h5tk.lua

local pkg_builder

local err_wrong_tag = "Wrong tag has been given!"
local err_twice_tag = "This bug could not have happened, please report it!"

local buffer_get, buffer_tostring, buffer_add
local is_html_normal, is_html_special
local tree_get, tree_addnode
local fmt_traverse_attr, fmt_traverse_data
local fmt_traverse_aux_data, fmt_traverse_aux_attr
local fast_traverse_aux, fast_traverse_attr, fast_traverse_data
local fmt_helper, fast_helper
	
local html_elements_special = {
    ["area"] = true, ["base"] = true, ["br"] = true, ["col"] = true, ["embed"] = true, ["track"] = true,
    ["hr"] = true, ["source"] = true, ["param"] = true, ["meta"] = true, ["img"] = true, ["link"] = true,
    ["keygen"] = true, input= true
}

local html_elements_normal = {
    ["a"] = true, ["abbr"] = true, ["address"] = true, ["article"] = true, ["aside"] = true,
    ["audio"] = true, ["b"] = true, ["bdi"] = true, ["bdo"] = true, ["blockquote"] = true,
    ["body"] = true, ["button"] = true, ["canvas"] = true, ["caption"] = true, ["code"] = true,
    ["colgroup"] = true, ["datalist"] = true, ["dd"] = true, ["del"] = true, ["details"] = true,
    ["dfn"] = true, ["dialog"] = true, ["div"] = true, ["dl"] = true, ["dt"] = true, ["em"] = true,
    ["fieldset"] = true, ["figcaption"] = true, ["figure"] = true, ["footer"] = true, ["form"] = true,
    ["h1"] = true, ["h2"] = true, ["h3"] = true, ["h4"] = true, ["h5"] = true, ["h6"] = true, ["head"] = true,
    ["header"] = true, ["html"] = true, ["i"] = true, ["iframe"] = true, ["ins"] = true, ["kbd"] = true,
    ["label"] = true, ["legend"] = true, ["li"] = true, ["main"] = true, ["map"] = true, ["mark"] = true,
    ["menu"] = true, ["menuitem"] = true, ["meter"] = true, ["nav"] = true, ["noscript"] = true, ["object"] = true,
    ["ol"] = true, ["optgroup"] = true, ["option"] = true, ["output"] = true, ["p"] = true, ["pre"] = true,
    ["progress"] = true, ["q"] = true, ["rp"] = true, ["rt"] = true, ["ruby"] = true, ["s"] = true, ["samp"] = true,
    ["script"] = true, ["section"] = true, ["select"] = true, ["small"] = true, ["span"] = true, ["style"] = true,
    ["sub"] = true, ["summary"] = true, ["sup"] = true, ["table"] = true, ["tbody"] = true, ["td"] = true,
    ["textarea"] = true, ["tfoot"] = true, ["th"] = true, ["thead"] = true, ["time"] = true, ["title"] = true,
    ["tr"] = true, ["u"] = true, ["ul"] = true, ["var"] = true, ["video"] = true, ["wbr"] = true
}

function buffer_get()
	return {""}
end

function buffer_tostring(buffer)
	return table.concat(buffer)
end

function buffer_add(buffer, string)
	buffer[#buffer + 1] = string
end

function is_html_normal(string)
    return html_elements_normal[string] 
end

function is_html_special(string)
    return html_elements_special[string]
end

function tree_get()
	return {}
end

function tree_addnode(tree, value)
	tree[#tree + 1] = value
end

-- auxillary table traversal function
-- returns either a scalar type or a 
-- table
function fmt_traverse_aux_data(tree)
	if tree == nil then
		return ""
	end
	
	if type(tree) == "string" then
		return tree
	elseif type(tree) == "table" then
		return fmt_traverse_data(tree)
	elseif type(tree) == "number" then
		return tostring(tree)
	elseif type(tree) == "function" then
		return fmt_traverse_data({tree()})
	elseif type(tree) == "boolean" then
		return tostring(tree)
	elseif type(tree) == "nil" then
		return "nil"
	elseif type(tree) == "userdata" then
		return "userdata"
	elseif type(tree) == "thread" then
		return "thread"
	end
end

-- collapses every table or evaluable function
-- to a single string
function fmt_traverse_aux_attr(tree)
	if tree == nil then
		return ""
	end
	
	if type(tree) == "string" then
		return tree
	elseif type(tree) == "table" then
		local buf = buffer_get()
		for k, v in pairs(tree) do
			buffer_add(buf, fmt_traverse_aux_attr(v))
		end
		return buffer_tostring(buf)
	elseif type(tree) == "number" then
		return tostring(tree)
	elseif type(tree) == "function" then
		return fmt_traverse_aux_attr(tree())
	elseif type(tree) == "boolean" then
		return tostring(tree)
	elseif type(tree) == "nil" then
		return "nil"
	elseif type(tree) == "userdata" then
		return "userdata"
	elseif type(tree) == "thread" then
		return "thread"
	end
end

