plugins/xkcd.lua

local parse_xkcd_list;
local xkcd_list_updated_at = 0;
local xkcd_list = { };

function riddim.plugins.xkcd(bot)
	require "net.httpclient_listener";
	local http = require("net.http");
	bot:hook("commands/xkcd", function(command)
		if os.difftime(os.time(), xkcd_list_updated_at) > (3 * 60 * 60) then -- Not refreshed within 3 hours
            --COMPAT We could have saved 6 bytes here, but Microsoft apparently hates %T, so you got this gigantic comment instead.
			-- http.request('http://xkcd.com/archive/', { headers = { ["If-Modified-Since"] = os.date("!%a, %d %b %Y %T %Z", xkcd_list_updated_at or 0) } }, function (data, code)
            http.request('http://xkcd.com/archive/', { headers = { ["If-Modified-Since"] = os.date("!%a, %d %b %Y %H:%M:%S %Z", xkcd_list_updated_at or 0) } }, function (data, code)
				if code == 200 then
					xkcd_list_updated_at = os.time();
					print("debug", "got "..(#data or 0).." bytes of data");
					parse_xkcd_list(data);
				elseif code == 304 then
					xkcd_list_updated_at = os.time();
				else
					if code > 0 then
						command:reply("Received HTTP "..code.." error trying to fetch the XKCD archive");
					else
						command:reply("Unable to fetch the XKCD archive from xkcd.com: "..data:gsub("%-", " "));
					end
					return;
				end
				command:reply(handle_xkcd_command(command));
			end);
		else
			return handle_xkcd_command(command);
		end
	end);
end

function handle_xkcd_command(command)
    local xkcdnum = command.param;
    if not xkcdnum then
			xkcdnum = #xkcd_list;
		end
    if not tonumber(xkcdnum) then -- Search for an xkcd
        xkcdnum = xkcdnum:lower()
        local xkcdpat = xkcdnum:gsub("[()]", function(s) return "%" .. s end)
            :gsub("[%[]",function(s) return "%" .. s end)
            :gsub("%%(%b[])",function(s) return (#s > 2 and "" or "%") .. s end);
        local results = {};
        for x, xkcd in pairs(xkcd_list) do
            name = xkcd:lower()
            if name == xkcdnum then -- exact match
                return xkcd..", http://xkcd.org/"..x.."/";
            elseif name:match(xkcdpat) then
                table.insert(results, x);
                --return commands.xkcd(msg, x);
            end
        end
        if #results == 0 then
            return "Sorry, I couldn't find a match";
        elseif #results == 1 then
            command.param = results[1];
            return handle_xkcd_command(command);
        else
            -- We have more than one match
            local ret = "Multiple matches:";
            for _, x in ipairs(results) do
                local xkcdnum = tostring(tonumber(x));
                local xkcd = xkcd_list[tostring(x)];
                ret = string.format("%s %s%s", ret, xkcd, ((_ < #results) and ",") or "");
                if _ > 5 then ret = ret .. " " .. (#results - 5) .. " more"; break; end
            end
            return ret;
        end
    end
    -- Check that xkcdnum is a valid number
    xkcdnum = tostring(tonumber(xkcdnum));
    if not xkcdnum then return "What XKCD strip number? Or enter a search string."; end
    xkcd = xkcd_list[xkcdnum];
    if not xkcd then return "Sorry, I don't think there is a XKCD #"..xkcdnum; end
    return xkcd..", http://xkcd.org/"..xkcdnum.."/";
end

function parse_xkcd_list(t)
	if not t then return nil; end
	for number, name in string.gmatch(t,"<a [^>]*href=\"/(%d+)/\"[^>]*>([^<]+)") do
		xkcd_list[number] = name;
	end
	return true;
end