From 32cea1030abb175c028d2508b04ce345810134b7 Mon Sep 17 00:00:00 2001
From: Webster Sheets <webster@web-eworks.com>
Date: Tue, 17 Oct 2023 18:01:22 -0400
Subject: [PATCH] Rework ProximityQuery API

- Remove storage of created proximity tests (callback function will prevent GC cleanup)
- Simplify and rename API to create a single object
- All created proximity queries are unique (little to no benefit in "sharing" queries due to large parameter space)
---
 .../{ProximityTest.lua => ProximityQuery.lua} | 76 +++++--------------
 1 file changed, 17 insertions(+), 59 deletions(-)
 rename data/modules/Common/{ProximityTest.lua => ProximityQuery.lua} (62%)

diff --git a/data/modules/Common/ProximityTest.lua b/data/modules/Common/ProximityQuery.lua
similarity index 62%
rename from data/modules/Common/ProximityTest.lua
rename to data/modules/Common/ProximityQuery.lua
index 5538274f19f..24cfcd249ed 100644
--- a/data/modules/Common/ProximityTest.lua
+++ b/data/modules/Common/ProximityQuery.lua
@@ -2,17 +2,12 @@
 -- Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
 
 local Engine     = require 'Engine'
-local Event      = require 'Event'
 local Space      = require 'Space'
 local Timer      = require 'Timer'
 local utils      = require 'utils'
 local Game       = require 'Game'
 
----@class Modules.Common.ProximityTest
-local ProximityTest = {}
-
----@type table<Body, table<string, Modules.Common.ProximityTest.Context>>
-local activeTests = utils.automagic()
+local ProximityQuery = {}
 
 -- ─── Context ─────────────────────────────────────────────────────────────────
 
@@ -25,15 +20,14 @@ local bodyListMt = {
 	__mode = "k"
 }
 
----@class Modules.Common.ProximityTest.Context
+---@class ProximityQuery.Context
 ---@field New fun(body, dist, interval, type): self
 ---@field body Body
 ---@field dist number
-local Context = utils.class 'Modules.Common.ProximityTest.Context'
+local Context = utils.class 'ProximityQuery.Context'
 
-function Context:Constructor(key, body, dist, type)
+function Context:Constructor(body, dist, type)
 	self.bodies = setmetatable({}, bodyListMt)
-	self.key = key
 	self.body = body
 	self.dist = dist
 	self.filter = type
@@ -44,52 +38,28 @@ function Context:Constructor(key, body, dist, type)
 end
 
 function Context:Cancel()
-	activeTests[self.body][self.key] = nil
 	self.iter = nil
 end
 
----@param fn fun(ctx: Modules.Common.ProximityTest.Context, enter: Body)
+---@param fn fun(ctx: ProximityQuery.Context, enter: Body)
 function Context:SetBodyEnter(fn)
 	self.onBodyEnter = fn
 	return self
 end
 
----@param fn fun(ctx: Modules.Common.ProximityTest.Context, leave: Body)
+---@param fn fun(ctx: ProximityQuery.Context, leave: Body)
 function Context:SetBodyLeave(fn)
 	self.onBodyLeave = fn
 	return self
 end
 
--- ─── Proximity Test ──────────────────────────────────────────────────────────
-
--- Class: ProximityTest
+-- Class: ProximityQuery
 --
 -- This class provides a helper utility to allow using Space.GetBodiesNear() in
 -- an efficient manner, providing an event-based API when bodies enter or leave
 -- a user-specified relevancy range of the reference body.
 
-local function makeTestKey(dist, interval, type)
-	return string.format("%d:%d:%s", dist, interval, type or "Body")
-end
-
--- Function: GetTest
---
--- Retrieves the Context object for an active proximity test currently queued
---
--- Parameters:
---
---   body - the reference body object of the proximity test
---   key  - the key value retrieved from the Context returned by RegisterTest
---
--- Returns:
---
---   context - the proximity test context object for the registered test
---
-function ProximityTest:GetTest(body, key)
-	return activeTests[body][key]
-end
-
--- Function: RegisterTest
+-- Function: CreateQuery
 --
 -- Register a new periodic proximity test relative to the given body
 --
@@ -107,14 +77,9 @@ end
 --
 --   context - the context object for the registered test
 --
-function ProximityTest:RegisterTest(body, dist, interval, type, overlap)
-	local key = makeTestKey(dist, interval, type)
-	if activeTests[body][key] then return activeTests[body][key] end
-
-	local context = Context.New(key, body, dist, type)
-	local cb = self:MakeCallback(context)
-
-	activeTests[body][key] = context
+function ProximityQuery.CreateQuery(body, dist, interval, type, overlap)
+	local context = Context.New(body, dist, type)
+	local cb = ProximityQuery.MakeCallback(context)
 
 	-- Queue the start of the timer at a random timestamp inside the first interval period
 	-- This provides natural load balancing for large numbers of callbacks created on the same frame
@@ -137,11 +102,12 @@ function ProximityTest:RegisterTest(body, dist, interval, type, overlap)
 end
 
 ---@private
----@param context Modules.Common.ProximityTest.Context
-function ProximityTest:MakeCallback(context)
+---@param context ProximityQuery.Context
+function ProximityQuery.MakeCallback(context)
 	return function()
-		-- Callback has been cancelled
-		if not context.iter then
+		-- Callback has been cancelled or query body no longer exists,
+		-- stop ticking this query
+		if not context.iter or not context.body:exists() then
 			return true
 		end
 
@@ -170,12 +136,4 @@ function ProximityTest:MakeCallback(context)
 	end
 end
 
-Event.Register("onGameStart", function()
-	activeTests = utils.automagic()
-end)
-
-Event.Register("onGameEnd", function()
-	activeTests = utils.automagic()
-end)
-
-return ProximityTest
+return ProximityQuery