使用Goldmark解析和处理Markdown文档

Goldmark是一个用Go编写的标准兼容且高度可扩展的Markdown解析器。它完全遵循CommonMark规范，同时提供了丰富的扩展机制。下面我将详细介绍如何使用Goldmark。

基本使用

首先安装Goldmark：

go get github.com/yuin/goldmark

基础解析示例

package main

import (
	"fmt"
	"os"
	
	"github.com/yuin/goldmark"
)

func main() {
	markdown := `# Hello Goldmark
	
This is a **Markdown** document.`

	md := goldmark.New()
	err := md.Convert([]byte(markdown), os.Stdout)
	if err != nil {
		fmt.Println("Error converting markdown:", err)
	}
}

扩展功能

Goldmark的强大之处在于它的可扩展性。下面是一些常见扩展的使用方式。

添加扩展

package main

import (
	"fmt"
	"os"
	
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/extension"
	"github.com/yuin/goldmark/parser"
	"github.com/yuin/goldmark/renderer/html"
)

func main() {
	markdown := `# Extended Features
	
- [x] Task list item
- [ ] Another task

| Tables   | Are      | Cool  |
|----------|---------|-------|
| col 1 is | left-aligned | $1600 |
| col 2 is | centered | $12 |
`

	md := goldmark.New(
		goldmark.WithExtensions(
			extension.GFM, // GitHub Flavored Markdown
			extension.Table,
			extension.TaskList,
		),
		goldmark.WithParserOptions(
			parser.WithAutoHeadingID(),
		),
		goldmark.WithRendererOptions(
			html.WithHardWraps(),
			html.WithXHTML(),
		),
	)
	
	err := md.Convert([]byte(markdown), os.Stdout)
	if err != nil {
		fmt.Println("Error converting markdown:", err)
	}
}

自定义渲染

你可以自定义HTML渲染方式：

package main

import (
	"fmt"
	"os"
	
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/ast"
	"github.com/yuin/goldmark/renderer"
	"github.com/yuin/goldmark/renderer/html"
	"github.com/yuin/goldmark/util"
)

type customHTMLRenderer struct {
	html.Config
}

// 自定义段落渲染
func (r *customHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
	reg.Register(ast.KindParagraph, r.renderParagraph)
}

func (r *customHTMLRenderer) renderParagraph(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
	if entering {
		_, _ = w.WriteString(`<p class="my-paragraph">`)
	} else {
		_, _ = w.WriteString(`</p>`)
	}
	return ast.WalkContinue, nil
}

func main() {
	markdown := `This is a custom rendered paragraph.`

	md := goldmark.New(
		goldmark.WithRendererOptions(
			html.WithWriter(w),
		),
		goldmark.WithRenderer(
			renderer.NewRenderer(
				renderer.WithNodeRenderers(
					util.Prioritized(&customHTMLRenderer{}, 1000),
				),
			),
		),
	)
	
	err := md.Convert([]byte(markdown), os.Stdout)
	if err != nil {
		fmt.Println("Error converting markdown:", err)
	}
}

解析为AST

Goldmark允许你将Markdown解析为抽象语法树(AST)，然后进行自定义处理：

package main

import (
	"fmt"
	"os"
	
	"github.com/yuin/goldmark"
	"github.com/yuin/goldmark/ast"
	"github.com/yuin/goldmark/text"
)

func printAST(node ast.Node, source []byte, level int) {
	for n := node.FirstChild(); n != nil; n = n.NextSibling() {
		fmt.Printf("%s%v\n", indent(level), n.Kind())
		printAST(n, source, level+1)
	}
}

func indent(level int) string {
	s := ""
	for i := 0; i < level; i++ {
		s += "  "
	}
	return s
}

func main() {
	markdown := `# AST Example
	
This demonstrates parsing to AST.`

	md := goldmark.New()
	doc := md.Parser().Parse(text.NewReader([]byte(markdown)))
	
	printAST(doc, []byte(markdown), 0)
}

性能优化

对于高性能场景，可以重用解析器和渲染器：

package main

import (
	"fmt"
	"os"
	"sync"
	
	"github.com/yuin/goldmark"
)

var (
	md     goldmark.Markdown
	mdOnce sync.Once
)

func getMarkdownParser() goldmark.Markdown {
	mdOnce.Do(func() {
		md = goldmark.New(
			// 你的配置选项
		)
	})
	return md
}

func main() {
	markdown := `# Performance optimized
	
This uses a singleton parser.`

	md := getMarkdownParser()
	err := md.Convert([]byte(markdown), os.Stdout)
	if err != nil {
		fmt.Println("Error converting markdown:", err)
	}
}

总结

Goldmark是一个功能强大且灵活的Markdown解析库，具有以下特点：

1. 完全兼容CommonMark规范
2. 丰富的扩展生态系统
3. 高性能解析和渲染
4. 灵活的AST操作接口
5. 易于自定义渲染输出

通过合理使用Goldmark的扩展和自定义功能，你可以构建出满足各种需求的Markdown处理流水线。