Refactors mech construction datums

code/datums/helper_datums/construction_datum.dm

@@ -1,44 +1,50 @@
-#define FORWARD -1
-#define BACKWARD 1
+#define FORWARD 1
+#define BACKWARD -1
+
+#define ITEM_DELETE "delete"
+#define ITEM_MOVE_INSIDE "move_inside"
+
 
 /datum/construction
 	var/list/steps
 	var/atom/holder
 	var/result
-	var/list/steps_desc
+	var/index = 1
 
 /datum/construction/New(atom)
 	..()
 	holder = atom
 	if(!holder) //don't want this without a holder
 		qdel(src)
-	set_desc(steps.len)
-	return
+	update_holder(index)
 
-/datum/construction/proc/next_step()
-	steps.len--
-	if(!steps.len)
+/datum/construction/proc/on_step()
+	if(index > steps.len)
 		spawn_result()
 	else
-		set_desc(steps.len)
-	return
+		update_holder(index)
 
-/datum/construction/proc/action(obj/item/I, mob/user)
-	return
+/datum/construction/proc/action(obj/item/I, mob/living/user)
+	return check_step(I, user)
 
-/datum/construction/proc/check_step(obj/item/I, mob/user) //check last step only
-	var/valid_step = is_right_key(I)
-	if(valid_step)
-		if(custom_action(valid_step, I, user))
-			next_step()
-			return 1
-	return 0
+/datum/construction/proc/update_index(diff)
+	index += diff
+	on_step()
 
-/datum/construction/proc/is_right_key(obj/item/I) // returns current step num if I is of the right type.
-	var/list/L = steps[steps.len]
+/datum/construction/proc/check_step(obj/item/I, mob/living/user)
+	var/diff = is_right_key(I)
+	if(diff && custom_action(I, user, diff))
+		update_index(diff)
+		return TRUE
+	return FALSE
+
+/datum/construction/proc/is_right_key(obj/item/I) // returns index step
+	var/list/L = steps[index]
 	if(check_used_item(I, L["key"]))
-		return steps.len
-	return 0
+		return FORWARD //to the first step -> forward
+	else if(check_used_item(I, L["back_key"]))
+		return BACKWARD //to the last step -> backwards
+	return FALSE
 
 /datum/construction/proc/check_used_item(obj/item/I, key)
 	if(!key)
@@ -52,77 +58,47 @@
 
 	return FALSE
 
-
-/datum/construction/proc/custom_action(step, obj/item/I, user)
-	return 1
-
-/datum/construction/proc/check_all_steps(obj/item/I, mob/user) //check all steps, remove matching one.
-	for(var/i=1;i<=steps.len;i++)
-		var/list/L = steps[i]
-		if(check_used_item(I, L["key"]))
-			if(custom_action(i, I, user))
-				steps[i] = null//stupid byond list from list removal...
-				listclearnulls(steps)
-				if(!steps.len)
-					spawn_result()
-				return 1
-	return 0
-
+/datum/construction/proc/custom_action(obj/item/I, mob/living/user, diff)
+	return TRUE
 
 /datum/construction/proc/spawn_result()
 	if(result)
-		new result(get_turf(holder))
+		new result(drop_location())
 		qdel(holder)
-	return
 
-/datum/construction/proc/spawn_mecha_result()
-	if(result)
-		var/obj/mecha/m = new result(get_turf(holder))
-		var/obj/item/oldcell = locate (/obj/item/stock_parts/cell) in m
-		QDEL_NULL(oldcell)
-		m.CheckParts(holder.contents)
-		SSblackbox.record_feedback("tally", "mechas_created", 1, m.name)
-		QDEL_NULL(holder)
+/datum/construction/proc/update_holder(step_index)
+	var/list/step = steps[step_index]
 
-/datum/construction/proc/set_desc(index as num)
-	var/list/step = steps[index]
-	holder.desc = step["desc"]
-	return
+	if(step["desc"])
+		holder.desc = step["desc"]
+
+	if(step["icon_state"])
+		holder.icon_state = step["icon_state"]
 
 /datum/construction/proc/drop_location()
 	return holder.drop_location()
 
-/datum/construction/reversible
-	var/index
 
-/datum/construction/reversible/New(atom)
-	..()
-	index = steps.len
-	return
 
-/datum/construction/reversible/proc/update_index(diff as num)
-	index+=diff
-	if(index==0)
-		spawn_result()
-	else
-		set_desc(index)
-	return
-
-/datum/construction/reversible/is_right_key(obj/item/I) // returns index step
-	var/list/L = steps[index]
-	if(check_used_item(I, L["key"]))
-		return FORWARD //to the first step -> forward
-	else if(check_used_item(I, L["backkey"]))
-		return BACKWARD //to the last step -> backwards
+// Unordered construction.
+// Takes a list of part types, to be added in any order, as steps.
+// Calls spawn_result() when every type has been added.
+/datum/construction/unordered/check_step(obj/item/I, mob/living/user)
+	for(var/typepath in steps)
+		if(istype(I, typepath) && custom_action(I, user, typepath))
+			steps -= typepath
+			on_step()
+			return TRUE
 	return FALSE
 
-/datum/construction/reversible/check_step(obj/item/I, mob/user)
-	var/diff = is_right_key(I)
-	if(diff)
-		if(custom_action(index, diff, I, user))
-			update_index(diff)
-			return 1
-	return 0
+/datum/construction/unordered/on_step()
+	if(!steps.len)
+		spawn_result()
+	else
+		update_holder(steps.len)
 
-/datum/construction/reversible/custom_action(index, diff, obj/item/I, user)
-	return 1
+/datum/construction/unordered/update_holder(steps_left)
+	return
+
+/datum/construction/unordered/custom_action(obj/item/I, mob/living/user, typepath)
+	return TRUE