Mercurial > repos > lgen / changeset

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/markdown.lua	Tue Mar 17 21:39:29 2009 +0200
@@ -0,0 +1,1359 @@
+#!/usr/bin/env lua
+
+--[[
+# markdown.lua -- version 0.32
+
+<http://www.frykholm.se/files/markdown.lua>
+
+**Author:** Niklas Frykholm, <niklas@frykholm.se>  
+**Date:** 31 May 2008
+
+This is an implementation of the popular text markup language Markdown in pure Lua.
+Markdown can convert documents written in a simple and easy to read text format
+to well-formatted HTML. For a more thourough description of Markdown and the Markdown
+syntax, see <http://daringfireball.net/projects/markdown>.
+
+The original Markdown source is written in Perl and makes heavy use of advanced
+regular expression techniques (such as negative look-ahead, etc) which are not available
+in Lua's simple regex engine. Therefore this Lua port has been rewritten from the ground
+up. It is probably not completely bug free. If you notice any bugs, please report them to
+me. A unit test that exposes the error is helpful.
+
+## Usage
+
+    require "markdown"
+    markdown(source)
+
+``markdown.lua`` exposes a single global function named ``markdown(s)`` which applies the
+Markdown transformation to the specified string.
+
+``markdown.lua`` can also be used directly from the command line:
+
+	lua markdown.lua test.md
+
+Creates a file ``test.html`` with the converted content of ``test.md``. Run:
+
+    lua markdown.lua -h
+
+For a description of the command-line options.
+
+``markdown.lua`` uses the same license as Lua, the MIT license.
+
+## License
+
+Copyright &copy; 2008 Niklas Frykholm.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this
+software and associated documentation files (the "Software"), to deal in the Software
+without restriction, including without limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+to whom the Software is furnished to do so, subject to the following conditions: 
+
+The above copyright notice and this permission notice shall be included in all copies
+or substantial portions of the Software. 
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+## Version history
+
+-	**0.32** -- 31 May 2008
+	- Fix for links containing brackets
+-	**0.31** -- 1 Mar 2008
+	-	Fix for link definitions followed by spaces
+-	**0.30** -- 25 Feb 2008
+	-	Consistent behavior with Markdown when the same link reference is reused
+-	**0.29** -- 24 Feb 2008
+	-	Fix for <pre> blocks with spaces in them
+-	**0.28** -- 18 Feb 2008
+	-	Fix for link encoding
+-	**0.27** -- 14 Feb 2008
+	-	Fix for link database links with ()
+-	**0.26** -- 06 Feb 2008
+	-	Fix for nested italic and bold markers
+-	**0.25** -- 24 Jan 2008
+	-	Fix for encoding of naked <
+-	**0.24** -- 21 Jan 2008
+	-	Fix for link behavior.
+-	**0.23** -- 10 Jan 2008
+	-	Fix for a regression bug in longer expressions in italic or bold.
+-	**0.22** -- 27 Dec 2007
+	-	Fix for crash when processing blocks with a percent sign in them.
+-	**0.21** -- 27 Dec 2007
+	- 	Fix for combined strong and emphasis tags
+-	**0.20** -- 13 Oct 2007
+	-	Fix for < as well in image titles, now matches Dingus behavior
+-	**0.19** -- 28 Sep 2007
+	-	Fix for quotation marks " and ampersands & in link and image titles.
+-	**0.18** -- 28 Jul 2007
+	-	Does not crash on unmatched tags (behaves like standard markdown)
+-	**0.17** -- 12 Apr 2007
+	-	Fix for links with %20 in them.
+-	**0.16** -- 12 Apr 2007
+	-	Do not require arg global to exist.
+-	**0.15** -- 28 Aug 2006
+	-	Better handling of links with underscores in them.
+-	**0.14** -- 22 Aug 2006
+	-	Bug for *`foo()`*
+-	**0.13** -- 12 Aug 2006
+	-	Added -l option for including stylesheet inline in document.
+	-	Fixed bug in -s flag.
+	-	Fixed emphasis bug.
+-	**0.12** -- 15 May 2006
+	-	Fixed several bugs to comply with MarkdownTest 1.0 <http://six.pairlist.net/pipermail/markdown-discuss/2004-December/000909.html>
+-	**0.11** -- 12 May 2006
+	-	Fixed bug for escaping `*` and `_` inside code spans.
+	-	Added license terms.
+	-	Changed join() to table.concat().
+-	**0.10** -- 3 May 2006
+	-	Initial public release.
+
+// Niklas
+]]
+
+
+-- Set up a table for holding local functions to avoid polluting the global namespace
+local M = {}
+local MT = {__index = _G}
+setmetatable(M, MT)
+setfenv(1, M)
+
+----------------------------------------------------------------------
+-- Utility functions
+----------------------------------------------------------------------
+
+-- Locks table t from changes, writes an error if someone attempts to change the table.
+-- This is useful for detecting variables that have "accidently" been made global. Something
+-- I tend to do all too much.
+function lock(t)
+	function lock_new_index(t, k, v)
+		error("module has been locked -- " .. k .. " must be declared local", 2)
+	end
+
+	local mt = {__newindex = lock_new_index}
+	if getmetatable(t) then mt.__index = getmetatable(t).__index end
+	setmetatable(t, mt)
+end
+
+-- Returns the result of mapping the values in table t through the function f
+function map(t, f)
+	local out = {}
+	for k,v in pairs(t) do out[k] = f(v,k) end
+	return out
+end
+
+-- The identity function, useful as a placeholder.
+function identity(text) return text end
+
+-- Functional style if statement. (NOTE: no short circuit evaluation)
+function iff(t, a, b) if t then return a else return b end end
+
+-- Splits the text into an array of separate lines.
