Port support for spell bifurcated crits (#9940)

* Port support for spell bifurcated crits

* Fix breakdown not showing and tidy up code

* Fix breakdown ordering

* Fix breakdown + move tests

---------

Co-authored-by: LocalIdentity <localidentity2@gmail.com>

Author: vaisest

spec/System/TestBifurcatedCrit_spec.lua

@@ -0,0 +1,90 @@
+describe("Bifurcated critical strikes", function()
+	local function setupBifurcate(socketGroup, bifurcate, lucky, extremeLuck, useDefaultCritMultiplier)
+		newBuild()
+		build.itemsTab:CreateDisplayItemFromRaw([[
+				New Item
+				Imbued Wand
+				Quality: 0
+				100% reduced lightning damage
+				adds 1 to 1 physical damage to spells
+				nearby enemies have 100% less armour
+			]])
+		build.itemsTab:AddDisplayItem()
+		runCallback("OnFrame")
+		build.skillsTab:PasteSocketGroup(socketGroup)
+		runCallback("OnFrame")
+
+		build.configTab.input.customMods = "+44% to critical hit chance\n"
+			.. (bifurcate and "spell critical strike chance bifurcates\n" or "")
+			.. (lucky and "your critical strike chance is lucky\n" or "")
+			.. (extremeLuck and "your lucky or unlucky effects use the best or worst from three rolls instead of two\n" or "")
+			.. (useDefaultCritMultiplier and "" or "your critical strike multiplier is 1000000%\n")
+		build.configTab:BuildModList()
+		runCallback("OnFrame")
+
+		return build.calcsTab.mainOutput
+	end
+
+	it("calculates bifurcated critical hit damage", function()
+		local normalOutput = setupBifurcate("Spark 1/0  1")
+		assert.are.equals(50, normalOutput.CritChance)
+		assert.are.equals(10000, normalOutput.CritMultiplier)
+		assert.are.equals(10001, normalOutput.AverageHit)
+
+		local bifurcateOutput = setupBifurcate("Spark 1/0  1", true)
+		assert.are.equals(50, bifurcateOutput.PreBifurcateCritChance)
+		assert.are.equals(75, bifurcateOutput.CritChance)
+		assert.are.near(1 + 1 / 3, bifurcateOutput.CritBifurcates, 10 ^ -9)
+		assert.are.equals(20000, bifurcateOutput.AverageHit)
+
+		local mysticalInfusion = build.spec.nodes[1945]
+		mysticalInfusion.alloc = true
+		build.spec.allocNodes[mysticalInfusion.id] = mysticalInfusion
+		build.configTab.input.customMods = "+44% to critical hit chance\nyour critical strike multiplier is 1000000%\n"
+		build.configTab:BuildModList()
+		build.buildFlag = true
+		runCallback("OnFrame")
+		assert.are.equals(35, build.calcsTab.mainOutput.PreBifurcateCritChance)
+		assert.are.near(57.75, build.calcsTab.mainOutput.CritChance, 10 ^ -9)
+	end)
+
+	it("accounts for guaranteed critical strikes", function()
+		local normalOutput = setupBifurcate("Spark 1/0  1", nil, nil, nil, true)
+		assert.are.equals(1.5, normalOutput.CritMultiplier)
+
+		local markedOutput = setupBifurcate("Spark 1/0  1\nAssassin's Mark 1/0  1", nil, nil, nil, true)
+		assert.are.equals(1.8, markedOutput.CritMultiplier)
+
+		local bifurcateOutput = setupBifurcate("Spark 1/0  1\nAssassin's Mark 1/0  1", true, nil, nil, true)
+		assert.are.equals(2.07, floor(bifurcateOutput.CritMultiplier, 2))
+
+		local tendrilsOutput = setupBifurcate("Lightning Tendrils 1/0  1", true)
+		assert.are.equals(50, tendrilsOutput.PreBifurcateCritChance)
+		assert.are.near(100 / 3 + (200 / 3) * 0.75, tendrilsOutput.CritChance, 10 ^ -6)
+		assert.are.equals(1.2, tendrilsOutput.CritBifurcates)
+
+		local eccentricityOutput = setupBifurcate("Lightning Tendrils of Eccentricity 1/0  1", true)
+		assert.are.equals(50, eccentricityOutput.PreBifurcateCritChance)
+		assert.are.equals(80, eccentricityOutput.CritChance)
+		assert.are.equals(1.25, eccentricityOutput.CritBifurcates)
+	end)
+
+	it("applies lucky rolls independently", function()
+		local luckyOutput = setupBifurcate("Spark 1/0  1", false, true)
+		assert.are.equals(75, luckyOutput.CritChance)
+		assert.are.equals(10000, luckyOutput.CritMultiplier)
+		assert.are.equals(15000.5, luckyOutput.AverageHit)
+
+		local bifurcateOutput = setupBifurcate("Spark 1/0  1", true, true)
+		assert.are.equals(75, bifurcateOutput.PreBifurcateCritChance)
+		assert.are.equals(93.75, bifurcateOutput.CritChance)
+		assert.are.equals(1.6, bifurcateOutput.CritBifurcates)
+		assert.are.equals(29999, bifurcateOutput.AverageHit)
+
+		local extremeLuckOutput = setupBifurcate("Spark 1/0  1", true, true, true)
+		assert.are.equals(87.5, extremeLuckOutput.PreBifurcateCritChance)
+		assert.are.equals(98.4375, extremeLuckOutput.CritChance)
+		assert.are.equals(1 + 0.875 ^ 2 / 0.984375, extremeLuckOutput.CritBifurcates)
+		assert.are.near(34998.5, extremeLuckOutput.AverageHit, 0.01)
+	end)
+end)

