Restore py halving tech costs each tier to autotech

autotech.lua

@@ -368,6 +368,7 @@ function auto_tech:set_tech_unit()
     local exponent = self.configuration.tech_cost_exponent
     local victory_node = self.technology_nodes:find_technology_node(self.dependency_graph.victory_node)
     local max_depth = victory_node.depth - 1
+    local depths_of_science_packs = {}
 
     if max_depth <= 0 then
         error("victory technology has a depth of " .. max_depth .. "\n" .. serpent.block(victory_node))
@@ -390,20 +391,99 @@ function auto_tech:set_tech_unit()
         error()
     end
 
+    -- get the depths of all science packs on the tech tree, assuming non-progression military science
+    self.technology_nodes:for_all_nodes(function(technology_node)
+        local factorio_tech = technology_node.object_node.object
+        local science_pack_unlocked_by_this_tech = data.raw.tool[technology_node.object_node.object.name]
+        if science_pack_unlocked_by_this_tech then
+            if factorio_tech.name ~= "military-science-pack" then
+                depths_of_science_packs[#depths_of_science_packs + 1] = technology_node.depth
+                if verbose_logging then
+                    log("Depth of a new science pack tech is " .. technology_node.depth)
+                end
+                return
+            end
+            if verbose_logging then
+                log("Depth of a military science pack tech is " .. technology_node.depth .. ". it will be ignored as a non-progression pack.")
+            end
+        end
+    end)
+
+
+
+    -- sort the table of depths from lowest to highest
+    table.sort(depths_of_science_packs)
+    if verbose_logging then
+        for _, pack_depth in pairs(depths_of_science_packs) do
+            log("Depth of a new science pack tech is " .. pack_depth)
+        end
+    end
+
+    local number_of_initial_trigger_techs = 0
+    -- count the amount of trigger techs leading to the initial science pack
+    for i = 1, math.min(#self.technology_nodes_array, depths_of_science_packs[1] + 1) do
+        local node = self.technology_nodes_array[i]
+        if not node.object_node.object.research_trigger then
+            break
+        end
+        if verbose_logging then
+            log(node.printable_name .. " is the new latest trigger tech")
+        end
+        number_of_initial_trigger_techs = node.depth + 1
+    end
+    if verbose_logging then
+        log("Number of initial trigger techs is " .. number_of_initial_trigger_techs)
+    end
+
+
     self.technology_nodes:for_all_nodes(function(technology_node)
         local factorio_tech = technology_node.object_node.object
         if factorio_tech.research_trigger then return end
         factorio_tech.unit = factorio_tech.unit or {}
-        local depth_percent = (technology_node.depth / max_depth)
+
+        -- get the relative depth of the technology compared to the science pack, as a percentage
+        local relative_depth_percent = -1
+        local absolute_depth_in_science_tier = technology_node.depth
+        for i = #depths_of_science_packs, 2, -1 do -- work from largest to smallest, end at 2 as we won't be adjusting automation tech costs
+            local current_tier_depth = depths_of_science_packs[i] + 1 -- Add one as we want the first tech, not the science pack
+            if technology_node.depth >= current_tier_depth then
+                local next_tier_depth = depths_of_science_packs[i + 1] or max_depth
+                local length_of_science_tier = next_tier_depth - current_tier_depth
+                absolute_depth_in_science_tier = absolute_depth_in_science_tier - current_tier_depth
+                relative_depth_percent = (technology_node.depth - current_tier_depth) / length_of_science_tier -- aka relative depth in science tier
+                break
+            end
+        end
+
+        local depth_percent = ((technology_node.depth - number_of_initial_trigger_techs) / (max_depth - number_of_initial_trigger_techs))
         factorio_tech.unit.count = start + (victory - start) * (depth_percent ^ exponent)
 
         if factorio_tech.unit.count == math.huge then
             error(depth_percent .. "\n" .. serpent.block(factorio_tech) .. serpent.block(self.configuration))
         end
         if verbose_logging then
-            log("Technology " .. factorio_tech.name .. " has a depth of " .. technology_node.depth .. ". Calculated science pack cost is " .. factorio_tech.unit.count)
+            log(table.concat{
+                "Technology ",
+                factorio_tech.name,
+                " has a depth of ",
+                technology_node.depth,
+                ", absolute depth from last science pack of ",
+                absolute_depth_in_science_tier,
+                " and a relative depth in the science tier of ",
+                relative_depth_percent,
+                ". Calculated science pack cost is ",
+                factorio_tech.unit.count
+            })
+        end
+        if relative_depth_percent >= 0 then
+            if absolute_depth_in_science_tier < technology_node.depth then
+                factorio_tech.unit.count = factorio_tech.unit.count * (0.5 * (1.0 - relative_depth_percent) + relative_depth_percent) -- linear scaling between 0.5 and full cost across the science tier
+            end
         end
         factorio_tech.unit.count = math.max(cost_rounding(factorio_tech.unit.count), 1)
+        if verbose_logging then
+            log("Technology " .. factorio_tech.name .. " has the reduced and rounded cost of " .. factorio_tech.unit.count)
+        end
 
         local final_multiplier = self.configuration.tech_cost_additional_multipliers[factorio_tech.name]
         if final_multiplier then