Final reagent enhancements (#89289)

## About The Pull Request
**1. Code Improvements**
- `get_reagent_log_string()` now won't round reagent volumes cause they
are already rounded by `update_total()` so its slightly faster
- `trans_to()` now logs reagents faster as it does it in place without
the overhead of passing the list to `get_external_reagent_log_string()`
which parses our list into another list which is just unessassary
- `trans_to()` is now faster performance wise as it no longer relies on
`remove_reagent()` to remove the reagent
- Merged `multiply_single_reagent()` into a single proc `multiply()`
which does the job for both single & multiple reagents to reduce code.
it now no longer uses proc `remove_reagent()` making it faster when
reducing reagents
- `copy_to()` no longer rounds its return value thus improving
performance & won't return false negatives for values lesser than 0.01

**2. Fixes**
- Fixes `multiply_single_reagent()` multiplying reagent subtypes as well
instead of just the target type as it uses `locate()`
- Fixes `multiply_reagents()` multiplying reagents twice. Notice how it
would call `_multiply_reagent()` & then again do the exact same thing as
that proc in the next line

https://github.com/tgstation/tgstation/blob/dfe9f50ad74507dabf8b9a534f385cad170c53c1/code/modules/reagents/chemistry/holder/holder.dm#L605-L609
- `convert_reagent()` actually uses the weighted ph. I was wrong in what
I assumed `override_base_ph` did

Just lesser & faster code overall

## Changelog
🆑
fix: multiplying reagents in cases like fishing & chem splash will yield
accurate results. New amounts differ from present values
fix: converting reagents actually yields correct ph again
code: improved performance of reagent logging
code: copying reagents won't return false negatives for values lesser
than 0.01
/🆑

code/modules/fishing/fish/_fish.dm

@@ -338,7 +338,7 @@
 		adjust_reagents_capacity((protein_volume - old_blood_volume) * volume_mult)
 		///Add the extra nutriment
 		if(protein)
-			reagents.multiply_single_reagent(/datum/reagent/consumable/nutriment/protein, 2)
+			reagents.multiply(2, /datum/reagent/consumable/nutriment/protein)
 
 	var/datum/component/edible/edible = GetComponent(/datum/component/edible)
 	edible.foodtypes &= ~(RAW|GORE)
@@ -457,8 +457,7 @@
 			if(!result_reagent)
 				created.reagents.add_reagent(reagent.type, transfer_vol, reagents.copy_data(reagent), reagents.chem_temp, reagent.purity, reagent.ph, no_react = TRUE)
 				continue
-			var/multiplier = transfer_vol / result_reagent.volume
-			created.reagents.multiply_single_reagent(reagent.type, multiplier)
+			created.reagents.multiply(transfer_vol / result_reagent.volume, reagent.type)
 	return ..()
 
 /obj/item/fish/update_icon_state()
@@ -609,7 +608,7 @@
 				var/amount_to_gen = bites_left / initial_bites_left * multiplier
 				generate_fish_reagents(amount_to_gen)
 			else
-				reagents.multiply_reagents(new_weight_ratio)
+				reagents.multiply(new_weight_ratio)
 				adjust_reagents_capacity(volume_diff)
 
 	weight = new_weight

code/modules/fishing/fish/fish_traits.dm

@@ -669,7 +669,7 @@ GLOBAL_LIST_INIT(spontaneous_fish_traits, populate_spontaneous_fish_traits())
 	if(cooked_time >= FISH_SAFE_COOKING_DURATION)
 		fish.reagents.del_reagent(/datum/reagent/consumable/liquidelectricity)
 	else
-		fish.reagents.multiply_single_reagent(/datum/reagent/consumable/liquidelectricity, 0.66)
+		fish.reagents.multiply(0.66, /datum/reagent/consumable/liquidelectricity)
 
