Implement blocking death nukes using shields

lua/ShieldAbsorptionValues.lua

@@ -0,0 +1,33 @@
+--**********************************************************************************
+--** Copyright (c) 2024 FAForever
+--**
+--** Permission is hereby granted, free of charge, to any person obtaining a copy
+--** of this software and associated documentation files (the "Software"), to deal
+--** in the Software without restriction, including without limitation the rights
+--** to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+--** copies of the Software, and to permit persons to whom the Software is
+--** furnished to do so, subject to the following conditions:
+--**
+--** The above copyright notice and this permission notice shall be included in all
+--** copies or substantial portions of the Software.
+--**
+--** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+--** IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+--** FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+--** AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+--** LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+--** OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+--** SOFTWARE.
+--**********************************************************************************
+
+---@alias AbsorptionType
+---| "Default"
+
+--- Defines what proportion of damage a shield of `AbsorptionType` absorbs from a specific `DamageType`
+--- Overrides the behavior of shields absorbing damage depending on their owner's armor type
+---@type table<AbsorptionType, table<DamageType, number>>
+shieldAbsorptionValues = {
+	["Default"] = {
+		["Deathnuke"] = 1.0
+	},
+}

lua/shield.lua

@@ -31,6 +31,8 @@ local Entity = import("/lua/sim/entity.lua").Entity
 local EffectTemplate = import("/lua/effecttemplates.lua")
 local Util = import("/lua/utilities.lua")
 
+local shieldAbsorptionValues = import("/lua/ShieldAbsorptionValues.lua").shieldAbsorptionValues
+
 local DeprecatedWarnings = {}
 
 local VectorCached = Vector(0, 0, 0)
@@ -147,6 +149,7 @@ end
 ---@field PassOverkillDamage boolean
 ---@field ImpactMeshBp string
 ---@field SkipAttachmentCheck boolean
+---@field AbsorptionType AbsorptionType
 Shield = ClassShield(moho.shield_methods, Entity) {
 
     RemainEnabledWhenAttached = false,
@@ -212,13 +215,17 @@ Shield = ClassShield(moho.shield_methods, Entity) {
         EntityAttachBoneTo(self, -1, spec.Owner, -1)
 
         -- lookup as to whether we're static or a commander shield
-        local ownerCategories = self.Owner.Blueprint.CategoriesHash
+        local ownerBp = self.Owner.Blueprint
+        local ownerCategories = ownerBp.CategoriesHash
         if ownerCategories.STRUCTURE then
             self.StaticShield = true
         elseif ownerCategories.COMMAND then
             self.CommandShield = true
         end
 
+        -- lookup our damage absorption type
+        self.AbsorptionType = ownerBp.Defense.Shield.AbsorptionType or "Default"
+
         -- use trashbag of the unit that owns us
         self.Trash = self.Owner.Trash
 
@@ -440,10 +447,19 @@ Shield = ClassShield(moho.shield_methods, Entity) {
     -- under the shield. The default is to always absorb as much as possible
     -- but the reason this function exists is to allow flexible implementations
     -- like shields that only absorb partial damage (like armor).
+    --- How much of incoming damage is absorbed by the shield. Used by the engine to calculate remainder spillover damage
+    ---@param self Shield
+    ---@param instigator Unit
+    ---@param amount number
+    ---@param type DamageType
+    ---@return number damageAbsorbed If not all damage is absorbed, the remainder passes to targets under the shield.
     OnGetDamageAbsorption = function(self, instigator, amount, type)
+        -- Allow decoupling the shield from the owner's armor multiplier
+        local absorptionMulti = shieldAbsorptionValues[self.AbsorptionType][type] or self.Owner:GetArmorMult(type)
+
         -- Like armor damage, first multiply by armor reduction, then apply handicap
         -- See SimDamage.cpp (DealDamage function) for how this should work
-        amount = amount * (self.Owner:GetArmorMult(type))
+        amount = amount * absorptionMulti
         amount = amount * (1.0 - ArmyGetHandicap(self.Army))
 
         local health = EntityGetHealth(self)
@@ -454,6 +470,12 @@ Shield = ClassShield(moho.shield_methods, Entity) {
         end
     end,
 
+    -- Used by PersonalShield and PersonalBubble to pass damage to the Owner Unit
+    ---@param self Shield
+    ---@param instigator Unit
+    ---@param amount number
+    ---@param type DamageType
+    ---@return number overkillDamage
     GetOverkill = function(self, instigator, amount, type)
         -- Like armor damage, first multiply by armor reduction, then apply handicap
         -- See SimDamage.cpp (DealDamage function) for how this should work