add on_remove hook

ROADMAP.md

@@ -2,5 +2,4 @@
 
 ## Backlog
 
-- add on_remove hook
- 
+- add tag-fragment trait

develop/untests.lua

@@ -458,6 +458,49 @@ do
     assert(last_assign_component == 45)
 end
 
+do
+    local f1, f2 = evo.id(2)
+    local e = evo.id()
+
+    local remove_count = 0
+    local last_removed_component = nil
+
+    evo.set(f1, evo.ON_REMOVE, function(entity, fragment, component)
+        assert(entity == e)
+        assert(fragment == f1)
+        remove_count = remove_count + 1
+        last_removed_component = component
+    end)
+
+    evo.set(f2, evo.ON_REMOVE, function(entity, fragment, component)
+        assert(entity == e)
+        assert(fragment == f2)
+        remove_count = remove_count + 1
+        last_removed_component = component
+    end)
+
+    assert(evo.insert(e, f1, 42))
+    evo.remove(e, f1, f2)
+    assert(remove_count == 1)
+    assert(last_removed_component == 42)
+
+    assert(evo.insert(e, f1, 42))
+    assert(evo.insert(e, f2, 43))
+    evo.remove(e, f1, f2)
+    assert(remove_count == 3)
+    assert(last_removed_component == 43)
+
+    assert(evo.insert(e, f1, 44))
+    assert(evo.insert(e, f2, 45))
+    evo.clear(e)
+    assert(remove_count == 5)
+
+    assert(evo.insert(e, f1, 46))
+    assert(evo.insert(e, f2, 47))
+    evo.destroy(e)
+    assert(remove_count == 7)
+end
+
 do
     local f = evo.id()
     local e = evo.id()

evolved.lua

@@ -122,6 +122,7 @@ evolved.CONSTRUCT = __acquire_id()
 evolved.ON_SET = __acquire_id()
 evolved.ON_ASSIGN = __acquire_id()
 evolved.ON_INSERT = __acquire_id()
+evolved.ON_REMOVE = __acquire_id()
 
 ---
 ---
@@ -159,6 +160,14 @@ local function __on_insert(entity, fragment, component)
     if on_insert then on_insert(entity, fragment, component) end
 end
 
+---@param entity evolved.entity
+---@param fragment evolved.fragment
+---@param component evolved.component
+local function __on_remove(entity, fragment, component)
+    local on_remove = evolved.get(fragment, evolved.ON_REMOVE)
+    if on_remove then on_remove(entity, fragment, component) end
+end
+
 ---
 ---
 ---
@@ -787,8 +796,21 @@ function evolved.remove(entity, ...)
 
     local old_chunk_size = #old_chunk.__entities
     local old_chunk_entities = old_chunk.__entities
+    local old_chunk_fragments = old_chunk.__fragments
     local old_chunk_components = old_chunk.__components
 
+    for i = 1, select('#', ...) do
+        local old_f = select(i, ...)
+        if old_chunk_fragments[old_f] then
+            local old_cs = old_chunk_components[old_f]
+            __on_remove(entity, old_f, old_cs[old_place])
+        end
+    end
+
+    if old_chunk ~= __entity_chunks[index] then
+        error('entity structural changes are prohibited in ON_REMOVE hooks', 2)
+    end
+
     if new_chunk and assert(new_place) then
         local new_chunk_entities = new_chunk.__entities
         local new_chunk_components = new_chunk.__components
@@ -844,8 +866,18 @@ function evolved.clear(entity)
 
     local chunk_size = #chunk.__entities
     local chunk_entities = chunk.__entities
+    local chunk_fragments = chunk.__fragments
     local chunk_components = chunk.__components
 
+    for f, _ in pairs(chunk_fragments) do
+        local cs = chunk_components[f]
+        __on_remove(entity, f, cs[place])
+    end
+
+    if chunk ~= __entity_chunks[index] then
+        error('entity structural changes are prohibited in ON_REMOVE hooks', 2)
+    end
+
     if place == chunk_size then
         chunk_entities[place] = nil