new plugin glitch.lua

.gitignore

@@ -45,4 +45,5 @@ plugins/dantest.lua
 plugins/flickr.lua
 plugins/flickr_search.lua
 plugins/google_books.lua
-plugins/safebrowsing.lua
+plugins/safebrowsing.lua
+plugins/stats2.lua

plugins/glitch.lua

@@ -0,0 +1,144 @@
+-- JPEG Glitcher v1.1
+-- Contributed by Francesco <https://github.com/Francesco149>
+do
+	local KILOBYTE = 1000
+	local MEGABYTE = KILOBYTE * 1000
+
+	function handle_http_response(code, status)
+		if code ~= 200 then
+			if status then
+				print(status)
+			else
+				print("http.request failed! (invalid url?)")
+			end
+			return false
+		end
+		return true
+	end
+
+	function get_jpg_header_size(data)
+		local res = 417
+		for i, byte in ipairs(data) do
+			if byte == 255 and data[i + 1] == 218 then
+				res = i + 2
+				break
+			end
+		end
+		return res
+	end
+
+	function simple_file_size(bytes)
+		local simplesize = bytes
+		local unit = "B"
+		if bytes >= MEGABYTE then 
+			simplesize = simplesize / MEGABYTE
+			unit = "MB"
+		elseif bytes >= KILOBYTE then
+			simplesize = simplesize / KILOBYTE
+			unit = "KB"
+		end
+		return simplesize, unit
+	end
+
+	local GLITCH_MAX_FILE = MEGABYTE
+	
+	function run(msg, matches)
+		http = require("socket.http")
+		local stamp = os.time()
+
+		-- try checking file size from a HEAD request
+		local default_timeout = http.TIMEOUT
+		http.TIMEOUT = 5
+		local _, code, headers, status = http.request {
+			url = matches[1], 
+			method = "HEAD"
+		}
+		if not handle_http_response(code, status) then
+			return "HTTP request failed or file not found"
+		end
+		
+		if not string.find(headers["content-type"], "jpeg") then
+			-- TODO: convert to jpg?
+			return "Not a JPEG file!"
+		end
+		
+		local filesize = tonumber(headers["content-length"])
+		local response = nil
+		
+		-- if the HEAD request doesn't contain content-length, 
+		-- send a full GET request. the timeout will abort the request 
+		-- after 5 seconds if the file is too large or takes too long
+		-- to download
+		if not filesize then
+			print("No content-length, performing a full request...")
+			response = http.request(matches[1])
+			filesize = #response
+		end
+
+		-- show user-friendly filesize
+		simplesize, unit = simple_file_size(filesize)
+		print("File Size: " .. simplesize .. unit .. " (" .. filesize .. " bytes)")
+		
+		-- check filesize limit
+		if filesize > GLITCH_MAX_FILE then
+			return "Sorry, maximum filesize is " .. GLITCH_MAX_FILE / MEGABYTE .. "MB!"
+		end
+		
+		-- if we previously got the file size through a HEAD request, 
+		-- retrieve the actual data with a full request
+		if not response then
+			response, code, _, status = http.request(matches[1])
+			if not handle_http_response(code, status) then
+				return "HTTP request failed or file not found"
+			end
+		end
+		
+		-- convert to byte array for manipulation
+		local arr = {}
+		response:gsub(".", function(c) table.insert(arr, string.byte(c)) end)
+		response = nil
+		
+		-- skip jpeg header
+		local header_size = get_jpg_header_size(arr)
+		print("JPEG header size: " .. header_size .. " bytes")
+		
+		-- corrupt a set amount of bytes
+		local data_end = #arr - 4
+		local corrupt_count = matches[2]
+		if not corrupt_count then
+			corrupt_count = 20
+		end
+		for i=1, corrupt_count do
+			local index = math.random(header_size, data_end)
+			print("Corrupting byte " .. index)
+			arr[index] = math.floor(math.random() * 255)
+		end
+		
+		-- write glitched jpg
+		print("Writing glitched.jpg")
+		local out = assert(io.open("tmp/"..stamp..".jpg", "wb"))
+		local glitched = ""
+		for i=1, #arr do
+			out:write(string.char(arr[i]))
+		end
+		arr = nil
+		assert(out:close())
+		
+		-- send glitched jpg
+		local receiver = get_receiver(msg)
+		send_photo(receiver, "tmp/"..stamp..".jpg", function() end, function() end)
+		
+		http.TIMEOUT = default_timeout
+	end
+	
+	return {
+		description = "Randomly glitches a JPEG image", 
+		usage = "!glitch [url] [amount]: glitches the JPEG image retrieved from _url_ " .. 
+				"by corrupting _amount_ bytes. Amount is optional and defaults to 20 bytes.", 
+		patterns = {
+			"^/glitch ([^ ]*) ([0-9]*)$", 
+			"^/glitch ([^ ]*)$"
+		}, 
+		run = run
+	}
+end