experimental removable events

utils/event.lua

@@ -5,6 +5,8 @@ local debug_mode = false
 local init_event_name = -1
 local load_event_name = -2
 
+local control_stage = true
+
 local event_handlers = {}-- map of event_name to handlers[]
 local on_nth_tick_event_handlers = {}-- map of nth_tick to handlers[]
 
@@ -83,4 +85,68 @@ function Event.on_nth_tick(tick, handler)
     end
 end
 
+local Token = require "utils.global_token"
+global.event_tokens = {}
+
+function Event.add_removable(event_name, token)
+    local event_tokens = global.event_tokens
+    
+    local tokens = event_tokens[event_name]
+    if not tokens then
+        event_tokens[event_name] = {token}
+    else
+        table.insert(tokens, token)
+    end
+    
+    if not control_stage then
+        local handler = Token.get(token)
+        Event.add(event_name, handler)
+    end
+end
+
+local function remove(t, e)
+    for i, v in ipairs(t) do
+        if v == e then
+            table.remove(t, i)
+            break
+        end
+    end
+end
+
+function Event.remove_removable(event_name, token)
+    local event_tokens = global.event_tokens
+    
+    local tokens = event_tokens[event_name]
+    
+    if not tokens then
+        return
+    end
+    
+    local handler = Token.get(token)
+    local handlers = event_handlers[event_name]
+    
+    remove(tokens, token)
+    remove(handlers, handler)
+    
+    if #handlers == 0 then
+        script.on_event(event_name, nil)
+    end
+end
+
+local function add_token_handlers()
+	control_stage = false
+
+    local event_tokens = global.event_tokens
+    
+    for event_name, tokens in pairs(event_tokens) do
+        for _, token in ipairs(tokens) do
+            local handler = Token.get(token)
+            Event.add(event_name, handler)
+        end
+    end
+end
+
+Event.on_init(add_token_handlers)
+Event.on_load(add_token_handlers)
+
 return Event