Fixes some burn reactions deleting energy (#28659)

* makes energy production make sense

* Build Rust library

* Build Rust library

* Build Rust library

* Build Rust library

* Build Rust library

* Build Rust library

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Co-authored-by: paradisess13[bot] <165046124+paradisess13[bot]@users.noreply.github.com>

code/__DEFINES/atmospherics_defines.dm

@@ -157,6 +157,11 @@
 /// The coefficient c for a function of the form: 1 - (a / (x + c)^2) which gives a decomposition rate of 0.5 at 50000 Kelvin
 /// And a decomposition rate close to 0 at 1400 Kelvin
 #define N2O_DECOMPOSITION_COEFFICIENT_C 115930.77913
+/// Agent B starts working at this temperature
+#define AGENT_B_CONVERSION_MIN_TEMP 900
+/// Agent B released this much energy per mole of CO2 converted to O2
+#define AGENT_B_CONVERSION_ENERGY_RELEASED 20000
+
 // From milla/src/model.rs, line 126
 #define ATMOS_MODE_SPACE 0						//! Tile is exposed to space and loses air every second
 #define ATMOS_MODE_SEALED 1						//! Tile has no special behaviour

code/modules/atmospherics/gasmixtures/gas_mixture.dm

@@ -560,16 +560,20 @@ What are the archived variables for?
 /datum/gas_mixture/proc/react(atom/dump_location)
 	var/reacting = FALSE //set to TRUE if a notable reaction occured (used by pipe_network)
 
-	if((private_agent_b > MINIMUM_MOLE_COUNT) && private_temperature > 900)
+	if((private_agent_b > MINIMUM_MOLE_COUNT) && private_temperature > AGENT_B_CONVERSION_MIN_TEMP)
 		if(private_toxins > MINIMUM_HEAT_CAPACITY && private_carbon_dioxide > MINIMUM_HEAT_CAPACITY)
 			var/reaction_rate = min(private_carbon_dioxide * 0.75, private_toxins * 0.25, private_agent_b * 0.05)
+			var/old_heat_capacity = heat_capacity()
+			var/energy_released = reaction_rate * AGENT_B_CONVERSION_ENERGY_RELEASED
 
 			private_carbon_dioxide -= reaction_rate
 			private_oxygen += reaction_rate
 
 			private_agent_b -= reaction_rate * 0.05
 
-			private_temperature += (reaction_rate * 20000) / heat_capacity()
+			var/new_heat_capacity = heat_capacity()
+			if(new_heat_capacity > MINIMUM_HEAT_CAPACITY)
+				private_temperature = (private_temperature * old_heat_capacity + energy_released) / new_heat_capacity
 
 			reacting = TRUE
 

rust/src/milla/simulate.rs

@@ -560,10 +560,9 @@ pub(crate) fn react(my_next_tile: &mut Tile, hotspot_step: bool) {
         my_next_tile
             .gases
             .set_agent_b(my_next_tile.gases.agent_b() - co2_converted * 0.05);
-        // Recalculate existing thermal energy to account for the change in heat capacity.
+        // Recalculate heat capacity.
         cached_heat_capacity = fraction * my_next_tile.heat_capacity();
-        thermal_energy = cached_temperature * cached_heat_capacity;
-        // THEN we can add in the new thermal energy.
+        // Add in the new thermal energy.
         thermal_energy += AGENT_B_CONVERSION_ENERGY * co2_converted;
         // Recalculate temperature for any subsequent reactions.
         cached_temperature = thermal_energy / cached_heat_capacity;
@@ -588,10 +587,9 @@ pub(crate) fn react(my_next_tile: &mut Tile, hotspot_step: bool) {
             .gases
             .set_oxygen(my_next_tile.gases.oxygen() + nitrous_decomposed / 2.0);
 
-        // Recalculate existing thermal energy to account for the change in heat capacity.
+        // Recalculate heat capacity.
         cached_heat_capacity = fraction * my_next_tile.heat_capacity();
-        thermal_energy = cached_temperature * cached_heat_capacity;
-        // THEN we can add in the new thermal energy.
+        // Add in the new thermal energy.
         thermal_energy += NITROUS_BREAKDOWN_ENERGY * nitrous_decomposed;
         // Recalculate temperature for any subsequent reactions.
         cached_temperature = thermal_energy / cached_heat_capacity;
@@ -634,9 +632,8 @@ pub(crate) fn react(my_next_tile: &mut Tile, hotspot_step: bool) {
             .gases
             .set_oxygen(my_next_tile.gases.oxygen() - plasma_burnt * PLASMA_BURN_OXYGEN_PER_PLASMA);
 
-        // Recalculate existing thermal energy to account for the change in heat capacity.
+        // Recalculate heat capacity.
         cached_heat_capacity = fraction * my_next_tile.heat_capacity();
-        thermal_energy = cached_temperature * cached_heat_capacity;
         // THEN we can add in the new thermal energy.
         thermal_energy += PLASMA_BURN_ENERGY * plasma_burnt;
         // Recalculate temperature for any subsequent reactions.
@@ -681,8 +678,9 @@ pub(crate) fn apply_tile_mode(
             if my_next_tile.temperature() > SPACE_COOLING_THRESHOLD {
                 let excess_thermal_energy = my_next_tile.thermal_energy
                     - SPACE_COOLING_THRESHOLD * my_next_tile.heat_capacity();
-                let cooling = (SPACE_COOLING_FLAT + SPACE_COOLING_TEMPERATURE_RATIO * my_next_tile.temperature())
-                    .min(excess_thermal_energy);
+                let cooling = (SPACE_COOLING_FLAT
+                    + SPACE_COOLING_TEMPERATURE_RATIO * my_next_tile.temperature())
+                .min(excess_thermal_energy);
                 my_next_tile.thermal_energy -= cooling;
             }
         }