scansion/pretty.lua

require "verse"
local xml = require "scansion.xml";
local s_format, s_gsub = string.format, string.gsub;

local escape_table = { ["'"] = "&apos;", ["\""] = "&quot;", ["<"] = "&lt;", [">"] = "&gt;", ["&"] = "&amp;" };
local function xml_escape(str) return (s_gsub(str, "['&<>\"]", escape_table)); end

-- Dummy functions compatible with util.termcolours,
-- just in case we add colour in the future
local function getstyle() return "" end
local function getstring(style, text)
	if not style then
		text = style;
	end
	return text;
end

local default_config = {
	indent = 2;
	preserve_whitespace = false;
};

local function new(user_config)
	local config = setmetatable({}, { __index = function (_, k) return user_config[k] or default_config[k]; end });
	local style_attrk = getstyle("yellow");
	local style_attrv = getstyle("red");
	local style_tagname = getstyle("red");
	local style_punc = getstyle("magenta");

	local attr_format = " "..getstring(style_attrk, "%s")..getstring(style_punc, "=")..getstring(style_attrv, "'%s'");
	local open_tag_format = getstring(style_punc, "<")..getstring(style_tagname, "%s").."%s"..getstring(style_punc, ">");
	local close_tag_format = getstring(style_punc, "</")..getstring(style_tagname, "%s")..getstring(style_punc, ">");
	local tag_format = open_tag_format.."%s"..close_tag_format;
	local short_close_tag_format = getstring(style_punc, "<")..getstring(style_tagname, "%s").."%s"..getstring(style_punc, "/>");
	local function pretty_print(t, ind)
		ind = ind or config.indent;
		local children_text = "";
		for i, child in ipairs(t) do
			if type(child) == "string" then
				if config.preserve_whitespace or child:match("%S") then
					children_text = children_text .. "\n"..string.rep(" ", ind) .. xml_escape(child);
				end
			else
				children_text = children_text .. "\n" .. pretty_print(child, ind+config.indent);
			end
		end

		local attr_string = "";
		if t.attr then
			for k, v in pairs(t.attr) do
				if type(k) == "string" then
					attr_string = attr_string .. s_format(attr_format, k, tostring(v));
				end
			end
		end

		local use_tag_format = tag_format;
		if #t == 0 then
			use_tag_format = short_close_tag_format;
		end
		if children_text ~= "" then
			children_text = children_text .. "\n" .. string.rep(" ", ind);
		end

		return string.rep(" ", ind)..s_format(use_tag_format, t.name, attr_string, children_text, t.name);
	end

	return function (s, ind)
		local doc = xml.parse(s);
		if not doc then
			return s; -- Not valid XML, don't prettify
		end
		return pretty_print(doc, ind);
	end
end

return {
	new = new;
}