Ignore full coop pickups

gamemode/weaponsystem.lua

@@ -26,6 +26,39 @@ local persistentItemClasses = {
     item_suitcharger = true
 }
 
+local itemAmmoTypes = {
+    item_ammo_357 = "357",
+    item_ammo_357_large = "357",
+    item_ammo_ar2 = "AR2",
+    item_ammo_ar2_altfire = "AR2AltFire",
+    item_ammo_ar2_large = "AR2",
+    item_ammo_crossbow = "XBowBolt",
+    item_ammo_pistol = "Pistol",
+    item_ammo_pistol_large = "Pistol",
+    item_ammo_smg1 = "SMG1",
+    item_ammo_smg1_grenade = "SMG1_Grenade",
+    item_ammo_smg1_large = "SMG1",
+    item_box_buckshot = "Buckshot",
+    item_rpg_round = "RPG_Round"
+}
+
+local function CanReceiveAmmo(ply, ammoType)
+    if ammoType == nil or ammoType < 0 then return false end
+
+    local maximum
+    local maxAmmoOverride = GetConVar("gmod_maxammo")
+    if maxAmmoOverride and maxAmmoOverride:GetInt() > 0 then
+        maximum = maxAmmoOverride:GetInt()
+    else
+        maximum = game.GetAmmoMax(ammoType)
+    end
+
+    -- Unknown/custom ammo types are left to their own pickup implementation.
+    if maximum == nil or maximum < 0 then return true end
+
+    return ply:GetAmmoCount(ammoType) < maximum
+end
+
 local function IsRespawnable(ent)
     if not IsValid(ent) then return false end
 
@@ -146,6 +179,32 @@ hook.Add("WeaponEquip", "CustomCoopRespawnCollectedWeapon", function(weapon)
     ScheduleRespawn(template)
 end)
 
+-- A duplicate weapon is removed through WEAPON:EquipAmmo even when the player
+-- cannot accept more ammo. Refusing only the useless attempt leaves the pickup
+-- available and silent until this player spends ammunition (or someone else
+-- who needs it touches it).
+hook.Add("PlayerCanPickupWeapon", "CustomCoopIgnoreFullDuplicateWeapons", function(ply, weapon)
+    if not trackedItems[weapon] or not ply:HasWeapon(weapon:GetClass()) then return end
+
+    if not CanReceiveAmmo(ply, weapon:GetPrimaryAmmoType())
+        and not CanReceiveAmmo(ply, weapon:GetSecondaryAmmoType()) then
+        return false
+    end
+end)
+
+-- Stock ammo items normally reject a full player themselves. Checking here as
+-- well avoids pickup effects from engine branches or addons that remove the
+-- item even when GiveAmmo accepted zero rounds.
+hook.Add("PlayerCanPickupItem", "CustomCoopIgnoreFullAmmoItems", function(ply, item)
+    if not trackedItems[item] then return end
+
+    local ammoName = itemAmmoTypes[item:GetClass()]
+    if not ammoName then return end
+
+    local ammoType = game.GetAmmoID(ammoName)
+    if not CanReceiveAmmo(ply, ammoType) then return false end
+end)
+
 -- Prevent +use from dragging a map pickup away. Touch pickup still works, and
 -- duplicate weapons are left to the engine's EquipAmmo path so they correctly
 -- replenish reserve ammo and disappear only when ammo was actually accepted.