fix(tip): round a converted DM fee floor up

FlipcashCore/Sources/FlipcashCore/Extensions/Decimal+Operations.swift

@@ -22,6 +22,13 @@ extension Decimal {
         return rounded
     }
 
+    public func roundedUp(to decimalPlaces: Int) -> Decimal {
+        var current = self
+        var rounded = Decimal()
+        NSDecimalRound(&rounded, &current, decimalPlaces, .up)
+        return rounded
+    }
+
     private func pow10(_ n: Int) -> Decimal {
         var result: Decimal = 1
         for _ in 0..<n {

FlipcashCore/Sources/FlipcashCore/Models/FiatAmount.swift

@@ -79,19 +79,27 @@ extension FiatAmount {
     }
 
     /// This amount restated in `currency`, routed through USD the way the rate
-    /// table is keyed, and rounded to the target's display precision. `nil` when
-    /// either leg of the conversion has no rate.
-    public func converted(to currency: CurrencyCode, rates: [CurrencyCode: Rate]) -> FiatAmount? {
+    /// table is keyed, and rounded to the target's display precision — half-up
+    /// by default, or up when `roundingUp` so the result never falls short of
+    /// this amount. `nil` when either leg of the conversion has no rate.
+    public func converted(
+        to currency: CurrencyCode,
+        rates: [CurrencyCode: Rate],
+        roundingUp: Bool = false
+    ) -> FiatAmount? {
         if self.currency == currency {
             return self
         }
         guard let ownRate = rates[self.currency] else { return nil }
         let usd = convertingToUSD(rate: ownRate)
+        let unrounded: FiatAmount
         if currency == .usd {
-            return usd.roundedToSmallestUnit()
+            unrounded = usd
+        } else {
+            guard let targetRate = rates[currency] else { return nil }
+            unrounded = usd.converting(to: targetRate)
         }
-        guard let targetRate = rates[currency] else { return nil }
-        return usd.converting(to: targetRate).roundedToSmallestUnit()
+        return roundingUp ? unrounded.ceiledToSmallestUnit() : unrounded.roundedToSmallestUnit()
     }
 }
 
@@ -227,6 +235,16 @@ extension FiatAmount {
             currency: currency
         )
     }
+
+    /// This value raised to its currency's smallest displayable unit (e.g.
+    /// $6.2533 → $6.26). For values whose defining invariant rounding down
+    /// would break, such as a floor that has to cover a fee.
+    public func ceiledToSmallestUnit() -> FiatAmount {
+        FiatAmount(
+            value: value.roundedUp(to: currency.maximumFractionDigits),
+            currency: currency
+        )
+    }
 }
 
 // MARK: - Description -

FlipcashCore/Sources/FlipcashCore/Models/TipFloor.swift

@@ -64,7 +64,9 @@ extension TipFloor {
         in currency: CurrencyCode,
         rates: [CurrencyCode: Rate]
     ) -> TipFloor? {
-        if let fee = recipientFee?.converted(to: currency, rates: rates), fee.isPositive {
+        // Rounded up: a half-up floor can land under the fee, pass `isMet`,
+        // and be denied by the server.
+        if let fee = recipientFee?.converted(to: currency, rates: rates, roundingUp: true), fee.isPositive {
             return .recipientFee(fee)
         }
         return systemMinimum(presets: presets)

FlipcashTests/Regressions/Regression_6a677815fdca5cb0d6a9ef7e.swift

@@ -0,0 +1,72 @@
+//
+//  Regression_6a677815fdca5cb0d6a9ef7e.swift
+//  FlipcashTests
+//
+//  Server denial: "tip amount is below the recipient's chat initialization
+//  fee". The Start Chatting sheet submits the floor `TipFloor.toOpenDM` states,
+//  which is the recipient's fee converted into the entry currency. The
+//  conversion rounded half-up, so it could land under the fee — 600 INR at
+//  95.95 INR/USD is $6.2533, stated as $6.25, which is 599.69 INR. `isMet`
+//  judged the entry against that same figure, so it passed locally and the
+//  server denied it.
+//
+//  Fix: `toOpenDM` rounds the converted fee up, so the stated floor always
+//  covers the fee at the rate it was converted with.
+//
+
+import Foundation
+import Testing
+@testable import FlipcashCore
+
+@Suite("Regression: 6a67781 – converted DM fee floor rounds below the fee", .bug("6a677815fdca5cb0d6a9ef7e"))
+struct Regression_6a67781 {
+
+    private let usdRate = Rate(fx: 1, currency: .usd)
+    private let inrRate = Rate(fx: Decimal(string: "95.95")!, currency: .inr)
+    private let ngnRate = Rate(fx: 1326, currency: .ngn)
+
+    private var rates: [CurrencyCode: Rate] {
+        [.usd: usdRate, .inr: inrRate, .ngn: ngnRate]
+    }
+
+    private func floor(for fee: FiatAmount) -> TipFloor? {
+        TipFloor.toOpenDM(recipientFee: fee, presets: nil, in: .usd, rates: rates)
+    }
+
+    @Test("A 600 INR fee is stated as $6.26, which covers it, not $6.25")
+    func inrFee_floorCoversFee() throws {
+        let floor = try #require(floor(for: FiatAmount(value: 600, currency: .inr)))
+
+        #expect(floor.displayed == .usd(Decimal(string: "6.26")!))
+        #expect(floor.displayed.converting(to: inrRate).value >= 600)
+    }
+
+    @Test("The $6.25 the sheet used to submit no longer clears the floor locally")
+    func inrFee_roundedDownEntryIsRejected() throws {
+        let floor = try #require(floor(for: FiatAmount(value: 600, currency: .inr)))
+        let entered = ExchangedFiat(nativeAmount: .usd(Decimal(string: "6.25")!), rate: usdRate)
+
+        #expect(!floor.isMet(by: entered))
+    }
+
+    @Test("A 1500 NGN fee is stated as $1.14, which covers it, not $1.13")
+    func ngnFee_floorCoversFee() throws {
+        let floor = try #require(floor(for: FiatAmount(value: 1500, currency: .ngn)))
+
+        #expect(floor.displayed == .usd(Decimal(string: "1.14")!))
+        #expect(floor.displayed.converting(to: ngnRate).value >= 1500)
+    }
+
+    @Test("A fee that converts exactly is not bumped a cent")
+    func exactConversion_isUnchanged() throws {
+        let exactRates: [CurrencyCode: Rate] = [.usd: usdRate, .inr: Rate(fx: 100, currency: .inr)]
+        let floor = try #require(TipFloor.toOpenDM(
+            recipientFee: FiatAmount(value: 600, currency: .inr),
+            presets: nil,
+            in: .usd,
+            rates: exactRates
+        ))
+
+        #expect(floor.displayed == .usd(6))
+    }
+}