require 'lfs'
local p = {} -- processor
local docs = {}
local concat = table.concat
local targetDir = arg[1] or './docs/'

function fread(file)
	local h = io.open(file,'r')
	return coroutine.wrap(function()
		for l in h:lines() do
			coroutine.yield(l)
		end
		h:close()
	end)
end

function pexec (cmd)
	local h = io.popen(cmd,'r')
	return coroutine.wrap(function()
		for l in h:lines() do
			coroutine.yield(l)
		end
		h:close()
	end)
end

local ENDED, STARTED, WRITING = 1,2,3

p.processed = {}
p.mdHeadLvl = 3

function p:slugify(str)
	return str:gsub('%W+','-'):gsub('^%-*',''):gsub('%-*$',''):lower()
end


function p:excerptOpen(line)
	if self.state == ENDED then
		local m,l,md = line:match('^%s*(%-%--)%[(=*)%[(md.*)$')
		if m then
			local file = md:match('^md%s*:%s*([^%s./]+)') or 'reference'
			if not docs[file] then docs[file] = {toc={}, body={}, name=file} end
			self.doc = docs[file]
			self.doc.body[#(self.doc.body)+ 1] = "\n"
			self._cmtLvl = l or ''
			self.state = STARTED
		end
		return true
	end
	return false
end

-- Treat the lines considered the body of markdown
-- first line of block can be considered topics if starts with #
-- Observe that the if you jump the # level (ex. # to ###) you may
-- break the table of contents (toc)
function p:excerptBody(line)
	local indent,content = line:match('^(%s*)(%S.*)$')
	-- we map the indent variations to make it consistent
	indent = indent and indent:gsub("\t",'    ') or ''

	if self.state == STARTED then
		if content and #content then
			local body
			self.indent = indent
			local hmark, hcontent = content:match('^(#+)%s*(%S.+)')
			if hmark and #hmark then
				content=hcontent
				local hurl = concat{'#',self:slugify(self.doc.name),'_',self:slugify(content)}
				self.doc.toc[#(self.doc.toc) + 1] = concat{
					string.rep('    ',#hmark - 1),
					#hmark <= 2 and '1. ' or '* ',
					'[```',content,'```](',hurl,')\n'
				}
				body = {hmark,hmark and ' ','``',content,'`` {',hurl,"}\n\n"}
			else
				body = {content,'\n'}
			end
			self.doc.body[#(self.doc.body) + 1] = concat(body)

		else
			self.doc.body[#(self.doc.body) + 1] = "\n"
		end
		self.state = WRITING
		return true
	elseif self.state == WRITING then
		if content then
			self.doc.body[#(self.doc.body) + 1] = concat{string.rep(' ',#(indent or '') - #self.indent),content,"\n"}
		else
			self.doc.body[#(self.doc.body) + 1] = "\n"
		end
		return true
	end

	return false
end

function p:excerptClose(line)
	local m = line:match('%]'..self._cmtLvl..'%]')
	if self.state ~= ENDED and m then
		self.doc.body[#(self.doc.body) + 1] = ''
		self.state = ENDED
		return true
	end
	return false
end

function p:file(f)
	-- memoize init.lua inside directory
	if self.processed[f] then
		return
	else
		f = lfs.attributes(f).mode == 'directory' and f..'/init.lua' or f
		self.processed[f]=1
	end

	-- read each file line
	local fattr = lfs.attributes(f)
	local _ = false

	if fattr and fattr.mode == 'file' then
		self._cmtLvl = ''
		self.state = ENDED
		for line in fread(f) do
			_ = self:excerptClose(line) or self:excerptOpen(line) or self:excerptBody(line)
		end
	end
end

function p.addTimestamp(d)
	d[#(d) + 1]='\n----------\n'
	d[#(d) + 1]='Last update: '..os.date('%F %T %z')
end

--TODO: Needs a way system independent do get list of files
for pathItem in pexec('find .|sort') do
	p:file(pathItem)
end
lfs.mkdir(targetDir)
for i,v in pairs(docs) do
	local f = io.open(concat{targetDir,'/',i,'.md'},'w+')
	p.addTimestamp(v.body)
	v.body=concat(v.body):gsub('\n\n+','\n\n')
	f:write(concat(v.toc),'\n\n',v.body)
	f:close()
end