From 69fc4989d8f77f1c53ada67886a80f2e7790897f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tr=E1=BA=A7n=20=C4=90=C3=ACnh=20Huy?= <kingonwork@gmail.com>
Date: Sat, 22 Aug 2026 22:32:41 +0700
Subject: [PATCH] fix: handle graph points sharing one pixel

---
 src/CreateGraphPath.ts                |  6 +++-
 src/__tests__/CreateGraphPath.test.ts | 45 +++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 src/__tests__/CreateGraphPath.test.ts

diff --git a/src/CreateGraphPath.ts b/src/CreateGraphPath.ts
index 5676695..0c7f1c0 100644
--- a/src/CreateGraphPath.ts
+++ b/src/CreateGraphPath.ts
@@ -162,7 +162,11 @@ function createGraphPathBase({
     horizontalPadding;
 
   const getGraphDataIndex = (pixel: number) =>
-    Math.round(((pixel - startX) / (endX - startX)) * (graphData.length - 1));
+    endX === startX
+      ? 0
+      : Math.round(
+          ((pixel - startX) / (endX - startX)) * (graphData.length - 1)
+        );
 
   const getNextPixelValue = (pixel: number) => {
     if (pixel === endX || pixel + PIXEL_RATIO < endX)
diff --git a/src/__tests__/CreateGraphPath.test.ts b/src/__tests__/CreateGraphPath.test.ts
new file mode 100644
index 0000000..dc015dd
--- /dev/null
+++ b/src/__tests__/CreateGraphPath.test.ts
@@ -0,0 +1,45 @@
+const mockPath = {
+  copy: jest.fn(),
+  cubicTo: jest.fn(),
+  lineTo: jest.fn(),
+  moveTo: jest.fn(),
+};
+
+jest.mock('@shopify/react-native-skia', () => ({
+  Skia: {
+    Path: {
+      Make: () => mockPath,
+    },
+  },
+}));
+
+import { createGraphPath } from '../CreateGraphPath';
+
+beforeEach(() => jest.clearAllMocks());
+
+it('creates a finite path when every graph point maps to the same pixel', () => {
+  const points = [
+    { date: new Date(2024, 1, 1), value: 10 },
+    { date: new Date(2024, 2, 1), value: 100 },
+  ];
+
+  expect(() =>
+    createGraphPath({
+      pointsInRange: points,
+      range: {
+        x: {
+          min: new Date(2024, 1, 1),
+          max: new Date(2070, 2, 1),
+        },
+        y: { min: 0, max: 100 },
+      },
+      horizontalPadding: 0,
+      verticalPadding: 0,
+      canvasHeight: 200,
+      canvasWidth: 300,
+    })
+  ).not.toThrow();
+
+  expect(mockPath.moveTo).toHaveBeenCalledTimes(1);
+  expect(mockPath.moveTo.mock.calls[0]?.every(Number.isFinite)).toBe(true);
+});