feat(getFontUrl): create a helper function to choose font url

src/entities/Font/lib/getFontUrl/getFontUrl.ts

@@ -0,0 +1,29 @@
+import type {
+    FontWeight,
+    UnifiedFont,
+} from '../../model';
+
+const SIZES = [100, 200, 300, 400, 500, 600, 700, 800, 900];
+
+/**
+ * Constructs a URL for a font based on the provided font and weight.
+ * @param font - The font object.
+ * @param weight - The weight of the font.
+ * @returns The URL for the font.
+ */
+export function getFontUrl(font: UnifiedFont, weight: number): string | undefined {
+    if (!SIZES.includes(weight)) {
+        throw new Error(`Invalid weight: ${weight}`);
+    }
+
+    const weightKey = weight.toString() as FontWeight;
+
+    // 1. Try exact match (Backend now maps "100".."900" to VF URL if variable)
+    if (font.styles.variants?.[weightKey]) {
+        return font.styles.variants[weightKey];
+    }
+
+    // 2. Fallbacks for Static Fonts (if exact weight missing)
+    // Try 'regular' or '400' as safe defaults
+    return font.styles.regular || font.styles.variants?.['400'] || font.styles.variants?.['regular'];
+}