderCell writes table header cell
func (r *ASCIIRenderer) TableHeaderCell(out *bytes.Buffer, text []byte, align int) { r.fw(out, text) }

// TableCell writes table cell
func (r *ASCIIRenderer) TableCell(out *bytes.Buffer, text []byte, align int) { r.fw(out, text) }

// Footnotes writes footnotes
func (r *ASCIIRenderer) Footnotes(out *bytes.Buffer, text func() bool) { text() }

// FootnoteItem writes footnote item
func (r *ASCIIRenderer) FootnoteItem(out *bytes.Buffer, name, text []byte, flags int) { r.fw(out, text) }

// AutoLink writes autolink
func (r *ASCIIRenderer) AutoLink(out *bytes.Buffer, link []byte, kind int) { r.fw(out, link) }

// CodeSpan writes code span
func (r *ASCIIRenderer) CodeSpan(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// DoubleEmphasis writes double emphasis
func (r *ASCIIRenderer) DoubleEmphasis(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// Emphasis writes emphasis
func (r *ASCIIRenderer) Emphasis(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// RawHtmlTag writes raw htlm tag
func (r *ASCIIRenderer) RawHtmlTag(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// TripleEmphasis writes triple emphasis
func (r *ASCIIRenderer) TripleEmphasis(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// StrikeThrough writes strike through
func (r *ASCIIRenderer) StrikeThrough(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// FootnoteRef writes footnote ref
func (r *ASCIIRenderer) FootnoteRef(out *bytes.Buffer, ref []byte, id int) { r.fw(out, ref) }

// Entity writes entity
func (r *ASCIIRenderer) Entity(out *bytes.Buffer, entity []byte) { r.fw(out, entity) }

// Smartypants writes smartypants
func (r *ASCIIRenderer) Smartypants(out *bytes.Buffer, text []byte) { r.fw(out, text) }

// DocumentHeader does nothing
func (r *ASCIIRenderer) DocumentHeader(out *bytes.Buffer) {}

// DocumentFooter does nothing
func (r *ASCIIRenderer) DocumentFooter(out *bytes.Buffer) {}

// TocHeaderWithAnchor does nothing
func (r *ASCIIRenderer) TocHeaderWithAnchor(text []byte, level int, anchor string) {}

// TocHeader does nothing
func (r *ASCIIRenderer) TocHeader(text []byte, level int) {}

// TocFinalize does nothing
func (r *ASCIIRenderer) TocFinalize() {}

// Table writes a table
func (r *ASCIIRenderer) Table(out *bytes.Buffer, header []byte, body []byte, columnData []int) {
	r.fw(out, header, body)
}

// Link writes a link
func (r *ASCIIRenderer) Link(out *bytes.Buffer, link []byte, title []byte, content []byte) {
	r.fw(out, link)
}

// Image writes image
func (r *ASCIIRenderer) Image(out *bytes.Buffer, link []byte, title []byte, alt []byte) {
	r.fw(out, link)
}

func (r *ASCIIRenderer) fw(out io.Writer, text ...[]byte) {
	for _, t := range text {
		out.Write(t)
	}
}