add initialization callback for filters

scripts/webfinger_allowlist.lua

@@ -1,24 +1,23 @@
-function webfingerCallback(cfg)
+function webfingerInit(cfg)
+    local accounts_set = {}
+    for _, account in ipairs(cfg.accounts) do
+        accounts_set["acct:" .. account] = true
+    end
+    return accounts_set
+end
+
+function webfingerCallback(cfg, accounts_set)
     local args, err = ngx.req.get_uri_args()
     if err == "truncated" then
-      return false, 'uri args too long'
+      return 400, 'uri args too long'
     end
 
     local resource = args['resource']
-    if resource ~= nil then
-      -- TODO this is O(n) but we can make it O(1) by doing a funny and making
-      -- cfg.accounts be transformed into keys in a table
-      --
-      -- this would require us to do some setup() callback as well as
-      -- the request() callback
-      for _, account in ipairs(cfg.accounts) do
-        if resource == account then
-          return true
-        end
-      end
+    if accounts_set[resource] then
+        return nil
+    else
+        return 404, "Couldn't find user"
     end
-
-    return false
 end
 
 return {
@@ -32,6 +31,7 @@ return {
     Useful for small instances.
     ]],
     apiVersion=1,
+    init=webfingerInit,
     callbacks = {
         ['/.well-known/webfinger'] = webfingerCallback
     },