+function split(text, sep)
+	sep = sep or "\n"
+	local lines = {}
+	local pos = 1
+	while true do
+		local b,e = text:find(sep, pos)
+		if not b then table.insert(lines, text:sub(pos)) break end
+		table.insert(lines, text:sub(pos, b-1))
+		pos = e + 1
+	end
+	return lines
+end
+
+-- Converts tabs to spaces
+function detab(text)
+	local tab_width = 4
+	local function rep(match)
+		local spaces = -match:len()
+		while spaces<1 do spaces = spaces + tab_width end
+		return match .. string.rep(" ", spaces)
+	end
+	text = text:gsub("([^\n]-)\t", rep)
+	return text
+end
+
+-- Applies string.find for every pattern in the list and returns the first match
+function find_first(s, patterns, index)
+	local res = {}
+	for _,p in ipairs(patterns) do
+		local match = {s:find(p, index)}
+		if #match>0 and (#res==0 or match[1] < res[1]) then res = match end
+	end
+	return unpack(res)
+end
+
+-- If a replacement array is specified, the range [start, stop] in the array is replaced
+-- with the replacement array and the resulting array is returned. Without a replacement
+-- array the section of the array between start and stop is returned.
+function splice(array, start, stop, replacement)
+	if replacement then
+		local n = stop - start + 1
+		while n > 0 do
+			table.remove(array, start)
+			n = n - 1
+		end
+		for i,v in ipairs(replacement) do
+			table.insert(array, start, v)
+		end
+		return array
+	else
+		local res = {}
+		for i = start,stop do
+			table.insert(res, array[i])
+		end
+		return res
+	end
+end
+
+-- Outdents the text one step.
+function outdent(text)
+	text = "\n" .. text
+	text = text:gsub("\n  ? ? ?", "\n")
+	text = text:sub(2)
+	return text
+end
+
+-- Indents the text one step.
+function indent(text)
+	text = text:gsub("\n", "\n    ")
+	return text
+end
+
+-- Does a simple tokenization of html data. Returns the data as a list of tokens. 
+-- Each token is a table with a type field (which is either "tag" or "text") and
+-- a text field (which contains the original token data).
+function tokenize_html(html)
+	local tokens = {}
+	local pos = 1
+	while true do
+		local start = find_first(html, {"<!%-%-", "<[a-z/!$]", "<%?"}, pos)
+		if not start then
+			table.insert(tokens, {type="text", text=html:sub(pos)})
+			break
+		end
+		if start ~= pos then table.insert(tokens, {type="text", text = html:sub(pos, start-1)}) end
+		
+		local _, stop
+		if html:match("^<!%-%-", start) then
+			_,stop = html:find("%-%->", start)
+		elseif html:match("^<%?", start) then
+			_,stop = html:find("?>", start)
+		else
+			_,stop = html:find("%b<>", start)
+		end
+		if not stop then
+			-- error("Could not match html tag " .. html:sub(start,start+30)) 
+		 	table.insert(tokens, {type="text", text=html:sub(start, start)})
+			pos = start + 1
+		else
+			table.insert(tokens, {type="tag", text=html:sub(start, stop)})
+			pos = stop + 1
+		end
+	end
+	return tokens
+end
+
+----------------------------------------------------------------------
+-- Hash
+----------------------------------------------------------------------
+
+-- This is used to "hash" data into alphanumeric strings that are unique
+-- in the document. (Note that this is not cryptographic hash, the hash
+-- function is not one-way.) The hash procedure is used to protect parts
+-- of the document from further processing.
+
+local HASH = {
+	-- Has the hash been inited.
+	inited = false,
+	
+	-- The unique string prepended to all hash values. This is to ensure
+	-- that hash values do not accidently coincide with an actual existing
+	-- string in the document.
+	identifier = "",
+	
+	-- Counter that counts up for each new hash instance.
+	counter = 0,
+	
+	-- Hash table.
+	table = {}
+}
+
+-- Inits hashing. Creates a hash_identifier that doesn't occur anywhere
+-- in the text.
+function init_hash(text)
+	HASH.inited = true
+	HASH.identifier = ""
+	HASH.counter = 0
+	HASH.table = {}
+	
+	local s = "HASH"
+	local counter = 0
+	local id
+	while true do
+		id  = s .. counter
+		if not text:find(id, 1, true) then break end
+		counter = counter + 1
+	end
+	HASH.identifier = id
+end
+
+-- Returns the hashed value for s.
+function hash(s)
+	assert(HASH.inited)
+	if not HASH.table[s] then
+		HASH.counter = HASH.counter + 1
+		local id = HASH.identifier .. HASH.counter .. "X"
+		HASH.table[s] = id
+	end
+	return HASH.table[s]
+end
+
+----------------------------------------------------------------------
+-- Protection
+----------------------------------------------------------------------
+
+-- The protection module is used to "protect" parts of a document
+-- so that they are not modified by subsequent processing steps. 
+-- Protected parts are saved in a table for later unprotection
+
+-- Protection data
+local PD = {
+	-- Saved blocks that have been converted
+	blocks = {},
+
+	-- Block level tags that will be protected
+	tags = {"p", "div", "h1", "h2", "h3", "h4", "h5", "h6", "blockquote",
+	"pre", "table", "dl", "ol", "ul", "script", "noscript", "form", "fieldset",
+	"iframe", "math", "ins", "del"}
+}
+
+-- Pattern for matching a block tag that begins and ends in the leftmost
+-- column and may contain indented subtags, i.e.
+-- <div>
+--    A nested block.
+--    <div>
+--        Nested data.
