bbcode

frustra/bbcode is a fast BBCode compiler for Go. It supports custom tags, safe html output (for user-specified input), and allows for graceful parsing of syntax errors similar to the output of a regex bbcode compiler.

Visit the godoc here: http://godoc.org/github.com/frustra/bbcode

Usage

To get started compiling some text, create a compiler instance:

compiler := bbcode.NewCompiler(true, true) // autoCloseTags, ignoreUnmatchedClosingTags
fmt.Println(compiler.Compile("[b]Hello World[/b]"))

// Output:
// <b>Hello World</b>

Supported BBCode Syntax

[tag]basic tag[/tag]
[tag1][tag2]nested tags[/tag2][/tag1]

[tag=value]tag with value[/tag]
[tag arg=value]tag with named argument[/tag]
[tag="quote value"]tag with quoted value[/tag]

[tag=value foo="hello world" bar=baz]multiple tag arguments[/tag]

Default Tags

• [b]text[/b] --> <b>text</b> (b, i, u, and s all map the same)
• [url]link[/url] --> <a href="link">link</a>
• [url=link]text[/url] --> <a href="link">text</a>
• [img]link[/img] --> <img src="link">
• [img=link]alt[/img] --> <img alt="alt" title="alt" src="link">
• [center]text[/center] --> <div style="text-align: center;">text</div>
• [color=red]text[/color] --> <span style="color: red;">text</span>
• [size=2]text[/size] --> <span class="size2">text</span>
• [quote]text[/quote] --> <blockquote><cite>Quote</cite>text</blockquote>
• [quote=Somebody]text[/quote] --> <blockquote><cite>Somebody said:</cite>text</blockquote>
• [quote name=Somebody]text[/quote] --> <blockquote><cite>Somebody said:</cite>text</blockquote>
• [code][b]anything[/b][/code] --> <pre>[b]anything[/b]</pre>

Lists are not currently implemented as a default tag, but can be added as a custom tag.
A working implementation of list tags can be found here

Notes

• If using with user-supplied input, it's recommended to modify the url tag to sanitize links. By default, urls such as javascript:alert(1); are valid.

• For HTML tags with multiple attributes, the ordering is not sorted by default. If you need deterministic output, set compiler.SortOutputAttributes to true. This may slightly reduce the compiler performance.

Adding Custom Tags

Custom tag handlers can be added to a compiler using the compiler.SetTag(tag, handler) function:

compiler.SetTag("center", func(node *bbcode.BBCodeNode) (*bbcode.HTMLTag, bool) {
	// Create a new div element to output
	out := bbcode.NewHTMLTag("")
	out.Name = "div"

	// Set the style attribute of our output div
	out.Attrs["style"] = "text-align: center;"

	// Returning true here means continue to parse child nodes.
	// This should be false if children are parsed by this tag's handler, like in the [code] tag.
	return out, true
})

Tag values can be read from the opening tag like this:
Main tag value [tag={value}]: node.GetOpeningTag().Value
Tag arguments [tag name={value}]: node.GetOpeningTag().Args["name"]

bbcode.NewHTMLTag(text) creates a text node by default. By setting tag.Name, the node because an html tag prefixed by the text. The closing html tag is not rendered unless child elements exist. The closing tag can be forced by adding a blank text node:

out := bbcode.NewHTMLTag("")
out.Name = "div"
out.AppendChild(nil) // equivalent to out.AppendChild(bbcode.NewHTMLTag(""))

For more examples of tag definitions, look at the default tag implementations in compiler.go

Overriding Default Tags

The built-in tags can be overridden simply by redefining the tag with compiler.SetTag(tag, handler)

To remove a tag, set the tag handler to nil:

compiler.SetTag("quote", nil)

The default tags can also be modified without completely redefining the tag by calling the default handler:

compiler.SetTag("url", func(node *bbcode.BBCodeNode) (*bbcode.HTMLTag, bool) {
	out, appendExpr := bbcode.DefaultTagCompilers["url"](node)
	out.Attrs["class"] = "bbcode-link"
	return out, appendExpr
})

Auto-Close Tags

Input:

[center][b]text[/center]

Enabled Output:

<div style="text-align: center;"><b>text</b></div>

Disabled Output:

<div style="text-align: center;">[b]text</div>

Ignore Unmatched Closing Tags

Input:

[center]text[/b][/center]

Enabled Output:

<div style="text-align: center;">text</div>

Disabled Output:

<div style="text-align: center;">text[/b]</div>