使用LPeg将markdown转成html

lmd.lua

local lpeg = require 'lpeg'

local P,S,C,Cs,Cg = lpeg.P,lpeg.S,lpeg.C,lpeg.Cs,lpeg.Cg

local test = [[
A title
---
BTitle
--
CTitle
===
## A title

here _we go_ and `a:bonzo()`:

    <
    one line
    two line
    three line
       
<and `more_or_less_something`

[A reference](http://bonzo.dog)

> quoted
> lines
 
]]

function subst(openp,repl,endp)
    openp = P(openp)  -- make sure it's a pattern
    endp = endp and P(endp) or openp
    -- pattern is 'bracket followed by any number of non-bracket followed by bracket'
    local contents = C((1 - endp)^1)
    local patt = openp * contents * endp    
    if repl then patt = patt/repl end
    return patt
end

function empty(p)
    return C(p)/''
end

local lf = P'\n'
local rest_of_line = C((1 - lf)^1)
local rest_of_line_nl = C((1 - lf)^0*lf)

-- indented code block
local indent = P'\t' + P'    '
local indented = empty(indent)*rest_of_line_nl
-- which we'll assume are Lua code
local block = Cs(indented^1)/'<pre>%1</pre>\n'

-- use > to get simple quoted block
-- quoted_line = empty('> ')*rest_of_line_nl 
local quoted_line = subst('> ','<p>%1</p>\n','\n')
local quote = Cs (quoted_line^1)/"<blockquote>\n%1</blockquote>"
 
local code = subst('`','<code>%1</code>')
local italic = subst('*',"<em>%1</em>") + subst('_',"<em>%1</em>")
local bold = subst('**',"<strong>%1</strong>") + subst('__',"<strong>%1</strong>")
local special = C('<')/'&lt;' + C('&')/'&amp;'
local title1 = P'#' * rest_of_line/'<h1>%1</h1>' + C((1 - lf)^0)*lf*P'='^1/'<h1>%1</h1>'
local title2 = P'##' * rest_of_line/'<h2>%1</h2>' + C((1 - lf)^0)*lf*P'-'^1/'<h2>%1</h2>'
local title3 = P'###' * rest_of_line/'<h3>%1</h3>'
local title4 = P'####' * rest_of_line/'<h4>%1</h4>'
local title5 = P'#####' * rest_of_line/'<h5>%1</h5>'
local title6 = P'######' * rest_of_line/'<h6>%1</h6>'

local url = (subst('[',nil,']')*subst('(',nil,')'))/'<a href="%2">%1</a>'
 
local item = block + title6 + title5 + title4 + title3 + title2 + title1 + code + italic + bold + quote + url + special + 1
local text = Cs(item^1)

if arg[1] then
    local f = io.open(arg[1])
    test = f:read '*a'
    f:close()
end

print("<pre>"..test.."</pre><hr>")
print(text:match(test))