Reduced dynamic budget at low player count (#28300)

* Reduced dynamic budget at low player count

* Tests

* One linty boy

* I was, uh, making sure the test worked. That definitely wasn't a typo. <.<

code/game/gamemodes/dynamic/dynamic.dm

@@ -3,7 +3,7 @@ GLOBAL_LIST_EMPTY(dynamic_forced_rulesets)
 /datum/game_mode/dynamic
 	name = "Dynamic"
 	config_tag = "dynamic"
-	required_players = 10
+	required_players = 0
 	/// Non-implied rulesets in play
 	var/list/datum/ruleset/rulesets = list()
 	/// Implied rulesets that are in play
@@ -26,9 +26,27 @@ GLOBAL_LIST_EMPTY(dynamic_forced_rulesets)
 			possible_rulesets |= ruleset.implied_ruleset_type.name
 	to_chat(world, "<b>Possible Rulesets:</b> [english_list(possible_rulesets)]")
 
+/// Calculates the dynamic budget based on the number of players in the round
+/datum/game_mode/dynamic/proc/calculate_budget(players)
+	switch(players)
+		if(0 to 4)
+			// Flat budget of 7
+			return 7
+		if(5 to 20)
+			// +0.5 budget each for players 5-20
+			// Cumulative total at 20 players: 15
+			return 7 + 0.5 * (players - 4)
+		if(21 to 30)
+			// +1.5 budget each for players 21 to 30
+			// Cumulative total at 30 players: 30
+			return 15 + 1.5 * (players - 20)
+		else
+			// +1 budget each for players 31+, so just player count.
+			return players
+
 /datum/game_mode/dynamic/proc/allocate_ruleset_budget()
 	var/ruleset_budget = text2num(GLOB.dynamic_forced_rulesets["budget"] || pickweight(list("0" = 3, "1" = 8, "2" = 12, "3" = 3)))
-	antag_budget = num_players()
+	antag_budget = calculate_budget(num_players())
 	log_dynamic("Allocated gamemode budget: [ruleset_budget]")
 	var/list/possible_rulesets = list()
 	for(var/datum/ruleset/ruleset as anything in subtypesof(/datum/ruleset))

code/tests/game_tests.dm

@@ -21,6 +21,7 @@
 #include "test_components.dm"
 #include "test_config_sanity.dm"
 #include "test_crafting_lists.dm"
+#include "test_dynamic_budget.dm"
 #include "test_elements.dm"
 #include "test_emotes.dm"
 #include "test_init_sanity.dm"

code/tests/test_dynamic_budget.dm

@@ -0,0 +1,15 @@
+/datum/game_test/dynamic_budget/Run()
+	var/datum/game_mode/dynamic/dynamic = new()
+
+	// If calculate_budgets updates, and these need to change to match, the pattern is to put an assert at the beginning and end of each distinct range of players (with 100 here standing in for a non-existent upper limit).
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(0), 7, "Flat budget incorrect.")
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(4), 7, "Flat budget incorrect.")
+
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(5), 7.5, "Lowpop budget incorrect.")
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(20), 15, "Lowpop budget incorrect.")
+
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(21), 16.5, "Midpop budget incorrect.")
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(30), 30, "Midpop budget incorrect.")
+
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(31), 31, "Highpop budget incorrect.")
+	TEST_ASSERT_EQUAL(dynamic.calculate_budget(100), 100, "Highpop budget incorrect.")