feat(tip): support tiered coffee gifts

src/lib/tip/tip_coffee.ts

@@ -0,0 +1,57 @@
+import { ROUTES } from "@/router/routes";
+
+export const TIP_COFFEE_TYPE_PARAM = "coffee_type";
+export const DEFAULT_TIP_COFFEE_TYPE = "small";
+
+export type TipCoffeeType = "small" | "medium" | "large";
+
+export interface TipCoffeeOption {
+  type: TipCoffeeType;
+  amountCents: number;
+  fallbackName: string;
+  planId: string;
+}
+
+const TIP_COFFEE_OPTIONS: Record<TipCoffeeType, TipCoffeeOption> = {
+  small: {
+    type: "small",
+    amountCents: 499,
+    fallbackName: "Small Coffee",
+    planId: "tip_coffee_small",
+  },
+  medium: {
+    type: "medium",
+    amountCents: 999,
+    fallbackName: "Medium Coffee",
+    planId: "tip_coffee_medium",
+  },
+  large: {
+    type: "large",
+    amountCents: 1999,
+    fallbackName: "Large Coffee",
+    planId: "tip_coffee_large",
+  },
+};
+
+export function resolveTipCoffeeType(
+  value: string | null | undefined,
+): TipCoffeeType | null {
+  const normalized = value?.trim().toLowerCase();
+  if (
+    normalized === "small" ||
+    normalized === "medium" ||
+    normalized === "large"
+  ) {
+    return normalized;
+  }
+  return null;
+}
+
+export function getTipCoffeeOption(type: TipCoffeeType): TipCoffeeOption {
+  return TIP_COFFEE_OPTIONS[type];
+}
+
+export function buildTipCoffeePath(type: TipCoffeeType): string {
+  const params = new URLSearchParams({ [TIP_COFFEE_TYPE_PARAM]: type });
+  return `${ROUTES.tip}?${params.toString()}`;
+}