Enable adding, removing, and replacing unit attacks through the Lua unit attacks table

src/scripting/lua_unit_attacks.cpp

@@ -130,11 +130,65 @@ static int impl_unit_attacks_get(lua_State *L)
 		const_attack_ptr atk = lua_isnumber(L, 2) ? find_attack(ut, luaL_checkinteger(L, 2) - 1) : find_attack(ut, luaL_checkstring(L, 2));
 		luaW_pushweapon(L, atk);
 	} else {
-		return luaL_argerror(L, 1, "unknown unit");
+		return luaL_argerror(L, 1, "unit not found");
 	}
 	return 1;
 }
 
+static attack_itors::iterator get_attack_iter(unit& u, attack_ptr atk)
+{
+	// This is slightly inefficient since it walks the attack list a second time...
+	return std::find_if(u.attacks().begin(), u.attacks().end(), [&atk](const attack_type& atk2) {
+		return &atk2 == atk;
+	});
+}
+
+static int impl_unit_attacks_set(lua_State* L)
+{
+	if(!lua_istable(L, 1)) {
+		return luaL_typerror(L, 1, "unit attacks");
+	}
+	lua_rawgeti(L, 1, 0);
+	const unit_type* ut = luaW_tounittype(L, -1);
+	if(ut) {
+		return luaL_argerror(L, 1, "unit type attack table is immutable");
+	}
+
+	unit& u = luaW_checkunit(L, -1);
+	attack_ptr atk = lua_isnumber(L, 2) ? find_attack(&u, luaL_checkinteger(L, 2) - 1) : find_attack(&u, luaL_checkstring(L, 2));
+	if(lua_isnumber(L, 2) && lua_tonumber(L, 2) - 1 > u.attacks().size()) {
+		return luaL_argerror(L, 2, "attack can only be added at the end of the list");
+	}
+
+	if(lua_isnil(L, 3)) {
+		// Delete the attack
+		u.remove_attack(atk);
+		return 0;
+	}
+
+	auto iter = get_attack_iter(u, atk), end = u.attacks().end();
+	if(const_attack_ptr atk2 = luaW_toweapon(L, 3)) {
+		if(iter == end) {
+			atk = u.add_attack(end, *atk2);
+		} else {
+			iter.base()->reset(new attack_type(*atk2));
+			atk = *iter.base();
+		}
+	} else {
+		config cfg = luaW_checkconfig(L, 3);
+		if(iter == end) {
+			atk = u.add_attack(end, cfg);
+		} else {
+			iter.base()->reset(new attack_type(cfg));
+			atk = *iter.base();
+		}
+	}
+	if(!lua_isnumber(L, 2)) {
+		atk->set_id(lua_tostring(L, 2));
+	}
+	return 0;
+}
+
 /**
  * Counts the attacks of a unit (__len metamethod).
  * - Arg 1: table containing the userdata containing the unit id.
@@ -245,6 +299,8 @@ namespace lua_units {
 		luaL_newmetatable(L, uattacksKey);
 		lua_pushcfunction(L, impl_unit_attacks_get);
 		lua_setfield(L, -2, "__index");
+		lua_pushcfunction(L, impl_unit_attacks_set);
+		lua_setfield(L, -2, "__newindex");
 		lua_pushcfunction(L, impl_unit_attacks_len);
 		lua_setfield(L, -2, "__len");
 		lua_pushstring(L, uattacksKey);

src/units/unit.cpp

@@ -2428,6 +2428,17 @@ const std::string& unit::effect_image_mods() const{
 	return image_mods_;
 }
 
+// Called by the Lua API after resetting an attack pointer.
+bool unit::remove_attack(attack_ptr atk)
+{
+	auto iter = std::find(attacks_.begin(), attacks_.end(), atk);
+	if(iter == attacks_.end()) {
+		return false;
+	}
+	attacks_.erase(iter);
+	return true;
+}
+
 void unit::remove_attacks_ai()
 {
 	if (attacks_left_ == max_attacks_) {

src/units/unit.hpp

@@ -254,6 +254,11 @@ public:
 
 	const_attack_itors attacks() const { return make_attack_itors(attacks_); }
 	attack_itors attacks() { return make_attack_itors(attacks_); }
+	bool remove_attack(attack_ptr atk);
+	template<typename... Args>
+	attack_ptr add_attack(attack_itors::iterator position, Args... args) {
+		return *attacks_.emplace(position.base(), new attack_type(args...));
+	}
 
 	int damage_from(const attack_type& attack,bool attacker,const map_location& loc) const { return resistance_against(attack,attacker,loc); }