Move clamp function to lib directory (#250)

* clamp refactoring

* pr template

.github/pull_request_template.md

@@ -0,0 +1,5 @@
+## Summary
+
+-
+
+## Closes #

src/lib/math.test.ts

@@ -0,0 +1,30 @@
+import { describe, it, expect } from "vitest"
+import { clamp } from "./math"
+
+describe("clamp", () => {
+    it("should return value when within range", () => {
+        expect(clamp(5, 0, 10)).toBe(5)
+    })
+
+    it("should return min when value is below range", () => {
+        expect(clamp(-1, 0, 10)).toBe(0)
+    })
+
+    it("should return max when value is above range", () => {
+        expect(clamp(15, 0, 10)).toBe(10)
+    })
+
+    it("should return min when value equals min", () => {
+        expect(clamp(0, 0, 10)).toBe(0)
+    })
+
+    it("should return max when value equals max", () => {
+        expect(clamp(10, 0, 10)).toBe(10)
+    })
+
+    it("should work with negative ranges", () => {
+        expect(clamp(-5, -10, -1)).toBe(-5)
+        expect(clamp(-15, -10, -1)).toBe(-10)
+        expect(clamp(0, -10, -1)).toBe(-1)
+    })
+})

src/lib/math.ts

@@ -0,0 +1,9 @@
+export function clamp(val: number, min: number, max: number): number {
+    if (val < min) {
+        return min
+    }
+    if (val > max) {
+        return max
+    }
+    return val
+}

src/store/theme.ts

@@ -1,4 +1,5 @@
 import { proxy, subscribe } from "valtio"
+import { clamp } from "@/lib/math"
 
 export type ThemeName = "default" | "contrast"
 export type ColorSchemeVariant = "black-on-white" | "white-on-black" | "blue-on-blue" | "brown-on-yellow" | "green-on-brown"
@@ -8,16 +9,6 @@ const MIN_FONT_SIZE = 8
 const MAX_FONT_SIZE = 48
 const CHANGE_FONT_SIZE_DELTA = 1
 
-function clamp(val: number, min: number, max: number): number {
-    if (val < min) {
-        return min
-    }
-    if (val > max) {
-        return max
-    }
-    return val
-}
-
 export type ThemeOptions = {
     theme: ThemeName
     fontType: FontTypeVariant