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package markdown
import (
"bytes"
"io"
"github.com/gomarkdown/markdown/ast"
"github.com/gomarkdown/markdown/html"
"github.com/gomarkdown/markdown/parser"
)
// Renderer is an interface for implementing custom renderers.
type Renderer interface {
// RenderNode renders markdown node to w.
// It's called once for a leaf node.
// It's called twice for non-leaf nodes:
// * first with entering=true
// * then with entering=false
//
// Return value is a way to tell the calling walker to adjust its walk
// pattern: e.g. it can terminate the traversal by returning Terminate. Or it
// can ask the walker to skip a subtree of this node by returning SkipChildren.
// The typical behavior is to return GoToNext, which asks for the usual
// traversal to the next node.
RenderNode(w io.Writer, node ast.Node, entering bool) ast.WalkStatus
// RenderHeader is a method that allows the renderer to produce some
// content preceding the main body of the output document. The header is
// understood in the broad sense here. For example, the default HTML
// renderer will write not only the HTML document preamble, but also the
// table of contents if it was requested.
//
// The method will be passed an entire document tree, in case a particular
// implementation needs to inspect it to produce output.
//
// The output should be written to the supplied writer w. If your
// implementation has no header to write, supply an empty implementation.
RenderHeader(w io.Writer, ast ast.Node)
// RenderFooter is a symmetric counterpart of RenderHeader.
RenderFooter(w io.Writer, ast ast.Node)
}
// Parse parsers a markdown document using provided parser. If parser is nil,
// we use parser configured with parser.CommonExtensions.
//
// It returns AST (abstract syntax tree) that can be converted to another
// format using Render function.
func Parse(markdown []byte, p *parser.Parser) ast.Node {
if p == nil {
p = parser.New()
}
return p.Parse(markdown)
}
// Render uses renderer to convert parsed markdown document into a different format.
//
// To convert to HTML, pass html.Renderer
func Render(doc ast.Node, renderer Renderer) []byte {
var buf bytes.Buffer
renderer.RenderHeader(&buf, doc)
ast.WalkFunc(doc, func(node ast.Node, entering bool) ast.WalkStatus {
return renderer.RenderNode(&buf, node, entering)
})
renderer.RenderFooter(&buf, doc)
return buf.Bytes()
}
// ToHTML converts markdownDoc to HTML.
//
// You can optionally pass a parser and renderer. This allows to customize
// a parser, use a customized html render or use completely custom renderer.
//
// If you pass nil for both, we use parser configured with parser.CommonExtensions
// and html.Renderer configured with html.CommonFlags.
func ToHTML(markdown []byte, p *parser.Parser, renderer Renderer) []byte {
doc := Parse(markdown, p)
if renderer == nil {
opts := html.RendererOptions{
Flags: html.CommonFlags,
}
renderer = html.NewRenderer(opts)
}
return Render(doc, renderer)
}
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