 /datum/fish_trait/electrogenesis/add_reagents(obj/item/fish/fish, list/reagents)
 	. = ..()

code/modules/plumbing/plumbers/_plumb_reagents.dm

@@ -55,7 +55,6 @@
 	transfer_reactions(target_holder)
 
 	var/list/cached_reagents = reagent_list
-	var/list/reagents_to_remove = list()
 	var/transfer_amount
 	var/transfered_amount
 	var/total_transfered_amount = 0
@@ -93,23 +92,18 @@
 		transfered_amount = target_holder.add_reagent(reagent.type, transfer_amount, copy_data(reagent), chem_temp, reagent.purity, reagent.ph, no_react = TRUE, ignore_splitting = reagent.chemical_flags & REAGENT_DONOTSPLIT) //we only handle reaction after every reagent has been transferred.
 		if(!transfered_amount)
 			continue
-		reagents_to_remove += list(list("R" = reagent, "T" = transfer_amount))
 		total_transfered_amount += transfered_amount
 		if(round_robin)
 			to_transfer -= transfered_amount
+		reagent.volume -= transfered_amount
 
 		if(!isnull(target_id))
 			break
-
-	//remove chemicals that were added above
-	for(var/list/data as anything in reagents_to_remove)
-		var/datum/reagent/reagent = data["R"]
-		transfer_amount = data["T"]
-		remove_reagent(reagent.type, transfer_amount)
+	update_total()
 
 	//handle reactions
 	target_holder.handle_reactions()
-	src.handle_reactions()
+	handle_reactions()
 
 	return total_transfered_amount
 
@@ -199,7 +193,6 @@
 	//Set up new reagents to inherit the old ongoing reactions
 	transfer_reactions(target_holder)
 
-	var/list/reagents_to_remove = list()
 	var/working_volume
 	var/catalyst_volume
 	var/transfer_amount
@@ -247,22 +240,17 @@
 		transfered_amount = target_holder.add_reagent(reagent.type, transfer_amount, copy_data(reagent), chem_temp, reagent.purity, reagent.ph, no_react = TRUE, ignore_splitting = reagent.chemical_flags & REAGENT_DONOTSPLIT) //we only handle reaction after every reagent has been transferred.
 		if(!transfered_amount)
 			continue
-		reagents_to_remove += list(list("R" = reagent, "T" = transfer_amount))
 		total_transfered_amount += transfered_amount
 		if(round_robin)
 			to_transfer -= transfered_amount
+		reagent.volume -= transfered_amount
 
 		if(!isnull(target_id))
 			break
-
-	//remove chemicals that were added above
-	for(var/list/data as anything in reagents_to_remove)
-		var/datum/reagent/reagent = data["R"]
-		transfer_amount = data["T"]
-		remove_reagent(reagent.type, transfer_amount)
+	update_total()
 
 	//handle reactions
 	target_holder.handle_reactions()
-	src.handle_reactions()
+	handle_reactions()
 
 	return total_transfered_amount

code/modules/reagents/chem_splash.dm

@@ -43,11 +43,11 @@
 		tmp_holder = FALSE
 		original_max_volume = holder.maximum_volume
 		if(threatscale < 1)
-			holder.multiply_reagents(threatscale)
+			holder.multiply(threatscale)
 			holder.maximum_volume = maximum_reagents * threatscale
 		else
 			holder.maximum_volume = maximum_reagents * threatscale
-			holder.multiply_reagents(threatscale)
+			holder.multiply(threatscale)
 
 	for(var/datum/reagents/reactant as anything in reactants)
 		reactant.trans_to(holder, reactant.total_volume, threatscale, no_react = TRUE)

code/modules/reagents/chemistry/holder/holder.dm

@@ -1,6 +1,3 @@
-#define REAGENT_TRANSFER_AMOUNT "amount"
-#define REAGENT_PURITY "purity"
-
 ///////////////////////////////Main reagents code/////////////////////////////////////////////
 
 /// Holder for a bunch of [/datum/reagent]
@@ -377,7 +374,7 @@
 	//add the new target reagent with the averaged values from the source reagents
 	if(weighted_volume > 0)
 		update_total()
-		add_reagent(target_reagent_typepath, weighted_volume * multiplier, reagtemp = chem_temp, added_purity = (weighted_purity / weighted_volume), override_base_ph = TRUE, added_ph = (weighted_ph / weighted_volume))
+		add_reagent(target_reagent_typepath, weighted_volume * multiplier, reagtemp = chem_temp, added_purity = (weighted_purity / weighted_volume), added_ph = (weighted_ph / weighted_volume))
 