src/Modules/CalcOffence.lua

@@ -2901,6 +2901,7 @@ function calcs.offence(env, actor, activeSkill)
 
 			if critOverride == 100 then
 				output.PreEffectiveCritChance = 100
+				output.PreBifurcateCritChance = 100
 				output.CritChance = 100
 			else
 				local base = 0
@@ -2935,8 +2936,13 @@ function calcs.offence(env, actor, activeSkill)
 						output.CritChance = (1 - (1 - output.CritChance / 100) ^ (critRolls + 1)) * 100
 					end
 				end
+				output.PreBifurcateCritChance = output.CritChance
+				local preBifurcateCritChance = output.CritChance
+				if env.mode_effective and skillModList:Flag(cfg, "BifurcateCrit") then
+					output.CritChance = (1 - (1 - output.CritChance / 100) ^ 2) * 100
+				end
 				local preHitCheckCritChance = output.CritChance
-				local preSkillUseCritChance= output.CritChance
+				local preSkillUseCritChance = output.CritChance
 				if env.mode_effective then
 					if skillModList:Flag(skillCfg, "Every3UseCrit") then
 						output.CritChance = (2 * output.CritChance + 100) / 3
@@ -2966,7 +2972,7 @@ function calcs.offence(env, actor, activeSkill)
 						local overCap = preCapCritChance - 100
 						t_insert(breakdown.CritChance, s_format("Crit is overcapped by %.2f%% (%d%% increased Critical Strike Chance)", overCap, overCap / more / (baseCrit + base) * 100))
 					end
-					if env.mode_effective and (critRolls ~= 0 or skillModList:Flag(skillCfg, "Every3UseCrit") or skillModList:Flag(skillCfg, "Every5UseCrit")) then
+					if env.mode_effective then
 						if critRolls ~= 0 then
 							if skillModList:Flag(skillCfg, "Unexciting") then
 								t_insert(breakdown.CritChance, "Crit Chance is Unexciting:")
@@ -2975,14 +2981,22 @@ function calcs.offence(env, actor, activeSkill)
 								t_insert(breakdown.CritChance, "Crit Chance is Lucky:")
 								t_insert(breakdown.CritChance, s_format("1 - (1 - %.4f)^ %d", preLuckyCritChance / 100, critRolls + 1))
 							end
+							t_insert(breakdown.CritChance, s_format("= %.2f%%", preBifurcateCritChance))
+						end
+						if skillModList:Flag(cfg, "BifurcateCrit") then
+							t_insert(breakdown.CritChance, "Critical Strike Bifurcates:")
+							t_insert(breakdown.CritChance, s_format("1 - (1 - %.4f) x (1 - %.4f)", preBifurcateCritChance / 100, preBifurcateCritChance / 100))
+							t_insert(breakdown.CritChance, s_format("= %.2f%%", preSkillUseCritChance))
 						end
 						if skillModList:Flag(skillCfg, "Every3UseCrit") then
 							t_insert(breakdown.CritChance, s_format("+ %.2f%% ^8(crit every 3rd use)", (2 * preSkillUseCritChance + 100) / 3 - preSkillUseCritChance))
 						end
 						if skillModList:Flag(skillCfg, "Every5UseCrit") then
 							t_insert(breakdown.CritChance, s_format("+ %.2f%% ^8(crit every 5th use)", (4 * preSkillUseCritChance + 100) / 5 - preSkillUseCritChance))
 						end
-						t_insert(breakdown.CritChance, s_format("= %.2f%%", preHitCheckCritChance))
+						if skillModList:Flag(skillCfg, "Every3UseCrit") or skillModList:Flag(skillCfg, "Every5UseCrit") then
+							t_insert(breakdown.CritChance, s_format("= %.2f%%", preHitCheckCritChance))
+						end
 					end
 					if env.mode_effective and output.AccuracyHitChance < 100 then
 						t_insert(breakdown.CritChance, "Crit confirmation roll:")
@@ -3014,6 +3028,42 @@ function calcs.offence(env, actor, activeSkill)
 						}
 					end
 				end
+				-- if crit bifurcates are enabled, roll for crit twice and add multiplier for each
+				local critOverride = skillModList:Override(cfg, "CritChance")
+				if env.mode_effective and skillModList:Flag(cfg, "BifurcateCrit") and output.PreBifurcateCritChance and not (critOverride == 100) then
+					-- get crit chance and calculate odds of critting twice
+					local critChancePercentage = output.PreBifurcateCritChance
+					local bifurcateMultiChance = (critChancePercentage ^ 2) / 100
+					local effectiveCritChance = output.CritChance
+					local bifurcateUseChance = 1
+					-- Guaranteed crit uses do not roll crit chance and therefore cannot bifurcate
+					if skillModList:Flag(skillCfg, "Every3UseCrit") then
+						bifurcateUseChance = bifurcateUseChance * 2 / 3
+					end
+					if skillModList:Flag(skillCfg, "Every5UseCrit") then
+						bifurcateUseChance = bifurcateUseChance * 4 / 5
+					end
+					bifurcateMultiChance = bifurcateMultiChance * bifurcateUseChance
+					local conditionalBifurcateChance = effectiveCritChance > 0 and bifurcateMultiChance / effectiveCritChance or 0
+					output.CritBifurcates = 1 + conditionalBifurcateChance
+					local damageBonus = extraDamage
+					local bifurcatedBonus = conditionalBifurcateChance * extraDamage
+					if breakdown then
+						breakdown.CritBifurcates = {
+							s_format("%.2f%% ^8(pre-bifurcate crit chance)", critChancePercentage),
+							s_format("x %.2f%%", critChancePercentage),
+						}
+						if bifurcateUseChance < 1 then
+							t_insert(breakdown.CritBifurcates, s_format("x %.2f%% ^8(uses that can bifurcate)", bifurcateUseChance * 100))
+						end
+						t_insert(breakdown.CritBifurcates, s_format("= %.2f%% ^8(chance both crit rolls succeed)", bifurcateMultiChance))
+						t_insert(breakdown.CritBifurcates, s_format("/ %.2f%% ^8(effective crit chance)", effectiveCritChance))
+						t_insert(breakdown.CritBifurcates, s_format("= %.2f ^8(crit Bifurcates effect)", 1 + conditionalBifurcateChance))
+					end
+					extraDamage = damageBonus + bifurcatedBonus
+					-- mod doesn't affect output and is purely descriptive
+					skillModList:NewMod("CritMultiplier", "MORE", floor(conditionalBifurcateChance * 100, 2), "Bifurcated Crit Damage Bonus", ModFlag.Hit)
+				end
 				output.CritMultiplier = 1 + m_max(0, extraDamage)
 			end
 			local critChancePercentage = output.CritChance / 100