-- queries all values with string keys and
-- folds the together to one single string
-- using fmt_traverse_aux_attr
function fmt_traverse_attr(tree)
	local attr = buffer_get()

	for k, v in pairs(tree) do
		if type(k) == "string" then
			buffer_add(attr, " " .. k .. "=\"")
			buffer_add(attr, fmt_traverse_aux_attr(v))
			buffer_add(attr, "\"")
		end
	end
	
	return buffer_tostring(attr)
end

function fmt_traverse_data(source)
	local tree = tree_get()

	for k, v in pairs(source) do
		if type(k) == "number" then
			if type(v) == "table" and getmetatable(v) ~= nil then
				-- no traversal needed because it's the result of
				-- a h5tk function
				tree_addnode(tree, v)
			else
				tree_addnode(tree, fmt_traverse_aux_data(v))
			end
		end
	end

	return tree
end

-- ausillary table traversal function
function fast_traverse_aux(value)
	if value == nil then
		return ""
	end
	
	if type(value) == "string" then
		return value
	elseif type(value) == "table" then
		local buf = buffer_get()
		buffer_add(buf, fast_traverse_attr(value))
		buffer_add(buf, fast_traverse_data(value))
		return buffer_tostring(buf)
	elseif type(value) == "number" then
		return tostring(value)
	elseif type(value) == "function" then
		return fast_traverse_aux(value())
	elseif type(value) == "boolean" then
		return tostring(value)
	elseif type(value) == "nil" then
		return "nil"
	elseif type(value) == "userdata" then
		return "userdata"
	elseif type(value) == "thread" then
		return "thread"
	end
end

-- queries all 
function fast_traverse_data(table)
	local data = buffer_get()

	for k, v in pairs(table) do
		if type(k) == "number" then
			buffer_add(data, fast_traverse_aux(v))
		end
	end
	
	return buffer_tostring(data)
end

-- queries all values with string keys
function fast_traverse_attr(table)
	local attr = buffer_get()

	for k, v in pairs(table) do
		if type(k) == "string" then
			buffer_add(attr, " " .. k .. "=\"")
			buffer_add(attr, fast_traverse_aux(v) .. "\"")
		end
	end
	
	return buffer_tostring(attr)
end

function fmt_helper(sub, html)
	local tree = tree_get()
	local n, s = is_html_normal(sub), is_html_special(sub)
	setmetatable(tree, {"h5tk"})

	if not s and not n then error(err_wrong_tag .. " " .. sub) end
	if s and n then error(err_twice_tag .. " " .. sub) end
	
	tree_addnode(tree, "<" .. sub .. fmt_traverse_attr(html) .. ">")
	if n then
		tree_addnode(tree, fmt_traverse_data(html))
		tree_addnode(tree, "</" .. sub .. ">")
	end

	return tree
end

function fast_helper(sub, html)
	local buf = buffer_get()
	local n, s = is_html_normal(sub), is_html_special(sub)

	if not s and not n then error(err_wrong_tag .. " " .. sub) end
	if s and n then error(err_twice_tag .. " " .. sub) end

	buffer_add(buf, "<" .. sub)
	buffer_add(buf, fast_traverse_attr(html))
	buffer_add(buf, ">")

	if n then
		buffer_add(buf, fast_traverse_data(html))
		buffer_add(buf, "</" .. sub .. ">")
	end

	return buffer_tostring(buf)					
end
	
function emitter_builder(format, n_spaces, tabs)
	local emitter  = {}

	local this_format = format
	local this_num_sep = n_spaces
	local this_use_tabs = tabs 
	local this_lvl_sep = ""

	local tree_collapse
	local fmt_add_sep, fmt_calc_sep
	local emit

	if type(format) == "boolean" then this_format = format else
		this_format = true
	end
	if type(n_spaces) == "number" then this_num_sep = n_spaces else
		this_num_sep = 4
	end
	if type(tabs) == "boolean" then this_use_tabs = tabs else
		this_use_tabs = false
	end

	function tree_collapse(lvl, tree)
		local bigbuf = buffer_get()
		local meta = getmetatable(tree)

		for _, v in pairs(tree) do
			if type(v) == "table" then
				if meta == nil then
					buffer_add(bigbuf, tree_collapse(lvl, v))
				else
					buffer_add(bigbuf, tree_collapse(lvl + 1, v))
				end
			else
				buffer_add(bigbuf, fmt_add_sep(lvl, v) .. "\n")
			end
		end
	
		return buffer_tostring(bigbuf)
	end

	function fmt_add_sep(lvl, string)
		local buf = buffer_get()
	
		for i=1,lvl do
			buffer_add(buf, this_lvl_sep)
		end
		buffer_add(buf, string)
		return buffer_tostring(buf)
	end

	function fmt_calc_sep()
		local sep = " "
		local buf = buffer_get()
		if this_use_tabs then sep = "\t" end
	
		for i=1,this_num_sep do
			buffer_add(buf, sep)
		end
		
		return buffer_tostring(buf)
	end

	function emit(tree)
		if this_format then
			return tree_collapse(0, tree)
		else
			return tree
		end
	end

	this_lvl_sep = fmt_calc_sep()
	emitter.emit = emit	
	return emitter
end

function init(format, n_spaces, tabs)
    local h5tk_instance
	local h5tk_meta = { __index = nil}
	local emitter = emitter_builder(format, n_spaces, tabs)

	if format then
		h5tk_meta.__index = function(tab, sub)
			return function(html)
				return fmt_helper(sub, html)
			end
		end
	else
		h5tk_meta.__index = function(tab, sub)
			return function(html)
				return fast_helper(sub, html)
			end
		end
	end

	h5tk_instance = { emit = emitter.emit }
	setmetatable(h5tk_instance, h5tk_meta)

	return h5tk_instance
end

return { init = init }