Refactor billing components to improve price display and modularity (#132)

* Refactor billing components to improve price display and modularity
- Created new `PlanCostDisplay` component to centralize price formatting logic
- Simplified price rendering in plan picker and pricing table
- Removed redundant price calculation code
- Improved handling of metered and tiered pricing display

packages/billing/gateway/src/components/line-item-details.tsx

@@ -242,12 +242,8 @@ function Tiers({
     const isIncluded = tier.cost === 0;
 
     return (
-      <span
-        className={'text-secondary-foreground flex gap-x-2 text-xs'}
-        key={index}
-      >
-        <span>-</span>
-
+      <span className={'text-secondary-foreground text-xs'} key={index}>
+        <span>-</span>{' '}
         <If condition={isLastTier}>
           <span className={'font-bold'}>
             {formatCurrency({
@@ -255,8 +251,7 @@ function Tiers({
               value: tier.cost,
               locale,
             })}
-          </span>
-
+          </span>{' '}
           <If condition={tiersLength > 1}>
             <span>
               <Trans
@@ -268,7 +263,6 @@ function Tiers({
               />
             </span>
           </If>
-
           <If condition={tiersLength === 1}>
             <span>
               <Trans
@@ -279,15 +273,13 @@ function Tiers({
               />
             </span>
           </If>
-        </If>
-
+        </If>{' '}
         <If condition={!isLastTier}>
           <If condition={isIncluded}>
             <span>
               <Trans i18nKey={'billing:includedUpTo'} values={{ unit, upTo }} />
             </span>
-          </If>
-
+          </If>{' '}
           <If condition={!isIncluded}>
             <span className={'font-bold'}>
               {formatCurrency({
@@ -295,8 +287,7 @@ function Tiers({
                 value: tier.cost,
                 locale,
               })}
-            </span>
-
+            </span>{' '}
             <span>
               <Trans
                 i18nKey={'billing:fromPreviousTierUpTo'}

packages/billing/gateway/src/components/plan-cost-display.tsx

@@ -0,0 +1,98 @@
+'use client';
+
+import { useMemo } from 'react';
+
+import { useTranslation } from 'react-i18next';
+import { z } from 'zod';
+
+import type { LineItemSchema } from '@kit/billing';
+import { formatCurrency } from '@kit/shared/utils';
+import { Trans } from '@kit/ui/trans';
+
+type PlanCostDisplayProps = {
+  primaryLineItem: z.infer<typeof LineItemSchema>;
+  currencyCode: string;
+  interval?: string;
+  alwaysDisplayMonthlyPrice?: boolean;
+  className?: string;
+};
+
+/**
+ * @name PlanCostDisplay
+ * @description
+ * This component is used to display the cost of a plan. It will handle
+ * the display of the cost for metered plans by using the lowest tier using the format "Starting at {price} {unit}"
+ */
+export function PlanCostDisplay({
+  primaryLineItem,
+  currencyCode,
+  interval,
+  alwaysDisplayMonthlyPrice = true,
+  className,
+}: PlanCostDisplayProps) {
+  const { i18n } = useTranslation();
+
+  const { shouldDisplayTier, lowestTier, tierTranslationKey, displayCost } =
+    useMemo(() => {
+      const shouldDisplayTier =
+        primaryLineItem.type === 'metered' &&
+        Array.isArray(primaryLineItem.tiers) &&
+        primaryLineItem.tiers.length > 0;
+
+      const isMultiTier =
+        Array.isArray(primaryLineItem.tiers) &&
+        primaryLineItem.tiers.length > 1;
+
+      const lowestTier = primaryLineItem.tiers?.reduce((acc, curr) => {
+        if (acc && acc.cost < curr.cost) {
+          return acc;
+        }
+        return curr;
+      }, primaryLineItem.tiers?.[0]);
+
+      const isYearlyPricing = interval === 'year';
+
+      const cost =
+        isYearlyPricing && alwaysDisplayMonthlyPrice
+          ? Number(primaryLineItem.cost / 12)
+          : primaryLineItem.cost;
+
+      return {
+        shouldDisplayTier,
+        isMultiTier,
+        lowestTier,
+        tierTranslationKey: isMultiTier
+          ? 'billing:startingAtPriceUnit'
+          : 'billing:priceUnit',
+        displayCost: cost,
+      };
+    }, [primaryLineItem, interval, alwaysDisplayMonthlyPrice]);
+
+  if (shouldDisplayTier) {
+    const formattedCost = formatCurrency({
+      currencyCode: currencyCode.toLowerCase(),
+      value: lowestTier?.cost ?? 0,
+      locale: i18n.language,
+    });
+
+    return (
+      <span className={'text-lg'}>
+        <Trans
+          i18nKey={tierTranslationKey}
+          values={{
+            price: formattedCost,
+            unit: primaryLineItem.unit,
+          }}
+        />
+      </span>
+    );
+  }
+
+  const formattedCost = formatCurrency({
+    currencyCode: currencyCode.toLowerCase(),
+    value: displayCost,
+    locale: i18n.language,
+  });
+
+  return <span className={className}>{formattedCost}</span>;
+}

packages/billing/gateway/src/components/plan-picker.tsx

@@ -15,7 +15,6 @@ import {
   getPrimaryLineItem,
   getProductPlanPair,
 } from '@kit/billing';
-import { formatCurrency } from '@kit/shared/utils';
 import { Badge } from '@kit/ui/badge';
 import { Button } from '@kit/ui/button';
 import {
@@ -38,6 +37,7 @@ import { Trans } from '@kit/ui/trans';
 import { cn } from '@kit/ui/utils';
 
 import { LineItemDetails } from './line-item-details';
+import { PlanCostDisplay } from './plan-cost-display';
 
 export function PlanPicker(
   props: React.PropsWithChildren<{
@@ -108,8 +108,6 @@ export function PlanPicker(
   const isRecurringPlan =
     selectedPlan?.paymentType === 'recurring' || !selectedPlan;
 
