-- originally from http://lua-users.org/wiki/LuaXml
-- modified by me a bit

local entity_escapes = {
		["<"]="&lt;",
		[">"]="&gt;",
		["&"]="&amp;",
		['"']="&quot;",
		["'"]="&apos;"
}
local entity_unescapes = {}
for k,v in pairs(entity_escapes) do entity_unescapes[v]=k end

local function escape(s)
	return s:gsub("[<>&'\"]",entity_escapes)
end
local function unescape(s)
	return s:gsub("&[a-z]+;",entity_unescapes)
end

local function parseargs(s)
  local arg = {}
  string.gsub(s, "([%-%w]+)=([\"'])(.-)%2", function (w, _, a)
    arg[w] = a
  end)
  return arg
end

local function tag(x)
	return setmetatable(x, {__call=function(x, label)
		-- search for child with given label
		for _,c in ipairs(x) do
			if c.label == label then
				return c
			end
		end
		return nil
	end})
end

local psingle

local function pmulti(s, i, parent)
	::again::
	local nexti, child = psingle(s, i)
	if child.close and child.label == parent.label then
		return nexti, parent
	else
		table.insert(parent, child)
		i = nexti
		goto again
	end
end

psingle = function(s, i)
	i = i or 1
	local ts,j,c,label,xarg,empty = s:find("<(%/?)([%w:]+)(.-)(%/?)>", i)
	if not ts then
		local rest = s:sub(i)
		if rest:find("<",i) then
			error('ill formed (eof?)')
		elseif #rest == 0 then
			error('empty string')
		else
			return i+#rest, unescape(rest)
		end
	end
	local nexti = j+1

	local pretext = s:sub(i, ts-1)
	if not pretext:find("^%s*$") then -- not entirely whitespace
		return ts, unescape(pretext)
	end

	if empty == "/" then
		return nexti, tag{label=label, xarg=parseargs(xarg), empty=true}
	elseif c == "" then -- start tag
		return pmulti(s, nexti, tag{label=label, xarg=parseargs(xarg)})
	else -- end tag
		return nexti, tag{label=label, close=true}
	end
end

local wrap
do
	local _, cqa = pcall(require, 'cqueues.auxlib')
	wrap = cqa and cqa.wrap or coroutine.wrap
end

local function stanzae(getmore)
	return wrap(function()
		local buf = ''
		while true do
			local ok, ni, el = pcall(psingle, buf)
			if ok then
				coroutine.yield(el)
				buf = buf:sub(ni)
			else
				local more = assert(getmore())
				buf = buf .. more
			end
		end
	end)
end


local safestr_mt = {name='SAFESTR', __tostring=function(x) return x.s end}
local function safestr(s) return setmetatable({s=s}, safestr_mt) end

local function _xmlify(x)
	if getmetatable(x) == safestr_mt then
		return x
	elseif type(x) == 'string' then
		return safestr(escape(x))
	elseif type(x) == 'table' then -- must be a tag
		local function argstr(t)
			local argstring = ''
			for k,v in pairs(t) do
				argstring = argstring .. (" %s='%s'"):format(k, _xmlify(v))
			end
			return argstring
		end
		if x.empty then
			return safestr(("<%s%s/>"):format(x.label, argstr(x.xarg)))
		else
			local open = ("<%s%s>"):format(x.label, argstr(x.xarg))
			local close = ("</%s>"):format(x.label)
			local children = {}
			for _,child in ipairs(x) do
				table.insert(children, tostring(_xmlify(child)))
			end
			return safestr(open .. table.concat(children, '') .. close)
		end
	end
end

local function xmlify(...)
	local n = select('#',...)
	if n <= 1 then return _xmlify(...) end

	local out = {}
	for i = 1, n do
		out[i] = tostring(_xmlify(select(i, ...)))
	end
	return table.concat(out, '\n')
end

-- dsl for input to xmlify. doesn't do escaping or anything.
-- THERE IS NO ESCAPE
local X = setmetatable({}, {__index=function(_,label)
	return function(tab)
		local out = {}
		local xarg = {}
		local empty = true

		for k, v in pairs(tab) do
			if type(k) == 'number' then -- child
				empty = nil
				out[k] = v
			elseif type(k) == 'string' then -- attrib
				xarg[k] = v
			end
		end

		out.label = label
		out.xarg = xarg
		out.empty = empty
		return out
	end
end})

return { psingle = psingle, stanzae = stanzae, wrap=wrap, xmlify=xmlify, X=X }