Shift some attack and damage calculations to the attack_type class.

This is in anticipation of them being useful (later) in reports.

src/actions/attack.cpp

@@ -142,22 +142,16 @@ battle_context_unit_stats::battle_context_unit_stats(const unit &u,
 		chance_to_hit = cth_effects.get_composite_value();
 
 		// Compute base damage done with the weapon.
-		int base_damage = weapon->damage();
-		unit_ability_list dmg_specials = weapon->get_specials("damage");
-		unit_abilities::effect dmg_effect(dmg_specials, base_damage, backstab_pos);
-		base_damage = dmg_effect.get_composite_value();
+		int base_damage = weapon->modified_damage(backstab_pos);
 
 		// Get the damage multiplier applied to the base damage of the weapon.
 		int damage_multiplier = 100;
-
 		// Time of day bonus.
 		damage_multiplier += combat_modifier(u_loc, u.alignment(), u.is_fearless());
-
 		// Leadership bonus.
 		int leader_bonus = 0;
 		if (under_leadership(units, u_loc, &leader_bonus).valid())
 			damage_multiplier += leader_bonus;
-
 		// Resistance modifier.
 		damage_multiplier *= opp.damage_from(*weapon, !attacking, opp_loc);
 
@@ -184,26 +178,9 @@ battle_context_unit_stats::battle_context_unit_stats(const unit &u,
 		drains = drain_constant || drain_percent;
 
 		// Compute the number of blows and handle swarm.
-		unit_ability_list swarm_specials = weapon->get_specials("swarm");
-
-		num_blows = weapon->num_attacks();
-		unit_ability_list attacks_specials = weapon->get_specials("attacks");
-		unit_abilities::effect attacks_effect(attacks_specials,num_blows,backstab_pos);
-		const int num_blows_with_specials = attacks_effect.get_composite_value();
-		if(num_blows_with_specials >= 0) {
-			num_blows = num_blows_with_specials;
-		}
-		else { ERR_NG << "negative number of strikes after applying weapon specials\n"; }
-		if (!swarm_specials.empty()) {
-			swarm = true;
-			swarm_min = swarm_specials.highest("swarm_attacks_min").first;
-			swarm_max = swarm_specials.highest("swarm_attacks_max", num_blows).first;
-			num_blows = calc_blows(hp);
-		} else {
-			swarm = false;
-			swarm_min = num_blows;
-			swarm_max = num_blows;
-		}
+		weapon->modified_attacks(backstab_pos, swarm_min, swarm_max);
+		swarm = swarm_min != swarm_max;
+		num_blows = calc_blows(hp);
 	}
 }
 

src/unit_abilities.cpp

@@ -633,6 +633,45 @@ void attack_type::set_specials_context(const map_location& loc, bool attacking)
 }
 
 
+/**
+ * Calculates the number of attacks this weapon has, considering specials.
+ * This returns two numbers because of the swarm special. The actual number of
+ * attacks depends on the unit's health and should be:
+ *   min_attacks + (max_attacks - min_attacks) * (current hp) / (max hp)
+ */
+void attack_type::modified_attacks(bool is_backstab, unsigned & min_attacks,
+                                   unsigned & max_attacks) const
+{
+	// Apply [attacks].
+	unit_abilities::effect attacks_effect(get_specials("attacks"),
+	                                      num_attacks(), is_backstab);
+	int attacks_value = attacks_effect.get_composite_value();
+	if ( attacks_value < 0 ) {
+		attacks_value = num_attacks();
+		ERR_NG << "negative number of strikes after applying weapon specials\n";
+	}
+
+	// Apply [swarm].
+	unit_ability_list swarm_specials = get_specials("swarm");
+	if ( !swarm_specials.empty() ) {
+		min_attacks = std::max<int>(0, swarm_specials.highest("swarm_attacks_min").first);
+		max_attacks = std::max<int>(0, swarm_specials.highest("swarm_attacks_max", attacks_value).first);
+	} else {
+		min_attacks = max_attacks = attacks_value;
+	}
+}
+
+
+/**
+ * Returns the damage per attack of this weapon, considering specials.
+ */
+int attack_type::modified_damage(bool is_backstab) const
+{
+	unit_abilities::effect dmg_effect(get_specials("damage"), damage(), is_backstab);
+	return dmg_effect.get_composite_value();
+}
+
+
 namespace { // Helpers for attack_type::special_active()
 
 	/**

src/unit_types.hpp

@@ -58,6 +58,12 @@ public:
 	                          bool attacking, const attack_type *other_attack) const;
 	void set_specials_context(const map_location& loc, bool attacking = true) const;
 
+	/// Calculates the number of attacks this weapon has, considering specials.
+	void modified_attacks(bool is_backstab, unsigned & min_attacks,
+	                      unsigned & max_attacks) const;
+	/// Returns the damage per attack of this weapon, considering specials.
+	int modified_damage(bool is_backstab) const;
+
 	// In unit_types.cpp:
 
 	bool matches_filter(const config& filter) const;