 /// Removes all reagents
 /datum/reagents/proc/clear_reagents()
@@ -496,7 +493,7 @@
 			continue
 		if(methods)
 			r_to_send += reagent
-		reagents_to_remove += list(list("R" = reagent, "T" = transfer_amount))
+		reagents_to_remove[reagent] = transfer_amount
 		total_transfered_amount += transfered_amount
 
 		if(!isnull(target_id))
@@ -507,26 +504,29 @@
 		target_holder.expose(isorgan(target_atom) ? target : target_atom, methods, part, show_message, r_to_send)
 
 	//remove chemicals that were added above
-	for(var/list/data as anything in reagents_to_remove)
-		var/datum/reagent/reagent = data["R"]
-		transfer_amount = data["T"]
+	for(var/datum/reagent/reagent as anything in reagents_to_remove)
+		transfer_amount = reagents_to_remove[reagent]
 		if(methods)
 			reagent.on_transfer(target_atom, methods, transfer_amount)
-		remove_reagent(reagent.type, transfer_amount)
-		transfer_log[reagent.type] = list(REAGENT_TRANSFER_AMOUNT = transfer_amount, REAGENT_PURITY = reagent.purity)
+		reagent.volume -= transfer_amount
+		update_total()
+		transfer_log += "[reagent.type] ([transfer_amount]u, [reagent.purity] purity)"
 
 	//combat log
 	if(transferred_by && target_atom)
+		//logging mob holder
 		var/atom/log_target = target_atom
 		if(isorgan(target_atom))
 			var/obj/item/organ/organ_item = target_atom
 			log_target = organ_item.owner ? organ_item.owner : organ_item
 		log_target.add_hiddenprint(transferred_by) //log prints so admins can figure out who touched it last.
-		log_combat(transferred_by, log_target, "transferred reagents to", my_atom, "which had [get_external_reagent_log_string(transfer_log)]")
+
+		//logging reagents
+		log_combat(transferred_by, log_target, "transferred reagents to", my_atom, "which had [english_list(transfer_log)]")
 
 	if(!no_react)
 		target_holder.handle_reactions()
-		src.handle_reactions()
+		handle_reactions()
 
 	return total_transfered_amount
 
@@ -585,54 +585,50 @@
 	if(!no_react)
 		// pass over previous ongoing reactions before handle_reactions is called
 		transfer_reactions(target_holder)
-
-		target_holder.update_total()
 		target_holder.handle_reactions()
 
-	return round(total_transfered_amount, CHEMICAL_VOLUME_ROUNDING)
+	return total_transfered_amount
 
 /**
- * Multiplies the reagents inside this holder by a specific amount
+ * Multiplies reagents inside this holder by a specific amount
  * Arguments
- * * multiplier - the amount to multiply each reagent by
+ *
+ * * multiplier - the amount to multiply each reagent, its a percentile value where < 1 will reduce the volume and
+ * * > 1 will increase the volume. Final multiplier applied to the reagent volume is (1 - multiplier)
+ * * datum/reagent/target_id - multiply only this reagent in this holder leaving others untouched
  */
-/datum/reagents/proc/multiply_reagents(multiplier = 1)
+/datum/reagents/proc/multiply(multiplier = 1, datum/reagent/target_id)
+	if(!total_volume)
+		return
+
+	multiplier = round(min(multiplier, maximum_volume / total_volume), CHEMICAL_QUANTISATION_LEVEL)
+	if(multiplier < 0 || multiplier == 1)
+		return
+
+	if(!isnull(target_id) && !ispath(target_id))
+		stack_trace("Bad reagent path [target_id] passed to multiply")
+		return
+
+	var/change = (multiplier - 1) //Get the % change
+	var/reagent_change
 	var/list/cached_reagents = reagent_list
-	if(!total_volume || multiplier == 1)
-		return
-	var/change = (multiplier - 1) //Get the % change
 	for(var/datum/reagent/reagent as anything in cached_reagents)
-		_multiply_reagent(reagent, change)
+		if(!isnull(target_id) && reagent.type != target_id)
+			continue
+
+		reagent_change = reagent.volume * change
 		if(change > 0)
-			add_reagent(reagent.type, reagent.volume * change, added_purity = reagent.purity, ignore_splitting = reagent.chemical_flags & REAGENT_DONOTSPLIT)
+			add_reagent(reagent.type, reagent_change, added_purity = reagent.purity, added_ph = reagent.ph, no_react = TRUE, ignore_splitting = reagent.chemical_flags & REAGENT_DONOTSPLIT)
 		else
-			remove_reagent(reagent.type, abs(reagent.volume * change)) //absolute value to prevent a double negative situation (removing -50% would be adding 50%)
+			reagent.volume += reagent_change
 