+--     </div>
+-- </div>
+function block_pattern(tag)
+	return "\n<" .. tag .. ".-\n</" .. tag .. ">[ \t]*\n"
+end
+
+-- Pattern for matching a block tag that begins and ends with a newline
+function line_pattern(tag)
+	return "\n<" .. tag .. ".-</" .. tag .. ">[ \t]*\n"
+end
+
+-- Protects the range of characters from start to stop in the text and
+-- returns the protected string.
+function protect_range(text, start, stop)
+	local s = text:sub(start, stop)
+	local h = hash(s)
+	PD.blocks[h] = s
+	text = text:sub(1,start) .. h .. text:sub(stop)
+	return text
+end
+
+-- Protect every part of the text that matches any of the patterns. The first
+-- matching pattern is protected first, etc.
+function protect_matches(text, patterns)
+	while true do
+		local start, stop = find_first(text, patterns)
+		if not start then break end
+		text = protect_range(text, start, stop)
+	end
+	return text
+end
+
+-- Protects blocklevel tags in the specified text
+function protect(text)
+	-- First protect potentially nested block tags
+	text = protect_matches(text, map(PD.tags, block_pattern))
+	-- Then protect block tags at the line level.
+	text = protect_matches(text, map(PD.tags, line_pattern))
+	-- Protect <hr> and comment tags
+	text = protect_matches(text, {"\n<hr[^>]->[ \t]*\n"})
+	text = protect_matches(text, {"\n<!%-%-.-%-%->[ \t]*\n"})
+	return text
+end
+
+-- Returns true if the string s is a hash resulting from protection
+function is_protected(s)
+	return PD.blocks[s]
+end
+
+-- Unprotects the specified text by expanding all the nonces
+function unprotect(text)
+	for k,v in pairs(PD.blocks) do
+		v = v:gsub("%%", "%%%%")
+		text = text:gsub(k, v)
+	end
+	return text
+end
+
+
+----------------------------------------------------------------------
+-- Block transform
+----------------------------------------------------------------------
+
+-- The block transform functions transform the text on the block level.
+-- They work with the text as an array of lines rather than as individual
+-- characters.
+
+-- Returns true if the line is a ruler of (char) characters.
+-- The line must contain at least three char characters and contain only spaces and
+-- char characters.
+function is_ruler_of(line, char)
+	if not line:match("^[ %" .. char .. "]*$") then return false end
+	if not line:match("%" .. char .. ".*%" .. char .. ".*%" .. char) then return false end
+	return true
+end
+
+-- Identifies the block level formatting present in the line
+function classify(line)
+	local info = {line = line, text = line}
+	
+	if line:match("^    ") then
+		info.type = "indented"
+		info.outdented = line:sub(5)
+		return info
+	end
+	
+	for _,c in ipairs({'*', '-', '_', '='}) do
+		if is_ruler_of(line, c) then
+			info.type = "ruler"
+			info.ruler_char = c
+			return info
+		end
+	end
+	
+	if line == "" then
+		info.type = "blank"
+		return info
+	end
+	
+	if line:match("^(#+)[ \t]*(.-)[ \t]*#*[ \t]*$") then
+		local m1, m2 = line:match("^(#+)[ \t]*(.-)[ \t]*#*[ \t]*$")
+		info.type = "header"
+		info.level = m1:len()
+		info.text = m2
+		return info
+	end
+	
+	if line:match("^ ? ? ?(%d+)%.[ \t]+(.+)") then
+		local number, text = line:match("^ ? ? ?(%d+)%.[ \t]+(.+)")
+		info.type = "list_item"
+		info.list_type = "numeric"
+		info.number = 0 + number
+		info.text = text
+		return info
+	end
+	
+	if line:match("^ ? ? ?([%*%+%-])[ \t]+(.+)") then
+		local bullet, text = line:match("^ ? ? ?([%*%+%-])[ \t]+(.+)")
+		info.type = "list_item"
+		info.list_type = "bullet"
+		info.bullet = bullet
+		info.text= text
+		return info
+	end
+	
+	if line:match("^>[ \t]?(.*)") then
+		info.type = "blockquote"
+		info.text = line:match("^>[ \t]?(.*)")
+		return info
+	end
+	
+	if is_protected(line) then
+		info.type = "raw"
+		info.html = unprotect(line)
+		return info
+	end
+	
+	info.type = "normal"
+	return info
+end
+
+-- Find headers constisting of a normal line followed by a ruler and converts them to
+-- header entries.
