From 8187bedcb66203bb35b267dfeaa36984b3f03cc1 Mon Sep 17 00:00:00 2001
From: Přemysl Janouch <p.janouch@gmail.com>
Date: Tue, 24 Nov 2015 02:26:07 +0100
Subject: degesch: add a URL cleaning Lua plugin

---
 plugins/degesch/utm-filter.lua | 61 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 plugins/degesch/utm-filter.lua

diff --git a/plugins/degesch/utm-filter.lua b/plugins/degesch/utm-filter.lua
new file mode 100644
index 0000000..5fa70c6
--- /dev/null
+++ b/plugins/degesch/utm-filter.lua
@@ -0,0 +1,61 @@
+--
+-- utm-filter.lua: filter out Google Analytics bullshit from URLs
+--
+-- Copyright (c) 2015, Přemysl Janouch <p.janouch@gmail.com>
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+-- SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+-- OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+-- CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+--
+
+-- A list of useless URL parameters that don't affect page function
+local banned = {
+	utm_source   = 1,
+	utm_medium   = 1,
+	utm_term     = 1,
+	utm_content  = 1,
+	utm_campaign = 1,
+}
+
+-- Go through a parameter list and throw out any banned elements
+local do_args = function (args)
+	local filtered = {}
+	for part in args:gmatch ("[^&]+") do
+		if not banned[part:match ("^[^=]*")] then
+			table.insert (filtered, part)
+		end
+	end
+	return table.concat (filtered, "&")
+end
+
+-- Filter parameters in both the query and the fragment part of an URL
+local do_single_url = function (url)
+	return url:gsub ('^([^?#]*)%?([^#]*)', function (start, query)
+		local clean = do_args (query)
+		return #clean > 0 and start .. "?" .. clean or start
+	end, 1):gsub ('^([^#]*)#(.*)', function (start, fragment)
+		local clean = do_args (fragment)
+		return #clean > 0 and start .. "#" .. clean or start
+	end, 1)
+end
+
+local do_text = function (text)
+	return text:gsub ('%f[%g]https?://%g+', do_single_url)
+end
+
+degesch.hook_irc (function (hook, server, line)
+	local start, message = line:match ("^(.* :)(.*)$")
+	return message and start .. do_text (message) or line
+end)
+
+degesch.hook_input (function (hook, buffer, input)
+	return do_text (input)
+end)
-- 
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