-  const locale = useTranslation().i18n.language;
-
   return (
     <Form {...form}>
       <div
@@ -238,30 +236,6 @@ export function PlanPicker(
                         throw new Error(`Base line item was not found`);
                       }
 
-                      const shouldDisplayTier =
-                        primaryLineItem.type === 'metered' &&
-                        Array.isArray(primaryLineItem.tiers) &&
-                        primaryLineItem.tiers.length > 0;
-
-                      const isMultiTier =
-                        Array.isArray(primaryLineItem.tiers) &&
-                        primaryLineItem.tiers.length > 1;
-
-                      const lowestTier = primaryLineItem.tiers?.reduce(
-                        (acc, curr) => {
-                          if (acc && acc.cost < curr.cost) {
-                            return acc;
-                          }
-
-                          return curr;
-                        },
-                        primaryLineItem.tiers[0],
-                      );
-
-                      const tierTranslationKey = isMultiTier
-                        ? 'billing:startingAtPriceUnit'
-                        : 'billing:priceUnit';
-
                       return (
                         <RadioGroupItemLabel
                           selected={selected}
@@ -341,34 +315,14 @@ export function PlanPicker(
                               }
                             >
                               <div>
-                                <If
-                                  condition={shouldDisplayTier}
-                                  fallback={
-                                    <Price key={plan.id}>
-                                      <span>
-                                        {formatCurrency({
-                                          currencyCode:
-                                            product.currency.toLowerCase(),
-                                          value: primaryLineItem.cost,
-                                          locale,
-                                        })}
-                                      </span>
-                                    </Price>
-                                  }
-                                >
-                                  <Trans
-                                    i18nKey={tierTranslationKey}
-                                    values={{
-                                      price: formatCurrency({
-                                        currencyCode:
-                                          product.currency.toLowerCase(),
-                                        value: lowestTier?.cost ?? 0,
-                                        locale,
-                                      }),
-                                      unit: primaryLineItem.unit,
-                                    }}
+                                <Price key={plan.id}>
+                                  <PlanCostDisplay
+                                    primaryLineItem={primaryLineItem}
+                                    currencyCode={product.currency}
+                                    interval={selectedInterval}
+                                    alwaysDisplayMonthlyPrice={true}
                                   />
-                                </If>
+                                </Price>
 
                                 <div>
                                   <span className={'text-muted-foreground'}>

packages/billing/gateway/src/components/pricing-table.tsx

@@ -14,7 +14,6 @@ import {
   getPlanIntervals,
   getPrimaryLineItem,
 } from '@kit/billing';
-import { formatCurrency } from '@kit/shared/utils';
 import { Badge } from '@kit/ui/badge';
 import { Button } from '@kit/ui/button';
 import { If } from '@kit/ui/if';
@@ -23,6 +22,7 @@ import { Trans } from '@kit/ui/trans';
 import { cn } from '@kit/ui/utils';
 
 import { LineItemDetails } from './line-item-details';
+import { PlanCostDisplay } from './plan-cost-display';
 
 interface Paths {
   signUp: string;
@@ -152,8 +152,7 @@ function PricingItem(
   }>,
 ) {
   const highlighted = props.product.highlighted ?? false;
-
-  const lineItem = props.primaryLineItem;
+  const lineItem = props.primaryLineItem!;
 
   // we exclude flat line items from the details since
   // it doesn't need further explanation
@@ -218,11 +217,10 @@ function PricingItem(
 
         <div className={'flex flex-col space-y-2'}>
           <Price isMonthlyPrice={props.alwaysDisplayMonthlyPrice}>
-            <LineItemPrice
-              plan={props.plan}
-              product={props.product}
+            <PlanCostDisplay
+              primaryLineItem={lineItem}
+              currencyCode={props.product.currency}
               interval={interval}
-              lineItem={lineItem}
               alwaysDisplayMonthlyPrice={props.alwaysDisplayMonthlyPrice}
             />
           </Price>
@@ -492,46 +490,3 @@ function DefaultCheckoutButton(
     </Link>
   );
 }
-
-function LineItemPrice({
-  lineItem,
-  plan,
-  interval,
-  product,
-  alwaysDisplayMonthlyPrice = true,
-}: {
-  lineItem: z.infer<typeof LineItemSchema> | undefined;
-  plan: {
-    label?: string;
-  };
-  interval: Interval | undefined;
-  product: {
-    currency: string;
-  };
-  alwaysDisplayMonthlyPrice?: boolean;
-}) {
-  const { i18n } = useTranslation();
-  const isYearlyPricing = interval === 'year';
-
-  const cost = lineItem
-    ? isYearlyPricing
-      ? alwaysDisplayMonthlyPrice
-        ? Number(lineItem.cost / 12).toFixed(2)
-        : lineItem.cost
-      : lineItem?.cost
-    : 0;
-
-  const costString =
-    lineItem &&
-    formatCurrency({
-      currencyCode: product.currency,
-      locale: i18n.language,
-      value: cost,
-    });
-
-  const labelString = plan.label && (
-    <Trans i18nKey={plan.label} defaults={plan.label} />
-  );
-
-  return costString ?? labelString ?? <Trans i18nKey={'billing:custom'} />;
-}