BlameOmar/content_negotiation.lua

## content_negotiation.lua
-- Content negotiation for nginx using the lua module
-- Version 0.2
-- ©2013 Omar Stefan Evans

-- Based on the content negotiation script for Lighttpd written by Michael Gorven
-- (http://michael.gorven.za.net/blog/2009/04/13/content-negotiation-lighttpd-lua)
-- It is licensed under a BSD license.

-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

-- Preconditions:
-- (1) try_files failed for $uri and $uri/
-- (2) ngx.shared.types and ngx.shared.mime_type_scores have been created and
--     have been set.  See init.lua

-- Caveats:
-- (1) Currently only negotiates MIME types, not languages

local path = ngx.var.uri

-- path must not refer to a directory
if path:match("[/]$") then
	return ngx.exit(404)
end

local resource = path:match("[^/]*$")
local directory = path:sub(1, path:len() - resource:len())
local directory_fspath = ngx.var.document_root..directory

local lfs = require "lfs"

if lfs.attributes(directory_fspath, "mode") ~= "directory" then
	return ngx.exit(404)
end

local variants = {}
local variant_count = 0
for filename in lfs.dir(directory_fspath) do
	if filename:match(resource.."%.+") then
		local mime_type = ngx.shared.types:get(filename:match(resource.."%.(.+)"))  or "application/octet-stream"
		variants[mime_type] = filename
		variant_count = variant_count + 1
	end
end

if variant_count == 0 then
	return ngx.exit(404)
end

-- Parse Accept header
local accepted_mimetype_scores = {}
if not ngx.req.get_headers()["Accept"] then
	accepted_mimetype_scores["*/*"] = 1.0
else
	for range in ngx.req.get_headers()["Accept"]:gmatch(" *([^,]+) *") do
		accepted_mimetype_scores[range:match("([^;]+)")] = range:match("q *= *([0-9.]+)") or 1.0
	end
end

-- Hack for user agents which don't send quality values for wildcards
if ngx.req.get_headers()["Accept"] and not ngx.req.get_headers()["Accept"]:find("q=") then
	for mimetype, score in pairs(accepted_mimetype_scores) do
		if mimetype == "*/*" then
			accepted_mimetype_scores[mimetype] = 0.01
		elseif mimetype:find("*") then
			accepted_mimetype_scores[mimetype] = 0.02
		end
	end
end

-- Calculate the scores of each variant
local variant_scores = {}
for mimetype, filename in pairs(variants) do
	s1 = accepted_mimetype_scores[mimetype] or accepted_mimetype_scores["*/*"] or 0.0
	s2 = ngx.shared.mime_type_scores:get(mimetype) or ngx.shared.mime_type_scores:get("*/*") or 1.0
	variant_scores[filename] =  s1 * s2
end

-- Choose the variant with the highest score
local highscore = 0.0
local choice = ""
for filename, score in pairs(variant_scores) do
	if score > highscore then
		highscore = score
		choice = filename
	elseif score == highscore and filename < choice then
		choice = filename
	end
end

-- Return '406 Not Acceptable' if no variants match
if choice == "" then
	local html_page_header = [[
<!DOCTYPE html>
<html>
	<head><title>406 Not Acceptable</title></head>
	<body style='text-align: center;'>
		<h1>406 Not Acceptable</h1>
		<p>The requested resource is only capable of generating content not acceptable according to the Accept headers sent in the request.  Alternative content may be available.</p>
		<ul>
	]]

	local html_page_footer = [[
		</ul>
	</body>
</html>
	]]

	ngx.status = 406
	ngx.header.content_type = "text/html; charset=utf-8"
	ngx.print(html_page_header)
	for mimetype, filename in pairs(variants) do
		ngx.print("<li><a href='"..directory..filename.."'>"..directory..filename.."("..mimetype..")</a></li>\n")
	end
	ngx.print(html_page_footer)
end

