feat: colour opponents' mods by server mod policy

Receive the server's banned/approved mod policy (setModPolicy action) and colour
each opponent mod in the lobby list: red (banned), green (approved), white
(unknown). Unknown stays white — we never auto-flag what we can't classify.

- matchmaking.lua: classify_mod / get_banned_mods match the policy case- and
  punctuation-insensitively, with version-prefix matching and a dash-boundary
  heuristic so a glued "id-version" wire string still resolves (e.g.
  "Saturn-0.2.2-E"). The approved list mirrors banned.
- action_handlers.lua: setModPolicy handler sets MP.BANNED_MODS / MP.APPROVED_MODS.
- lobby.lua: colour mod rows via classify_mod.
- start_ready_button.lua: banned warning text uses light/white (readable on the
  lobby background).
- core.lua: MP.APPROVED_MODS default fallback.

Pairs with the server (BalatroMultiplayerAPI-Server), which sends the policy on
lobby join, and the website (www), where staff manage the lists.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ChronoFinale

core.lua

@@ -11,6 +11,16 @@ MP.BANNED_MODS = {
 	["FantomsPreview"] = true,
 }
 
+-- Approved (allowed) mods, shown green in the lobby mod list. Mods in neither
+-- list show white (unknown). Both lists are normally replaced by the server's
+-- setModPolicy message on connect; these are fallbacks for older/offline servers.
+MP.APPROVED_MODS = {
+	["Lovely"] = true,
+	["Steamodded"] = true,
+	["Multiplayer"] = true,
+	["Preview"] = true,
+}
+
 MP.LOBBY = {
 	connected = false,
 	temp_code = "",

lib/matchmaking.lua

@@ -245,33 +245,97 @@ function MP.UTILS.version_mismatches()
 	return results
 end
 
+-- Mod-policy keys are matched case- and punctuation-insensitively, so staff can
+-- key the banned/approved lists by display name (e.g. "Joker Display") and still
+-- match the wire-reported SMODS id (e.g. "JokerDisplay" or "jokerdisplay").
+function MP.UTILS.normalize_mod_name(name)
+	if type(name) ~= "string" then return "" end
+	return (name:lower():gsub("[^%w]", ""))
+end
+
+-- Cache the normalized index per source table; keyed weakly by table identity so
+-- it auto-refreshes when the server replaces MP.BANNED_MODS / MP.APPROVED_MODS.
+local _norm_index_cache = setmetatable({}, { __mode = "k" })
+local function normalized_index(map)
+	if type(map) ~= "table" then return {} end
+	local cached = _norm_index_cache[map]
+	if cached then return cached end
+	local idx = {}
+	for k, v in pairs(map) do
+		idx[MP.UTILS.normalize_mod_name(k)] = v
+	end
+	_norm_index_cache[map] = idx
+	return idx
+end
+
+-- A rule version matches the wire version on exact string OR on the X.Y.Z
+-- (clean semver) prefix, so a rule like "1.0.0" still matches "1.0.0~BETA-1620a"
+-- or "1.0.0-DEV". version_prefix is defined earlier in this file.
+local function version_matches(rule_version, version)
+	if version == rule_version then return true end
+	local rp = MP.UTILS.version_prefix(rule_version)
+	local vp = MP.UTILS.version_prefix(version)
+	return rp ~= nil and rp == vp
+end
+
+-- A rule is true (any version), an exact version string, or a list of versions.
+local function rule_matches(rule, version)
+	if rule == nil then return false end
+	if type(rule) == "boolean" then return rule end
+	if type(rule) == "string" then return version_matches(rule, version) end
+	if type(rule) == "table" then
+		for _, v in ipairs(rule) do
+			if version_matches(v, version) then return true end
+		end
+	end
+	return false
+end
+
+-- A version-like segment starts with a digit, 'v', or '~' (e.g. "0.2.2", "v1",
+-- "~BETA"). Used to guess where a mod id ends and its version begins.
+local function looks_like_version(seg)
+	return seg ~= nil and seg:match("^[%dv~]") ~= nil
+end
+
+-- Matches a parsed mod entry against a normalized index. A mod's version can
+-- contain dashes (e.g. Saturn "0.2.2-E-ALPHA"), and parse_modlist splits on the
+-- last dash, so mod_name can arrive with version fragments glued on
+-- ("Saturn-0.2.2-E"). Walk the dash-delimited prefixes and treat a prefix as the
+-- id only when the next segment looks like a version — so "Saturn|0.2.2" splits
+-- but a genuinely dashed id like "Saturn-Extras|1.0" stays intact. First (shortest)
+-- valid match wins. Heuristic, not airtight; special-case real collisions if any
+-- ever show up.
+local function index_match(idx, mod_name, mod_version)
+	local segs = {}
+	for seg in tostring(mod_name):gmatch("[^%-]+") do
+		segs[#segs + 1] = seg
+	end
+	local candidate
+	for i = 1, #segs do
+		candidate = candidate and (candidate .. "-" .. segs[i]) or segs[i]
+		if segs[i + 1] == nil or looks_like_version(segs[i + 1]) then
+			if rule_matches(idx[MP.UTILS.normalize_mod_name(candidate)], mod_version) then return true end
+		end
+	end
+	return false
+end
+
+-- Returns "banned" | "approved" | "unknown". Banned takes precedence.
+function MP.UTILS.classify_mod(mod_name, mod_version)
+	if index_match(normalized_index(MP.BANNED_MODS), mod_name, mod_version) then return "banned" end
+	if index_match(normalized_index(MP.APPROVED_MODS), mod_name, mod_version) then return "approved" end
+	return "unknown"
+end
+
 function MP.UTILS.get_banned_mods(mods)
 	local banned_mods = {}
 	if not mods then return banned_mods end
 