+function headers(array)
+	local i = 1
+	while i <= #array - 1 do
+		if array[i].type  == "normal" and array[i+1].type == "ruler" and 
+			(array[i+1].ruler_char == "-" or array[i+1].ruler_char == "=") then
+			local info = {line = array[i].line}
+			info.text = info.line
+			info.type = "header"
+			info.level = iff(array[i+1].ruler_char == "=", 1, 2)
+			table.remove(array, i+1)
+			array[i] = info
+		end
+		i = i + 1
+	end
+	return array
+end
+
+-- Find list blocks and convert them to protected data blocks
+function lists(array, sublist)
+	local function process_list(arr)
+		local function any_blanks(arr)
+			for i = 1, #arr do
+				if arr[i].type == "blank" then return true end
+			end
+			return false
+		end
+		
+		local function split_list_items(arr)
+			local acc = {arr[1]}
+			local res = {}
+			for i=2,#arr do
+				if arr[i].type == "list_item" then
+					table.insert(res, acc)
+					acc = {arr[i]}
+				else
+					table.insert(acc, arr[i])
+				end
+			end
+			table.insert(res, acc)
+			return res
+		end
+		
+		local function process_list_item(lines, block)
+			while lines[#lines].type == "blank" do
+				table.remove(lines)
+			end
+			
+			local itemtext = lines[1].text
+			for i=2,#lines do
+				itemtext = itemtext .. "\n" .. outdent(lines[i].line)
+			end
+			if block then
+				itemtext = block_transform(itemtext, true)
+				if not itemtext:find("<pre>") then itemtext = indent(itemtext) end
+				return "    <li>" .. itemtext .. "</li>"
+			else
+				local lines = split(itemtext)
+				lines = map(lines, classify)
+				lines = lists(lines, true)
+				lines = blocks_to_html(lines, true)
+				itemtext = table.concat(lines, "\n")
+				if not itemtext:find("<pre>") then itemtext = indent(itemtext) end
+				return "    <li>" .. itemtext .. "</li>"
+			end
+		end
+		
+		local block_list = any_blanks(arr)
+		local items = split_list_items(arr)
+		local out = ""
+		for _, item in ipairs(items) do
+			out = out .. process_list_item(item, block_list) .. "\n"
+		end
+		if arr[1].list_type == "numeric" then
+			return "<ol>\n" .. out .. "</ol>"
+		else
+			return "<ul>\n" .. out .. "</ul>"
+		end
+	end
+	
+	-- Finds the range of lines composing the first list in the array. A list
+	-- starts with (^ list_item) or (blank list_item) and ends with
+	-- (blank* $) or (blank normal).
+	--
+	-- A sublist can start with just (list_item) does not need a blank...
+	local function find_list(array, sublist)
+		local function find_list_start(array, sublist)
+			if array[1].type == "list_item" then return 1 end
+			if sublist then
+				for i = 1,#array do
+					if array[i].type == "list_item" then return i end
+				end
+			else
+				for i = 1, #array-1 do
+					if array[i].type == "blank" and array[i+1].type == "list_item" then
+						return i+1
+					end
+				end
+			end
+			return nil
+		end
+		local function find_list_end(array, start)
+			local pos = #array
+			for i = start, #array-1 do
+				if array[i].type == "blank" and array[i+1].type ~= "list_item" 
+					and array[i+1].type ~= "indented" and array[i+1].type ~= "blank" then
+					pos = i-1
+					break
+				end
+			end
+			while pos > start and array[pos].type == "blank" do
+				pos = pos - 1
+			end
+			return pos
+		end
+		
+		local start = find_list_start(array, sublist)
+		if not start then return nil end
+		return start, find_list_end(array, start)
+	end
+	
+	while true do
+		local start, stop = find_list(array, sublist)
+		if not start then break end
+		local text = process_list(splice(array, start, stop))
+		local info = {
+			line = text,
+			type = "raw",
+			html = text
+		}
+		array = splice(array, start, stop, {info})
+	end
+	
+	-- Convert any remaining list items to normal
+	for _,line in ipairs(array) do
+		if line.type == "list_item" then line.type = "normal" end
+	end
+	
+	return array
+end
+
+-- Find and convert blockquote markers.
+function blockquotes(lines)
+	local function find_blockquote(lines)
+		local start
+		for i,line in ipairs(lines) do
+			if line.type == "blockquote" then
+				start = i
+				break
+			end
+		end
+		if not start then return nil end
+		
+		local stop = #lines
+		for i = start+1, #lines do
+			if lines[i].type == "blank" or lines[i].type == "blockquote" then
+			elseif lines[i].type == "normal" then
+				if lines[i-1].type == "blank" then stop = i-1 break end
+			else
+				stop = i-1 break
+			end
+		end
+		while lines[stop].type == "blank" do stop = stop - 1 end
+		return start, stop
+	end
+	
+	local function process_blockquote(lines)
+		local raw = lines[1].text
+		for i = 2,#lines do
+			raw = raw .. "\n" .. lines[i].text
+		end
+		local bt = block_transform(raw)
+		if not bt:find("<pre>") then bt = indent(bt) end
+		return "<blockquote>\n    " .. bt ..
+			"\n</blockquote>"
+	end
+	
+	while true do
+		local start, stop = find_blockquote(lines)
+		if not start then break end
+		local text = process_blockquote(splice(lines, start, stop))
+		local info = {
+			line = text,
+			type = "raw",
+			html = text
+		}
+		lines = splice(lines, start, stop, {info})
+	end
+	return lines
+end
+
+-- Find and convert codeblocks.
