Lua port of Slimdown.

README.md

Slimdown

This is a Lua port of of jbroadway's PHP project of the same name.

A very basic pattern-based Markdown parser. Supports the following elements (and can be extended via slimdown.addRule()):

• Headers
• Links
• Bold
• Emphasis
• Deletions
• Quotes
• Inline code
• Code blocks
• Blockquotes
• Ordered/unordered lists

Usage

Here is the general use case:

local slimdown = require 'slimdown'
local html = slimdown.render '# Page title\n\nAnd **now** for something _completely_ different.'

Adding rules

A simple rule to convert :) to an image:

local slimdown = require 'slimdown'
slimdown.addRule(':%)', '<img src="smiley.png" />')

print(slimdown.render 'Know what I\'m sayin? :)')

A longer example

local slimdown = require 'slimdown'

print(slimdown.render [[# Title

And *now* [a link](http://www.google.com) to **follow** and [another](http://yahoo.com/).

* One
* Two
* Three

## Subhead

One **two** three **four** five.

One __two__ three _four_ five __six__ seven _eight_.

1. One
2. Two
3. Three

More text with `inline($code)` sample.

> A block quote
> across two lines.

More text...]])

slimdown.lua

-------------------------------------------------------------------------------
-- Slimdown - A very basic pattern-based Markdown parser. 
-- Supports the following elements (and can be extended via addRule()):
--
-- * Headers
-- * Links
-- * Bold
-- * Emphasis
-- * Deletions
-- * Quotes
-- * Inline code
-- * Blockquotes
-- * Ordered/unordered lists
-- * Horizontal rules
--
-- Website: 
-- PHP: https://gist.github.com/jbroadway/2836900
-- Lua: https://gist.github.com/paulcuth/8967731
--
-- @module Slimdown
-- @author Johnny Broadway <[email protected]>
-- @author Paul Cuthbertson <[email protected]>
-- @license MIT
--


-------------------------------------------------------------------------------
-- Trims whitespace from the beginning and end of a string.
-- @tparam string str String to be trimmed.
-- @treturn string Trimmed string.
--
local function trim (str)
	return str:match '^[%s\n]*(.-)[%s\n]*$'
end




-------------------------------------------------------------------------------
-- Mark up a line as an HTML paragraph.
-- @tparam string line The line to mark up.
-- @treturn string HTML tag.
--
local function parseParagraph (line)
	local trimmed = trim(line)
 
	if 
		string.find(trimmed, '^</?ul')
		or string.find(trimmed, '^</?ol')
		or string.find(trimmed, '^</?li')
		or string.find(trimmed, '^</?h')
		or string.find(trimmed, '^</?p')
		or string.find(trimmed, '^</?bl') 
	then
		return '\n'..line..'\n'
	end
 
	return string.format('\n<p>%s</p>\n', trimmed)
end




-------------------------------------------------------------------------------
-- Mark up a line as an HTML unordered list.
-- @tparam string item The line to mark up.
-- @treturn string HTML tag.
--
local function parseUnorderedList (item)
	return string.format('\n<ul>\n\t<li>%s</li>\n</ul>', trim(item))
end




-------------------------------------------------------------------------------
-- Mark up a line as an HTML ordered list.
-- @tparam string item The line to mark up.
-- @treturn string HTML tag.
--
local function parseOrderedList (item)
	return string.format('\n<ol>\n\t<li>%s</li>\n</ol>', trim(item))
end




-------------------------------------------------------------------------------
-- Mark up a line as an HTML blockquote.
-- @tparam string item The line to mark up.
-- @treturn string HTML tag.
--
local function parseBlockquote (item)
	return string.format('\n<blockquote>%s</blockquote>', trim(item))
end




-------------------------------------------------------------------------------
-- Mark up a line as an HTML ordered list.
-- @tparam string chars The characters used to markdown the header.
-- @tparam string header Header string.
-- @treturn string HTML tag.
--
local function parseHeader (chars, header)
	local level = #chars
	return string.format('<h%d>%s</h%d>', level, trim(header), level)
end




-------------------------------------------------------------------------------
-- Conversion rules.
--
local rules = {
	{ '(#+)(.-%\n)', parseHeader 					},	-- headers
	{ '%[(.-)%]%((.-)%)', '<a href="%2">%1</a>'		},	-- links
	{ '%*%*([^%\n]-)%*%*', '<strong>%1</strong>'	},	-- bold *
	{ '__([^%\n]-)__', '<strong>%1</strong>'		},	-- bold _
	{ '%*([^%\n]-)%*', '<em>%1</em>'				},	-- emphasis *
	{ '_([^%\n]-)_', '<em>%1</em>'					},	-- emphasis _
	{ '~~([^%\n]-)~~', '<del>%1</del>'				},	-- del
	{ ':"([^%\n]-)":', '<q>%1</q>'					},	-- quote
	{ '`([^%\n]-)`', '<code>%1</code>'				},	-- inline code
	{ '```(.-)```', '<code>%1</code>'				},	-- code block
	{ '%\n%*([^%\n]*)', parseUnorderedList			},	-- ul lists
	{ '%\n[0-9]+%.([^%\n]*)', parseOrderedList		},	-- ol lists
	{ '%\n%-%-%-%-%-%-*', '\n<hr />'				},	-- horizontal rule
	{ '%\n&gt;([^%\n]*)', parseBlockquote			},	-- blockquotes &gt;
	{ '%\n>([^%\n]*)', parseBlockquote				},	-- blockquotes >
	{ '%\n([^%\n]+)%\n', parseParagraph 			},	-- add paragraphs
	{ '</ul>%s*<ul>%\n', ''							},	-- fix extra ul
	{ '</ol>%s*<ol>%\n', ''							},	-- fix extra ol
	{ '</blockquote>%s*<blockquote>', '</br>'		},	-- fix extra blockquote
}




-------------------------------------------------------------------------------
-- Adds a new rule to the mix.
-- @usage slimdown.addRule(':%)', '<img src="smiley.png" />')
-- @tparam string pattern Pattern to match.
-- @tparam string|function replacement Replacement string or parsing function.
--
function addRule (pattern, replacement)
	table.insert(rules, { pattern, replacement })
end




-------------------------------------------------------------------------------
-- Renders markdown text as HTML.
-- @usage slimdown.render('[Slimdown in Lua](https://gist.github.com/paulcuth/8967731)')
-- @tparam string text Markdown content.
-- @treturn string HTML.
--
function render (text)
	text = '\n'..text..'\n'
 
	for i = 1, #rules do
		text = string.gsub(text, unpack(rules[i]))
	end
 
	return trim(text)
end




-------------------------------------------------------------------------------
-- Module definition
return {
	addRule = addRule,
	render = render
}