-- Try to make caches do the right thing
local http_version = ngx.req.http_version()
if http_version >= 1.1 then
	ngx.header.vary = "Accept"
else
	ngx.header.expires = "Thu, 01 Jan 1970 00:00:00 GMT"
end

local res = ngx.location.capture(directory..choice)
ngx.status = res.status
for k,v in pairs(res.header) do
	ngx.header[k] = v
end
ngx.print(res.body)

## init.lua
-- ©2013 Omar Stefan Evans

-- Based on the content negotiation script for Lighttpd written by Michael Gorven
-- (http://michael.gorven.za.net/blog/2009/04/13/content-negotiation-lighttpd-lua)
-- It is licensed under a BSD license.

-- Permission is hereby granted, free of charge, to any person obtaining a copy of
-- this software and associated documentation files (the "Software"), to deal in
-- the Software without restriction, including without limitation the rights to
-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-- of the Software, and to permit persons to whom the Software is furnished to do
-- so, subject to the following conditions:
--
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

function load_nginx_mime_types(file_absolute_path)
  local types = {}
	local f = io.open(file_absolute_path)
	local t = ""
	if f ~= nil then
		t = f:read("*all")
	end
	io.close(f)

	t = t:match("types%s+{(.-)}")
	t = t:gsub("#.-\n", "\n")

	for s in t:gmatch("%s*([^;]+)%s*") do
		local mimetype = s:match("[%S]+/[%S]+")
		if mimetype ~= nil then
			for extension in s:sub(mimetype:len() + 1):gmatch("%S+") do
				types[extension] = mimetype
			end
		end
	end

	return types
end

local mime_type_scores = {
	["application/xhtml+xml"] = 1.0,
	["text/html"] = 0.99,
	["application/xml"] = 0.98,
	["text/plain"] = 0.95,
	["image/svg+xml"] = 1.0,
	["image/png"] = 0.99,
	["image/gif"] = 0.98,
	["image/jpeg"] = 0.98,
	["*/*"] = 0.9,
}

for k,v in pairs(load_nginx_mime_types("/etc/nginx/mime.types")) do
        ngx.shared.types:set(k, v)
end

local scores = ngx.shared.mime_type_scores
for k,v in pairs(mime_type_scores) do
	ngx.shared.mime_type_scores:set(k, v)
end

## nginx.conf
http {

...

    lua_shared_dict  types 10m;
    lua_shared_dict  mime_type_scores 10m;
    init_by_lua_file lua/init.lua;

...

    location / {
        try_files                  $uri $uri/ @content_negotiation;
    }

    location @content_negotiation {
         content_by_lua_file       lua/content_negotiation.lua;
    }

...

}
	-- Content negotiation for nginx using the lua module
	-- Version 0.2
	-- ©2013 Omar Stefan Evans

	-- Based on the content negotiation script for Lighttpd written by Michael Gorven
	-- (http://michael.gorven.za.net/blog/2009/04/13/content-negotiation-lighttpd-lua)
	-- It is licensed under a BSD license.

	-- Permission is hereby granted, free of charge, to any person obtaining a copy of
	-- this software and associated documentation files (the "Software"), to deal in
	-- the Software without restriction, including without limitation the rights to
	-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
	-- of the Software, and to permit persons to whom the Software is furnished to do
	-- so, subject to the following conditions:
	--
	-- The above copyright notice and this permission notice shall be included in all
	-- copies or substantial portions of the Software.
	--
	-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	-- SOFTWARE.