+function codeblocks(lines)
+	local function find_codeblock(lines)
+		local start
+		for i,line in ipairs(lines) do
+			if line.type == "indented" then start = i break end
+		end
+		if not start then return nil end
+		
+		local stop = #lines
+		for i = start+1, #lines do
+			if lines[i].type ~= "indented" and lines[i].type ~= "blank" then
+				stop = i-1
+				break
+			end
+		end
+		while lines[stop].type == "blank" do stop = stop - 1 end
+		return start, stop
+	end
+	
+	local function process_codeblock(lines)
+		local raw = detab(encode_code(outdent(lines[1].line)))
+		for i = 2,#lines do
+			raw = raw .. "\n" .. detab(encode_code(outdent(lines[i].line)))
+		end
+		return "<pre><code>" .. raw .. "\n</code></pre>"
+	end
+	
+	while true do
+		local start, stop = find_codeblock(lines)
+		if not start then break end
+		local text = process_codeblock(splice(lines, start, stop))
+		local info = {
+			line = text,
+			type = "raw",
+			html = text
+		}
+		lines = splice(lines, start, stop, {info})
+	end
+	return lines
+end
+
+-- Convert lines to html code
+function blocks_to_html(lines, no_paragraphs)
+	local out = {}
+	local i = 1
+	while i <= #lines do
+		local line = lines[i]
+		if line.type == "ruler" then
+			table.insert(out, "<hr/>")
+		elseif line.type == "raw" then
+			table.insert(out, line.html)
+		elseif line.type == "normal" then
+			local s = line.line
+			
+			while i+1 <= #lines and lines[i+1].type == "normal" do
+				i = i + 1
+				s = s .. "\n" .. lines[i].line
+			end
+			
+			if no_paragraphs then
+				table.insert(out, span_transform(s))
+			else
+				table.insert(out, "<p>" .. span_transform(s) .. "</p>")
+			end
+		elseif line.type == "header" then
+			local s = "<h" .. line.level .. ">" .. span_transform(line.text) .. "</h" .. line.level .. ">"
+			table.insert(out, s)
+		else
+			table.insert(out, line.line)
+		end
+		i = i + 1
+	end
+	return out
+end
+
+-- Perform all the block level transforms
+function block_transform(text, sublist)
+	local lines = split(text)
+	lines = map(lines, classify)
+	lines = headers(lines)
+	lines = lists(lines, sublist)
+	lines = codeblocks(lines)
+	lines = blockquotes(lines)
+	lines = blocks_to_html(lines)
+	local text = table.concat(lines, "\n")
+	return text
+end
+
+-- Debug function for printing a line array to see the result
+-- of partial transforms.
+function print_lines(lines)
+	for i, line in ipairs(lines) do
+		print(i, line.type, line.text or line.line)
+	end
+end
+
+----------------------------------------------------------------------
+-- Span transform
+----------------------------------------------------------------------
+
+-- Functions for transforming the text at the span level.
+
+-- These characters may need to be escaped because they have a special
+-- meaning in markdown.
+escape_chars = "'\\`*_{}[]()>#+-.!'"
+escape_table = {}
+
+function init_escape_table()
+	escape_table = {}
+	for i = 1,#escape_chars do
+		local c = escape_chars:sub(i,i)
+		escape_table[c] = hash(c)
+	end
+end
+
+-- Adds a new escape to the escape table.
+function add_escape(text)
+	if not escape_table[text] then
+		escape_table[text] = hash(text)
+	end
+	return escape_table[text]
+end	
+
+-- Escape characters that should not be disturbed by markdown.
+function escape_special_chars(text)
+	local tokens = tokenize_html(text)
+	
+	local out = ""
+	for _, token in ipairs(tokens) do
+		local t = token.text
+		if token.type == "tag" then
+			-- In tags, encode * and _ so they don't conflict with their use in markdown.
+			t = t:gsub("%*", escape_table["*"])
+			t = t:gsub("%_", escape_table["_"])
+		else
+			t = encode_backslash_escapes(t)
+		end
+		out = out .. t
+	end
+	return out
+end
+
+-- Encode backspace-escaped characters in the markdown source.
+function encode_backslash_escapes(t)
+	for i=1,escape_chars:len() do
+		local c = escape_chars:sub(i,i)
+		t = t:gsub("\\%" .. c, escape_table[c])
+	end
+	return t
+end
+
+-- Unescape characters that have been encoded.
+function unescape_special_chars(t)
+	local tin = t
+	for k,v in pairs(escape_table) do
+		k = k:gsub("%%", "%%%%")
+		t = t:gsub(v,k)
+	end
+	if t ~= tin then t = unescape_special_chars(t) end
+	return t
+end
+
+-- Encode/escape certain characters inside Markdown code runs.
+-- The point is that in code, these characters are literals,
+-- and lose their special Markdown meanings.
+function encode_code(s)
+	s = s:gsub("%&", "&amp;")
+	s = s:gsub("<", "&lt;")
+	s = s:gsub(">", "&gt;")
+	for k,v in pairs(escape_table) do
+		s = s:gsub("%"..k, v)
+	end
+	return s
+end
+
+-- Handle backtick blocks.
+function code_spans(s)
+	s = s:gsub("\\\\", escape_table["\\"])
+	s = s:gsub("\\`", escape_table["`"])
+
+	local pos = 1
+	while true do
+		local start, stop = s:find("`+", pos)
+		if not start then return s end
+		local count = stop - start + 1
+		-- Find a matching numbert of backticks
+		local estart, estop = s:find(string.rep("`", count), stop+1)
+		local brstart = s:find("\n", stop+1)
+		if estart and (not brstart or estart < brstart) then
+			local code = s:sub(stop+1, estart-1)
+			code = code:gsub("^[ \t]+", "")
+			code = code:gsub("[ \t]+$", "")
+			code = code:gsub(escape_table["\\"], escape_table["\\"] .. escape_table["\\"])
+			code = code:gsub(escape_table["`"], escape_table["\\"] .. escape_table["`"])
+			code = "<code>" .. encode_code(code) .. "</code>"
+			code = add_escape(code)
+			s = s:sub(1, start-1) .. code .. s:sub(estop+1)
+			pos = start + code:len()
+		else
+			pos = stop + 1
+		end
+	end
+	return s
+end
+
+-- Encode alt text... enodes &, and ".
