From 534b1ab435bbfaa35a31c4c4e6200c10a3830659 Mon Sep 17 00:00:00 2001
From: Linden <65407488+thelindat@users.noreply.github.com>
Date: Mon, 10 Mar 2025 12:29:14 +1100
Subject: [PATCH] feat(grid): add a grid system

Based on mkafrin's grid used by PolyZone's ComboZones.
---
 imports/grid/shared.lua | 187 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 187 insertions(+)
 create mode 100644 imports/grid/shared.lua

diff --git a/imports/grid/shared.lua b/imports/grid/shared.lua
new file mode 100644
index 0000000..9355f59
--- /dev/null
+++ b/imports/grid/shared.lua
@@ -0,0 +1,187 @@
+--[[
+    Based on PolyZone's grid system (https://github.com/mkafrin/PolyZone/blob/master/ComboZone.lua)
+
+    MIT License
+
+    Copyright (c) 2019-2021 Michael Afrin
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+    SOFTWARE.
+]]
+
+local mapMinX = -3700
+local mapMinY = -4400
+local mapMaxX = 4500
+local mapMaxY = 8000
+local xDelta = (mapMaxX - mapMinX) / 34
+local yDelta = (mapMaxY - mapMinY) / 50
+local grid = {}
+local lastCell = {}
+local lastNearbyEntries = {}
+local entrySet = {}
+
+lib.grid = {}
+
+---@class GridEntry
+---@field coords vector
+---@field length? number
+---@field width? number
+---@field radius? number
+---@field [string] any
+
+---@param point vector
+---@param length number
+---@param width number
+---@return number, number, number, number
+local function getGridDimensions(point, length, width)
+    local minX = (point.x - width - mapMinX) // xDelta
+    local maxX = (point.x + width - mapMinX) // xDelta
+    local minY = (point.y - length - mapMinY) // yDelta
+    local maxY = (point.y + length - mapMinY) // yDelta
+
+    return minX, maxX, minY, maxY
+end
+
+---@param point vector
+---@return number, number
+function lib.grid.getCellPosition(point)
+    local x = (point.x - mapMinX) // xDelta
+    local y = (point.y - mapMinY) // yDelta
+
+    return x, y
+end
+
+---@param point vector
+---@return GridEntry[]
+function lib.grid.getCell(point)
+    local x, y = lib.grid.getCellPosition(point)
+
+    if lastCell.x ~= x or lastCell.y ~= y then
+        lastCell.x = x
+        lastCell.y = y
+        lastCell.cell = grid[y] and grid[y][x] or {}
+    end
+
+    return lastCell.cell
+end
+
+---@param point vector
+---@return GridEntry[]
+function lib.grid.getNearbyEntries(point)
+    local minX, maxX, minY, maxY = getGridDimensions(point, xDelta, yDelta)
+
+    if lastNearbyEntries.minX == minX and
+        lastNearbyEntries.maxX == maxX and
+        lastNearbyEntries.minY == minY and
+        lastNearbyEntries.maxY == maxY then
+        return lastNearbyEntries.entries
+    end
+
+    local entries = {}
+    local n = 0
+
+    table.wipe(entrySet)
+
+    for y = minY, maxY do
+        local row = grid[y]
+
+        for x = minX, maxX do
+            local cell = row and row[x]
+
+            if cell then
+                for j = 1, #cell do
+                    local entry = cell[j]
+
+                    if not entrySet[entry] then
+                        n = n + 1
+                        entrySet[entry] = true
+                        entries[n] = entry
+                    end
+                end
+            end
+        end
+    end
+
+    lastNearbyEntries.minX = minX
+    lastNearbyEntries.maxX = maxX
+    lastNearbyEntries.minY = minY
+    lastNearbyEntries.maxY = maxY
+    lastNearbyEntries.entries = entries
+
+    return entries
+end
+
+---@param entry { coords: vector, length?: number, width?: number, radius?: number, [string]: any }
+function lib.grid.addEntry(entry)
+    entry.length = entry.length or entry.radius * 2
+    entry.width = entry.width or entry.radius * 2
+    local minX, maxX, minY, maxY = getGridDimensions(entry.coords, entry.length, entry.width)
+
+    for y = minY, maxY do
+        local row = grid[y] or {}
+
+        for x = minX, maxX do
+            local cell = row[x] or {}
+
+            cell[#cell + 1] = entry
+            row[x] = cell
+        end
+
+        grid[y] = row
+    end
+end
+
+---@param entry table A table that was added to the grid previously.
+function lib.grid.removeEntry(entry)
+    local minX, maxX, minY, maxY = getGridDimensions(entry.coords, entry.length, entry.width)
+    local success = false
+
+    for y = minY, maxY do
+        local row = grid[y]
+
+        if not row then goto continue end
+
+        for x = minX, maxX do
+            local cell = row[x]
+
+            if cell then
+                for i = 1, #cell do
+                    if cell[i] == entry then
+                        table.remove(cell, i)
+                        success = true
+                        break
+                    end
+                end
+
+                if #cell == 0 then
+                    row[x] = nil
+                end
+            end
+        end
+
+        if not next(row) then
+            grid[y] = nil
+        end
+
+        ::continue::
+    end
+
+    return success
+end
+
+return lib.grid