Change biter corpse remover.

The biter corpse remover was attempting to be clever about removing corpses and only remove them when they exceeded a certain threshold per chunk. For some reason it is no longer working and I can't figure out why.
So I replaced it with a simpler approach. Now we keep track of the corpses in a queue. When the queue size exceeds the threshold we remove and destroy the oldest corpse.

config.lua

@@ -402,8 +402,7 @@ global.config = {
     -- when biter corpses in an area are above a threshold, remove the desired amount
     biter_corpse_remover = {
         enabled = true,
-        chunk_size = 3, -- size of chunk in tiles
-        corpse_threshold = 3 -- number of corpses allowed on surface inside chunk
+        max_queue_size = 200 -- The number of corpses to keep in the queue before removing the oldest.
     },
     turret_active_delay = {
         enabled = true,

features/biter_corpse_remover.lua

@@ -1,117 +1,42 @@
 -- dependencies
 local Event = require 'utils.event'
 local Global = require 'utils.global'
-local table = require 'utils.table'
-local remove = table.remove
-local pairs = pairs
-local next = next
+local Queue = require 'utils.queue'
 
-local biter_utils_conf = global.config.biter_corpse_remover
+local queue_push = Queue.push
+local queue_pop = Queue.pop
+local queue_size = Queue.size
 
--- Factorio removes corpses that hit 15 minutes anyway
-local max_corpse_age = 15 * 60 * 60
-local kills_per_cleanup = 500
+-- config table for the max queue size
+-- Change at runtime with /sc global.config.biter_corpse_remover.max_queue_size = 100
+local biter_corpse_remover = global.config.biter_corpse_remover
 
--- x -> y -> array of {entity, tick}
-local corpse_chunks = {}
-local cleanup_count = {kills_per_cleanup}
+local corpse_queue = Queue.new()
 
-Global.register(
-    {
-        corpse_chunks = corpse_chunks,
-        cleanup_count = cleanup_count
-    },
-    function(tbl)
-        corpse_chunks = tbl.corpse_chunks
-        cleanup_count = tbl.cleanup_count
+Global.register(corpse_queue, function(tbl)
+    corpse_queue = tbl
+end)
+
+local function entity_died(event)
+    if not event.unit_number then
+        return
     end
-)
 
--- cleans up the stored list of corpses and chunks
-local function remove_outdated_corpses(now)
-    -- loop each stored chunk
-    for x, column in pairs(corpse_chunks) do
-        for y, corpses in pairs(column) do
-            local count = #corpses
-
-            for i = count, 1, -1 do
-                if corpses[i].tick < now then
-                    remove(corpses, i)
-                    count = count - 1
-                end
-            end
-
-            if count == 0 then
-                column[y] = nil
-            end
+    local corpses = event.corpses
+    for i = 1, #corpses do
+        local corpse = corpses[i]
+        if corpse.valid then
+            queue_push(corpse_queue, corpse)
         end
+    end
 
-        if next(column) == nil then
-            corpse_chunks[x] = nil
+    local to_remove = queue_size(corpse_queue) - biter_corpse_remover.max_queue_size
+    for _ = 1, to_remove do
+        local corpse = queue_pop(corpse_queue)
+        if corpse.valid then
+            corpse.destroy()
         end
     end
 end
 
-local function biter_died(event)
-    local prot = event.prototype
-
-    -- Only trigger on dead units
-    if prot.type ~= 'unit' then
-        return
-    end
-
-    local entity = event.corpses[1]
-    -- Ensure there is actually a corpse
-    if entity == nil then
-        return
-    end
-
-    local tick = event.tick
-
-    -- Chance to clean up old corpses and chunks
-    local cuc = cleanup_count[1] - 1
-    if cuc <= 0 then
-        remove_outdated_corpses(tick)
-        cleanup_count[1] = kills_per_cleanup
-    else
-        cleanup_count[1] = cuc
-    end
-
-    --Calculate the chunk position
-    local chunk_size = biter_utils_conf.chunk_size
-    local pos = entity.position
-    local x, y = pos.x, pos.y
-    x = x - (x % chunk_size)
-    y = y - (y % chunk_size)
-
-    -- check global table has this position, add if not
-    local corpse_chunks_column = corpse_chunks[x]
-    if corpse_chunks_column == nil then
-        corpse_chunks_column = {}
-        corpse_chunks[x] = corpse_chunks_column
-    end
-
-    local corpses = corpse_chunks_column[y]
-    if corpses == nil then
-        corpses = {}
-        corpse_chunks_column[y] = corpses
-    end
-
-    -- Add this entity
-    local count = #corpses + 1
-    corpses[count] = {
-        entity = entity,
-        tick = tick + max_corpse_age
-    }
-
-    -- Cleanup old corpse if above threshold
-    if count > biter_utils_conf.corpse_threshold then
-        local old_entity = remove(corpses, 1).entity
-
-        if old_entity.valid then
-            old_entity.destroy()
-        end
-    end
-end
-
-Event.add(defines.events.on_post_entity_died, biter_died)
+Event.add(defines.events.on_post_entity_died, entity_died)