+function encode_alt(s)
+	if not s then return s end
+	s = s:gsub('&', '&amp;')
+	s = s:gsub('"', '&quot;')
+	s = s:gsub('<', '&lt;')
+	return s
+end
+
+-- Handle image references
+function images(text)
+	local function reference_link(alt, id)
+		alt = encode_alt(alt:match("%b[]"):sub(2,-2))
+		id = id:match("%[(.*)%]"):lower()
+		if id == "" then id = text:lower() end
+		link_database[id] = link_database[id] or {}
+		if not link_database[id].url then return nil end
+		local url = link_database[id].url or id
+		url = encode_alt(url)
+		local title = encode_alt(link_database[id].title)
+		if title then title = " title=\"" .. title .. "\"" else title = "" end
+		return add_escape ('<img src="' .. url .. '" alt="' .. alt .. '"' .. title .. "/>")
+	end
+	
+	local function inline_link(alt, link)
+		alt = encode_alt(alt:match("%b[]"):sub(2,-2))
+		local url, title = link:match("%(<?(.-)>?[ \t]*['\"](.+)['\"]")
+		url = url or link:match("%(<?(.-)>?%)")
+		url = encode_alt(url)
+		title = encode_alt(title)
+		if title then
+			return add_escape('<img src="' .. url .. '" alt="' .. alt .. '" title="' .. title .. '"/>')
+		else
+			return add_escape('<img src="' .. url .. '" alt="' .. alt .. '"/>')
+		end
+	end
+	
+	text = text:gsub("!(%b[])[ \t]*\n?[ \t]*(%b[])", reference_link)
+	text = text:gsub("!(%b[])(%b())", inline_link)
+	return text
+end
+
+-- Handle anchor references
+function anchors(text)
+	local function reference_link(text, id)
+		text = text:match("%b[]"):sub(2,-2)
+		id = id:match("%b[]"):sub(2,-2):lower()
+		if id == "" then id = text:lower() end
+		link_database[id] = link_database[id] or {}
+		if not link_database[id].url then return nil end
+		local url = link_database[id].url or id
+		url = encode_alt(url)
+		local title = encode_alt(link_database[id].title)
+		if title then title = " title=\"" .. title .. "\"" else title = "" end
+		return add_escape("<a href=\"" .. url .. "\"" .. title .. ">") .. text .. add_escape("</a>")
+	end
+	
+	local function inline_link(text, link)
+		text = text:match("%b[]"):sub(2,-2)
+		local url, title = link:match("%(<?(.-)>?[ \t]*['\"](.+)['\"]")
+		title = encode_alt(title)
+		url  = url or  link:match("%(<?(.-)>?%)") or ""
+		url = encode_alt(url)
+		if title then
+			return add_escape("<a href=\"" .. url .. "\" title=\"" .. title .. "\">") .. text .. "</a>"
+		else
+			return add_escape("<a href=\"" .. url .. "\">") .. text .. add_escape("</a>")
+		end
+	end
+	
+	text = text:gsub("(%b[])[ \t]*\n?[ \t]*(%b[])", reference_link)
+	text = text:gsub("(%b[])(%b())", inline_link)
+	return text
+end
+
+-- Handle auto links, i.e. <http://www.google.com/>.
+function auto_links(text)
+	local function link(s)
+		return add_escape("<a href=\"" .. s .. "\">") .. s .. "</a>"
+	end
+	-- Encode chars as a mix of dec and hex entitites to (perhaps) fool
+	-- spambots.
+	local function encode_email_address(s)
+		-- Use a deterministic encoding to make unit testing possible.
+		-- Code 45% hex, 45% dec, 10% plain.
+		local hex = {code = function(c) return "&#x" .. string.format("%x", c:byte()) .. ";" end, count = 1, rate = 0.45}
+		local dec = {code = function(c) return "&#" .. c:byte() .. ";" end, count = 0, rate = 0.45}
+		local plain = {code = function(c) return c end, count = 0, rate = 0.1}
+		local codes = {hex, dec, plain}
+		local function swap(t,k1,k2) local temp = t[k2] t[k2] = t[k1] t[k1] = temp end
+		
+		local out = ""
+		for i = 1,s:len() do
+			for _,code in ipairs(codes) do code.count = code.count + code.rate end
+			if codes[1].count < codes[2].count then swap(codes,1,2) end
+			if codes[2].count < codes[3].count then swap(codes,2,3) end
+			if codes[1].count < codes[2].count then swap(codes,1,2) end
+			
+			local code = codes[1]
+			local c = s:sub(i,i)
+			-- Force encoding of "@" to make email address more invisible.
+			if c == "@" and code == plain then code = codes[2] end
+			out = out .. code.code(c)
+			code.count = code.count - 1
+		end	
+		return out
+	end
+	local function mail(s)
+		s = unescape_special_chars(s)
+		local address = encode_email_address("mailto:" .. s)
+		local text = encode_email_address(s)
+		return add_escape("<a href=\"" .. address .. "\">") .. text .. "</a>"
+	end
+	-- links
+	text = text:gsub("<(https?:[^'\">%s]+)>", link)
+	text = text:gsub("<(ftp:[^'\">%s]+)>", link)
+	
+	-- mail
+	text = text:gsub("<mailto:([^'\">%s]+)>", mail)
+	text = text:gsub("<([-.%w]+%@[-.%w]+)>", mail)
+	return text
+end
+
+-- Encode free standing amps (&) and angles (<)... note that this does not
+-- encode free >.
+function amps_and_angles(s)
+	-- encode amps not part of &..; expression
+	local pos = 1
+	while true do
+		local amp = s:find("&", pos)
+		if not amp then break end
+		local semi = s:find(";", amp+1)
+		local stop = s:find("[ \t\n&]", amp+1)
+		if not semi or (stop and stop < semi) or (semi - amp) > 15 then
+			s = s:sub(1,amp-1) .. "&amp;" .. s:sub(amp+1)
+			pos = amp+1
+		else
+			pos = amp+1
+		end
+	end
+	
+	-- encode naked <'s
+	s = s:gsub("<([^a-zA-Z/?$!])", "&lt;%1")
+	s = s:gsub("<$", "&lt;")
+	
+	-- what about >, nothing done in the original markdown source to handle them
+	return s
+end
+
+-- Handles emphasis markers (* and _) in the text.