src/Modules/CalcSections.lua

@@ -527,6 +527,10 @@ return {
 		{ label = "Player modifiers", modName = "CritMultiplier", cfg = "skill" }, 
 		{ label = "Enemy modifiers", modName = "SelfCritMultiplier", enemy = true }, 
 	}, },
+	{ label = "Crit Bifurcates", notFlag = "attack", haveOutput = "CritBifurcates", { format = "x {2:output:CritBifurcates}",
+		{ breakdown = "CritBifurcates" },
+		{ label = "Player modifiers", modName = "BifurcateCrit", cfg = "skill" },
+	}, },
 	{ label = "Crit Effect Mod", notFlag = "attack", { format = "x {3:output:CritEffect}", { breakdown = "CritEffect" }, }, },
 	-- Main Hand
 	{ label = "MH Inc. Crit Chance", bgCol = colorCodes.MAINHANDBG, flag = "weapon1Attack", { format = "{0:mod:1,2}%", 

src/Modules/ModParser.lua

@@ -3408,6 +3408,7 @@ local specialModList = {
 	["minion critical strikes do not deal extra damage"] = { mod("MinionModifier", "LIST", { mod = flag("NoCritMultiplier") }) },
 	["lightning damage with non%-critical strikes is lucky"] = { flag("LightningNoCritLucky") },
 	["your damage with critical strikes is lucky"] = { flag("CritLucky") },
+	["spell critical strike chance bifurcates"] = { flag("BifurcateCrit", nil, ModFlag.Spell) },
 	["critical strikes deal no damage"] = { mod("Damage", "MORE", -100, { type = "Condition", var = "CriticalStrike" }) },
 	["critical strike chance is increased by uncapped lightning resistance"] = { flag("CritChanceIncreasedByUncappedLightningRes") },
 	["critical strike chance is increased by lightning resistance"] = { flag("CritChanceIncreasedByLightningRes") },