-	update_total()
+		if(!isnull(target_id))
+			break
+
+	if(change < 0)
+		update_total()
 	handle_reactions()
 
-/**
- * Multiplies a single inside this holder by a specific amount
- * Arguments
- * * reagent_path - The path of the reagent we want to multiply the volume of.
- * * multiplier - the amount to multiply each reagent by
- */
-/datum/reagents/proc/multiply_single_reagent(reagent_path, multiplier = 1)
-	var/datum/reagent/reagent = locate(reagent_path) in reagent_list
-	if(!reagent || multiplier == 1)
-		return
-	var/change = (multiplier - 1) //Get the % change
-	_multiply_reagent(reagent, change)
-	update_total()
-	handle_reactions()
-
-///Proc containing the operations called by both multiply_reagents() and multiply_single_reagent()
-/datum/reagents/proc/_multiply_reagent(datum/reagent/reagent, change)
-	if(change > 0)
-		add_reagent(reagent.type, reagent.volume * change, added_purity = reagent.purity, ignore_splitting = reagent.chemical_flags & REAGENT_DONOTSPLIT)
-	else
-		remove_reagent(reagent.type, abs(reagent.volume * change)) //absolute value to prevent a double negative situation (removing -50% would be adding 50%)
-
 /// Updates [/datum/reagents/var/total_volume]
 /datum/reagents/proc/update_total()
 	var/list/cached_reagents = reagent_list
@@ -829,24 +825,6 @@
 
 
 //===============================Logging==========================================
-/**
- * Outputs a log-friendly list of reagents based on an external reagent list.
- *
- * Arguments:
- * * external_list - Assoc list of (reagent_type) = list(REAGENT_TRANSFER_AMOUNT = amounts, REAGENT_PURITY = purity)
- */
-/datum/reagents/proc/get_external_reagent_log_string(external_list)
-	if(!length(external_list))
-		return "no reagents"
-
-	var/list/data = list()
-
-	for(var/reagent_type in external_list)
-		var/list/qualities = external_list[reagent_type]
-		data += "[reagent_type] ([round(qualities[REAGENT_TRANSFER_AMOUNT], CHEMICAL_QUANTISATION_LEVEL)]u, [qualities[REAGENT_PURITY]] purity)"
-
-	return english_list(data)
-
 /// Outputs a log-friendly list of reagents based on the internal reagent_list.
 /datum/reagents/proc/get_reagent_log_string()
 	if(!length(reagent_list))
@@ -855,9 +833,6 @@
 	var/list/data = list()
 
 	for(var/datum/reagent/reagent as anything in reagent_list)
-		data += "[reagent.type] ([round(reagent.volume, CHEMICAL_QUANTISATION_LEVEL)]u, [reagent.purity] purity)"
+		data += "[reagent.type] [reagent.volume]u, [reagent.purity] purity)"
 
 	return english_list(data)
-
-#undef REAGENT_TRANSFER_AMOUNT
-#undef REAGENT_PURITY

code/modules/reagents/chemistry/holder/properties.dm

@@ -32,7 +32,7 @@
 
 		//short cut to break when we have found our one exact type
 		if(type_check == REAGENT_STRICT_TYPE)
-			return total_amount
+			break
 
 	return total_amount
 

code/modules/reagents/chemistry/machinery/chem_recipe_debug.dm

@@ -172,7 +172,7 @@
 
 	var/target_temperature = decode_target_temperature()
 	if(!isnull(target_temperature))
-		target_reagents.adjust_thermal_energy((target_temperature - target_reagents.chem_temp) * 0.45 * seconds_per_tick * target_reagents.heat_capacity())
+		target_reagents.adjust_thermal_energy((target_temperature - target_reagents.chem_temp) * 0.4 * seconds_per_tick * target_reagents.heat_capacity())
 
 	if(use_forced_purity)
 		target_reagents.set_all_reagents_purity(forced_purity)