Refactor: Build tier table

Each element of the array indicates the minimum amount of licenses that have to be purchased to get the corresponding unit price.

When filtering this array, the first element of the filtered array is the tier to be applied.

Author: xetxeberria

exercises/tiered_pricing/solutions/xetxeberria-ts/src/tieredPricing.ts

@@ -1,16 +1,20 @@
+const priceTiers = [
+  { minAmount: 1, unitPrice: 299 },
+  { minAmount: 3, unitPrice: 239 },
+  { minAmount: 11, unitPrice: 219 },
+  { minAmount: 26, unitPrice: 199 },
+  { minAmount: 51, unitPrice: 149 },
+];
+
 export function tieredPricing(licenseAmount: number): number {
   const licensePrice = calculateLicensePrice(licenseAmount);
 
   return licensePrice * licenseAmount;
 }
 
 function calculateLicensePrice(licenseAmount: number): number {
-  let licensePrice = 299;
-
-  if (licenseAmount >= 3) licensePrice = 239;
-  if (licenseAmount >= 11) licensePrice = 219;
-  if (licenseAmount >= 26) licensePrice = 199;
-  if (licenseAmount >= 51) licensePrice = 149;
-
-  return licensePrice;
+  const applicableTier = priceTiers
+    .filter((tier) => licenseAmount >= tier.minAmount)
+    .pop();
+  return applicableTier?.unitPrice || 299;
 }