+function emphasis(text)
+	for _, s in ipairs {"%*%*", "%_%_"} do
+		text = text:gsub(s .. "([^%s][%*%_]?)" .. s, "<strong>%1</strong>")
+		text = text:gsub(s .. "([^%s][^<>]-[^%s][%*%_]?)" .. s, "<strong>%1</strong>")
+	end
+	for _, s in ipairs {"%*", "%_"} do
+		text = text:gsub(s .. "([^%s_])" .. s, "<em>%1</em>")
+		text = text:gsub(s .. "(<strong>[^%s_]</strong>)" .. s, "<em>%1</em>")
+		text = text:gsub(s .. "([^%s_][^<>_]-[^%s_])" .. s, "<em>%1</em>")
+		text = text:gsub(s .. "([^<>_]-<strong>[^<>_]-</strong>[^<>_]-)" .. s, "<em>%1</em>")
+	end
+	return text
+end
+
+-- Handles line break markers in the text.
+function line_breaks(text)
+	return text:gsub("  +\n", " <br/>\n")
+end
+
+-- Perform all span level transforms.
+function span_transform(text)
+	text = code_spans(text)
+	text = escape_special_chars(text)
+	text = images(text)
+	text = anchors(text)
+	text = auto_links(text)
+	text = amps_and_angles(text)
+	text = emphasis(text)
+	text = line_breaks(text)
+	return text
+end
+
+----------------------------------------------------------------------
+-- Markdown
+----------------------------------------------------------------------
+
+-- Cleanup the text by normalizing some possible variations to make further
+-- processing easier.
+function cleanup(text)
+	-- Standardize line endings
+	text = text:gsub("\r\n", "\n")  -- DOS to UNIX
+	text = text:gsub("\r", "\n")    -- Mac to UNIX
+	
+	-- Convert all tabs to spaces
+	text = detab(text)
+	
+	-- Strip lines with only spaces and tabs
+	while true do
+		local subs
+		text, subs = text:gsub("\n[ \t]+\n", "\n\n")
+		if subs == 0 then break end
+	end
+	
+	return "\n" .. text .. "\n"
+end
+
+-- Strips link definitions from the text and stores the data in a lookup table.
+function strip_link_definitions(text)
+	local linkdb = {}
+	
+	local function link_def(id, url, title)
+		id = id:match("%[(.+)%]"):lower()
+		linkdb[id] = linkdb[id] or {}
+		linkdb[id].url = url or linkdb[id].url
+		linkdb[id].title = title or linkdb[id].title
+		return ""
+	end
+
+	local def_no_title = "\n ? ? ?(%b[]):[ \t]*\n?[ \t]*<?([^%s>]+)>?[ \t]*"
+	local def_title1 = def_no_title .. "[ \t]+\n?[ \t]*[\"'(]([^\n]+)[\"')][ \t]*"
+	local def_title2 = def_no_title .. "[ \t]*\n[ \t]*[\"'(]([^\n]+)[\"')][ \t]*"
+	local def_title3 = def_no_title .. "[ \t]*\n?[ \t]+[\"'(]([^\n]+)[\"')][ \t]*"
+	
+	text = text:gsub(def_title1, link_def)
+	text = text:gsub(def_title2, link_def)
+	text = text:gsub(def_title3, link_def)
+	text = text:gsub(def_no_title, link_def)
+	return text, linkdb
+end
+
+link_database = {}
+
+-- Main markdown processing function
+function markdown(text)
+	init_hash(text)
+	init_escape_table()
+	
+	text = cleanup(text)
+	text = protect(text)
+	text, link_database = strip_link_definitions(text)
+	text = block_transform(text)
+	text = unescape_special_chars(text)
+	return text
+end
+
+----------------------------------------------------------------------
+-- End of module
+----------------------------------------------------------------------
+
+setfenv(1, _G)
+M.lock(M)
+
+-- Expose markdown function to the world
+markdown = M.markdown
+
+-- Class for parsing command-line options
+local OptionParser = {}
+OptionParser.__index = OptionParser
+
+-- Creates a new option parser
+function OptionParser:new()
+	local o = {short = {}, long = {}}
+	setmetatable(o, self)
+	return o
+end
+
+-- Calls f() whenever a flag with specified short and long name is encountered
+function OptionParser:flag(short, long, f)
+	local info = {type = "flag", f = f}
+	if short then self.short[short] = info end
+	if long then self.long[long] = info end
+end
+
+-- Calls f(param) whenever a parameter flag with specified short and long name is encountered
+function OptionParser:param(short, long, f)
+	local info = {type = "param", f = f}
+	if short then self.short[short] = info end
+	if long then self.long[long] = info end
+end
+
+-- Calls f(v) for each non-flag argument
+function OptionParser:arg(f)
+	self.arg = f
+end
+
+-- Runs the option parser for the specified set of arguments. Returns true if all arguments
+-- where successfully parsed and false otherwise.