	-- Preconditions:
	-- (1) try_files failed for $uri and $uri/
	-- (2) ngx.shared.types and ngx.shared.mime_type_scores have been created and
	-- have been set. See init.lua

	-- Caveats:
	-- (1) Currently only negotiates MIME types, not languages

	local path = ngx.var.uri

	-- path must not refer to a directory
	if path:match("[/]$") then
	return ngx.exit(404)
	end

	local resource = path:match("[^/]*$")
	local directory = path:sub(1, path:len() - resource:len())
	local directory_fspath = ngx.var.document_root..directory

	local lfs = require "lfs"

	if lfs.attributes(directory_fspath, "mode") ~= "directory" then
	return ngx.exit(404)
	end

	local variants = {}
	local variant_count = 0
	for filename in lfs.dir(directory_fspath) do
	if filename:match(resource.."%.+") then
	local mime_type = ngx.shared.types:get(filename:match(resource.."%.(.+)")) or "application/octet-stream"
	variants[mime_type] = filename
	variant_count = variant_count + 1
	end
	end

	if variant_count == 0 then
	return ngx.exit(404)
	end

	-- Parse Accept header
	local accepted_mimetype_scores = {}
	if not ngx.req.get_headers()["Accept"] then
	accepted_mimetype_scores["/"] = 1.0
	else
	for range in ngx.req.get_headers()["Accept"]:gmatch(" ([^,]+) ") do
	accepted_mimetype_scores[range:match("([^;]+)")] = range:match("q = ([0-9.]+)") or 1.0
	end
	end

	-- Hack for user agents which don't send quality values for wildcards
	if ngx.req.get_headers()["Accept"] and not ngx.req.get_headers()["Accept"]:find("q=") then
	for mimetype, score in pairs(accepted_mimetype_scores) do
	if mimetype == "/" then
	accepted_mimetype_scores[mimetype] = 0.01
	elseif mimetype:find("*") then
	accepted_mimetype_scores[mimetype] = 0.02
	end
	end
	end

	-- Calculate the scores of each variant
	local variant_scores = {}
	for mimetype, filename in pairs(variants) do
	s1 = accepted_mimetype_scores[mimetype] or accepted_mimetype_scores["/"] or 0.0
	s2 = ngx.shared.mime_type_scores:get(mimetype) or ngx.shared.mime_type_scores:get("/") or 1.0
	variant_scores[filename] = s1 * s2
	end

	-- Choose the variant with the highest score
	local highscore = 0.0
	local choice = ""
	for filename, score in pairs(variant_scores) do
	if score > highscore then
	highscore = score
	choice = filename
	elseif score == highscore and filename < choice then
	choice = filename
	end
	end

	-- Return '406 Not Acceptable' if no variants match
	if choice == "" then
	local html_page_header = [[
	<!DOCTYPE html>
	<html>
	<head><title>406 Not Acceptable</title></head>
	<body style='text-align: center;'>
	<h1>406 Not Acceptable</h1>
	<p>The requested resource is only capable of generating content not acceptable according to the Accept headers sent in the request. Alternative content may be available.</p>
	<ul>
	]]

	local html_page_footer = [[
	</ul>
	</body>
	</html>
	]]

	ngx.status = 406
	ngx.header.content_type = "text/html; charset=utf-8"
	ngx.print(html_page_header)
	for mimetype, filename in pairs(variants) do
	ngx.print("<li><a href='"..directory..filename.."'>"..directory..filename.."("..mimetype..")</a></li>\n")
	end
	ngx.print(html_page_footer)
	end

	-- Try to make caches do the right thing
	local http_version = ngx.req.http_version()
	if http_version >= 1.1 then
	ngx.header.vary = "Accept"
	else
	ngx.header.expires = "Thu, 01 Jan 1970 00:00:00 GMT"
	end

	local res = ngx.location.capture(directory..choice)
	ngx.status = res.status
	for k,v in pairs(res.header) do
	ngx.header[k] = v
	end
	ngx.print(res.body)
	http {

	...

	lua_shared_dict types 10m;
	lua_shared_dict mime_type_scores 10m;
	init_by_lua_file lua/init.lua;

	...

	location / {
	try_files $uri $uri/ @content_negotiation;
	}

	location @content_negotiation {
	content_by_lua_file lua/content_negotiation.lua;
	}

	...

	}