Web: unshield (move money back out)

frontend/wallet/app/privacy/unshield/amounts.ts

@@ -0,0 +1,46 @@
+/**
+ * The arithmetic and the asset list behind the unshield screen.
+ *
+ * Separate from `page.tsx` so it can be tested without rendering, which is how
+ * `app/swap/direction.ts` and `app/earn/prefill.ts` are arranged.
+ */
+
+import { getSppConfig } from '@/lib/privacy/config'
+import type { VeilNetworkName } from '@/lib/network'
+
+/**
+ * What can actually be withdrawn.
+ *
+ * Derived from the pools the project pins in `lib/privacy/config.ts`, never
+ * from a list written by hand. Both configured testnet pools are
+ * `assetKind: 'native'`, so XLM is the only answer today — offering USDC or
+ * EURC would offer a pool that does not exist, and nobody can unshield from
+ * one of those.
+ */
+export function withdrawableAssetCodes(network: VeilNetworkName): string[] {
+  const pools = getSppConfig(network)?.pools ?? []
+  const codes = new Set<string>()
+  for (const pool of pools) if (pool.assetKind === 'native') codes.add('XLM')
+  return [...codes]
+}
+
+/**
+ * XLM as typed, to stroops as the pool counts them.
+ *
+ * Returns null rather than NaN or a silent truncation: `parseFloat` accepts
+ * `"1.2.3"`, `"1e9"` and `"  12abc"`, and this value decides how much money
+ * leaves a shielded pool.
+ */
+export function xlmToStroops(value: string): bigint | null {
+  const trimmed = value.trim()
+  if (!/^\d+(\.\d{1,7})?$/.test(trimmed)) return null
+  const [whole, fraction = ''] = trimmed.split('.')
+  return BigInt(whole) * 10_000_000n + BigInt(fraction.padEnd(7, '0'))
+}
+
+/** Stroops back to a display string, without trailing zeros. */
+export function stroopsToXlm(value: bigint): string {
+  const whole = value / 10_000_000n
+  const fraction = (value % 10_000_000n).toString().padStart(7, '0').replace(/0+$/, '')
+  return fraction ? `${whole}.${fraction}` : `${whole}`
+}