+function OptionParser:run(args)
+	local pos = 1
+	while pos <= #args do
+		local arg = args[pos]
+		if arg == "--" then
+			for i=pos+1,#args do
+				if self.arg then self.arg(args[i]) end
+				return true
+			end
+		end
+		if arg:match("^%-%-") then
+			local info = self.long[arg:sub(3)]
+			if not info then print("Unknown flag: " .. arg) return false end
+			if info.type == "flag" then
+				info.f()
+				pos = pos + 1
+			else
+				param = args[pos+1]
+				if not param then print("No parameter for flag: " .. arg) return false end
+				info.f(param)
+				pos = pos+2
+			end
+		elseif arg:match("^%-") then
+			for i=2,arg:len() do
+				local c = arg:sub(i,i)
+				local info = self.short[c]
+				if not info then print("Unknown flag: -" .. c) return false end
+				if info.type == "flag" then
+					info.f()
+				else
+					if i == arg:len() then
+						param = args[pos+1]
+						if not param then print("No parameter for flag: -" .. c) return false end
+						info.f(param)
+						pos = pos + 1
+					else
+						param = arg:sub(i+1)
+						info.f(param)
+					end
+					break
+				end
+			end
+			pos = pos + 1
+		else
+			if self.arg then self.arg(arg) end
+			pos = pos + 1
+		end
+	end
+	return true
+end
+
+-- Handles the case when markdown is run from the command line
+local function run_command_line(arg)
+	-- Generate output for input s given options
+	local function run(s, options)
+		s = markdown(s)
+		if not options.wrap_header then return s end
+		local header = ""
+		if options.header then
+			local f = io.open(options.header) or error("Could not open file: " .. options.header) 
+			header = f:read("*a")
+			f:close()
+		else
+			header = [[
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html>
+<head>
+	<meta http-equiv="content-type" content="text/html; charset=CHARSET" />
+	<title>TITLE</title>
+	<link rel="stylesheet" type="text/css" href="STYLESHEET" />
+</head>
+<body>
+]]
+			local title = options.title or s:match("<h1>(.-)</h1>") or s:match("<h2>(.-)</h2>") or 
+				s:match("<h3>(.-)</h3>") or "Untitled"
+			header = header:gsub("TITLE", title)
+			if options.inline_style then
+				local style = ""
+				local f = io.open(options.stylesheet)
+				if f then 
+					style = f:read("*a") f:close() 
+				else
+					error("Could not include style sheet " .. options.stylesheet .. ": File not found")
+				end
+				header = header:gsub('<link rel="stylesheet" type="text/css" href="STYLESHEET" />',
+					"<style type=\"text/css\"><!--\n" .. style .. "\n--></style>")
+			else
+				header = header:gsub("STYLESHEET", options.stylesheet)
+			end
+			header = header:gsub("CHARSET", options.charset)
+		end
+		local footer = "</body></html>"
+		if options.footer then
+			local f = io.open(options.footer) or error("Could not open file: " .. options.footer)
+			footer = f:read("*a")
+			f:close()
+		end
+		return header .. s .. footer
+	end
+	
+	-- Generate output path name from input path name given options.	
+	local function outpath(path, options)
+		if options.append then return path .. ".html" end
+		local m = path:match("^(.+%.html)[^/\\]+$") if m then return m end
+		m = path:match("^(.+%.)[^/\\]*$") if m and path ~= m .. "html" then return m .. "html" end
+		return path .. ".html"
+	end
+	
+	-- Default commandline options
+	local options = {
+		wrap_header = true,
+		header = nil,
+		footer = nil,
+		charset = "utf-8",
+		title = nil,
+		stylesheet = "default.css",
+		inline_style = false
+	}
+	local help = [[
+Usage: markdown.lua [OPTION] [FILE]
+Runs the markdown text markup to HTML converter on each file specified on the
+command line. If no files are specified, runs on standard input.
+
+No header:
+    -n, --no-wrap        Don't wrap the output in <html>... tags.
+Custom header:
+    -e, --header FILE    Use content of FILE for header.
+    -f, --footer FILE    Use content of FILE for footer.
+Generated header:
+    -c, --charset SET    Specifies charset (default utf-8).
+    -i, --title TITLE    Specifies title (default from first <h1> tag).
+    -s, --style STYLE    Specifies style sheet file (default default.css).
+	-l, --inline-style   Include the style sheet file inline in the header.
+Generated files:
+    -a, --append         Append .html extension (instead of replacing).
+Other options:
+    -h, --help           Print this help text.
+    -t, --test           Run the unit tests.
+]]
+
+	local run_stdin = true
+	local op = OptionParser:new()
+	op:flag("n", "no-wrap", function () options.wrap_header = false end)
+	op:param("e", "header", function (x) options.header = x end)
+	op:param("f", "footer", function (x) options.footer = x end)
+	op:param("c", "charset", function (x) options.charset = x end)
+	op:param("i", "title", function(x) options.title = x end)
+	op:param("s", "style", function(x) options.stylesheet = x end)
+	op:flag("l", "inline-style", function(x) options.inline_style = true end)
+	op:flag("a", "append", function() options.append = true end)
+	op:flag("t", "test", function() 
+		local n = arg[0]:gsub("markdown.lua", "markdown-tests.lua")
+		local f = io.open(n)
+		if f then 
+			f:close() dofile(n) 
+		else
+			error("Cannot find markdown-tests.lua")
+		end
+		run_stdin = false 
+	end)
+	op:flag("h", "help", function() print(help) run_stdin = false end)
+	op:arg(function(path) 
+			local file = io.open(path) or error("Could not open file: " .. path)
+			local s = file:read("*a")
+			file:close()
+			s = run(s, options)
+			file = io.open(outpath(path, options), "w") or error("Could not open output file: " .. outpath(path, options))
+			file:write(s)
+			file:close()
+			run_stdin = false
+		end
+	)
+	
+	if not op:run(arg) then
+		print(help)
+		run_stdin = false
+	end
+
+	if run_stdin then
+		local s = io.read("*a")
+		s = run(s, options)
+		io.write(s)
+	end
+end
+	
+-- If we are being run from the command-line, act accordingly
+if arg and arg[0]:find("markdown%.lua$") then
+	run_command_line(arg)
+else
+	return markdown
+end
\ No newline at end of file