+-- Copyright (C) 2019 all contributors <meta@public-inbox.org>
+-- License: GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+--
+-- This filter accesses the PublicInbox::WwwHighlight PSGI endpoint
+-- (see examples/highlight.psgi)
+--
+-- Dependencies: lua-http
+--
+-- disclaimer: written by someone who does not know Lua.
+--
+-- This requires cgit linked with Lua
+-- Usage (in your cgitrc(5) config file):
+--
+-- source-filter=lua:/path/to/this/script.lua
+-- about-filter=lua:/path/to/this/script.lua
+--
+local wwwhighlight_url = 'http://127.0.0.1:9090/'
+local req_timeout = 10
+local too_big = false
+
+-- match $PublicInbox::HTTP::MAX_REQUEST_BUFFER
+local max_len = 10 * 1024 * 1024
+
+-- about-filter needs surrounding <pre> tags if all we do is
+-- highlight and linkify
+local pre = true
+
+function filter_open(...)
+ req_body = ""
+
+ -- detect when we're used in an about-filter
+ local repo_url = os.getenv('CGIT_REPO_URL')
+ if repo_url then
+ local path_info = os.getenv('PATH_INFO')
+ rurl = path_info:match("^/(.+)/about/?$")
+ pre = rurl == repo_url
+ end
+
+ -- hand filename off for language detection
+ local fn = select(1, ...)
+ if fn then
+ local http_util = require 'http.util'
+ wwwhighlight_url = wwwhighlight_url .. http_util.encodeURI(fn)
+ end
+end
+
+-- try to buffer the entire source in memory
+function filter_write(str)
+ if too_big then
+ html(str)
+ elseif (req_body:len() + str:len()) > max_len then
+ too_big = true
+ req_body = ""
+ html(req_body)
+ html(str)
+ else
+ req_body = req_body .. str
+ end
+end
+
+function fail(err)
+ io.stderr:write(tostring(err), "\n")
+ if pre then
+ html("<pre>")
+ end
+ html_txt(req_body)
+ if pre then
+ html("</pre>")
+ end
+ return 1
+end
+
+function filter_close()
+ if too_big then
+ return 0
+ end
+ local request = require 'http.request'
+ local req = request.new_from_uri(wwwhighlight_url)
+ req.headers:upsert(':method', 'PUT')
+ req:set_body(req_body)
+
+ -- don't wait for 100-Continue message from the PSGI app
+ req.headers:delete('expect')
+
+ local headers, stream = req:go(req_timeout)
+ if headers == nil then
+ return fail(stream)
+ end
+ local status = headers:get(':status')
+ if status ~= '200' then
+ return fail('status ' .. status)
+ end
+ local body, err = stream:get_body_as_string()
+ if not body and err then
+ return fail(err)
+ end
+ if pre then
+ html("<pre>")
+ end
+ html(body)
+ if pre then
+ html("</pre>")
+ end
+ return 0
+end