+	local idx = normalized_index(MP.BANNED_MODS)
 	for mod_name, mod_version in pairs(mods) do
-		local ban_info = MP.BANNED_MODS[mod_name]
-		local is_banned = false
-
-		if ban_info then
-			if type(ban_info) == "boolean" then
-				-- Old format: ban all versions
-				is_banned = ban_info
-			elseif type(ban_info) == "string" then
-				-- New format: ban specific version
-				is_banned = (mod_version == ban_info)
-			elseif type(ban_info) == "table" then
-				-- Table format: ban multiple specific versions
-				for _, banned_version in ipairs(ban_info) do
-					if mod_version == banned_version then
-						is_banned = true
-						break
-					end
-				end
-			end
+		if index_match(idx, mod_name, mod_version) then
+			table.insert(banned_mods, mod_name)
 		end
-
-		if is_banned then table.insert(banned_mods, mod_name) end
 	end
 
 	return banned_mods

networking/action_handlers.lua

@@ -1319,6 +1319,15 @@ local last_game_seed = nil
 
 local function noop() end
 
+-- Server-authoritative mod policy. The server sends this on connect (and again
+-- via the admin setModPolicy command), overriding the hardcoded fallbacks in
+-- core.lua so staff can update bans/approvals without a mod release. If the
+-- server never sends it (older server), the core.lua defaults remain.
+local function action_set_mod_policy(p)
+	if type(p.banned) == "table" then MP.BANNED_MODS = p.banned end
+	if type(p.approved) == "table" then MP.APPROVED_MODS = p.approved end
+end
+
 local HANDLERS = {
 	connected = action_connected,
 	version = action_version,
@@ -1329,6 +1338,7 @@ local HANDLERS = {
 	enemyDisconnected = action_enemyDisconnected,
 	enemyReconnected = action_enemyReconnected,
 	lobbyInfo = action_lobbyInfo,
+	setModPolicy = action_set_mod_policy,
 	startGame = action_start_game,
 	startBlind = action_start_blind,
 	enemyInfo = action_enemy_info,

ui/lobby/lobby.lua

@@ -236,7 +236,9 @@ function MP.UI.modlist_to_view(mods, text_colour)
 
 	local function add_mod_row(mod)
 		local mod_name, mod_version = MP.UTILS.resolve_mod_name_and_version(mod.name, mod.version)
-		local color = MP.BANNED_MODS[mod.name] and G.C.RED or text_colour
+		-- red = banned, green = approved, default (white) = unknown
+		local class = MP.UTILS.classify_mod(mod.name, mod_version)
+		local color = (class == "banned" and G.C.RED) or (class == "approved" and G.C.GREEN) or text_colour
 		table.insert(t, {
 			n = G.UIT.R,
 			config = {

ui/lobby/start_ready_button.lua

@@ -81,7 +81,7 @@ local function get_warnings()
 	if #host_banned_mods > 0 or #guest_banned_mods > 0 then
 		table.insert(warnings, {
 			localize("k_warning_banned_mods"),
-			G.C.RED,
+			G.C.UI.TEXT_LIGHT, -- white reads better than red on the lobby background
 			0.4,
 		})
 	end