From 83b022bf6fbe73f472f0ed5829c7a47c8d1d2590 Mon Sep 17 00:00:00 2001
From: "Namhyeon, Go" <gnh1201@gmail.com>
Date: Wed, 20 Aug 2025 17:10:58 +0900
Subject: [PATCH] Refactor grid functions and update exports in extramath.js

Improved clusteredCellsDensity to validate cell indices and refactored coordinate calculation to be 1-based. Replaced tileStartPos with estimateTileStartPosition for more flexible tile positioning, updated exports accordingly, and bumped VERSIONINFO to 1.0.3.
---
 lib/extramath.js | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/lib/extramath.js b/lib/extramath.js
index 0b1556b..2a7254f 100644
--- a/lib/extramath.js
+++ b/lib/extramath.js
@@ -72,13 +72,22 @@ function cartesianProduct(arr) {
 
 function clusteredCellsDensity(numbers, size, minDensity) {
     if (!numbers || !numbers.length) return false;
-    if (typeof minDensity === 'undefined') minDensity = 0.6;
     if (typeof size !== 'number' || size <= 0) size = 4; // default grid size = 4
+    if (typeof minDensity === 'undefined') minDensity = 0.6;
 
-    // 1. Convert cell number → (x,y) coordinates
-    var coords = numbers.map(function (n) {
-        return { x: n % size, y: Math.floor(n / size) };
-    });
+    var maxIndex = size * size; // because it's 1-based (1..size*size)
+
+    // 1. Convert cell number → (x,y) coordinates with 1-based check
+    var coords = [];
+    for (var i = 0; i < numbers.length; i++) {
+    var n = numbers[i];
+    // must be within 1..maxIndex
+    if (typeof n !== 'number' || n < 1 || n > maxIndex) {
+      return false; // invalid index -> immediately return false
+    }
+    var idx = n - 1; // shift to 0-based
+        coords.push({ x: idx % size, y: Math.floor(idx / size) });
+    }
 
     var xs = coords.map(function (c) { return c.x; });
     var ys = coords.map(function (c) { return c.y; });
@@ -96,14 +105,17 @@ function clusteredCellsDensity(numbers, size, minDensity) {
     return density >= minDensity;
 }
 
-function tileStartPos(index, size, cols) {
-    if (typeof size !== 'number') size = 130;
-    if (typeof cols !== 'number') cols = 4;
+function estimateTileStartPosition(index, tiles, spreadSize, gap) {  
+    var tileSize = (spreadSize - gap * (tiles - 1)) / tiles;
 
-    var i = index - 1;                  // convert 1-based -> 0-based
-    var col = i % cols;
-    var row = Math.floor(i / cols);
-    return { x: col * size, y: row * size };
+    var i = index - 1;
+    var col = i % tiles;
+    var row = Math.floor(i / tiles);
+  
+    return {  
+        x: col * (tileSize + gap),
+        y: row * (tileSize + gap)
+    };
 }
 
 exports.DTM = DTM;
@@ -112,9 +124,9 @@ exports.measureSimilarity = measureSimilarity;
 exports.export_measureSimilarity = export_measureSimilarity;
 exports.cartesianProduct = cartesianProduct;
 exports.clusteredCellsDensity = clusteredCellsDensity;
-exports.tileStartPos = tileStartPos;
+exports.estimateTileStartPosition = estimateTileStartPosition;
 
-exports.VERSIONINFO = "ExtraMath module (extramath.js) version 1.0.1";
+exports.VERSIONINFO = "ExtraMath module (extramath.js) version 1.0.3";
 exports.AUTHOR = "gnh1201@catswords.re.kr";
 exports.global = global;
 exports.require = global.require;