Diff

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_report_affiliations/traits.lib.lua	Fri Nov 22 19:05:49 2024 +0000
@@ -0,0 +1,58 @@
+local known_traits = {};
+
+local function trait_added(event)
+	local trait = event.item;
+	local name = trait.name;
+	if known_traits[name] then return; end
+
+	known_traits[name] = trait.probabilities;
+end
+
+local function trait_removed(event)
+	local trait = event.item;
+	known_traits[trait.name] = nil;
+end
+
+module:handle_items("account-trait", trait_added, trait_removed);
+
+local function bayes_probability(prior, prob_given_true, prob_given_false)
+	local numerator = prob_given_true * prior;
+	local denominator = numerator + prob_given_false * (1 - prior);
+	return numerator / denominator;
+end
+
+local function prob_is_bad(traits, prior)
+	prior = prior or 0.50;
+
+	for trait, state in pairs(traits) do
+		local probabilities = known_traits[trait];
+		if probabilities then
+			if state then
+				prior = bayes_probability(
+					prior,
+					probabilities.prob_bad_true,
+					probabilities.prob_bad_false
+				);
+			else
+				prior = bayes_probability(
+					prior,
+					1 - probabilities.prob_bad_true,
+					1 - probabilities.prob_bad_false
+				);
+			end
+		end
+	end
+
+	return prior;
+end
+
+local function get_probability_bad(username, prior)
+	local user_traits = {};
+	module:fire_event("get-account-traits", { username = username, host = module.host, traits = user_traits });
+	local result = prob_is_bad(user_traits, prior);
+	return result;
+end
+
+return {
+	get_probability_bad = get_probability_bad;
+};